Organic Management of Cucumber Beetles in Cucurbits

Organic Management of Cucumber Beetles in Cucurbits

Summary

Striped (Acalymma vittatum) and spotted (Diabrotica undecimpunctata) cucumber beetles are major pest insects in the organic production of cucurbit crops including squash, cucumber, pumpkin, and melons. Larvae feed on roots, whereas adults feed on leaves, flowers, and fruit. Adult beetles also act as vectors of Erwinia tracheiphila, which causes bacterial wilt disease in cucurbits. Bacterial wilt is the most serious disease of muskmelon and cucumbers in Kentucky. In 2004, organic methods for managing cucumber beetles in muskmelon (Cucumis melo) grown on plastic mulch were examined using a factorial, split-plot, randomized block experimental design. Four main plot treatments consisted of an untreated control, aluminum-coated plastic mulch (Al-plastic), rows of companion plants between alternate muskmelon rows, and Al-plastic + companion plants. Subplot treatments were plus or minus use of row covers. Companion plants included a combination of radish (Raphanus sativus), which is believed to repel cucumber beetles, and buckwheat (Fagopyrum esculentum), which is believed to attract beneficial insects. Muskmelon yields were significantly (P < 0.05) greater in the Al-plastic + companion plant, Al-plastic, and companion plant treatments than in the control treatment. The highest yields were obtained using Al-mulch + companion plants. Al-plastic, companion planting and Al-plastic + companion planting significantly (P<0.05) increased vegetative cover compared to the control treatment. Use of lightweight row covers until flowering significantly (P < 0.05) increased melon yields and vine cover. Beetle populations are still being analyzed however it appears that using Al-mulch, companion plants, and row covers were useful organic methods of managing cucumber beetles in muskmelon.

Objectives/Performance Targets

1. Compare organic methods for managing cucumber beetles in muskmelon, including use of reflective mulches, beneficial insects, trap crops, cover crops, and companion plants.

2. Develop an organic system for managing cucumber beetles with muskmelon including combinations of management methods in a systems-oriented approach.

To accomplish objectives 1 and 2 field experiments were conducted during the growing season.

Accomplishments/Milestones

Objectives 1 and 2

2004 KSU Experiment. The 2003 experiment was repeated in 2004, except that the 2003 pyrethrin insecticide treatment was replaced with a 2004 treatment which included a combination of Al-mulch and companion plants. Thus, 2004 KSU farm treatments were:

Main Plot Treatments Split-plot treatments

(1) Control treatment (1) Row covers
(2) Al-coated plastic mulch (2) No Row covers
(3) Companion plants (radish + buckwheat)
(4) Al-coated plastic mulch + Companion plants (radish + buckwheat)

Muskmelon was planted on June 10 and harvested on Aug. 10, 13, 17, 23, and 27. The methods were the same as in 2003, and dates are included in Table 1.

Table 1. Schedule of activities for field experiments at K.S.U. Research Farm.

Activity Date

Soil Plowed March 20
Soil Disked April 4
1st Roto-tilling May 5
Companion plants planted June 14
Fertilizer added May 25
2nd Roto-tilling May 25
Plastic mulch laid May 27
Melons planted June 10
Row covers added June 21
Sticky Traps installed June 17
Weeds cultivated July 8, 16
Row covers removed July 15
Harvests Aug. 10
Aug. 13
Aug. 17
Aug. 23
Aug. 27

2004 On-Farm Research. In 2004 an on-farm demonstration project was conducted at the Linda McMaine (Anderson County) Farm. There were two treatments and no replications. “Eclipse” Muskmelon was planted in June. Treatments were aluminum-coated plastic mulch + companion plants (radish + buckwheat) and black plastic mulch. Plants in one half of each main plot received row covers and plants in the other half were not covered. Each plot was 4 rows wide and 40 ft long.

Results and Discussion

2004 KSU Farm Experiment

Main Plot Treatment Effects

Muskmelon yields. In 2004, mean muskmelon weights obtained in all four treatments were significantly different. Weights were greatest in the Al-plastic + companion plant treatment and lowest in the control treatment. Weights in the Al-plastic treatment were greater than in the companion plant treatment. Overall, melon weights were 30.4%, 72%, and 96.3% higher in the companion plant, Al-plastic, and Al-plastic + companion plant plots, respectively. Treatment effects on melon numbers were similar, except that no significant difference was detected between numbers in the Al-plastic and companion plant treatments. Melon numbers were 10.6%, 56.3%, and 72.3% higher in the companion plant, Al-plastic, and Al-plastic + companion plant plots. These data agreed with data from 2003, and suggested that beneficial effects derived from Al-plastic and companion plant treatments were synergistic.

Vine Cover. Responses of vine cover to main plot treatments on both sample dates were generally similar to responses of muskmelon yields. Vine cover was significantly (P<0.05) greater in Al-plastic, companion plant, and Al-plastic + companion plant plots than controls. Vine cover was lower for all treatments on the later sampling date due to beetle damage. Cucumber beetles. Beetle populations are still being analyzed and these data will be presented in the final report of this project.
Subplot Row Cover Effects

Muskmelon Yields. As in 2003, use of row covers significantly increased weights and numbers of muskmelons. Row covers increased melon weight 73.1% and melon numbers 37.2%

Vine cover. Muskmelon vine cover was greater with row covers than without row covers on both sampling dates. As with main plot treatments, effects of row covers on yields and vine cover were related to cucumber beetle damage.

Cucumber beetles. Beetle populations are still being analyzed and these data will be presented in the final report of this project.

2004 On-Farm Research. Results of this demonstration were eventually overwhelmed by local influences such as weed pressure. The grower did not adhere to the agreement that she would maintain the plots throughout the study period to its conclusion. Thus, any data collected was not considered valid.

Impacts and Contributions/Outcomes

General Impact

Striped and spotted cucumber beetles are important insect pests in the production of cucurbits because they feed on these plants and act as vectors of the pathogen which causes bacterial wilt disease. Current organic insecticides for cucumber beetles (e.g., rotenone, pyrethrins) are highly toxic to humans and/or easily degraded by sunlight. Cucumber beetles were the most important organic vegetable insect pest identified in a national survey and in a survey conducted in Kentucky by the authors in a SARE planning project. Thus, cucumber beetles are an important national and local problem. Organic vegetable production is especially appealing to small farmers. Improvement of organic management methods for cucumber beetles would make organic production of cucurbits more profitable for small farmers and help to preserve small farms. Also, such improvements should reduce use of inorganic insecticides, which are potential environmental pollutants and health hazards. Results from 2004 were similar to those of 2003 indicating that use of row covers, companion plants, and Al-coated plastic significantly increased organic muskmelon yields. Thus, adaptation of these methods by organic growers has potential impact locally and nationally.

Direct Impact

One farmer participated in on-farm research during 2004, which tested organic methods for managing cucumber beetles. Experimental plots in the large field experiment at the Kentucky State University Research Farm were visited by participants at monthly “Third Thursday” Sustainable Agriculture Workshops and at the KSU Farm Field Day. On-farm research plots were viewed by other local farmers. Results from the project were disseminated to growers and scientists in the following presentation:

Sedlacek, J.D., G.R. Cline, and S.L. Hillman. 2004. Research in organic control of cucumber beetles. May meeting of the Third Thursday Sustainable Agriculture Workshop. Kentucky State University, Frankfort, KY.

Collaborators: