Optimizing Row Covers and Perimeter Trap Crops for Cucurbit Pest Management

Optimizing Row Covers and Perimeter Trap Crops for Cucurbit Pest Management

Summary

Field experiments in Iowa and Ohio during 2011 and 2012 showed that two new pest management methods – perimeter trap cropping and delayed removal of row covers – have encouraging potential for control of bacterial wilt on muskmelon with less reliance on insecticides in organic and conventional production. In conventional production, perimeter trap cropping (PTC) reduced the use of insecticides on a muskmelon main crop by an average of about 50% while incidence of bacterial wilt was lowered and yield was equivalent to non-PTC plots. The presence of a double row of ‘Buttercup’ winter squash as a perimeter trap crop successfully intercepted most cucumber beetles (the insects that spread bacterial wilt) before they entered the muskmelon crop. Although these squash perimeter rows required several insecticide sprays to protect against squash bug and squash vine borer, total insecticide use on treatment plots was still lower than on control plots. Under organic production, delaying row cover removal until 10 days after anthesis resulted in lower incidence of bacterial wilt than in control treatments (no row covers, and removal of row covers at anthesis) in all three site-years in which the disease appeared. Row covers also significantly suppressed a fungal disease, Alternaria leaf spot, in both years in OH. In general, use of row covers resulted in higher marketable yield than no row covers. However, the yield impact of the two delayed row cover removal treatments – opening the ends at anthesis, or leaving them closed – was variable compared to the row cover control (removal at anthesis). To date, the project’s findings have been shared with cucurbit growers throughout the Midwest by presentations at state and regional grower meetings (Great Plains Fruit and Vegetable Growers Conference, PA Association for Sustainable Agriculture (PASA), and Great Lakes Fruit and Vegetable Expo) and two articles in the trade magazine American Vegetable Grower.

Bacterial wilt, caused by the bacterium Erwinia tracheiphila, is a severe threat to cucurbit crop production in the North Central Region. Bacterial wilt costs cucurbit growers more than $13 million annually (Adams and Riley, 1997; NASS, 2008).
Two insects spread the wilt bacterium: the striped cucumber beetle (Acalymma vittatum) and spotted cucumber beetle (Diabrotica undecimpunctata). The beetles carry the bacterium in their mouthparts and gut. When they feed and defecate on cucurbit plants, they transfer the bacterium, which then invades the plants and causes wilting. The highest risk of infection is in the springtime, when overwintering adult beetles emerge from the ground and seek out young cucurbit plants to feed on. Both organic and conventional muskmelon growers rank the cucumber beetle/bacterial wilt complex as their #1 pest problem (Hoffman, 1999; Bessin et al., 2003; Cavanagh et al., 2009).
Stopping cucumber beetles is the key to stopping the disease. Conventional growers rely primarily on neonicotinoid insecticides such as imidacloprid and thiomethoxam to suppress cucumber beetles, but this practice is not sustainable. Several insecticides can weaken or even kill pollinating insects when these chemicals are carried back to hives in pollen (Milkovich, 2009; Cavanagh et al., 2009). As a result, growers urgently need safer strategies to manage cucumber beetles and bacterial wilt.
Organic insecticides are considerably less effective than conventional ones, and frequently fail to prevent heavy losses from bacterial wilt epidemics. As a result, organic growers greatly over-plant in hopes of salvaging some marketable yield. Although some organic growers delay planting in order to avoid the highest-risk bacterial wilt period in the spring, planting late can result in lower market prices and greater losses from late-season diseases, particularly downy mildew. As a result, the threat of bacterial wilt limits crop diversification and marketing opportunities for organic cucurbit growers.
Our project was designed to explore the usefulness of two strategies – pertimeter trap cropping and delaying removal of row covers – for suppressing damage to muskmelon from bacterial wilt, reducing the need for insecticides, and improving profitability.

Objectives/Performance Targets

1. Assess ability of a) perimeter trap cropping, and b) extended-duration row covers, to suppress bacterial wilt and deliver acceptable yield in muskmelon.

