Location: Pest Management and Biocontrol Research
Project Number: 2020-22620-023-033-S
Project Type: Non-Assistance Cooperative Agreement
Start Date: Sep 1, 2023
End Date: Aug 31, 2024
Objective:
This project has three major objectives. The first is to establish and determine the best approach to maintain and expand a cotton seed bug (CSB) colony. This work and will occur at the University of California Riverside (UCR) campus, allowing ARS scientists in Maricopa, AZ to conduct experiment on CSB at UCR, thereby avoiding the importation of this invasive insect into a cotton-producing area where they do not currently occur. The second objective is to produce day-degree models for CSB by studying temperature-driven development. This data is needed for use in ecological niche modeling to predict their potential geographic spread. There appear to be no published studies on CSB development over a range of temperatures. These types of data are essential for the development of IPM programs as they help predict pest population phenology which can drive pest monitoring and control decision-making. The third objective is to determine the lethality of 12 different insecticides which are commonly used to treat pest insects within the southwestern cotton growing regions of the US. Varying doses and application methods with be assessed, to determine the best approaches for chemical control.
Approach:
Objective 1. Field collected CSB (moved under CDFA permit 3941) will be used to establish colonies. They will be housed in the Insectary and Quarantine Facility at UCR, with restricted personnel access. Colonies will be maintained inside sealed ventilated containers double-caged within larger bug dorms. Initially, containers will be provisioned with organic cotton seeds, okra pods, and water wicks. The cotton fibers on the seeds serve as oviposition substrates for the females. Modifications to the diet and housing conditions will be made to identify rearing conditions that promote rapid and stable colony expansion.
Objective 2. Using colony CSB, development times and survivorship rates for eggs and nymphs will be determined across seven temperature regimes. Incubators will be programmed with fluctuating hourly temperatures typical for Riverside County, that, when averaged over a 24 h period, equal the desired target temperature. Such fluctuations expose insects to temperatures that are more environmentally realistic than a constant temperature and result in periods when insects experience periods of cold and heat stress, and optimal temperature as they would in the field. Seven average temperatures (15, 20, 25, 27, 30, 32, and 35°C) reflecting a range of seasonal values, will be used. Eggs will be hatched at experimental temperatures and nymphs held individually in Petri dishes provisioned with cotton seeds and water. Insects will be observed every 24 h, and developmental stage and survivorship rates will be recorded. The generated curvilinear development rate data will be fitted with a suite of non-linear models (e.g., Lactin-2, Briere-2, Performance-2, Beta, LRF, etc.) that provide estimates of minimum threshold temperatures above which develop occurs, optimal temperature for development, and upper lethal temperatures above which physiological performance is impaired and death results. Analyses will also provide estimates of day-degree accumulation above the minimum threshold temperature necessary to complete development. Stage-specific durations in days and survivorship rates will be calculated and statistically compared across temperatures.
Objective 3. CSB will be tested against four concentrations (0, 10, 100, 1000 ppm) of commercial formulations of 12 contact insecticides: flonicamid, flupyradifurone, pyrifluquinazon, sulfloxaflor, acetamiprid, clothianidin, dinotefuran, acephate, imidacloprid, lambda cyhalothrin, plinazolin, and thiamethoxam. For each insecticide and dosage, five petri dishes, each containing five adult CSB will be tested. The bioassay will be replicated three times on separate days. Test insects will be provisioned with cotton seeds and a water source. Mortality will be recorded every 24 h, with the criterion that the test subjects show complete absence of movement. Tests will be run for 120 hours or until all subjects are dead. Effective insecticides will be further tested under more natural conditions by presenting CSB with open cotton bolls that have been treated. Survivorship will be checked at 2, 24, and 48 hours.
