Developing Sustainable Management Tactics for Cucumber Beetles in Cucurbits

Final Report for ANE95-022

Project Type: Research and Education
Funds awarded in 1995: $135,832.00
Projected End Date: 12/31/1999
Matching Non-Federal Funds: $61,296.00
Region: Northeast
State: New York
Project Leader:
Michael Hoffman
Cornell University
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Project Information

Summary:

[Note to online version: The report for this project includes tables and figures that could not be included here. The regional SARE office will mail a hard copy of the entire report at your request. Just contact Northeast SARE at (802)-656-0471 or nesare@uvm.edu.]

The cucurbits (cucumber, melon, squash, pumpkin, etc.), are an exceptionally diverse and valuable commodity grown on many farms in the northeastern states and across the US. Cucumber beetles are considered a serious pest of cucurbits and growers often take a conservative approach and treat frequently with insecticides to control these pests. Organic growers rank cucumber beetles to be the most important insect pest of cucurbits. The objective of this project was to develop environmentally benign and cost-effective management tactics for cucumber beetles.

To reach our objective we developed a trapping system for cucumber beetles and investigated trap crops and cultural practices to improve beetle management. Attractant-baited traps containing a very small amount of insecticide showed promise for mass-trapping adult beetles under field conditions. Up to 65% of the beetles were removed using this tactic. This trapping system is unique in that it requires very little toxicant, the toxicant is removed from the field after a relatively short time, and none is applied directly to the crop. The research also showed that a highly preferred trap crop in combination with a few attractant-baited traps will significantly reduce the number of beetles (>75%) and injury to less preferred cucurbits. Trap cropping and mass trapping were tested on commercial vegetable farms in central New York. However, due to low beetle densities at test sites, we were not able to fully demonstrate the potential of these tactics. On farm trials did however show that these tactics, in particular trap cropping, would be very practical and cost effective for growers.

To determine the potential of fall cultivation as a means of suppressing overwintering beetles we monitored beetle populations in and around cucurbit fields until the onset of winter. Results indicate that populations aggregate on remaining green vegetation and fruit where control could be focused in the form of spot treatments with insecticide or physical destruction with deep plowing. Trials simulating deep plowing showed that ~45% of beetles are killed if buried 6 and 12 inches deep, but none survive if buried at 18 inches. The use of attractant-baited traps after harvest was shown to hold potential as a means of suppressing overwintering populations. Suppression of immature cucumber beetles with entomopathogenic nematodes appears possible and could be especially effective if applied to trap crop plants to control progeny of aggregated adults. Tests on the effectiveness of insecticides used by organic farmers showed that rotenone was better then cryolite or neem. Results indicate that feeding stimulants enhanced the effectiveness of rotenone, permitting the use of reduced rates.

The use of trap cropping and cultural controls for suppression of cucumber beetles will result in significant reductions in the amount of insecticide used for managing cucumber beetles. This will save growers money and minimize risks to the environment.

Introduction:

The cucurbits (cucumber, melon, squash, pumpkin, etc.) are an exceptionally diverse and valuable commodity grown on many farms and in many urban gardens in the northeast and across the US. Cucumber beetles are very serious pests that can rapidly destroy plantings of cucurbits through direct feeding damage or by transmission of plant diseases. Consequently, growers often take a conservative approach and treat frequently with insecticides to control these pests. Organic growers rank cucumber beetles to be the most important insect pest of cucurbits in the US. The objective of this project was to develop environmentally benign and cost-effective management tactics for cucumber beetles, thereby reducing the use of insecticides.

Project Objectives:

A. Develop trapping techniques to control early season infestations of cucumber beetles.

B. Develop cultural and biological control methods for control of cucumber beetles.

C. Improve the effectiveness of botanical insecticides

Research

Materials and methods:

Field activities have been conducted at the Department of Entomology Farm, Freeville, NY. In addition, trials on trap cropping, mass trapping and fall cultural practices were conducted on cooperating farms (all in New York) including Iron Kettle Farm, Candor, Strawberry Valley Farm, Whitney Point, Stoughton Farm, Newark Valley, Blue heron, Lodi, and Early Bird Farm, Ithaca. These farms represent the typical diverse vegetable farms common throughout the northeastern US. They included both conventional and organic farms.