2. Calculate costs and profits of applying perimeter trap cropping in conventional muskmelon production, and extended-duration row covers in organic production.

3. Communicate the findings to cucurbit growers throughout the North Central Region by means of on-farm demonstration trials, field days, webinars, a project website, trade journal articles, and regional meeting presentations.

Performance targets for research, stated in the project proposal:
• In 2 years of replicated field trials on muskmelon in Iowa and Ohio (2011 and 2012), determine the ability of perimeter trap cropping (PTC) to suppress bacterial wilt and reduce insecticide use under conventional production.
• In 2 years of replicated field trials in Iowa and Ohio, determine the ability of delayed row cover removal (DRCR) to suppress bacterial wilt and reduce insecticide use under organic production practices.
• Estimate costs and returns to each practice (PTC and DRCR) for North Central Region growers, using a partial budget analysis, based on results from the 2011-2012 field trials.
Outreach targets:
• Four on-farm demonstration trials per year, focusing on the DRCR tactic.
• A field day in each state in both years, highlighting the project at an experimental trial site or at the farm of a cooperating grower.
• Two 20-minute webinars, each highlighting one of the new practices (PTC and DRCR) used in the project.
• Two articles on the project’s findings in regional or national trade journals (for example, American Vegetable Grower).
• Presentations on project findings at regional grower meetings: the Great Plains Vegetable Growers Conference in St. Joseph, MO, the Great Lakes Fruit and Vegetable Expo, Grand Rapids, MI, and the Pennsylvania Society for Sustainable Agriculture (PASA).

OBJECTIVE 1 – Field trials

This Objective included two field trials on muskmelon in OH and IA in each year (2011 and 2012): 1) Evaluation of PTC in conventional production and 2) evaluation of DRCR in organic production.

Trial 1 – Perimeter trap cropping

Perimeter trap cropping (PTC) involves planting one or more rows of a cucurbit crop that is highly attractive to cucumber beetles around the border of a main cucurbit cash crop that is less attractive to the beetles. Cucumber beetles attempting to migrate into the field are concentrated in the relatively more attractive border crop, where they can be controlled by insecticides.
Methods were similar in both states, although details differed.
Iowa. Four replications of two subplots each (PTC vs. No PTC) were isolated from each other at the central, and north, east, west of the ISU Horticultural Research Station near Gilbert, IA, in order to minimize interference between the plots. Replications were separated from each other by at least 800 ft. The locations of the subplots was changed from year to year.
(NOTE: “Interplot interference” is a significant concern for diseases that are spread by flying insects, such as bacterial wilt, particularly when the insects can move readily from one treatment plot to another, and potentially contaminate the experiment. It is a particular concern for the small-size plots that are often used in replicated field experiments. We attempted to minimize this risk by separating the replications from each other as far as possible given the relatively small size (170 acres) of our university farm.)
Paired sub-plots were 50 ft apart. To reduce interplot interference between the paired plots, we planted field corn between then in 2011 and soybeans in 2012. Main-crop subplots (50 x 50 ft) each included 360 melon plants. Three-week-old transplants of muskmelon (cv. Strike) were placed 2 ft apart in black plastic mulch with drip irrigation and 6-ft row centers in mid-June.
Two to 3 weeks before muskmelon were transplanted, semi-bush buttercup (cv. Space Station) seedlings were planted as the perimeter trap crop. The perimeter trap crop consisted of two border rows surrounding the perimeter trap cropping subplots as well as 2 plants at each end of the muskmelon rows (164 squash plants per subplot)(Figure 2A) . Immediately after transplanting, a drench of Admire-Pro 4.6F (imidacloprid) was applied. In the ‘No PTC’ subplots, 12-ft-wide border strips of annual rye grass (the same dimensions as the perimeter trap crop strips in the treatment plots) were seeded at the same time as the squash were transplanted.
Populations of cucumber beetles were monitored weekly in both border rows and main-crop rows along three transects within each plot. Synthetic pyrethroid insecticide sprays (Asana XL) were applied to the squash border rows or main crop muskmelons when a threshold number (an average of one beetle per plant) was reached. Bacterial wilt incidence was also monitored weekly, and total number of plants with bacterial wilt was recorded one week before harvest. Conventional practices were followed for managing weeds and fungal diseases. Squash vine borer sprays for the buttercup squash were timed according to counts from a pheromone trap (Hartstack trap). Muskmelon yield (fruit number and weight) was totaled over several harvests per year.
Ohio. The experiment was conducted at 4 sites with one replicate per site. Two sites were at the Ohio Agricultural Research and Development Center (OARDC), Fry Farm and Snyder Farm in Wooster, one was at the OARDC North Central Ag Research Station in Fremont, and one was at the Waterman Ag and Natural Resources Laboratory in Columbus. Farmore Dl 400-treated ‘Space Station’ buttercup squash seeds were sown a week earlier than Thiram-treated ‘Strike’ muskmelon seeds. The insecticide Admire Pro 4.6F was drenched on buttercup squash transplants 24 hours before transplanting, and also on these plants in the field. Squash was transplanted on 2 weeks before muskmelon. Two replications of two subplots (perimeter trap crop (PTC) and the control (No-PTC)) were separated from each other by at least 50 ft at each farm. Main-crop subplots were 50 x 50 ft. For the PTC subplots, squash plants used in two border rows surrounding the muskmelon plots as well as 2 plants at each end of each muskmelon row. Plants were spaced 2 ft apart on 6-ft centers. For the No-PTC subplots, a border strip, with the same dimensions as the perimeter trap crop strips, was seeded with annual ryegrass on 22 May.
Sevin XLR PLUS was applied to the squash border rows or main crop muskmelons when the cucumber beetles reached the monitoring threshold of an average of one beetle per plant. Data were analyzed using SAS proc mixed, and significance determined using ANOVA test.

Trial 2 – Delayed row cover removal (DRCR)

Iowa. Transitioning organic land was at the ISU Horticultural Research Station. Organic transplants of ‘Strike’ muskmelon were planted 2 ft apart in black plastic mulch with drip irrigation on 8-ft centers. Subplots consisted of 30 ft rows of 15 plants. Spunbond polypropylene row covers (Agribon® AG-30) were installed on wire hoops immediately after transplanting.
A Latin square experimental design using 16 subplots (4 replicates of 4 treatments) was used to examine impacts of row cover treatments: 1) no row covers; 2) standard organic-grower practice: row covers applied at transplanting and removed at anthesis (start of perfect flower bloom); 3) row covers applied at transplanting with the ends opened at anthesis and covers removed 10 days later; and 4) row covers applied at transplanting and removed 10 days after anthesis.
Striped and spotted cucumber beetle adult numbers were monitored weekly from transplant through the beginning of harvest using yellow sticky cards and weekly counts from 5 randomly chosen plants. Disease incidence was monitored weekly. Melons were harvested twice weekly to optimize fruit quality for four weeks beginning Jul 29. The number and weight of marketable and cull melons harvested from each subplot was recorded.
Applications of OMRI-registered insecticides and fungicides were triggered by results of weekly monitoring. Pyganic® was applied to control picnic beetle damage on ripening fruit during harvest in 2011. Champ 50WG® (copper hydroxide) was also used to control anthracnose due to prolonged rainy weather in 2011. Weed management was achieved with 6 inches of corn stalk mulch between rows, and composted bark was placed around the opening in the plastic around each seedling before row cover placement in order to suppress weeds near the transplants.
Ohio. The experiment was conducted at the Ohio Agricultural Research and Development Center, Fry Farm in Wooster and at the Waterman Agricultural and Natural Resources Laboratory in Columbus, with four replicates at each site. Prior to planting on 22 May, 100 lb/A Replenish 3-4-3 (N-P-K) fertilizer was applied. Untreated ‘Strike’ muskmelon seeds were sown on 7 May into 50-cell plug trays containing Muskmelon seedlings were transplanted and covered with Dewitt row covers (Pro 34) over wire hoops, held in place with sand bags. Organic rye straw mulch was placed between beds the same day. Treatments were arranged in a randomized complete block design with four replications. Each treatment consisted of one row of 15 plants spaced 2 ft apart on 8 ft centers. Row covers were removed using timing as described above for the Iowa experiments. Incidence of bacterial wilt and percentage of foliage with symptoms of Alternaria leaf spot were determined weekly. Yield (number and weight of marketable and non- marketable fruit were determined on three picking dates per year).

