Location: Pest Management and Biocontrol Research
Project Number: 2020-22620-023-037-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Sep 1, 2025
End Date: Aug 31, 2026
Objective:
This project has four major objectives. The first is to determine the efficacy of three compounds previously identified by the PI and the Riverside collaborators against cotton seed bug (CSB) at its various life stages in the laboratory. Previous work showed efficacy for <7-day-old adults, understanding effects on nymphs and older adults is paramount to developing effective mitigation plans. The second objective is to determine if foliar exposure to one or more of the compounds would provide sufficient mortality in CSB to proceed with the development of management recommendations. The third objective is to determine CSB development and survival on several cultivars of cotton. Some preliminary lab work shows CSB develop and reproduce on one novel variety of cottonseed (Bayer’s ThryvOn) that is beginning to see widespread adoption (approximately 25% of acreage in 2023) in the Southwest US, but not on other varieties of cottonseed. While CSB is currently contained in mostly urban areas, their absence in cotton may be due to incompatibility with current cultivars in the southwestern US. The final objective will examine the effect of boll damage on CSB survival and reproduction. In areas where CSB is a major pest, its distribution overlaps with two important lepidopteran pests, the cotton bollworm, Helicoverpa armigeraI, and corn earworm Helicoverpa zea, which is a major pest of cotton if current control strategies fail. Previous feeding damage from lepidopterans likely allows CSB access to developing seeds in cotton bolls. To test this hypothesis, we will deliberately damage cotton bolls to simulate entry holes made by feeding lepidopteran larvae and evaluate CSB survival and reproduction.
Approach:
Objective 1. Using the CSB colony maintained at UC Riverside, we will assess CSB mortality when exposed to Assail (acetamiprid), Transform (sulfoxaflor) and Sivanto (flupyradifurone). CSB will be reared and separated at five developmental stages 1st-3rd instar nymphs, 4th and 5th instar nymphs, <7-day-old adults, 7-14-day-old adults, and >14-day-old adults. Glass vials will be coated in field rates of the above insecticides. After vials are dry CSB of the corresponding developmental period will be placed inside. Mortality will be assessed at 2, 24, 48, and 72 hours post-exposure. Multiple replicates will be run, and data will be statistically analyzed. This methodology has been used successfully in previous insecticide trials with CSB.
Objective 2. This objective will use the same rearing and allocation of developmental periods of objective 1. Leaf discs will be taken from cotton plants grown in greenhouses at the UC Riverside campus. These discs will be dipped into field-rate solutions of Assail, Transform, and Sivanto. Leaf discs will be placed in individual petri dishes on top of an agar solution to prevent the plant tissue from desiccating. Discs will be allowed to dry for 24, 72, and 96 hours before the disc and a CSB from each developmental period will be placed on individual discs. Mortality will be assessed at 2, 24, 48 and 96 hours. Multiple replicates will be run, and data will be statistically analyzed.
Objective 3. CSB colonies will be presented with cottonseed from the top three cultivars (by acreage) in the southwestern US as well as ThryvOn cottonseed, a new cultivar gaining in popularity with growers. Approximately 50 adults (a 1:1 ratio of males:females) will be allowed to feed and reproduce for 48 hours. After which, all adults will be removed from the container. Mortality rates and development times will be recorded for individual CSB including: days to appearance of nymphs, days to adult emergence, and time to death. Fresh cottonseed will be provided weekly. Multiple replicates will be run and analyzed statistically.
Objective 4. Selected cotton cultivars will be grown in greenhouses at UC Riverside. After the plants reach the development of at least 4 bolls they will be segregated into two treatments. For the first treatment we will mechanically damage bolls with a 10-gauge piercing needle (approximately the size of a lepidopteran exit hole) by puncturing them one time. The other treatment will leave the plants unharmed. Plants will be individually bagged with a fine mesh bag. Twenty mated CSB females will be introduced onto each bagged plant. After seven days we will remove the bolls and examine them for the presence of CSB eggs and nymphs. Multiple replicates will be run, and data will be statistically analyzed.