Impact of precipitation and aging on the performance of insecticides to control the Japanese beetle on grape leaves
Hulbert, Daniel L.
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Pest management is one of the greatest challenges facing growers of specialty crops. Currently the most effective methods for controlling insect pests is through spraying chemical insecticides. While effective, there are serious risks to the environment associated with use of most insecticides. An important production challenge growers face is rainfall following insecticide application. There are several key factors known to influence an insecticide’s susceptibility to wash-off from rainfall. Many insecticides are highly toxic to a wide range of non-target organisms including endangered species. This makes it is important to understand how rainfall affects the fate of recently sprayed pesticides so that measures can be taken to prevent unnecessary poisoning and contamination of sensitive areas. Five major classes of insecticides currently used in the United States are: organophosphates, carbamates, pyrethroids, neonicotinoids, and oxadiazines. Insecticides in these classes are all nerve toxins, which work through different pathways to disrupt normal nerve function in insects as well as mammals. In North America, the Japanese beetle (JB), Popillia japonica, is an invasive species of great importance for growers. JB feeds on more than 300 species of plants and is a major pest of fruit and vegetable crops. Grapes (Vitus spp.) are a preferred host of JB and are of economic importance to the Michigan growing industry. Currently, insecticides are the preferred method of control. Despite the efficacy of controlling JB by spraying insecticides, wash-off of the insecticides can reduce the overall performance of a spray. The risk of insecticide leeching into the water of surrounding environments is also a serious concern. The objectives of this study were to 1) determine the effect of rainfall on the effectiveness against Japanese beetles of 5 different insecticides representing the 5 major classes of pesticides; 2) determine the relative effect of aging in the field for these insecticides; and 3) compare the relative performance of these insecticides against each other as they age and receive rainfall.