OBJECTIVE 2 – Economic analysis of field trials

We will calculate a partial budget annually from results of the perimeter trap cropping and extended-duration row cover experiments (Objective 1) to compare the relative profitability of each strategy with control treatments. Under Objective 1b, scenarios assessed will include direct cost of installing and removing row covers, as well as re-using them for one to four seasons. Returns will be calculated based on local retail prices for conventional (Objective 1a) and organic (Objective 1b) muskmelon in Iowa and Ohio.

OBJECTIVE 3 – Outreach

On-farm demonstration trials. Cooperators selected delayed row cover removal for demonstration trials. This strategy was tested against appropriate control treatments in non-replicated plots on the cooperators’ farms. Project scouts assisted growers in field operations such as transplanting seedlings, establishing row covers, monitoring populations of cucumber beetles, and assessing damage from insect pests and diseases. In Ohio, demonstration trials with row covers were done at four farms: Riehm, Weaver, Moreland, and Bongue.

Accomplishments/Milestones

OBJECTIVE 1 – Field Trials

Trial 1 – Perimeter trap cropping

Iowa. Insecticide sprays in the PTC muskmelon plots (see photo A, top left; muskmelon is in center, with the much larger buttercup squash plants along borders) were less frequent than in the non-PTC control plots (photo B, top right) In 2011, the PTC plots required an average of 0.25 insecticide sprays whereas the control plots required an average of 3.75 sprays. In 2012, the control plots required an average of 2.0 insecticide sprays compared to 1.5 sprays for the PTC plots. The mean insecticide-spray reduction for the two Iowa trials was 59%, or about 2 sprays per year. This result showed that the PTC was effective in keeping cucumber beetles (C, lower left photo) out of the main crop (muskmelon). The butternut PTC received a total of 4 to 6 Asana sprays for cucumber beetle and squash vine borer control; this heavier spray regime in the perimeter trap crop was expected, because the squash rows were designed to trap cucumber beetles. However, the trials also highlighted the fact that several additional pests need to be controlled in squash: squash vine borer and squash bug. Over both years, mean bacterial wilt incidence (D, lower right photo) in the muskmelon main crop was considerably lower in the PTC treatment (1.5%) than the control treatment (11%). Bacterial wilt incidence in the trap crop was negligible. Based on these results, PTC was effective in reducing the need for insecticide use in the main crop, and in suppressing bacterial wilt. There were no significant treatment differences in melon yield. Perimeter plots yielded a mean of 1812 lbs of buttercup squash that weighed an average of 3.6 lb.

Ohio. In 2011, there were no significant differences in bacterial wilt incidence between PTC and control plots, and no impact on yield. However, incidence of bacterial wilt in the perimeter trap crop reached 37.2% by the end of the season. In 2012, there was no significant difference in yield between the two treatments but the PTC melon plots received an average of 1.5 Sevin sprays compared to 2.5 sprays for the non-PTC control plot. Bacterial wilt incidence was significantly higher in the non-PTC control (7.3%) than in the PTC plots (2.2%). As in 2011, incidence of bacterial wilt in the trap crop in 2012 was quite high (44.4%) by the end of July despite 2 drench treatments of Admire insecticide and 7 sprays of Sevin insecticide. Marketable and total muskmelon yield did not differ significantly among treatments. These results for Ohio indicated that 1) the PTC strategy reduced insecticide spraying and bacterial wilt in muskmelon while safeguarding yield, and 2) high levels of wilt in the buttercup-squash trap crop despite heavy insecticide protection suggests that buttercup may not be robust enough to serve as a trap crop for muskmelon in Ohio.

