Performance target: Fifty brassica growers adopt or improve ecological pest management approaches including scouting, cultural practices, conservation biocontrol, and use of reduced-risk pesticides on 500 acres, reducing crop damage, increasing marketable yield, and increasing annual gross revenue by $500,000.
Growers consistently identify management of insect pests of brassicas as a major production challenge and priority for research and education (UMass Extension Stakeholder Meeting Notes 2017, 2016, 2015). Nearly 9,000 vegetable farmers across New England and NY grow approximately 15,000 acres of brassica crops. On most mixed vegetable operations around the Northeast, brassica crops make up a very large percentage of the total crop mix and total acreage, and are now also commonly grown throughout the winter to satisfy unceasing consumer demand for local, leafy greens. This increase in production and season length has intensified pressure from a suite of perennial insect pests including cabbage maggots, cabbage aphids, flea beetles, several caterpillar species, and new emerging pests including Swede midge and cabbage whitefly. Successful brassica pest control necessitates a high level of understanding of pest life cycles and integration of multiple strategies. This can be difficult and time-consuming to achieve and many growers lack confidence in the controls available or their ability to implement them, and struggle to produce quality brassica crops.
A regional, collaborative research and education program is necessary to improve management of this suite of insect pests. Our educational efforts will help growers increase their knowledge of brassica pest biology and confidence to implement best management practices by 1) participating in web and phone based educational opportunities with experts from around the region through a Brassica Pest Collaborative and 2) attending field day demonstrations where key individuals will share their experiences implementing new and alternative control strategies. The proposed research will evaluate the efficacy of tactics like mulches, netting, and conservation biocontrol to combat multiple pests, reduce overall pest damage, and increase yield. Constraints like labor and time will be addressed by using cost to benefit analyses to help growers to identify new ways to increase profits growing brassicas. By coordinating research efforts, we are able to tackle a wide range of topics with a high degree of rigor, as treatments and protocols can be standardized and results can be considered together across site-years.
Our education program will focus on giving growers the knowledge and confidence they need to be successful implementing current best management practices, and will support them in incorporating cultural practices and conservation biocontrol strategies listed above on their farms. Education efforts will also include improving grower understanding of pest life cycles, which will help them to better utilize crop rotations to disrupt pest life cycles, improve timing and efficacy of sprays, apply and remove netting only when needed, and so on. We will also develop resources to help growers identify pest and beneficial insects, scouting protocols and recordkeeping sheets to facilitate monitoring of pest populations and crop damage over time, so that they can keep track of their progress.
Our research program will further our scientific understanding of the efficacy and impacts of cultural practices and conservation biocontrol strategies, as well as the efficacy of organic-compatible and/or reduced risk alternative chemical control options. Through our research trials, which will be designed in collaboration with actual growers on the advisory board, we will demonstrate practical application of these methods. This will further empower growers to begin to implement these more time-consuming and preventive practices.
Several experiments will be conducted to test the following hypotheses: 1) reduced-risk and organic-compatible pesticides effectively control brassica pest populations 2) cultural practices (e.g. netting, mulches, and residue management) disrupt pest life cycles and reduce crop damage; 3) conservation biocontrol strategies attract predators and parasitoids of brassica pests, reducing pest population size and crop damage and 4) integration of these approaches improves control of multiple pests and increases marketable yields of brassica crops.
Ecological management approaches reduce insect populations and crop damage, increasing marketable yield of
Several experiments will be conducted to test the following hypotheses:
1) reduced-risk and organic-compatible pesticides effectively control brassica pest populations
2) cultural practices (e.g. netting, mulches, and residue management) disrupt pest life cycles and reduce crop damage;
3) conservation biocontrol strategies attract predators and parasitoids of brassica pests, reducing pest population size and crop damage and
4) integration of these approaches improves control of multiple pests and increases marketable yields of brassica crops.
Reports can be found on our website at: https://ag.umass.edu/vegetable/resources-services/brassica-pest-collaborative/research-reports-on-management-of-brassica
Hypothesis 1: Reduced-risk and organic-compatible pesticides effectively control brassica pest populations. In 2018, two studies were undertaken to evaluate the use of reduced-risk and organic-compatible pesticides to effectively control brassica pest populations. The first was conducted at CCE-SC by F. Zaman and D. Gilrein and was entitled, “Foliar Insecticides for Control of Cabbage Flea Beetles in Cabbage and Pak choy,” and is described below under subsection (a). A second study relating to hypothesis 1 was conducted by M. Meder, G. Higgins and S. Scheufele and was entitled, “Beneficial Nematodes to Reduce Flea Beetle Population Size, 2018,” and is described below under subsection (b). In 2019, both studies were repeated with slight variations in methods and results (see section c and d below) and another study investigating organic and reduced-risk pesticides for control of cabbage root maggot was also conducted on Long Island, NY (see section e).
- In this study, several conventional and OMRI-listed organic insecticides were compared for control of flea beetles (Phyllotreta cruciferae Goeze) in fresh-market cabbage and pak choy production. Materials tested included one rate each of Entrust SC (spinosad 1SC, Dow Agrosciences, OMRI-listed = Organic Materials Review Institute), Surround WP (95% kaolin, Tessenderlo, OMRI), PyGanic 5.0 (5% pyrethrins, Valent/MGK, OMRI), M-Pede (49% potassium salts of fatty acids, Gowan, OMRI), SuffOil-X (80% mineral oil, BioWorks, OMRI), Molt-X (azadirachtin 0.28EC, BioWorks, OMRI), Assail 30SG (acetamipridm UPI), Warrior II (lambda-cyhalothrin 2.08EC, Syngenta), and Harvanta 50SL (cyclaniliprole 0.42SL, Summit Agro). Unsprayed blocks were used as a control for both crops.
Treatments were compared in two large-plot field experiments on transplanted “Cheers” cabbage and pak choy at the Long Island Horticulture Research and Extension Center (LIHREC) in Riverhead, NY. On June 5 and July 7, 2018, respectively, cabbage and pak choy seeds were sowed in Speedling trays. Trays were maintained on a greenhouse bench with overhead irrigation as needed including a commercial soluble fertilizer (15-5-15 Cal-Mg, 150 ppm N, Jack’s Professional). On July 17 (cabbage) and August 6 (pak choy) seedlings were transplanted to the field spaced 11” apart in 34” rows in the main field at LIHREC. Four 30’ rows (approximately 340 sq. ft.) per replication and four replications per treatment were used for both experiments. One day after transplanting the area was treated with Devrinol 50DF (2 lbs/A) for weed control. Treatments were assigned randomly to plot, arranged in a randomized complete block design. Treatments were applied as foliar sprays to wet using a CO2-powered backpack sprayer fitted with TJ60 8003EVS nozzles operating at 40 psi. Treatments were applied at 10-day intervals on 7/27, 8/6, and 8/15 for cabbage and at weekly intervals on 8/10, 8/17, and 8/23 for pak choy. Number of cabbage flea beetles, flea beetle damage ratings (Ohio Scale, 1 – 6), and % foliage feeding damage from flea beetles (0 – 100%) to new growth (since previous application) were taken from 10 randomly selected plants per replication at a weekly interval from 7/25 to 8/30 in cabbage and 8/10 to 8/30 in pak choy. Plant quality data at harvest were collected including head diameter and weight for cabbage on 10/3 and above-ground plant height, width, and weight for pak choy on 9/7, respectively. Marketable quality ratings (0 – 5, 0 = dead plants, 3 = marketable, 5 = excellent) were done at harvest for both crops. ANOVA and multiple comparisons among treatments were performed on data using Tukey’s HSD (JMP Pro 10.0 SAS Institute). Treatments and data are shown in Tables 1 – 8 in the report posted online.
- Flea beetle adults lay their eggs at the base of brassica plants after mating. The eggs hatch and larvae feed on the fine roots for several weeks, pupate, and adults re-emerge from the soil to find new brassica leaf tissue to eat. Studies have shown that nematodes in the families Steinermena and Heterorhabditidae can attack the larval stage of flea beetles in the soil, thereby reducing the overall size of the population within a field over time. We wanted to know if this strategy would cause noticeable results in a real field, and try to estimate the impact on flea beetle survival and reproduction. We used a mixture of Steinermena carpocapsae plus Heterorhabditis bacteriophora nematodes applied to the soil as a drench at the base of the plants and monitored adult flea beetle emergence from the soil over the following 5 weeks.
Our treatments were:
1. Untreated control
2. Low rate 5 x 107 nematodes/2500 sq. ft. (600,000 nematodes per plot)
3. High rate 5 x 107 nematodes/1000 sq. ft. (1,500,000 nematodes per plot)
4. Entrust SC at 10 fl oz/A ( the labeled rate for root maggot suppression via soil application)
‘Green Magic’ broccoli (Johnny’s Selected Seeds, ME) was started in the greenhouse on April 24. On June 24th 100# N/A organic fertilizer (7-2-4) was applied and broccoli was transplanted by hand into staggered double rows 18 in. apart and 11 in. in-row spacing. One line of drip tape was used to maintain adequate soil moisture but no mulch was used, so that we could later apply treatments to the soil and could monitor adult flight out of the soil. Borisol was applied on June 1, 8, and 30th. We ordered commercial nematodes from Koppert Biological Systems and on June 15th, the nematodes were re-constituted in water and we looked at the solution under the microscope to ensure the nematodes were alive and to quantify them accurately. We also checked that the treatment application method was not lethal to the nematodes by spraying the solution into a beaker and re-checking the percentage of living versus dead nematodes in the sprayed solution. The field was divided up into four replications of each of the four treatments, with plots consisting of 10 ft. of bed with a 5 ft. buffer in between. We then applied the treatments using a CO2-powered backpack sprayer with a Floodjet nozzle (TeeJet TK-7.5) and no filter, set to 15 PSI. We then setup emergence cages, which consisted of no-se’em netting sewn into a tube with 1 ft. diameter metal ring base, over individual broccoli plants to capture flea beetles as they emerge from the soil below over time. We monitored emergence of the adult beetles by placing a yellow sticky card inside the trap and checking the card once per week and recording the numbers of beetles present over time. We also happened to capture cabbage root maggot flies emerging on some days. There was one trap per plot. No harvest or yield data was recorded because the plants were damaged from heat waves that occurred during head formation and most crowns were not marketable.
c. In 2019, the foliar insecticides for flea beetle control was repeated nearly identically, using pak choy as the host crop. On August 22 (pak choy) seedlings were transplanted to the field spaced 11” apart in 34”. Four 30’ rows (approximately 340 sq. ft.) per replication and four replications per treatment were used for the experiment. Because of the high crucifer flea beetle population in the area at the time of transplanting, a twice per week treatment schedule was followed for the first 3 applications and a 4th (final) application was applied at 7 days after the 3rd application.
d. In 2019, the study entitled “Beneficial Nematodes to Reduce Flea Beetle Population Size” was repeated following the same methods as in 2018 except that we doubled the number of emergence traps in order to increase the sample size. We used two traps per plot, with five replications of each of the four treatments. Broccoli seedlings were transplanted on 28 Mayand nematodes were applied on 14 June, except for Heterorhabditis bacteriophora because the nematodes were not living when we inspected them in the lab. The H. bacteriophora were re-ordered and applied on 18 June. We maintained moist field conditions using drip irrigation and monitored emergence of adult FB using yellow sticky cards placed within the netted emergence traps.
e. In 2019, a study was conducted on alternative techniques for control of cabbage root maggot (CRM) in cabbage. This study includes treatments from hypothesis 1 and hypothesis 2–cultural practices. Several conventional and organic insecticides and other alternative methods were compared for control of cabbage maggot (Delia radicum) in fresh-market cabbage. Treatments tested included insecticides Verimark 1.67SC (cyantraniliprole, FMC) at 13.5 fl. oz/A, Entrust SC (spinosad, Corteva) at 8.0 fl. oz/A, Radiant 1SC (spinetoram, Corteva) at 10.0 fl. oz/A, Tek-Knit exclusion netting (80-gram) over a black plastic mulch planting bed, and black plastic mulch planting bed alone. Lorsban 75WG (chlorpyrifos, Gowan) at 1.8 oz/1000 ft row was used as a standard for comparison. Verimark, Entrust and Radiant were applied as a pre-plant transplant tray drench and followed by one directed application two weeks after transplanting. Lorsban was applied in a 4-inch band spray over the furrow 7 days after planting. Untreated plots were used as a control.
This trial was conducted from mid-April to August 30, 2019. On April 12th ‘Bravo’ cabbage was sown into Speedling transplant trays using a standard peat-based media (Pro-Mix BX with Mycorrhizae, Premier Horticulture Inc.). Plants were maintained in a greenhouse on overhead watering as needed including a commercial fertilizer (15-5-15 Cal-Mg, 150 ppm N Jack’s Professional). On May 24 plants were transplanted 11” apart in 34-inch rows in the main field except for black plastic mulch rows, where plants were set on a 31-inch wide bed in rows spaced 18” and 15” apart in an alternate planting design. For exclusion netting plots, 18-inch row spacing allows about 6.5-inch clearance between plants and sidewall of the net coverings. Four rows 30 feet long (approximately 340 sq. ft.) per replication and four replications per treatment were used. Insecticide treatments were applied using a CO2-powered backpack sprayer fitted with a TJ60 4003EVS nozzle operating at 20 psi. Pre-plant tray drenches were applied to transplants 24 hours prior to setting in the main field. Post-transplant targeted applications were made two weeks after transplanting, directing spray to the lower stems and soil at the base of plants. Exclusion netting rowcover was set within 24 hours following transplanting of the 6-week old cabbage seedlings in 2” x 2” holes on black plastic mulch and rows remained covered until harvest. Where black plastic mulch was used alone, plants were set in a similar way to those in the exclusion net+ mulch treatment. Transplant flat rates for tray drench treatments were calculated to provide an amount of active ingredient per plant equivalent to the field rate per plant, using 500 ml water per 26 5/8″ x 13 5/8” (200 cell) tray. Lorsban 75WG was applied per label in 64 gal water per acre as a 4-inch banded spray to soil at the base of plants immediately after setting (within 7 days of transplanting). Plants were watered lightly after transplanting and as needed afterwards. Drip tape irrigation was used both black plastic mulch plots. The other plots were irrigated by overhead sprinkler system. Fertilizer was applied at 500 lb/A rate prior to planting and no herbicides were used in either plastic mulch treatment. On June 24 cabbage maggot damage was evaluated (presence or absence of cabbage maggot damage and severity in roots) by digging up 20 randomly selected plants from the middle two rows of each plot (80 plants per treatment), then washing and inspecting for cabbage maggot damage (gallery or tunneling in main root) and rating severity (based on number and length of feeding marks) on a 0 – 10 scale (0 = no damage, 3 = moderate, 5 – 7 = high, 8 – 9 = extreme, 10 = plant dead). The percent damaged plants and mean damage severity were calculated for each treatment. Stem diameter at the soil line, cabbage head weight and diameter at harvest, foliage feeding by other insects, and marketable head quality were also measured (1 = 5 scale, 1 = poor quality, 3 = marketable, 5 = excellent). ANOVA and multiple comparisons among treatments were performed on raw data using the Tukey’s HSD (JMP Pro 14.0, SAS Institute). Treatments and data are shown in Figure 1 to 7.
Hypothesis 2: Cultural practices (e.g. netting, mulches, and residue management) disrupt pest life cycles and reduce crop damage. One study on using cultural practices to reduce crop damage was conducted at UMass by M. Meder, G. Higgins and S. Scheufele and was entitled, “Using Mulches to Reduce Flea Beetle Damage and Improve Crop Yield, 2018” and is described below. This study was repeated three times in 2019, but using different crop hosts and planting timings. We wanted to evaluate the effect of mulches on bok choy, and during the spring flush of FB and therefore the experiment was setup in spring using bok choy but the crop was too susceptible and there were no differences between treatments–all plants were severely damaged. Thus we set the experiment up again in the fall, using both bok choy and broccoli, in order to repeat both. However, the bok choy was again so susceptible that the damage was too high to see any treatment differences and also the FB were so attracted to the bok choy that there was no damage at all in the broccoli and therefore, no differences there either. A second study described in the previous section included use of mulch and/or netting to exclude cabbage root maggot and is described under hypothesis 1.
- In previous brassica pest management trials we observed a marked decrease in flea beetle damage in plants grown in certain types of mulches. In these cases, the mulched plants were much more vigorous than those growing on bare ground, and could be identified from across the field for their greater size. This was never the focus of study and so we did not collect data on flea beetle damage at the time, but decided to investigate this effect in a replicated trial in 2018. We set out to determine:
1. if mulches can reduce flea beetle damage to brassica crops,
2. if mulches can increase crop quality and/or yield, and
3. which mulches are best at reducing damage and increasing quality and yield
We compared six different mulch treatments, with each treatment replicated four times. We formed raised beds and laid mulches by hand over one line of drip tape. Plastic and paper mulches were secured with soil along the edges. Straw mulch was applied to a depth of 4”. Soil temperature monitors were buried 2” below the soil surface and under the mulch cover.
Four-week old ‘Arcadia’ broccoli seedlings were planted into two rows at 10” between plants and 12” between rows on July 6th. Fertilizer was applied according to soil test results. The plot was irrigated twice in early July but subsequent rainy weather precluded need for further irrigation. On August 3rd, all plants were sprayed with Dipel (1 lb/A) and M-Pede (2% v/v) to control caterpillar pests and aphids.
Each week we rated:
• Flea beetle pressure (# beetles/plant)
• Flea beetle damage, using the following scale: 0=0%; 1=0-10%; 2=11-25%; 3=26-50%; 4=>50%
• Whole plot vigor: a visual assessment of stand, plant size, and leaf color (0-100%)
• Plant height
Once the crop was established (5 weeks) we stopped rating until the crop was ready to harvest and yield data was collected. Because of erratic temperatures and heavy rains, broccoli heads developed very unevenly and we had very few marketable crowns. Therefore, we harvested entire plants by clipping the stem at the soil line and measured the total plant weight per plot, in order to capture the difference in plant growth observed across the mulch treatments.
Hypothesis 3: conservation biocontrol strategies attract predators and parasitoids of brassica pests, reducing pest population size and crop damage. Four studies on conservation biocontrol were conducted in 2018 at three cooperating institutions, they are described below.
- The first study was conducted at UConn during 2018 and 2019 by A. Legrand and was entitled, “Evaluations of Ammi majus as an insectary plant for cabbage caterpillar conservation biocontrol. This report is still in progress, as data are being summarized and analyzed now. This multi-year scientific study will be published and a full report will be published on our project website at: http://ag.umass.edu/vegetable/resources-services/brassica-pest-collaborative/research-reports-on-management-of-brassica
- A second study was conducted at all three institutions (UNH, UMass, and UConn) and in 2018 and 2019. Every effort was made to standardize our protocols for experiment setup, data collection and analysis. Full reports will be written by each institution and will be published on our project website. Therefore, we will report here the methods, results, and discussion from the UMass study. Overall conclusions will be presented below and updated annually, as this study will be repeated in multiple project years.
Cabbage aphid populations have been increasing in recent years and are now a major concern across New England. Brussels sprouts are especially susceptible, since aphids get into buds and are hard to reach with pesticide sprays. Therefore, alternative methods for controlling aphids are necessary. In other systems, interplanting with insectary plants (flowers that provide pollen and nectar and can serve as food and habitat for beneficial insects) is standard practice. One example of this is lettuce production in CA, where alyssum is planted every so often in the bed to support insects which are predators and parasitoids of aphid pests. Cabbage aphids are a little different than aphid pests of lettuce—they are larger and contain sulfur compounds that are not appealing to some predators—but nevertheless there is a large body of literature supporting the idea that predators (especially syrphid fly larvae) and parasitic wasps (especially the native braconid wasp, Diaretiella rapae) can impact cabbage aphid populations in the field. The purpose of this study was to compare several species of insectary flowers to see if any of them are more attractive to syphrids and parasitic wasps, and to identify which species of syrphids and wasps are present in New England. Similar studies were repeated in NH and CT in 2018 and 2019.
Brussels sprouts were planted around the experiment in order to provide cabbage aphid hosts to help attract predators and parasitoids. Each flower was grown in a 15 sq. ft. plot and replicated four times. The insectary flowers tested were:
Alyssum 32 plants/plot
Buckwheat direct seeded at 6” spacing
Phacelia direct seeded at 12” spacing
Calendula 32 plants/plot
Dill 36 plants/plot
Cilantro 36 plants/plot
Ammi 32 plants/plot
Plants were direct-seeded or transplanted on July 13th, except Ammi majus which was planted on July 6th, and cilantro and dill which were planted on July 20th. The Phacelia never germinated so we have no data on that plant this year; in past years it was very attractive to a diversity of insects. To assess the relative attractiveness of each species of flower, we did timed observations in which we recorded the number of syrphids, small wasps, and other insects landing on flowers within a 1 square foot area for four minutes per plot. We then did sweep net sampling using a 15 in. muslin sweep net to collect insects within the plots and later characterized the number and types of insects collected and recorded information about the weather, time of day, and flowering activity. Over the winter, we identified wasps and syrphids as best as possible. In 2019 we focused on syrphid flies and did not collect wasp specimen because the wasps proved to be too numerous and difficult to ID. We intended to also collect syrphid fly larvae from CA colonies in order to rear them to adults in the lab and determine their species identity. However, because of low CA pressure this year, we were not able to achieve this outcome. We will attempt to repeat it in 2020.
To see the full reports with figures please visit: http://ag.umass.edu/vegetable/resources-services/brassica-pest-collaborative/research-reports-on-management-of-brassica
Plots treated with conventional insecticides Warrior II and Harvanta had significantly fewer flea beetles and less damage throughout the trial period. Assail was moderately effective in cabbage but not in pak choy. The residual activity of Assail appears to last only a short period (several days?) and that may explain why it was less effective on a fast-growing crop like pak choy—we observed many new pak choy leaves between treatment applications. OMRI-listed insecticides were less effective against cabbage flea beetle in these trials. Surround WP-treated cabbage had significantly lower numbers of flea beetle on plants, but the foliar damage was relatively high, inconsistent with the numbers seen (Table 2). Application of Surround-WP on cabbage transplants was associated with stunted plant growth across all replications. Plants in these plots were comparatively smaller with less foliage and they failed to produce heads. The lower numbers of flea beetles in Surround-treated plots could be due to repellency from the kaolin clay coating to the newest leaves, but damage ratings, which were done on the entire plant, suggest feeding may be occurring where the residues wash off or beetles were choosing to feed on undersides of treated leaves.
Of the OMRI-listed insecticides, Entrust was most consistent in terms of reduction in flea beetle damage and improvements in yield and quality. It is important to note that the study area had a high flea beetle population at the time of the trial and the small plots were bordered by other less effective treatments and untreated plants, which would not be typical for a commercial setting where the entire field would be treated with a single insecticide with usually no untreated area. In such cases, the efficacy of some less effective products may be greater than that observed in small-scale trials. Near the end of the trial, collecting flea beetle damage data became more difficult due to presence of damage from other foliage feeding insects such as imported cabbage worm, cabbage loopers, and diamondback moth, since no insecticide was applied to control other insects (Harvanta, Entrust, and Warrior and to some extent Assail are generally effective to highly effective against these pests).
There were no significant differences between any treatments, on any of the collection dates. This might be because we didn’t get the timing right (we would want the nematodes to be present when larvae are present in soil but are not too old) or because we did not have enough traps to detect small differences. Next year we hope to repeat this experiment using more traps and repeating each application to increase the chances that active nematodes are present when flea beetle larvae are at the correct life stage.
