The same weather conditions that have proven conducive to large blueberry crops the past three years also have proven beneficial to increases in spotted wing drosophila populations, according to a Michigan State University grower e-newsletter.
On top of that, heavy rains over much of the area the past week have reduced the effectiveness of most insecticides registered for the past.
As a result, growers are wondering why their integrated pest management program aimed at spotted wing drosophila isn't working.
The answer is nothing is wrong, but the weather has not cooperated, writes Carlos Gracia-Salazar, fruit Extensionist.
He cited research conducted by John Wise that showed the rainfast characteristics of fruit crop insecticides.
If it rains just after application of many of the registered insecticies for spotted wing drosophila, the permanence of the product on the fruit is reduced. That, in turn, affects the insecticide's performance.
Before delivering fruit to processors, Salazar recommends evaluating the fruit for the fly using the university-recommended salt test method.
Unlike most fruit flies that seek out rotting fruit in which to lay eggs, spotted wing drosophila prefer fruit just reaching maturity in which to oviposit.