Research results and discussion:

Objective 1: Develop trapping techniques to control early season infestations of cucumber beetles.

A mixture of cucurbit blossom volatiles (TIC) is an effective attractant for cucumber beetles and rootworms when used in traps (Levine & Metcalf 1988 and others). We have improved the effectiveness of such traps through a series of studies (Hoffmann et al. 1996a). In an effort to find a better trap for cucumber beetles we investigated several designs, including a design that only requires beetles to land on the trap. Upon landing on the trap the beetles pick up a small dose of toxicant or spores of an insect pathogen. This design results in rapid control from the toxicant adhering to the beetle or slower control via infection by the pathogen. In this unique scenario it should be possible to trap enough beetles (mass trap) to reduce damage. The advantages of this tactic include: (1) an extremely small amount of toxicant is used, (2) the toxicant does not contact the crop) and, (3) the toxicant is removed from the field after a relatively short time and properly disposed elsewhere. We found that the most effective toxicant was a solution of carbaryl (0.3% ai) in mineral oil. For example, at 10 traps per acre this translates to 0.0022 lbs. active ingredient per acre. This is a 99% decrease over a traditional insecticide application. Thus this method could considerably reduce the amount of insecticides used for managing cucumber beetles. For organic growers the synthetic toxicant could be replaced with one appropriate for their needs. However, our trials showed that the traditional insecticides most often used by organic growers were only marginally effective when used in traps. Although slower in rate of control, a pathogen-containing trap may be best for organic systems.

In 1996, the effectiveness of the trapping system was evaluated in 12′ X 12′ field cages containing 12 young squash plants. The trap we tested consisted of a 16 oz. plastic cup baited with TIC and glued upside down on an 8 inch dia. plastic plate. The cup was covered with yellow felt, which was saturated with a mixture of mineral oil and carbaryl (0.3% ai). Three traps were installed each in 3 cages and another set of 3 cages were used as control (without traps). One hundred striped cucumber beetles were released into the control cages and 175 into cages with traps. Cages were observed 1, 3, and 5 days after release, and the number of dead and live beetles was recorded. The average percentage dead (trapped) beetles in the cages with traps was 38.7, 64.0, and 42.7 on the first, third, and fifth day, respectively. Although a high proportion of beetles were unaccounted for in cages (escaped or were not observed) these results indicate that this trapping system holds potential.

During the summer of 1997 we investigated the potential for mass trapping cucumber beetles and conducted studies to determine the optimal trap density per unit area. Studies were conducted in experimental plots located at the Cornell University, Department of Entomology Research Farm, Freeville, NY. The trap design was similar to the ones used in 1996. One, two, four, and eight traps were installed per plot (1/20 acre) (corresponding to 20, 80, 160 traps/ac) while the plants were at cotyledon stage. The attractant and toxicant were replaced or refreshed on a weekly basis. The number of beetles on plants and the injury they caused per plant were recorded.

These studies showed that plots with one or eight traps had more beetles per plant than plots with two or four traps (Table 1). When expressed as percentage of the beetles captured [(number of beetles on the traps ÷ (number of beetles on the traps + total beetles in the plot)) X 100], the percentage of beetles captured by 1, 2, 4, and 8 traps was 23, 54, 65, and 49 percent respectively. Therefore at two or four traps per plot the traps were removing over half of the beetles from the plot. One trap per plot did not remove a sufficient number of beetles (23%) whereas eight traps per plot may have attracted additional beetles from surrounding areas. Plant injury coincided with the number of beetles per plot and was less in plots with two or four traps (Table 1). For example, the mean cumulative injury per plant was less than 20% in plots with two traps. The mean number of beetles trapped/day/plot increased (~doubled) with increasing trap densities. In addition to striped cucumber beetles, hundreds of western and northern corn rootworms were also attracted to these traps. The number of western corn rootworm found dead on traps ranged from 10 – 740 per plot during the study period. We also observed that an unknown number of beetles landed on traps and left before the toxicant had its affect. Thus a potentially large number of beetles may have been killed, but not recorded as captured by the trap.