- Results were similar to those found in 2018.
Pretreatment cabbage flea beetle populations were extremely high in the study area and foliage feeding was started right after transplanting the 4 weeks old seedlings. As a result, treatment application was started within 72 hours of transplanting. Cabbage flea beetle populations were similar among treatment plots at the pretreatment counts on 8/26 (average 30.55 adult/plant). Plots treated with conventional insecticides Warrior II and Harvanta had significantly fewer flea beetles throughout the trial period. Entrust and Assail was moderately effective. The residual activity of Assail and Entrust appears to last only a short period (2 – 3 days) and that may explain why these two insecticides were less effective on a fast-growing crop like pak choy—we observed many new pak choy leaves between treatment applications. Last year we found some of the OMRI-listed insecticides were partially (at some time-points) effective in reducing flea beetle damage but this year because of the high population the effect from the OMRI-listed material were not much evident in this trial. Although some treatments had significantly lower numbers of flea beetle on plants, the foliar damage was relatively high, inconsistent with the number of flea beetles seen on plants. The inconsistent numbers of flea beetles in plots could be due to repellency and/or lack of green foliage, but % foliage feeding data, which were done on the new growth, suggest more effectiveness of the treatments. Percent leaf area with feeding damage by flea beetles was significantly lower in plots treated with conventional insecticides (Assail, Warrior, and Harvanta) compared with untreated plants. Of the OMRI-listed materials Entrust reduced foliar damage significantly greater than the other OMRI-listed materials and to the untreated control. It is important to note that the study area had a high flea beetle population at the time of the trial and the small plots were bordered by other less effective treatments and untreated plants, which would not be typical for a commercial setting where the entire field would be treated with a single insecticide with usually no untreated area. In such cases, the efficacy of some less effective products may be greater than that observed in this particular trial.
Plant quality such as height, width and weight were generally higher in the effective treatments (Warrior, Harvanta, Assail, and Entrust) at least partly due to less flea beetle damage. Marketable quality was also generally higher in the effective treatments.
- Again their were no significant differences between any nematode or Entrust control treatments, despite doubling the sample size. The impacts of treatments on soil-dwelling stages of FB are inherently difficult to study in the field. Our study was not able to demonstrate if nematodes are effective in controlling FB or not.
Cabbage maggot pressure in the area was moderate with 46.25% plants in untreated control plots showing some levels of root damage. Overall infestation level was slightly lower in the 2019 season compare to that observed in similar trials over the past several years. Besides normal population fluctuations, an unusually wet and cool spring season might also partly explain the slightly lower cabbage maggot pressure.
There was a significant effect due to treatment, with the lowest levels of maggot-damaged plants in exclusion netting + black plastic mulch plots (> 98% roots undamaged), and black plastic mulch alone (>95% roots undamaged), followed by Lorsban (9.0%), Radiant (12.5%), and Verimark SC (15%). Entrust SC appeared to provide a significant if moderate level control with nearly 70% undamaged roots (Figure 1). Control plants had 55% roots undamaged by cabbage maggot. Severity of root damage (0 – 10 scale, 0 = no damage, 10 = root completely consumed) was significantly lower in all insecticide and mulch treatments than in control plots (Figure 2), although the overall damage severity rating was minimal in the control plot averaging 1.21 out of 10. There was no phytotoxicity observed in any treatment.
Above-ground average stem diameter (N = 20/rep) for 4-week-old plants was significantly higher in plots covered with exclusion netting than in all other treatments (Figure 3). Climatic conditions such as temperature and soil moisture under the netting might have influenced greater plant growth. Among the seven treatments average head diameter at harvest (N = 20/rep) was not significantly different. However, compared with controls average cabbage head weight at harvest was significantly higher in all treatments with more than 80% undamaged roots (i.e. all except for Entrust).
There was moderate pressure in this trial from foliar-feeding insects, primarily crucifer flea beetle (Phyllotreta cruciferae) and lepidoptera (imported cabbage worm, Pieris rapae; cabbage looper, Trichoplusia ni) (Figure 6). Plants in Lorsban 75WG, black plastic mulch only, and untreated control plots had significantly higher (about 2.75 – 3.0%) foliar damage (defoliation)from cabbage flea beetle and worms than other treatments. There was almost no defoliation (<0.10%) in plots treated with Verimark and exclusion netting. There was a small but significantly higher level of foliar damage (1. 1 – 1.2%) observed in plots treated with Entrust and Radiant. Cabbage head quality (based on feeding holes on head and 5 wrapper leaves) was significantly higher in plots treated with Verimark and exclusion netting. Marketable quality (Figure 7) was also acceptable in plots with Entrust, Radiant and plastic mulch alone though the level of protection was significantly lower than where Verimark and exclusion netting were used. Foliar feeding damage was not controlled by Lorsban application and the level of damage was not significantly different from that in untreated control.
In our study planting cabbage under exclusion netting and/or over black plastic mulch may provide more than 95% root protection from cabbage maggot. Pre-transplant tray drench + one additional targeted spray application with Verimark 1.67SC and Radiant 1SC at 2-week interval may provide over 80% undamaged roots which is close to the protection from Lorsban 75WG (>90% undamaged roots). Further research will be done growing cabbage on black plastic mulch in 2020.
From the very beginning of the 2018 trial, we saw significant differences in flea beetle damage across the mulch treatments (Figure 2). The black plastic, paper, and reflective plastic mulches showed consistently less damage than other mulches or the bare ground control, but the reflective plastic mulch stood out as having the least damage of all, and the effect lasted for at least 6 weeks. All of the mulches improved plant growth relative to the bare ground plants, with straw and reflective silver mulches growing the tallest. Plant height was not directly correlated with flea beetle damage, but rather seems to correspond with soil temperature, which was cooler under these mulches.
Plants grown in reflective mulch were also more vigorous than bare ground plots. For other mulches, no consistent trend is evident; different mulches were more or less vigorous than others at different timepoints. Mulches influenced both the high and the low temperature of the soil, with the bare ground tending to have the highest high and the lowest low, and mulches acting to modulate the temperature to varying degrees. Soil in the bare ground plots got hottest, followed by black and white plastics, then paper, then straw and reflective silver. During the night, bare ground soil also got colder than mulched plots, followed by paper, then straw and white plastic. Black and reflective mulches stayed warmest. Brassicas are cool-season plants, and prefer a cooler soil and air temperature, so lower soil temperature under straw or reflective mulch could partly explain increased plant growth and vigor observed in those plots.
At the end of the season, we harvested whole plants to assess overall plant growth, since broccoli crowns could not be harvested. Only the reflective silver mulch increased harvest weight, relative to the bare ground control.
During 2019, none of the mulch treatments affected FB damage or plant growth because bok choy was too susceptible to FB feeding and no differences could be distinguished and the bok choy pulled FB away from the broccoli experiment and pressure there was too low to distinguish any treatment effects.
- This report is still in progress, as data are being summarized and analyzed now. A full report will be published on our project website at: http://ag.umass.edu/vegetable/resources-services/brassica-pest-collaborative/research-reports-on-management-of-brassica
The first flowers to open were from the Ammi plants, which were started earlier in the greenhouse, in late-July. Calendula, buckwheat and alyssum began flowering on August 3rd and dill and cilantro began flowering on August 23rd and September 4th, respectively. When we look at the total number of syrphids from aphid-eating (aphidophagous) groups collected in sweep nets, the alyssum had by far the most, followed by dill and then cilantro and Ammi (Figure 2-L). These flowers all have small petals and very open habits or umbels. In order to compare all the flowers side-by-side, we must look only at dates on which all flower species were open, which is unfortunately only two dates in September (Figure 2-R). On these dates, again we see far more aphidophagus syrphids on alyssum, and just a few T. Marginatus on dill, Ammi, and buckwheat. The greatest diversity of syrphids was found on dill.
Of the aphidophagus syrphids collected, Toxomerus marginatus was by far the most common; others we collected included Taxomerus germinatus, Melanostoma mellinum, Allograpta obliqua, and a Sphaerophoria species. When we looked at T. marginatus over time, its numbers began to increase in early-September and then plummeted in late-August, as weather became gray, windy, and rainy. When the sun came out again in October, we again were collecting large numbers. This species seems to be present during most of the fall brassica growing period and would be a useful species to continue to try to attract into our brassica fields.
Our collection of small and potentially parasitic wasps is quite large and diverse. These specimen have turned out to be much more difficult to identify to species or even to genus than the syrphids, and we are still working on identifying them. At least several of those we collected in large numbers are braconids or ichneumonids, which are both groups known to be parasitoids of vegetable pests, but others are from groups that parasitize the parasitoids (hyperparasitoids), making things more complicated. We have positively identified D. rapae, the native parasitoid of cabbage aphid, in our collections, and we have also observed it hatching out of mummified aphids collected from the field. We collected the most D. rapae fromAmmi, perhaps indicating a preference for that flower relative to other flower species tested (Figure 5). We believe that another wasp we collected often is a species in the genus Alloxysta, which is a genus of hyperparasitoids of braconid and apheliniid wasps. This wasp visited all of the flowers, but were collected in greatest numbers from the Ammi and alyssum (Figure 5).
In 2019, results were similar in all locations. Alyssum, buckwheat, cilantro, and dill had greater hoverfly densities than calendula, phacelia, and fennel. Alyssum attracted the cabbage fleabeetle and calendula attracted imported cabbage worm moths, but not at economically damaging levels. Fennel did not flower. In particular, alyssum was found to be a low maintenance plant that hosts the most prevalent aphid-eating hoverfly species (Toxomerus marginatus) from July until frost.
- Harvanta 50SL and Warrior II provided the best protection from flea beetles in both cabbage and pak choy. Assail provided intermediate efficacy and of the OMRI-listed materials tested, Entrust showed consistent reductions in flea beetle damage and increases in yield measures. Some of the OMRI-listed materials showed some efficacy on some dates but were not as effective or as consistent as Entrust.
- As tested, beneficial nematodes did not have a measurable effect on flea beetle survival in the soil in either study year.
Reflective silver mulch had the least flea beetle damage and plants were taller and more vigorous, and had significantly higher yields than plants grown in other mulches or in bare ground. This may be due to reduced plant stress from cooler soil temperature and more temperature buffering (lower highs and higher lows), or the reflected light may disorient or repel flea beetles, or it may be due to a combination of factors. The additional cost of the reflective silver mulch ($11/100 row ft compared to $3/100 row ft for black plastic) may be worth the investment, since a significant increase in plant growth and yield was observed. Furthermore, reduced feeding by flea beetles may contribute to reductions in black rot and Alternaria, since flea beetles are known to spread these diseases.
When repeated with bok choy there was no effect of mulch on FB damage or plant growth.
This report is in progress, as data are being summarized and analyzed now. A full report will be published on our project website at: http://ag.umass.edu/vegetable/resources-services/brassica-pest-collaborative/research-reports-on-management-of-brassica
- This long-term regional survey for predators and parasitoids of cabbage aphids has gotten off to a great start, with all three cooperating institutions developing shared protocols for planting, observing, and collecting beneficial insects in brassica fields. So far we have identified many aphidophagous syrphids and parasitic wasps collected from insectary flowers, and have determined that many are common across states. The most common aphidophagous syrphid species across states was Toxomerus marginatus. The most attractive to syrphid flies were dill, cilantro and alyssum while Ammi majus was most attractive to the parasitoid D. rapae. One challenge we encountered was that we collected such a large number and diversity of wasps that we had difficulty identifying all of them. Another challenge was erratic CA pressure across study years. In 2019 we attempted to collect aphid mummies from farms across New England and characterizing only wasps that hatch out of these mummies, in order to narrow down our survey to include only these species of wasp. We also attempted to collect syrphid fly larvae from CA colonies in order to determine which species of syrphid larvae are actively foraging on CA in the field but because of low CA pressure regionally we were unable to accomplish this goal–we will try again in 2020.
Education on biology and management of brassica pests will be accomplished by producing factsheets, newsletter articles and presentations, all to be housed on a project website hosted by UMass. The website will also serve as a portal to connect beneficiaries with other important online resources like the Northeast IPM Center and other regional Extension services. Field days will be held to showcase ongoing research and to increase grower confidence in implementing new pest management strategies. Results of before/after surveys at all outreach events will demonstrate changes in knowledge, and behavior. Further, a phone and web-based Brassica Pest Collaborative (BPC) will be established, through which Extension educators, ag service providers, and growers can discuss current issues in brassica pest management. Through these phone conversations, participants will have an opportunity to increase their knowledge and confidence in implementing best management practices. The phone calls will be recorded and posted to the project website so other growers can access them freely. Phone calls will be hosted at least quarterly, or more often during the growing season as determined by participants. Additional podcast-style webinars will also be recorded and posted online for educational topics identified by the survey and in BPC conversations.
1. 1500 farmers receive information about project objectives, resources, and educational activities including free e-alerts and phone-based or podcast-style education via the Brassica Pest Collaborative via our established Extension newsletters and email networks. May 2018.
2. 300 farmers and 25 agricultural service providers join Brassica Pest Collaborative and/or access project webpage and educational resources and increase their knowledge of brassica pest biology, pest management, and ongoing research efforts and results. Ongoing from March 2018 to March 2021.
The BPC email list serve has not been very effective means for communicating directly in-season with growers. There were 12 threads total going out to 47 members. Instead of email, we have been using our usual means for distributing brassica related pest alerts, Vegetable Notes, which reaches 2,884 growers, gardeners, and ag service providers. There are approximately 14 brassica pest alerts per season in this publication. In addition, we have been using our program Instagram pages to reach out to growers and ag service providers about our research activities in the season. Becky Sideman’s “Sideman Lab” page has 541 followers and had 12 related posts in 2019. Sue Scheufele’s “UMass Vegetable Team” Instagram page has 201 followers had 10 related posts in 2019.
Our website, “Brassica Pest Collaborative,” has been accessed 743 times, 641 of those representing unique views from different computers. This website houses factsheets, research reports and our webinar series videos. The webinars were hosted from Jan-March 2019 and had the following attendance, totaling 1,047 growers, gardeners, and ag service providers across the Northeast region.
Cabbage Loopers and Diamondback Moth: 57 attended, 337 subsequent views
Cabbage Aphids: 55 attendees, 125 subsequent views
Flea beetles: 47 attendees, 120 subsequent views
Cabbage Root Maggot: 29 attendees, 197 subsequent views
Imported Cabbageworm and Cross-Striped Cabbageworm: 43 attendees, 37 subsequent views
Webinar attendees were surveyed after each program and a few highlights are listed below:
Cabbage Loopers and Diamondback Moth: Knowledge increased on average from 2.56 to 4.13 (1-5 scale) and growers rated their interest in adopting a new practice they learned about an average of 4.2 out of 5. One grower wrote they took home this message: “Will try to be more diligent about scouting, treating regularly if needed, and record keeping.”
Cabbage Aphids: Knowledge increased on average from 2.89 to 4.28 (1-5 scale) and growers rated their interest in adopting a new practice they learned about an average of 4.1 out of 5. One grower wrote they took home this message: “I plan to implement weekly checks for cabbage aphids, instead of just doing it when I have time.” Another wrote: “Insectary plants was a new concept for me.”
Flea beetles: Knowledge increased on average from 3.1 to 4.1 (1-5 scale) and growers rated their interest in adopting a new practice they learned about an average of 3.8 out of 5. One grower wrote they took home this message: “Will try new products to control Flea Beetles.” Another said “Thank you !! This was a good series.”
Cabbage Root Maggot: Knowledge increased on average from 2.75 to 4.0 (1-5 scale) and growers rated their interest in adopting a new practice they learned about an average of 3.6 out of 5. One grower wrote they took home this message: “being on top of degree days and knowing when to scout!” Another wrote: “Multiple generations through the growing season. Surprised how effective exclusion is”.
Imported Cabbageworm and Cross-Striped Cabbageworm: Knowledge increased on average from 2.7 to 4.3 (1-5 scale) and growers rated their interest in adopting a new practice they learned about an average of 4.2 out of 5. One grower wrote they took home this message: “I am definitely going to plant herbs and flowers to attract more beneficials. Also, now I’ll know what I’m looking at when I see it!” Another wrote: “This talk was very clear and the visuals were great. I appreciate hearing where research is headed.”
BPC reseachers also wrote 14 factsheets and newsletter articles between 2018-2019.
Lastly, BPC researchers gave a total of 37 additional presentations for grower, ag service provider, gardener, scientist and student audiences reaching a total of 2,953 individuals.
3. 150 growers attend field days and increase their knowledge and confidence in implementation of ecologically based management strategies for reducing impacts of brassica pests and observe ongoing research trials. October 2020.
- F. Zaman and D. Gilrein. 2018 Long Island Agriculture Forum, January 11, 2018 Riverhead, NY: Diamondbacks, Earworms, Cabbage Maggot and Other Problem Pests; 85 vegetable growers attended.
- B. Sideman and A. Harris. Season extension and specialty crop research at UNH. Aug 2018. Durham Farm Day. Durham, NH; 45 gardeners and growers attended.
- S. Scheufele. Alternative strategies for managing cabbage aphid in fall brassicas. UMass Extension Agricultural Field Day 2018. South Deerfield, MA, August 2018; 45 growers and ag service providers attended. Survey respondents reported: 34.6% increase in knowledge about using mulches to reduce flea beetle damage and 72% were likely to implement this on their farms; and 22% increase in knowledge about using insectary habitat to attract beneficial insects for cabbage aphid control and were 55% likely to implement this on their farms.
