West central Michigan small fruit regional report – July 28, 2015
Spotted wing Drosophila populations and fruit infestations are on the rise. Keeping a strict surveillance of berry fields at this time is critical to successfully manage this pest.
Raspberry harvest continues in central Michigan with good quality fruit and excellent yield. Until two weeks ago, spotted wing Drosophila (SWD) infestations were nonexistent in most fields, but at the end of last week, fruit infestations started occurring in Ottawa, Kent and Mecosta counties.
Regarding strawberries, there are small fields of day-neutral varieties being harvested in low volumes. Strawberry farms with summer- and day-neutral varieties that have been in harvest since the beginning of June are showing an increased number of SWD in traps, but fruit infestation remains low.
On the other hand, blueberry harvest has continued in the entire region. So far, harvest volume is good and quality excellent. In Allegan County and southern counties, hand-harvest of early varieties is almost complete and growers are machine-harvesting the remnants of the crop. Harvest of Jersey and other mid-season varieties has started. In Ottawa County and other central Michigan counties, hand-harvest of Bluecrop for fresh pack has continued with excellent fruit quality.
Currently, there are reports of fruit fly infestations, but numbers are lower in comparison with last year’s. Although there are report of fruit rejected for fresh pack due to SWD infestation, most growers are keeping a strict control of SWD and no major infestations are reported at this time.
There are a few recommendations for SWD management for this portion of the season. First, make sure your traps are properly installed and serviced. If you are using the standard bait of sugar and brewer’s yeast, clean the trap weekly to prevent excessive accumulation of insects that make it difficult sorting out SWD from other flies or insects.
Second, DO NOT try to relate the number of flies trapped at your field with fruit infestation levels. There is not a correlation between number of flies in the trap and the number of larvae on harvested fruit. Therefore, use the traps as indicator of the presence or absence of the pest in your fields. If present, spray immediately. Otherwise, continue checking fruit and traps for the presence of SWD larvae and flies.
We currently do not have a perfect synthetic lure, so if you find your fruit is getting SWD infested and no flies have been observed in your traps, switch immediately to the sugar and yeast bait.
Finally, consider the weather conditions before selecting or spraying those insecticides recommended for SWD management. The advanced weather forecast in central Michigan indicated that for the next seven days, daily maximum temperatures are going to fluctuate around the upper 80s and low 90s. Those temperatures affect the persistence and efficacy of Malathion and pyrethroid insecticides. Malathion will not last for more than 24 hours and pyrethroids will not be as effective as they are at temperatures below 80s. So, do not expect a seven-day protection from Mustang Max or other pyrethroids, and a shorter interval between applications might be necessary to ensure protection against SWD infestations.
For insecticide options and recommendations, please consult the “2015 Michigan Fruit Management Guide,” (Michigan State University Extension Bulletin E0154), or the “SWD Management Recommendations for Michigan Blueberry” fact sheet.