Use of a buttercup-squash perimeter trap crop saved 1 to 4 insecticide sprays on a muskmelon main crop in Iowa and Ohio, and also reduced the incidence of bacterial wilt on muskmelon in the three site-years in which the disease appeared. Yield of muskmelon was not affected by the perimeter trap crop. These preliminary results suggest that the PTC strategy has encouraging potential to manage bacterial wilt on muskmelon in the North Central Region with fewer insecticide sprays.
The much higher incidence of wilt in the buttercup-squash trap crop in Ohio and Iowa, despite a fairly intensive pesticide regime, suggests that the optimal trap crop for use with muskmelon may differ in different parts of the North Central Region. It also indicates that use of buttercup squash for PTC on a muskmelon main crop in the North Central Region increases the complexity of pest management, because the squash trap crop requires monitoring and spraying for two additional insect pests (squash vine borer and squash bug) as well as cucumber beetles. In addition, the vigorous growth habit of ‘Space Station’ buttercup squash required that vines be pruned back in order not to overgrow the outer edge of the muskmelon crop. It is likely that these additional management needs will be relatively smaller under larger-scale muskmelon production, where a boom sprayer can spray the two-row perimeter trap crop, and shading of edge of the melon fields by squash vines would have a negligible impact on yield. In addition, the reduction in pesticide spraying from PTC is likely to be much greater with larger-scale plots, because the ration of main crop to PTC will increase substantially. However, these assumptions will need to be tested in larger-scale field trials.

Trial 2 – Delayed row cover removal (DRCR)

Iowa. Cucumber beetle pressure was low in both years, and the beetles appeared in trial plots relatively late in the season. As a result, the impact of delayed row cover removal (DRCR) on bacterial wilt suppression was minimal, since this strategy is aimed mainly at early-season populations of cucumber beetles. Nevertheless, it was a good opportunity to evaluate the impact of this management strategy under low-risk conditions. In 2011, neither number of organic insecticide sprays nor marketable yield was impacted by treatment, even though late-season incidence of bacterial wilt was slightly higher in the non-covered and removal-at-anthesis control treatments than when removal was delayed by 10 days. In 2012, an exceptionally hot and dry year, bacterial wilt again developed only late in the growing season; incidence was high (37-50%) but occurred so late that it had minimal impact on yield, and differences in wilt incidence were minimal among treatments although slightly lower for the row-covered treatments. Yield was significantly higher in the row-covered treatments that the non-covered control, and significantly higher than the other row cover treatments in the DRCR treatment in which ends were row cover ends were opened.

Ohio. In 2011, no bacterial wilt appeared in the experimental plot. However, low pressure from the foliar fungal disease Alternaria leaf spot was present; all row-covered treatments had significantly less leaf damage than the no-cover control on August 16 and 23, as well as over the entire season (area under the disease progress curve, or AUDPC), but the row-covered treatments did not differ significantly from one another. The non-cover plots had higher numbers of marketable fruit than the covered plots, but weight of harvested fruit did not differ among treatments. In 2012, in contrast, bacterial wilt pressure was moderate to high during a growing season in which premature springtime warming followed by exceptionally hot and dry weather. All of the row-covered treatments had significantly fewer wilted plants than the non-covered control, but again the covered treatments did not differ significantly among themselves. Under low disease pressure, damage by Alternaria leaf spot was also significantly less in the covered treatments than the non-covered treatment. At Wooster, the number and weight of marketable fruit were significantly higher for the removal-at-anthesis and delayed-removal-with-open-ends treatments than the other two treatments, and all three row-covered treatments had significantly higher total fruit number and weight than the no-cover control, but did not differ from each other. At Columbus, there was no significant difference in the total yield among the four treatments, but when early yield was analyzed separately from late yield, differences were seen: there were significantly more early fruit in the no cover and in plots where covers were removed at anthesis; there were significantly more late fruit in plots that had the row cover treatment removed after 10 days. When data from the 4 replicates at Wooster and 4 replicates at Columbus and the single replicates at Riehm and Weavers were pooled, there was a significantly lower yield in the treatment with no row covers than in any if the other three treatments, and there was significantly higher late yield where covers were removed 10 days after anthesis.