- On 9/4/2019, a cover crop and vegetable research twilight meeting/demonstration program was organized in the project site at the Cornell University Long Island Horticulture Research and Extension Center (LIHREC). 34 attendees were participated in the program.
- A. Harris. Using insectary plants to promote biological control of pests. 6th Annual Farm Day. 17 Aug 2019. Woodman Horticultural Research Farm, University of New Hampshire, Durham. (45 farmers, researchers, community members)
- S. Scheufele. 8/20/2019 Vegetable IPM Research Twilight Meeting: UMass Research Tour and Pest Roundtable UMass Extension South Deerfield, MA 45 attendees
- A. LeGrand. Vegetable IPM Field Workshop, August 13, 2019. 25 attendees. Attendees on average rated their before- and after-program knowledge as follows (1-5 rating scale with 5 being most knowledge):
Brassica insect pest management topics Before After
Insect life cycles & identification 2 4
Insect Monitoring 2.8 4.1
Insectary Plant Use 2.3 4.1
4. 100 growers express interest in implementing one of the strategies identified as improving pest control and crop yield such as adopting a weekly scouting program, planting insectary plots on their farms, or incorporating reduced-risk pesticides into their spray programs. March 2019.
Growers who participated in webinars and field days were surveyed for their interest in implementing new practices as a result of our educational activities. Growers surveyed at a UMass field day were 55% likely to implement a new practice, while webinar attendees were, on average, 40% likely to implement a new practice. Given that we reached 1,372 individuals through field days and webinars so far, a conservative estimate of grower willingness to adopt new practices to control brassica insect pests is 549 growers.
5. 75 growers receive support documents including factsheets, scouting sheets, and other resources and/or receive support via BPC phone calls. September 2019.
In a 2019 survey of LI brassica growers, among the 6 respondent, five growers have responded positive (at a scale of 4 out of 5) for adoption of the new brassica pest management techniques developed from this project. Two growers partially adopted the exclusion netting techniques for controlling cabbage maggot and other pests. Consultation through demonstration and power point presentation. Impacting ~10 acres.
Ana Legrand worked with 3 growers in 2019 to implement new practices. One grower commented that this was the best quality brassica crop he has obtained by implementing the practice (protekt net).
Sue Scheufele worked with 5 growers in 2018 and 2019 to implement new practices including use of Surround on transplants, regular scouting technique and thresholds, spray timing and coverage, use of insectary plantings, identification of beneficial insects, use of insect netting. Impacting ~25 acres.
Becky Sideman helped one grower identify a brassica problem (black rot), visited their farm, and provided in-person and followup consultation with info about how to manage black rot in the future, including seed treatments. Since this only pertains to future seed purchases, there is no measurable impact yet. Identification did result in fewer pesticide applications, since the grower was uncertain as to the cause of the problem and was treating with several pesticides to manage the problem. She also repeatedly put out info about brassica pests, and specifically reached out to growers who had previously had trouble with cabbage aphid – and did not get any participants who were having trouble and needed assistance.
This will be a major area of focus in 2020.
Milestone Activities and Participation Summary
Pest Alerts: 31 in 2 newsletters (Veg Notes and LI Fruit and Vegetable Update, 2,884 and 225 subscribers, respectively).
Instagram posts: 9
Email list-serve threads: 10
Attendees surveyed at a 2018 field day at UMass reported: 34.6% increase in knowledge about using mulches to reduce flea beetle damage and 72% were likely to implement this on their farms; and 22% increase in knowledge about using insectary habitat to attract beneficial insects for cabbage aphid control and were 55% likely to implement this on their farms.
Vegetable IPM Field Workshop, August 13, 2019. Attendees on average rated their before- and after-program knowledge as follows (1-5 rating scale with 5 being most knowledge):
Brassica insect pest management topics
Insect life cycles & identification
Insectary Plant Use
Nuts and bolts of Farmscaping for beneficial insects. NOFA Winter Conference. Feb. 23, 2019. 93% of attendees indicated an increase in knowledge.
In a 2019 survey conducted with brassica grower on Long Island, among the 6 respondent, five growers have responded positive (at a scale of 4 out of 5) for adoption of the new brassica pest management techniques developed from this project.
Our webinar series resulted in consistent increases in knowledge, from 20-31% increases in knowledge of pest biology and management practices, on average.
Performance Target Outcomes
adopt or improve ecological pest management approaches including scouting, cultural practices, conservation biocontrol, and use of reduced-risk pesticides
reduced crop damage, increased marketable yield, and increased annual gross revenue (+$500,000)
adopted at least one new practice
growers report improved quality and/or improved marketable yield
Before our outreach could begin, the Office of Research & Engagement at UMass had to review all of our outreach plans and tools to ensure compliance with human subjects research and be approved by the Institutional l Review Board (IRB). This resulted in a significant delay of our planning and implementation of our outreach objectives. We did design a project announcement that went out to our stakeholder groups and included a survey and way for growers to sign up for different educational activities.
The survey was completed by just 16 growers from across the region and Nebraska, but our results indicated that: flea beetles were the biggest pest issue on greens and radishes, cabbage aphid is the main pest of Brussels sprouts, and caterpillars are the biggest pests of cabbage; respondents were most interested in interview-style educational opportunities, and in-depth discussion and description of pest biology and management; and respondents were most interested in learning how to use resistant varieties, biocontrols, and conservation biocontrol practices to control pests. The survey will be re-sent in spring 2019 to get a better response rate and to help us prioritize education topics and design the best possible educational resources.
Five growers expressed interest in participating as collaborators, implementing a strategy on their farm and documenting changes in pest pressure and crop damage and yields, but unfortunately, we were unable to assist them this year because of the delays in planning and getting our research efforts underway.
In 2019, we were able to work directly with 15 growers on approximately 35 acres. These growers learned to scout, use thresholds to time sprays, improve spray coverage, improve selection of spray materials, plant insectaries, use insect netting, and use surround on transplants. In 2020 we will plant to work with these growers to collect better documentation of the economic costs and benefits of these practices, and demonstrate changes in yield, quality, and/or profits.