Grand Rapids, Mich., area small fruit regional report – July 30, 2013
The beginning of the spotted wing Drosophila control season brought the need for reviewing pesticide options and the non-target impact of increased used of pyrethroids in berry production.
The beginning of the spotted wing Drosophila (SWD) control season also brought the need for reviewing the pesticide options available for its control within the grower’s current integrated pest management (IPM) program. Michigan State University Extension small fruit recommendations include organophosphate, pyrethroids and reduced-risk insecticides which must be used in a rational manner within a spray program that may limit the non-target impact on other insects that could complicate even more the control of a key pest like the SWD.
During the past week, the harvest of berry crops in west Michigan has proceeded without much of a problem. So far, blueberries are the major crops being harvested followed by summer red raspberries. Up until now, the most outstanding problem for those two crops is the presence of SWD. Although the SWD attack has not been as severe as observed in 2012, it has created secondary problems associated with its control.
During the past week, we conducted two investigations on outbreaks of SWD in blueberries and raspberries. In both cases, the outbreak was controlled by the grower, but there were secondary problems resulting from its control. In one situation, SWD control was achieved using a pre-mixed insecticide, Hero, made of Bifenthrin, a broad-spectrum pyrethroid insecticide that works by interfering with a nerve cell’s ability to send a normal signal by jamming open tiny gates on the cell that need to open and close rapidly to carry the message.
The second component is Zeta-cypermethrin. This is another pyrethroid insecticide with similar action of Bifenthrin. The application of this mixture of pyrethroids was preceded by several applications of Mustang Max.
In the second case, the outbreak in raspberries was controlled with back-to-back applications of a high dose of Mustang Max. Although in both cases the control was good, the secondary problems created by the non-target impact on secondary pests could make the chemical control of SWD more costly. In raspberries, after the multiple applications of pyrethroids, two-spotted spider mite populations exploited and further applications of miticide products were required to control this pest. On blueberries, the treated field had a history of scale insects and bud mite problems which may result in further secondary pest problems.
In both cases, there was no rotation of insecticides as it has been recommended by the MSU Extension Small Fruit Program. Growers need to be aware of the danger that represents to create secondary pest problems or insect resistance to insecticides being used. In either case, once the problem is created there is no turning back.
One of the major MSU Extension recommendations has been to read the label. Growers need to ask questions about the product they are going to spray against SWD. The commercial name of the product may not always provide information on the active ingredient (a.i.). Pyrethroid insecticides are a great tool and many times less expensive than other insecticides, but they need to be used in a rational manner to maintain their affectivity for a longer time.