Since the initial studies under field cages on the potential of these traps in 1996 and subsequent elaborate trials in 1997 under field conditions gave promising results. We further tested the effectiveness of mass-trapping during the summer of 1998. Studies were conducted in experimental plots located at the Cornell University, Department of Entomology Research Farm, Freeville, NY. Trials were conducted during mid June and mid August. The experimental set-up was similar to our 1997 studies. We did not find any significant difference in the number of beetles per plant or plant injury rating during either trial. Frequent heavy rainfall during the early season trials presumably reduced the effectiveness of the traps and late season trials were inconclusive because of low beetle densities.

We also conducted trials on two farms to demonstrate the effectiveness of mass trapping. An area of 100 X 80 ft was flagged in pumpkin fields and 6 traps (corresponds to 120 traps per acre) were installed, while the plants were at first leaf stage. The set-up was replicated twice on each farm and beetle densities and plant injury monitored. On both farms, the growers applied insecticide to control the beetle infestation across the entire field including the test areas. This experience emphasized the importance of the pest in the growers’ mind and that this tactic has to be very effective for growers to adopt.

In addition, we set-up TIC baited traps during fall in a pumpkin field at Whitney Point, NY, to determine whether traps could be installed in the fall to control the beetle population that overwinters. Data on the number of dead beetles on trap were recorded on a weekly basis. Our results show that these traps could be effective in reducing the beetle population in fall (Table 2). Over about a one month period (October 2 to November 5), total catch per trap averaged >200 beetles. Results from this study suggest that the use of traps in the fall and when cucurbit vegetation has been greatly reduced, holds considerable promise.

In conclusion, our studies indicate that with little modification these traps will be effective in mass-trapping striped cucumber beetle population, both during early and late season, using an extremely small amount of toxicant. We have demonstrated that traps are effective, but they need to be made more durable and able to remain effective under even adverse environmental conditions.

Objective 2: Develop cultural and biological control methods for control of cucumber beetles.

(a) Cultural control – Trap Crop:
Cucumber beetle management can also be improved through the development of cultural and biological control tactics. Certain types of cucurbits are highly preferred by cucumber beetles and these preferred types could aggregate beetles and their progeny for more efficient control. Our ongoing cucurbit screening and breeding program with Dr. Molly Kyle, Dept. of Plant Breeding, Cornell University, focuses on developing resistance to beetle pests and has identified highly preferred genotypes for use as trap crops (Hoffmann et al. 1996b, Reiners et al. 1999). The potential for spring trap crops has been further supported by work in Maine (Radin & Drummond 1994) and more recent work in Oklahoma (Pair 1997). Trap crops could be further enhanced by the addition of the long range attractant (TIC).

During the summer of 1996, we investigated the trap crop tactic in experimental plots. A highly preferred squash type (Seneca Zucchini) was transplanted either before (June 6, 1996), the same date (June 16, 1996), or following (June 24, 1996) the planting of the main crop of “Munchkin” pumpkins. Our objective was not only to determine if trap cropping would work, but also to determine if the time of planting of the trap crop was important. Each plot consisted of 68 plants planted in four rows (spacing 3′ X 5′ for squash and 2’X 5′ for zucchini). Fifteen percent of each plot was planted to trap crop (first 5 hills / 25 ft of each outer row on opposing corners of plot). Immediately following the transplanting of the trap crops and main crop, beetle counts were recorded 2-3 times per week. Injury caused by beetles was recorded 1-2 times per week on all plants.

Results of the early season test showed the trap crop was not effective in reducing the number of beetles on the main crop. The reasons for this lack of control include the rapid destruction of the trap crop by beetle infestations and because of the unexpected presence of some highly preferred Munchkin plants in the main crop. Apparently, there was sufficient variability in the commercial Munchkin seed that some plants were highly attractive to beetles (>50 beetles per plant). Although this indicates that commercial seed has an unacceptable level of variability and a potential limitation for this tactic, it offered another opportunity. Instead of using a different variety for trap crop and main crop, we have now initiated a breeding program to select for, and develop, a highly preferred type of Munchkin pumpkin. This would simplify the trap crop method by permitting the use of a single variety in a field, except that some of it would be used as the trap crop.

The trap crop tactic was repeated late in the 1996 season, but modified to include TIC-baited traps (0.3% ai carbaryl + mineral oil design as described above) in the trap crop. Also, 15-20 zucchini (trap crop) plants were planted in a solid row instead of 5-6 plants in the previous experiments to minimize the total loss of the trap crop due to beetle feeding damage. The addition of TIC to the trap crop provided a long range attractant, while the traps provided a means to control beetles attracted to the trap crop. Results showed that the average number of live beetles on munchkins was reduced substantially (>75%) when the trap crop and TIC-baited traps were present (Fig. 1).

The trap crop tactic was tested again during summer 1997. The experimental set-up was similar to the late season trials in 1996. Immediately following the transplanting of the trap crops and main crop, beetle counts were recorded twice per week. Injury caused by beetles was recorded twice during the experimental period. No reduction in the average number of live beetles was observed. However, the data on the cumulative injury on munchkins two weeks after planting showed some significant differences between treatments and control. Average cumulative damage on munchkins was ~30% on treatment plots compared to 50% on control plots. The addition of traps with TIC reduced the number of beetles on the trap crop thereby minimizing the total loss of trap crop due to beetle feeding damage as observed during the first trial. Also, there were 3-4 times more beetles (including beetles dead on the trap) on the trap crop segment of the plots with TIC traps than beetles on the trap crop segment on plots with trap crops alone (Table 3).

Since the results of our 1996 and 1997 experiments showed that trap cropping with highly preferred cucurbits in combination with TIC traps is effective in reducing striped cucumber beetle numbers and injury, we conducted trials on three farms in 1998 to demonstrate the trap cropping technique. Unfortunately, all the growers applied insecticides upon the first arrival of beetles and therefore the effect of trap cropping on the protected crop could not be observed on any of these demonstration plots.

The results of our experiments shows that trap cropping is effective in reducing the injury caused by striped cucumber beetle adults to pumpkin seedlings at their early stages of development. Also, the addition of traps with TIC lures attracts and kills many adult beetles thereby reducing the population of striped cucumber beetle adults in the field.

(b) Cultural Control – Fall Cultivation
In addition to trap cropping, cultural practices such as fall cultivation may affect survival of overwintering cucumber beetles. The beetles present in the field late in the summer and fall, overwinter to infest fields the next spring and their control could minimize infestations the next season. Our objective was to monitor the fall population of beetles and also to study the effect of fall cultivation and fall clean-up on the beetle mortality.

In 1997, one field located on the Strawberry Valley Farm, Whitney Point, NY, and two fields located at Freeville, NY were monitored with yellow sticky cards and weekly visual sampling, starting early fall to study the beetle activity during fall. Ten sticky cards were installed at random inside each of the fields. Sticky cards were also installed around the fields to monitor the dispersal of beetles (if any) away from the field to overwintering sites. The beetle population at Freeville was very low when compared to Whitney Point. During late September when the plants were still green the beetles were found spread throughout the field, as the fall season progresses leaves started drying leaving only few green patches for the beetles to aggregate. After the first frost there were no more green patches and the beetles moved to decayed/damaged and some undamaged fruits left out in the field. The beetle count in the field started decreasing from the third week of Oct. Both visual sampling and sticky card counts showed almost no beetle activity during the first week of Nov.

In 1998, beetle activity during the fall and into winter was monitored in four fields located near Newark Valley, Ithaca, Whitney Point, and Freeville, NY. A combination of yellow sticky cards and weekly sampling of plants was used to monitor beetle populations. The beetle population at Newark Valley and Freeville was low and did not provide sufficient information.

Beetle populations during fall showed a similar trend to what was observed in 1997 (Fig. 2). During late September when the plants were still green the beetles were found throughout the field, as the fall season progressed leaves started drying leaving only a few green patches for the beetles to aggregate. After the first frost there was limited green vegetation and the beetles moved to decayed/damaged and some undamaged fruit in the field. The beetle count in the field started decreasing from the fourth week of October. Both visual sampling and sticky card counts showed almost no beetle activity during the second week of November. This indicates that if one wants to cause some mortality to the beetle population, the fall cultivation should be done while the beetles are still active during early fall. Waiting too long, may result in beetles leaving the field or their survival by burying themselves deeply in the soil. We installed sticky cards outside the field to monitor the dispersal of beetles, if any, away from the field. But the data obtained does not show any increase in the number of beetles on sticky cards installed outside the field, as the season progresses (Fig. 3), and therefore does not indicate that beetles move out of the field during fall. Research elsewhere, has shown that at least a portion of the beetles do overwinter in the field.

Low levels of beetles during fall prevented us from testing a range of cultivation equipment at Freeville, NY as planned. In 1996, we conducted simulated cultivation trials under field conditions. This trial consisted of placing 50 beetles each in a series of small cages. Cages contained crop residue or no crop residue and were either disked (simulated with hand shovel) or left undisturbed. Each treatment was replicated 5 times. Activity of beetles was observed into the late fall and the number of surviving beetles under the cages were recorded next spring. Unfortunately, no beetles survived overwinter in any treatments.

To better investigate the effect of cultivation on beetle survival we set up simulated cultivation trials under greenhouse conditions. We used 2 ft long sections of PVC pipe and buried fifteen beetles at 6, 12, and 18 inches below the soil line (to simulate burial by different cultivation tactics). Also, the effect of fall clean-up was tested by including plant debris or no plant debris on top of the soil in PVC pipes. Each treatment was replicated 5 times. The top and bottom of the PVC tubes were covered and the number of beetles surviving was recorded two weeks later. Results showed that 58 and 61 percent of beetles that were buried under 6 and 12 inches, respectively, were able to crawl up to the soil surface and survive (Fig. 4). However, none of the beetles that were buried at the 18 inch depth made it to the surface. This shows that deep cultivation in the fall can cause mortality and should help reduce overwintering populations. Shallower cultivation will also result in some mortality.

Suppression of immature cucumber beetles with entomopathogenic nematodes appears possible and could be especially effective if applied to trap crop plants to control progeny of aggregated adults. Unfortunately, the commercial nematode industry has dwindled drastically since this project started and we have not been able to obtain commercial formulations of the nematode species that we intended to test. However, complimentary research to that discussed herein has discovered two species of striped cucumber beetle parasitoids not previously recorded in this region: Celatoria setosa (Coquillett) (Diptera: Tachinidae), and Centistes (Syrrhizus) diabrotica Gahan (Hymenoptera: Braconidae). Maximum rates of C. diabroticae parasitism were more than 3 X greater than the only other published rate for this species (Fig. 5). This new biological control information demonstrated higher rates of parasitism than anticipated and indicated promise for enhancement of these parasitoids for biological control, thereby reducing the usage of insecticides to control beetles.

Objective 3: Improving the effectiveness of botanical insecticides.

In 1994, our preliminary experiments on rotenone dust plus the feeding stimulant, buffalo gourd root powder (BGRP), gave encouraging results. We therefore proposed to conduct studies to determine efficacy of rotenone and cryolite alone and in combination with a feeding stimulant that might improve control and permit reduced use of these insecticides. Pumpkin (Munchkin) seedlings were transplanted at cotyledon stage in groups of three and immediately covered with cages consisting of 2’X2’X3′ PVC frame covered with netting material. Hills within cages were separated by 1′ and cages were separated by ~5 m. Treatments include: rotenone full (2.5 lbs/acre), rotenone full + BGRP (0.5 lbs/ac), rotenone half (1.25 lbs/ac+ BGRP), cryolite full (10 lbs/ac), cryolite full + BGRP (0.5 lbs/ac), neem, an untreated control. Treatments were applied by hand, sprinkled onto the plants from a 7 dram polystyrene snap cap vial affixed with a cloth mesh top. After application of treatments, 25 striped cucumber beetle adults were released into each cage. Cages were examined and number of live and dead beetles and percent defoliation (rating scale: 0=0%, 1 =1-20%, 3=41-60%, 4=61-80%, 5=81-100%) on each leaf were recorded.

The result of our experiments show that all the botanicals tested caused a reduction in the damage caused by beetles. Rotenone at full (with and without the feeding stimulant), and 1/2 rate (with the feeding stimulant) had the lowest damage and highest beetle mortality (Table 4). The addition of feeding stimulant seemed to enhance the effectiveness of rotenone and permitted its use at half the full rate without significant reduction in the effectiveness. However, feeding stimulants did not alter the effectiveness of cryolite. Neem did not have any significant effect on the beetle survival or mortality but being an antifeedant it significantly reduced damage caused by beetles to plants. Overall, rotenone at 1/2 rate + feeding stimulant gave good control which permits reduced rates of rotenone.

Participation Summary

Education

Educational approach:

As information was gained regarding the feasibility and ultimate application of these potential insect management tactics, it was passed onto growers and extension staff through grower meetings and extension publications. The following presentations or publications are devoted entirely to cucumber beetles or at least include a section on these pests. New information generated from this project is included in all.

Conferences:

Hoffmann. M. P. 1997. New approaches to insect management in vine crops: Colored mulches, baits, and trap crops. New York State Vegetable Conference. Syracuse, NY.
Hoffmann, M. P. 1998. Integrated pest management for cucumber beetles. Farmer/Scientist Conference on Alternatives to Insecticides in Managing Vegetable Insects. Dec. 5-6, New Haven, CN.
Master Gardener Conference (Freeville, NY)

Workshops:

Hoffmann, M. P. 1997. Pest management for pumpkins. Great Pumpkin Growers School. Voorheesville, NY. (included hands-on displays of pest and beneficial insects).
Hoffmann, M. P. 1997. Insect pest management. Sweet corn/Pumpkin School. Middletown, NY.
Hoffmann, M. P. 1997. Vegetable growers Insect Workshop. Canandaigua, NY. (all day workshop covering insect pests and natural enemies important to vegetable growers)
Hoffmann, M. P. 1998. Basic bugs – knowing and controlling insects. NOFA-NY 16th Annual Education Conference, Cortland Community College, Dryden, NY. (Combination lecture and hands-on displays of pest and beneficial insects.)

Field days/trips:

SARE field trip (Candor, NY)
Cucurbit field day for growers and extension educators, Freeville, NY.
Twilight meeting, (Schuylerville, NY)
IPM basics for vegetables. Cornell University Student Farm.

Publications:

Ayyappath, R. M. P. Hoffmann and J. Gardner. Squash trap crops for control of striped cucumber beetle, Acalymma vittatum (F.) (Coleoptera: Chrysomelidae) in pumpkins. J. Econ. Entomol. (in prep.)
Cornell University, IPM Program. Elements for cucurbits. Web site document. http://www.nysaes.cornell.edu/ipmnet/ny/vegetables/elements/index.html
Hoffmann, M. P. 1998. Integrated pest management for cucumber beetles. Farmer/Scientist Conference on Alternatives to Insecticides in Managing Vegetable Insects. Dec. 5-6, New Haven, CN. (proceedings in press)
Hoffmann, M. P. Arthropod Pests of Pumpkin. In NRAES Pumpkin Production Man. (in prep.)
Hoffmann, M. P., R. Ayyappath and J. J. Kirkwyland. Comparison of kairomone-baited traps for capture of cucumber beetles and corn rootworms (Coleoptera: Chrysomelidae) in cucurbits. J. Entomol. Sci. (in prep.)
Hoffmann. M. P. R. Ayyappath and J. Gardner. 1997. Trap crops and mulches for control of insect pests in vine crops. pp. 204-206. In Proceedings, New York State Vegetable Conference. Feb. 11-13, Syracuse, NY.
Reiners, S., C. H. Petzoldt, M. P. Hoffmann and C. C. Schoenfeld. (eds.). 1999. Integrated crop and pest management recommendations for commercial vegetable production. Cornell Cooperative Extension. Also at: http://www.nysaes.cornell.edu/recommends/.
Zitter, T. A., M. P. Hoffmann, M .T. McGrath, C. H. Petzoldt, A. J. Seaman, and L. H. Pedersen. 1999. Cucurbit IPM Scouting Procedures. New York State Integrated Pest Management Program. Cornell University. New York State Department of Agriculture and Markets. IPM Bulletin No. 113

Project Outcomes

Impacts of Results/Outcomes

The primary goal of this project was to reduce the use of insecticides. Both mass trapping and trap cropping would reduce insecticide inputs substantially. Successful mass trapping could reduce insecticide input by ~99%. Since the traps are removed after about 3 weeks, there actually is no insecticide applied to the crop. With no insecticide applied to the crop, there is an environmental benefit and with the recent discovery of striped cucumber beetle parasitoids, the elimination of insecticide, insures their presence. Trap cropping would also reduce insecticide inputs. If the trap crop were treated the reduction in insecticide inputs would be 85%, i.e., only the trap crop (15% of the field) would be treated. The tactics will be of particular value to organic growers from a standpoint of better cucumber beetle control. Their control options at present are very limited. The use of spot treating infestations in the fall or fall cultivation to suppress overwinter populations of beetles, involves little additional expense to the farmer.

The following are the most commonly used insecticides (all are restricted use) in cucurbits for the control of cucumber beetles (source: 1998 Pest Management Recommendations for Commercial Vegetable and Potato Production, Cornell Cooperative Extension). The use of all of these could be reduced by the development and adoption of the tactics described in this report. Implementation of the Food Quality Protection Act (FQPA) may dramatically change the availability of certain insecticides. Currently, there is no recommended alternative to insecticides for immediate control of cucumber beetles.

Common Name____Trade Name____Application rate (AI/ac.)
Azinphosmethyl____Guthion________0.5 lb
Methomyl________Lannate L______0.45 – 0.9 lb
Permethrin_______Pounce_________0.1 – 0.2 lb
Endosulfan_______Thiodan 50 WP___0.5 – 1.0 lb
Esfenvelarate_____Asana_________0.025 – 0.05 lb

Economic Analysis

Trap cropping and use of TIC traps is relatively effective against adults of striped cucumber beetles. The use of trap cropping would be more feasible for small growers who normally plant many varieties of cucurbits on their farm. The cost involved should be minimal because all that is involved is rearranging specific crops (preferred and non preferred) which most plant anyway. Relative preference of 59 cultivars of cucurbits is available to growers in the 1999 Cornell Recommendations for Vegetables (Reiners et al. 1999). Likewise, the cost involved in fall cultivation should also be minimal. Most farmers cultivate their farms during late fall, advancing the time of cultivation a little earlier than their normal schedule would help in controlling overwintering populations, at almost no additional cost. The mass trapping method would cost about $23.60/acre (at 40 traps per acre). There would be an additional cost related to labor for trap installation. A single insecticide application costs about $19/acre, however it is not unusual for growers to apply more than one application for cucumber beetles. If traps were produced in large number the unit cost would decrease considerably and be more competitive with a single insecticide treatment.

Farmer Adoption

• Changes in Practice. Because this was mostly a research effort we have yet to see the extent of farmer adoption of these practices. The on-farm demonstrations conducted on several farms should encourage consideration of these new practices. Growers were very interested in the project and were very willing to cooperate. The striped cucumber beetle is considered a serious pest and they want to have good management tactics for it.

• Operational Recommendations. It is important to point out that the squashes, watermelon and pumpkin are not highly susceptible to bacterial wilt (vectored by beetles) so plants can sustain some damage. In contrast melon (muskmelon) and cucumbers are susceptible to wilt and far less damage can be tolerated. Consequently, the users of the following tactics need to be aware that they will help suppress infestations, but especially for wilt susceptible varieties, may not provide sufficient control to prevent the occurrence of bacterial wilt.

1. The use of trap crops is relatively easy and recommended. The choice of cultivar can be made by reference to Reiners, S., C. H. Petzoldt, M. P. Hoffmann and C. C. Schoenfeld. (eds.). 1999. Integrated crop and pest management recommendations for commercial vegetable production. Cornell Cooperative Extension or the equivalent web site http://www.nysaes.cornell.edu/recommends/. In the cucurbit section there is a list of 59 cucurbit cultivars and their relative preference by cucumber beetles. This list can be used to select types less preferred, as a means of reducing damage, or for selection of highly preferred types for use as trap crops. Beetles aggregating on the trap crop can be controlled with insecticides or traps can be installed in the trap crop to kill colonizing beetles. The trap crop should be overseeded to prevent total destruction by colonizing beetles.

