Exploiting plant genotypic diversity for sustainable insect pest management

Exploiting plant genotypic diversity for sustainable insect pest management

Summary

This research project began in the fall of 2010 and will investigate whether genotypic diversity within a crop species may be used to control pest insects. Recent evidence suggests that plant intraspecific (genotypic) diversity may be as important as interspecific (species) diversity in structuring arthropod communities and regulating herbivore populations.

Using soybeans as a model system, I will conduct field experiments to compare soybean aphid and natural enemy populations of low genotypic diversity to those of high diversity plots. Within this experiment, I will assess the strength of predation services between the two levels of diversity using predator-exclusion cages. Simultaneously, I will characterize the natural enemy community in soybean fields. Results from both aspects of the project will be shared with growers and extension educators and will be integrated into outreach events.

Objectives/Performance Targets

Soybean lines needed for Objective 1, as well as Objectives 2 and 3 have been chosen. Research farm space for the field plot scale experiment in summer 2011 has been reserved.

Objective 1) Compare the effects of genotypically diverse mixtures vs. single lines on plant growth and yield and on aphid population growth.

Objective 2) Compare the effects of genotypically diverse mixtures vs. single line monocultures on natural enemies of the soybean aphid.

Objective 3) Compare predation services provided by genotypically diverse mixtures vs. those provided by single lines.

Objective 4) Characterize the natural enemy community of soybeans in Central Pennsylvania

Preliminary sampling from the summer of 2010 has supported this objective by starting the identification of natural enemies and creating a reference collection that will be used to aid identification for this project. This accomplishment will also aid in the completion of Objective 2.

Objective 5) Transfer knowledge gained from Objectives 1-4 to growers, extension agents and members of the public.

No progress has been made on this objective.

Accomplishments/Milestones

Because this project began late in 2010, progress has primarily been made on preparing for upcoming experiments and gathering background information to aid with identification of natural enemies. For Objectives 1-3, a crucial step is the identification of soybean lines that will be used. Six lines have been chosen with the overall aim of maximizing potential genotypic diversity. To achieve this goal, we have chosen lines from five different seed companies as well as a publicly-developed line from Kansas State University. Space has been reserved at Penn State’s Rock Springs research farm to conduct the field plot component of this project comparing single-line and genetically diverse mixture plots. This space will work with the experimental design we will use (see Fig. 1).

Preliminary sampling from the previous summer will support future work on Objectives 2 and 4. Natural enemies in pitfall, sweep net and pan trap samples, collected with similar techniques as those that will be used for this project, are in the process of being identified. This will ensure that the proper taxonomic references are available and will provide reference specimens. Previous sampling experience may also be used to alter the sampling intensity initially proposed. For instance, weekly sampling for natural enemies in the field plots will not likely be feasible and will probably be reduced to biweekly sampling. This should still provide adequate resolution of the natural enemy community.

Impacts and Contributions/Outcomes

The soybean aphid is currently the foremost pest of soybeans in the United States. Current control methods are inadequate and rely primarily on insecticides, although resistant varieties are being developed. Nevertheless, alternate management tools are needed. The problem of the soybean aphid is particularly worrisome for organic farmers, who must frequently ignore surging aphid populations due to lack of control options. We believe that genotypic diversity will be a readily-adoptable tactic for growers. The natural enemy community in Pennsylvania is also relatively unknown and this project aims to fill this void in knowledge. We plan to work closely with growers and provide them with information on both genotypic diversity as a management tactic and on natural enemies. We will distribute this information through factsheets, outreach events, extension agents and publications. Thus far, results from this project have not been part of any events or presentations. However, we plan to share the results from the upcoming field season in a number of venues and will use the field plot experiment in a field day as a demonstration of genotypic diversity used for pest control .

Collaborators: