Making Pest Management More Sustainable in Cucurbit Production

View the project final report

• 2016 annual report

Commodities

• Vegetables: cucurbits

Practices

• Crop Production: no-till
• Pest Management: biological control, chemical control, integrated pest management

Pesticide use is excessive in many commercial cucurbit production systems. Foliar Insecticides are frequently tank mixed with fungicides because they are relatively cheap and growers feel that they are making a trip over the field anyway. However, frequent use of insecticides such as pyrethroids (the most commonly used), 1) destroys natural enemy complexes, 2) leads to outbreaks of secondary pests, and 3) is harmful to pollinators that are crucial to crop production.   Rationale: The purpose of this project is to improve upon the sustainability of pest management practices in cucurbit production. Current pest management practices utilize broad-spectrum insecticides that are applied at almost two-week intervals, regardless of pest pressure and crop maturation. While there are commonly six main insect pests of cucurbits in our region, there are only a few that frequently cause economic damage. The primary hemipteran pest is the squash bug, Anasa tristis DeGeer (Coreidae:). Squash bug prefers pumpkin (Cucurbita maxima) and squash (C. pepo), and damages plants in all stages with its piercing-sucking mouthparts by feeding on the vascular tissues of cucurbit leaves (Beard 1940). Squash bug overwinters as an adult and can vector Serratia marcescens, a bacterium that causes Cucurbit Yellow Vine Decline (CYVD) (Bruton et al. 2003) that can lead to stand and yield loss. The habit of adults and nymphs hiding under leaves makes control of squash bug difficult and risky when considering its potential to vector the virulent CYVD. While monitoring pumpkin plots in southwest Virginia for levels of squash bugs in the summer of 2013, a decline in egg hatch numbers led us to rear egg masses in the lab. Squash bug egg masses collected from the field and reared in the lab yielded multiple species of parasitoid wasps. The level of parasitism for a total of 84 egg masses was 66%, two times higher than ever reported. The predominant species was Gryon pennslyvanicum (Ashmead: Hymenoptera: Platygastridae), which had been previously reared from field-collected eggs in North Carolina and Kentucky (Schell 1943, Decker and Yeargan 2008). Past studies have identified it as a potential augmentative biological control agent in Kansas (Nechols et al. 1989). This native natural enemy could play a significant role in the control of squash bug in our region. The effects of broad or narrow-spectrum insecticides on these natural enemies have not been examined. We propose to survey the Commonwealth of Virginia for the egg parasitoids of squash bug and to examine the effects of insecticides on squash bug eggs and nymphs, and squash bug egg parasitoids.

• • Objective 1: To survey the egg parasitoids of Anasa tristis throughout the Commonwealth of Virginia.

• • Objective 2: To assess the effects of narrow-spectrum insecticides on the eggs of Anasa tristis and its egg parasitoids.  Each year for two years we will coordinate with growers to visit the main regions of the state to actively scout cucurbit fields where we will perform:

• • Objective 1:

• • Materials and Methods:

• • Collections of squash bug egg masses

• • Sweeps of plants around areas with large numbers of egg masses The specimens collected will be taken to the Virginia Tech Vegetable Entomology Lab and reared in environmental chambers for identification to species where possible. Records of location, host plant, parasitism levels, and squash bug hatch rate will be made.

• • Objective 2:

• • Egg masses collected will be utilized in screening assays to by location. Assays will screen for effects of specific narrow-spectrum insecticides against the controls and a commonly used braod-spectrum insecticide. The controls will provide baseline data on the parasitism levels and squash bug hatch rates for each location. The assay will be structured as follows:

• • 10 Squash Bug egg masses (averaged 18 eggs / mass in 2013) per treatment
    • • Control = H₂O
    • • Narrow-spectrum :Sivanto, Pyrifluquinazon, Flonicamid, and Sulfoxaflor
    • • Broad-Spectrum (Lambda-Cyhalothrin – Pyrethroid)

• • All treatment concentrations will be at maximum label rate

• • Assays will be replicated as masses become available