Controlling Squash Bugs (Anasa tristis) Using Cover Crops and Organic Insecticides

Controlling Squash Bugs (Anasa tristis) Using Cover Crops and Organic Insecticides

Summary

Squash bugs are a notorious pest on organic farms for cucurbits, in particular summer squash and pumpkin. The bugs cause damage by feeding on stems of plants and can also transmit a bacterium, Serratia marcescens. This bacterium is responsible for causing cucurbit yellow vine disease, which can kill up to 100% of plantings (Bruton et al 2003). This project focuses on utilizing diversified planting systems and organic sprays as an attempt to decrease squash bug populations in organic systems. Cover crops were planted alongside summer squash to determine if the cover crops help to increase beneficial insects and/or diversify the farm landscape to make it more difficult for squash bugs to find squash plants. Nymphs will be exposed to several organic insecticides to determine which is most effective.

Objectives/Performance Targets

1) Evaluate cover crops as a strategy to decrease squash bug damage in summer squash 
            a) Evaluate effectiveness of cover crops as method of attracting beneficial insects 
            b) Evaluate effectiveness of cover crops as a barrier for squash bugs
2) Evaluate OMRI -approved insecticides for squash bug control

Accomplishments/Milestones

Objective 1: Cover crop field experiment

During the summer of 2014, two field trials were completed at UGArden demonstration farm in Athens, Georgia. For Trial 1, buckwheat, cow peas, and sunn hemp were planted alongside summer squash in a randomized complete block design. Cover crops were seeded in plots of 14 x 22 ft, by broadcasting seed. There were four replicates of each treatment. After cover crops were established, three rows were tilled and summer squash (‘Multi-pik’) transplants planted in each plot. A control treatment was created by leaving a blank space in place of a cover crop. Squash was harvested every 2-3 days. Harvested squash was sorted according to USDA standards. Every week, squash bug eggs, nymphs, and adults were counted. Insects were collected using pan traps, sticky traps, sweep nets, and pitfall traps in order to analyze beneficial insect populations in the plots. These traps were placed within the row of cover crop and within the row of squash in order to learn about movement of the insects. Findings from Trial 1 suggest squash bug presence is not affected by cover crop treatments. There was no significant difference in squash bug adult or egg masses in all plots (Poisson distribution, p=0.066 and p=0.09 respectively). Cover crops competed with the squash since there was significantly higher yield in control plots than cover crop plots (1 way ANOVA, p=0).

For Trial 2, several modifications were made to the experimental design based on results from Trial 1. Cover crops were sown with a seeder instead of broadcasting to insure denser, more rapidly growing stands to outcompete weeds. Buckwheat was planted three weeks later than the cowpea and sunn hemp to better match buckwheat flowering with squash plant growth. The space between cover crops and squash was also increased to decrease competition from the cover crops. These changes resulted in more distinct differences between treatments. Results showed that squash plants grown near buckwheat had significantly lower squash bug adults than control plots (Poisson distribution, p=0.026). All cover crop treatments had significantly lower egg masses than control plots (Poisson distribution, p=0). Yield was similar for the control, buckwheat, and cowpea plots, while sunn hemp significantly reduced squash yield (1 way ANOVA p=0.036). Trial 3 will be completed during summer 2015 to obtain more conclusive results about the effects of cover crops on squash bug populations. Beneficial insect population data is still being analyzed.

Objective 2: Nymphs and organic insecticides

Several trials were conducted to determine the best method to isolate and treat squash bug adults with the various organic (NOP approved) insecticides. This experiment will be carried out in full in the summer 2015. Nymphs will be classified by instar and exposed to organic insecticides: Neem, Pyganic, Horticulture Oil, Insecticidal Soap, Azera, Spinosad and mortality rates will be compared.

Impacts and Contributions/Outcomes

The findings of this study will provide direction for organic farmers seeking options for controlling squash bug populations. Current options for controlling squash bugs include row covers, trap crops, resistant squash varieties, organic insecticides, and field rotations, but are either ineffective or are too costly to implement. Many farmers do not plant summer squash due to the great damage inflicted by squash bugs. Farmers need several different strategies in order to control this pest and diversified planting with cover crops may help to decrease this pest.

Trial 2 demonstrated that buckwheat reduced squash bug adults and all cover crops had fewer egg masses. With another field season, more concrete conclusions can be made about this strategy. Once the collected beneficial insect populations are analyzed these result may show if the cover crops attract beneficial insects that prey upon squash bugs. The cover crops could also be making it more difficult for squash bugs to find their way to the squash.

 Organic insecticides are utilized by organic farmers for squash bug control, but there is little data confirming their effectiveness. By comparing the popular organic insecticides, it may be possible to make more accurate recommendation for squash bug control.

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