Cone and Seed Insect Pest Research: The Role of the Southwide Studies

A reliable supply of genetically improved pine seed is critical to the success of production forestry. The most significant environmental threat to the ability to meet this demand (over 100,000 pounds per year) is insect predation. Cone and seed insect pests can easily destroy half the potential orchard crop, and there have been instances in which 90% of the harvest was lost. Effective insect control is dependent on continued availability of pesticides, both because the economic loss threshold is low, and because alternative control methods have not been successful. Because seed orchards are a minor use, there is limited support from pesticide manufacturers for either efficacy testing or continued product registration. The tree improvement community has responded to this challenge by developing a collaborative working arrangement between entomologists and seed orchard managers that has resulted in a series of southwide efficacy studies. These studies, which have now included evaluations of Guthion®, Asana®, Capture®, and Imidan®, were coordinated through the Seed Orchard Pest Management Subcommittee, a working group of the Southern Forest Tree Improvement Committee. Southwide studies are the culmination of a multi-step process in which promising pesticide formulations and rates are first identified by USDA Forest Service entomologists through small-scale testing, typically with hydraulic spray applications to single trees. This method of application, while allowing for accurate treatment evaluations, does not reflect operational conditions. It is therefore necessary to evaluate the most promising treatments under operational conditions with aerial applications on large treatment blocks. Results from both published and unpublished studies have underscored the strengths and weaknesses of these large-scale tests. Efficacy studies are difficult to implement and have substantial direct and indirect costs to the participants. Seedbug control is easy to achieve. Coneworm control, however, is much more difficult both to achieve and to accurately document. Interpretation of composite traits such as the number of good seed produced per initial flower can lead to erroneous conclusions when efficacy is primarily due to seedbug control. Despite these deficiencies, southwide studies will continue to be needed to validate cone and seed insect control under operational conditions. Studies that will be needed in the future are discussed.