Proposal Description and Background:
In Illinois, insecticides are often applied during a specific soybean growth stage with little information on the actual insect populations present. These applications are often added to a fungicide or other crop protection application with the reasoning that the material will prevent subsequent pest infestations; however, infestations of one pest species or another might occur at different times throughout the growing season, and the residual activity of these materials is often poorly understood. Residual activity of insecticides can vary depending on several factors, including the particular insecticide material used (Dobrin and Hammond 1983),the susceptibility of the insect species to the material (Boyd and Boethel 1998), and weather conditions (Willis et al. 1996). Understanding the nature of residual activity provided is essential to making an effective control decision. For example, an insecticide applied at growth stage R3 that provides 10 days of effective residual control would be ineffective against stink bugs that begin damaging the crop at R5. Farmers and crop advisors in Illinois currently lack ready access to this information, and often must rely on their own experience or anecdotal information to make these decisions. We propose to evaluate the residual control provided by insecticides applied to soybean foliage for control of common pests, and to share this information widely with farmers and crop advisors.

The results of this project will equip producers to time insecticide applications more effectively, ultimately improving their return on investment for these inputs. Proper timing of an insecticide application optimizes its effectiveness, reducing the likelihood that a follow-up application is needed. Avoiding unnecessary or ineffective insecticide applications is key both to environmental sustainability and to preventing unnecessary exposure (and subsequent resistance development) to target pests. The ultimate goal of this project is to provide improved management recommendations to Illinois soybean producers, crop consultants, and other agricultural stakeholders (such as distributors and Extension personnel) who influence pest management decisions.
Continuing these experiments over multiple years is critical to reflect seasonal variability caused by changes in weather conditions and insect pest abundance, and to obtain this information on multiple insecticides and target pests. We have conducted pilot experiments over the last two years to (1) develop preliminary information on the residual activity provided by insecticides for
control of bean leaf beetle and (2) to refine methods that can be used for this and other insect pests (see Fig. 1 for an example pilot experiment). During the 2020 growing season (under the first year of funding from ISA) we will conduct four combined field and laboratory experiments targeting multiple pest species; we propose to conduct four more of these experiments in 2021 and, if successful, conduct a final year of testing in 2022.

Objective 1: Determine the duration of control provided by commonly used foliar insecticides for major insect pests (stink bugs, bean leaf beetles, Japanese beetles, and green cloverworm) when exposed to field conditions.
Objective 2: Develop a web-based platform to make this information available to farmers and crop advisors to help inform management decisions in Illinois soybean fields

Proposed Methods
A series of small-plot insecticide efficacy trials will be conducted at various locations in Illinois. These trials will be located in soybean fields (at University of Illinois research farms and/or on commercial soybean fields) that are experiencing a damaging infestation of one or more insect pests. Once spray applications are made, insect population densities will be assessed in the field at a minimum of three, seven, and ten days post-application, with additional intervals measured whenever feasible. In addition, soybean foliage (defoliating insects) or pods (stink bugs) will be collected, brought to the laboratory, and placed on benzamidazole-agar media (this prevents the plant tissues from wilting) in petri dishes. Pest insects (bean leaf beetles, Japanese beetles, and/or green cloverworm larvae) will be introduced to this insecticide-treated foliage, and mortality will be observed after 24 hours of exposure. Similar bioassays will be conducted on stink bugs; however, these insects will be exposed to insecticide-treated pods by caging them on pods in the field post-application. These bioassays will be conducted until all insecticide-treated material no longer results in mortality of the insects. We will conduct four of these experiments during summer of 2020, with each one testing mortality of at least one of our target pests. We are seeking continued funding for 2021 to repeat these studies across multiple growing seasons and environmental conditions, and would plan to seek a third year of funding the following year (FY 2022). University of Illinois Extension is currently expanding its online educational offerings, including the planned launch of “CropCentral,” a multi-media web resource that will house interdisciplinary management recommendations for crop production. An applied database of the results obtained through this project will be developed into this resource to inform clientele.

Timeline
Sept. 2019-present: Protocol development, cage construction (Year 1 funding; ongoing)
May 2020-Aug. 2020: Conduct four insecticide residual experiments (Year 1 funding)
Sept. 2020-Apr. 2021: Summarize results from 2020 field season. Discuss results during winter Extension meetings and webinars. Begin construction of web-based insecticide residual database. (proposed funding)
May-Aug. 2021: Conduct four insecticide residual experiments (proposed funding)

We will conduct a series of combined field and laboratory experiments to evaluate the duration of residual control provided by common insecticides targeting soybean pests. This information will be used to develop a web-based resource to inform farmers and crop advisors of the window of control expected from these materials.