West central Michigan small fruit regional report – August 26, 2014
Spotted wing Drosophila population is at its peak in west Michigan. As we enter the high SWD activity period, growers need to check fruit before harvest and before and after any insecticide application to verify successful control.
Weather conditions in west central Michigan reached the mid- to upper 80s, typical for summer temperatures. So far, the average daily maximum temperatures have been 81 degrees Fahrenheit and the minimum 64 F. There were some thunderstorms in the region that deposited more than 1 inch of rain in some areas. However, this precipitation has not been enough to supply all the hydric requirements of most fruit crops, including blueberries, and growers are supplementing those needs with irrigations.
We continue to see an increase in spotted wing Drosophila (SWD) populations in all small fruit crops. In raspberries, there are places that already are showing levels of infestations similar to the ones observed one year ago. However, early detection and control is preventing having a serious issue related to fruit infestation. Curative applications of some recommended insecticides are keeping SWD infestations on check.
In blueberries, the past week has seen the beginning of a large outbreak of SWD in all west Michigan blueberry fields. This outbreak is affecting the last portion of the harvest of mid-season varieties such as Jersey and the beginning of late-season cultivars like Elliott. It is expected that detection of larval infestations in fruit loads will increase as the season progress. Therefore, now more than ever, a conscious sampling of fruit before harvesting and before and after any insecticide applications should be conducted to avoid fruit infestations at harvest time.
If SWD larvae are found in samples of fruit taken before harvest, Michigan State University Extension recommends using a “rescue” application with any of the insecticides that have demonstrated good larval control such as Mustang Max. Due to the potential for large populations of SWD at this time, try to avoid using Malathion as a rescue application. High temperatures or potential rains during the protection period may render useless the application.
Remember to make sure you take into consideration the weather conditions at the time of the application and during the expected protection period. Check the weather and if the daily temperatures or rainy conditions may affect the durability of the insecticide you applied, repeat the application with a different insecticide. For insecticides and doses for blueberries, see “SWD Management Recommendations for Michigan Blueberry.” For insecticides and doses for raspberries, see “Spotted Wing Drosophila Management Recommendations for Michigan Raspberry and Blackberry Growers.”