Discussion
Considerable variability in bacterial wilt pressure among site-years led to a wide range of outcomes. Under negligible bacterial wilt pressure in 2 of the 4 site-years, the wilt suppression effect and yield advantage of row covers disappeared. However, when bacterial wilt pressure was moderate to high (Ohio 2012), and even when it came late in the season after covers had been removed (Iowa 2012), the row-covered treatments had higher yields than the non-covered controls. Part of this effect seems likely to have come through bacterial wilt suppression, but other forms of protection (from hail, high winds, etc.) conferred by row covers may have also played a role in safeguarding yield. There was no consistent yield advantage for either delayed-removal row cover treatment compared to the removal-at-anthesis treatment that is current practice for many Midwest organic cucurbit growers. Nevertheless, between the DRCR treatments, there was a trend for higher yield in the open-end treatment than in the closed treatment. Despite the variability among site-years, our study provided the first experimental evidence that row cover protection on muskmelon can suppress bacterial wilt season-long and safeguard yield in the North Central Region under organic production practices. Determining the ultimate value of delayed row-cover removal for the North Central Region will require further field testing over multiple sites and years.

Calculation of costs, returns, and profitability in a partial budget approach for both the PTC and DRCR strategies is ongoing, based on the data from the 2011 and 2012 field trials.

On-farm demonstration trials

Iowa. These trials were non-replicated demonstrations of the delayed row cover removal strategy. At Turtle Farm (Grainger, IA), ‘Betternut 401’ winter squash was transplanted every two feet (4 seeds per hill) in 150-foot long segments. At ZJ Farm (Solon, IA) and Growing Harmony Farm (Nevada, IA), ‘Athena’ muskmelon were transplanted into 30-ft-long rows of black plastic mulch. At each farm, single-row treatments using polymer row covers (Agribon AG-30) on wire hoops, with edges buried in soil were compared as follows: A) rows covers removed at anthesis; B) row covers removed 10 days after anthesis. At anthesis, both ends of row covers were opened to allow pollination; and C) no row covers. Beginning after row cover removal, the number of healthy, wilted, or dead plants in each row was assessed weekly by ISU scouts. The number and weight of squash and muskmelon harvested from each row were also recorded. Wilt data were recorded one week before the first harvest.
In 2011, a late spring frost at Growing Harmony Farm and ZJ Farm killed all seedlings in the non-covered control, but none in the row-covered treatments; this required replanting in the non-covered control. Bacterial wilt and cucumber beetle pressure was extremely low across all three farms. Under these circumstances, marketable yield (fruit weight) was highest for the removal-at-anthesis row cover treatment, and equivalent for the other two treatments. A crop failure in the test plots at Turtle Farm, apparently unrelated to the treatments themselves, prevented our taking data there in 2011.
In 2012, performance of the delayed row cover removal strategy was variable across the farms, but this treatment resulted in the most consistent yield across farms and crops (muskmelon and squash). AT ZJ Farms, bacterial wilt incidence was much higher (40%) in the no-cover and removal-at-anthesis plots than in the delayed-removal plot, but this did not translate to a yield advantage for the delayed-removal plot. No bacterial wilt was observed at Growing Harmony Farm, but the non-covered control has lower yield than the row-covered treatments. At Turtle Farm, row covers protected against heavy cucumber beetle and squash bug pressure, resulting in highest yield for the DRCR plot, minimal yield for the removal-at-anthesis plot, and complete crop failure for the no-cover control.

Field days

Iowa. Field days highlighting the project’s findings were held at the ISU Horticulture Research Station near Gilbert, Iowa on July 19, 2011, and July 23, 2012. Total attendance: 125. During wagon tours of the research plots, Dr. Jean Batzer explained the purposes and methods of the perimeter trap crop and delayed-removal row cover strategies to attendees. Additional field day presentations and handouts by Mark Gleason on the NCR-SARE project occurred during evening on-farm produce walks sponsored by Amish and Mennonite vegetable growers in eastern Iowa on July 12, 2011 (David Stutzman farm, Kalona) and July 11 (David Burkholder farm, Kalona) and August 1, 2012 (Bloomfield, IA); total attendance: 160.
The perimeter trap crop trial was featured in a presentation by Dr Mary Gardiner at the Northern Ohio Vegetable Crops Field Night on 8/7/2012, which was attended by 50 growers and industry personnel.

