The Influence of Time of Day and Insecticide Application on the Abundance of Spotted Winged Drosophila, Drosophila Suzukii, in Michigan

Abstract

Fruit production is an important component of United States agriculture. The arrival of spotted winged drosophila (SWD); Drosophila suzukii (Matsumura) has caused extensive economic damage across the globe to ripe small soft-skinned fruit. The most common method for conventional and organic growers to protect fruit from SWD infestation is insecticide application. Since there is a zero-tolerance policy for fruit contaminated with SWD larvae, it is important to provide information to growers on ways to control SWD. Information could be utilized to discover the most ideal time frames to apply insecticide and determine how long the insecticide protection will last before reapplication is needed. To address this, behavioral observations were conducted weekly on chemically treated and untreated rows of highbush blueberry in Michigan during August due to the presence of ripe fruit and active SWD. The goals were (1) to examine SWD abundance during four distinct time frames, (2) compare insecticide strength on SWD abundance one and three days after application (DAT), (3) and compare the effectiveness of insecticides as the number of SWD increased over season. The study demonstrates that SWD are most prominently abundant during the 6-8 AM time period with temperature/humidity dependent factors effecting the abundance of SWD. There were clear trends for an increased presence of SWD three DAT when high-bush blueberry bushes were treated with insecticides. The data is the first to display a stronger presence of SWD at the end of August despite insecticide application. Future research needs to investigate the efficacy of insecticide application and their effect on SWD abundance. Due to the high probability of insecticide resistance and their harmful effects on both consumers and producers, proactive measures need to be taken to discover more environmentally safe IPM programs to protect fruit from SWD.