2. Mass trapping of beetles also holds potential. We recommend 40 traps per acre, but fewer may also provide relief from infestations, especially if control options are limited. At present, no commercial company produces the traps or formulates TIC lures, so the availability of this tactic is limited. A back up trap design would be the same yellow cup described above, but coated with sticker. Even without TIC these traps will catch many beetles.

3. Timely destruction of crop residue and deep cultivation will help suppress overwintering populations. This should also be relatively easy to accomplish and requires little extra work or time. Spot treating (targeting beetle aggregations) of fields in the late summer and fall should also help. Some growers already practice this. Lastly, the use of attractant-baited traps late in the fall and when the vegetation is mostly dead should also help suppress fall populations.

4. Organic growers can reduce the rate of rotenone applied by adding buffalo gourd root powder, a feeding stimulant, to the insecticide. This does not constitute a recommendation. Check with the state lead agency for pesticide registration to insure the legality of modified use of rotenone.

5. The use of entomopathogenic nematodes is possible, but their commercial availability is limited. An efficient use of these relatively expensive agents, would be to apply them only to trap crops, where we believe more cucumber beetles would be lay eggs because of the aggregations of adults on these plants. Larvae hatching from eggs would be controlled by nematodes.

Producer Involvement
(Number of growers/Extension educators attending)
___178_ Workshops
___156_ Conferences
___79__ Field days

Areas needing additional study

The overwintering behavior of cucumber beetles and the mechanism by which cucumber beetles locate and aggregate on host plants needs additional investigation. Work currently underway has determined that male striped cucumber beetles release an aggregation pheromone that attracts large number of male and female beetles. The identification of the chemical nature of this pheromone and it synthesis for use in traps or as baits holds considerable potential. This compound is different than TIC now used in traps and we believe will be a far more potent attractant of beetles. Complimentary studies now underway and supported by a grant from the Northeast Regional IPM Program are addressing the economic importance of striped cucumber beetle feeding damage to young pumpkins and winter squash, as well as investigating the impact of larval feeding damage to cucurbit root systems and how this is affected by cucurbitacin content. These studies have also identified two, until now, unknown parasitoids of striped cucumber beetle. Levels of parasitism by these natural enemies are high (fig. 5) and no doubt important in helping suppress infestations. This is exceptionally interesting information, and with additional research may lead to enhanced biological control of this important pest. The parasitoids apparently use the newly discovered aggregation pheromone to find the beetle hosts.

References

Hoffmann, M. P., J. J. Kirkwyland, R. F. Smith, and R. F. Long. 1996a. Field tests with kairomone-baited traps for cucumber beetles and corn rootworms in cucurbits. Environ. Entomol. 25(5): 1173-1181.

Hoffmann, M. P., R. W. Robinson, M. M. Kyle, and J. J. Kirkwyland. 1996b. Defoliation and infestation of Cucurbita pepo genotypes by diabroticite beetles. HortScience 31(3): 439 – 442.

Levine, E., and R. L. Metcalf. 1988. Sticky attractant traps for monitoring corn rootworm beetles. III Nat. Hist. Surv. Rep. 279.

Pair, S. D. 1997. Evaluation of systemically treated squash trap plants and attracticidal baits for early-season control of striped and spotted cucumber beetles (Coleoptera: Chrysomelidae) and squash bug (Hemiptera: Coreidae) in cucurbit crops. J. Econ. Entomol. 90: 1307-1314.

Radin, A. M. & F. A. Drummond. 1994. An evaluation of the potential for the use of trap cropping for control of the striped cucumber beetle, Acalymma vittata (F.) (Coleoptera: Chrysomelidae). J. Agric. Entomol. 11: 95-113.

Reiners, S., C. H. Petzoldt, M. P. Hoffmann and C. C. Schoenfeld. (eds.). 1999. Integrated crop and pest management recommendations for commercial vegetable production. Cornell Cooperative Extension. Also at: http://www.nysaes.cornell.edu/recommends/.

Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.