Webinars

The two webinars – on will be developed by ISU and OSU project personnel during May-August 2013, and delivered to a region-wide audience of cucurbit growers and extension educators during November and December 2013.

Trade-journal articles

An article featuring the project team’s experiences with perimeter trap cropping and delayed-removal row covers was published in American Vegetable Grower in the October 2012 issue (“Protecting Against Bacterial Wilt,” pages 26 and 28, by Rebecca Bartels.).

Presentations at regional conferences

Project team members gave slide shows (PowerPoint presentations) summarizing project findings at the following meetings:
• School of Agricultural Sciences, Lincoln University, Jefferson City, MO ) March 22, 2013), attendance: 30.
• Great Lakes Vegetable Working Group, annual meeting, West Lafayette, IN (February 27, 2013), attendance: 25
• Ohio Ecological Food and Farm Association Conference (February 17, 2013), attendance: 35.
• Wisconsin Fruit and Vegetable Growers Association (January 16, 2012; attendance: 60)
• Iowa Fruit and Vegetable Growers Association (January 27, 2012, Des Moines, IA, and January 24, 2013, Ankeny, IA; total attendance: 51)
• Great Plains Fruit and Vegetable Conference, January 11, 2013; 110 attendees)
• Pennsylvania Association of Sustainable Agriculture (PASA), State College, PA, February 8, 2013; 85 attendees)
• Great Lakes Fruit, Vegetable, and Farm Market Expo, Grand Rapids, MI, December 6, 2011)

• Row cover with ends opened at anthesis
• Images A, B, C, and D

Impacts and Contributions/Outcomes

Our 2-year, 2-state study is the first to explore how perimeter trap cropping (PTC) and delayed row cover removal (DRCR) can fit into conventional and organic muskmelon production practices, respectively, in the North Central Region. Although economic analysis and production of some outreach and research products is ongoing during our current no-cost extension period, we foresee that our project will provide new ideas and IPM tactics that will be especially valuable for two groups of growers in the Region: 1) conventional muskmelon growers who wish to reduce their reliance on insecticides for management of cucumber beetles and bacterial wilt (the PTC strategy), and 2) organic growers looking for any effective ways to manage this pest/disease complex (the DRCR strategy).

Although our study confined evaluation of PTC to conventional production and DRCR to organic production, it is also possible that each strategy could be adapted to the other type of management. For example, Saalau Rojas et al (Plant Disease 95:729-734, 2011) showed in a simulation analysis based on field trial results that DRCR could be economical under conventional production if significant bacterial wilt pressure occurred in >50% of production years. It is likewise possible that PTC could be adapted to organic management, with the expectation that it would be less effective than under conventional production due to less effective organic than conventional insecticides. These possibilities merit examination in further field trials on multiple sites over multiple years.

Changes in grower behavior and readiness to try to try the new approaches will be assessed in an end-of-project survey.

This is ongoing, as discussed under Objective 2 above.

Refereed Publications

None.

Outreach Publications:

Bartels, R. 2012. Protecting against bacterial wilt. American Vegetable Grower, October 2012, pp. 26-28.

Batzer, J.C., Kearney, H., and Gleason, M.L. 2011. On-farm cooperator trials 2011: Effect of extended-duration row covers on muskmelon and winter squash on bacterial wilt and yield. . Annual Progress Reports – 2011. Iowa State University Extension and Outreach, ISU College of Agriculture and Life Sciences. 2 pp.

Batzer, J.C., and Gleason, M.L. 2011. On-farm cooperator trials 2011: Effect of extended-duration row covers on muskmelon and winter squash on bacterial wilt and yield. . Annual Progress Reports – 2011. Iowa State University Extension and Outreach, ISU College of Agriculture and Life Sciences. 2 pp.

Batzer, J.C., Johnson, S., and Gleason, M.L. 2011. Organic practices for the production of muskmelon: ISU Horticulture Farm, 2011. . Annual Progress Reports – 2011. Iowa State University Extension and Outreach, ISU College of Agriculture and Life Sciences. 3 pp.

Batzer, J.C., and Gleason, M.L. 2012. Organic practices for the production of muskmelon: ISU Horticulture Farm, 2011. Annual Progress Reports – 2012. Iowa State University Extension and Outreach, ISU College of Agriculture and Life Sciences. 4 pp.

Batzer, J.C., Day, E., and Gleason, M.L. 2011. Controlling bacterial wilt in muskmelon with perimeter trap cropping. . Annual Progress Reports – 2012. Iowa State University Extension and Outreach, ISU College of Agriculture and Life Sciences. 4 pp.

Batzer, J.C., and Gleason, M.L. 2012. Controlling bacterial wilt in muskmelon with perimeter trap cropping. . Annual Progress Reports – 2012. Iowa State University Extension and Outreach, ISU College of Agriculture and Life Sciences. 3 pp.

Baysal-Gurel, F., Gardiner, M., Welty, C., and Miller, S.A. 2011. Evaluation of row covers for the control of bacterial wilt and foliar diseases of muskmelon, 2011. Plant Disease Management Reports: p.

Baysal-Gurel, F., Gardiner, M., Welty, C., and Miller, S.A. 2012. Evaluation of row covers for the control of bacterial wilt and foliar diseases of muskmelon, 2012. Plant Disease Management Reports: p.

The project has just concluded analysis of field results from 2011-2012, and economic analysis is ongoing. We anticipate that the strongest impact on farmer adoption will come after summaries of the results for grower and extension audiences are developed in summer 2013.

Two areas have emerged as most in need of additional study:
1) Perimeter trap cropping showed encouraging results in our preliminary trials, in terms of reducing the need for insecticide sprays under conventional production. To have significant impact on grower practices, however, it became clear that field trials need to be replicated at a larger spatial scale than was undertaken in the present study. The reasons that larger field scales are needed are: a) the full impact of insecticide reduction will be more evident to growers at a scale large enough to resemble commercial muskmelon fields in the North Central Region; b) the risk of interplot interference by cucumber beetles between control and treatment plots – an artifact of small-plot trials that will not be relevant to field-scale production – needs to be eliminated by increasing distance between treated and untreated plots; and c) we need to verify that the phenomena seen in small plots is replicated commercial-scale plots. In addition, there is a need to determine whether PTC is a viable strategy for organic muskmelon producers, since these growers lack effective options for bacterial wilt management, and some are not willing to use row covers because they are opposed to increasing the use of agricultural plastics.
2) The jury is still out on whether and how row covers can benefit North Central Region organic muskmelon growers for bacterial wilt control, although they clearly provide additional benefits in terms of environmental protection. Inconsistency in trial outcomes among states, sites, and years is partly attributable to wide swings in cucumber beetle pressure and the consequent risk of bacterial wilt. In general, row covers help to suppress bacterial wilt and foliar fungal diseases such as Alternaria leaf spot (as we noted), whether removed at anthesis or 10 days later. However, additional benefit of the 10-day delay in row cover removal – the DRCR strategy – provides further disease suppression, but sometimes appears to delay and even suppress yield. Based on our field observations in this project, we suspect that some bacterial wilt is entering formerly row-covered plots after covers are removed, via transmission from adjacent, diseased control plots. This is another example of an interplot interference situation; as for PTC, it can unfairly bias results against the experimental treatments. To minimize this effect, we propose two tandem approaches: a) increasing plot size and creating interplot barriers (rows of corn); and b) improving effectiveness of organic insecticides against cucumber beetles once the row covers come off, by using the product Cidetrak D (feeding stimulant) along with the insecticide Entrust.

Collaborators: