The Berry DisPatch

Newsletter of the Wisconsin Berry Growers Association

February, 2003

Newer Fungicides for Berries

By Patricia McManus

UW-Department of Plant Pathology

The past few years have seen several important changes in fungicides available for disease control in berry crops. However, fungicides are effective and economical only when used in conjunction with good cultural practices. For example, if berry rows are wide and full of weeds, then fungicides will not penetrate to where they’re needed. Standing water contributes to root diseases and fruit rots, and no fungicide can succeed under those conditions!

The most significant loss has been Benlate (benomyl), which was discontinued by its manufacturer. Since this was a voluntary action (they weren’t forced by EPA), growers can go ahead and use up any remaining Benlate stocks on hand. Topsin-M (thiophanate-methyl) has the same mode of action as Benlate and can be used in its place on strawberries. However, Topsin-M is not registered on other berry crops. Ronilan (vinclozolin) is no longer permitted on strawberries. Rovral (iprodione) is still labeled for strawberry, but with the preharvest interval not allowing sprays after “first fruiting flower,” this fungicide is worthless for gray mold control. Rovral is not effective against other strawberry diseases, so it is essentially worthless.

The relatively new fungicides Switch (a combination of cyprodinil and fludioxonil) and Elevate are very effective against gray mold. Switch is registered on strawberry; Elevate is registered on strawberry, raspberry, blueberry, grape, currants, and gooseberries. Both products are deemed “reduced-risk,” because of their relatively low toxicity to mammals and other non-target organisms.

Cabrio and Quadris are the first strobilurin fungicides with labels that include berry crops. Cabrio is registered on a long list of berries (see its label), whereas Quadris is registered on strawberry and numerous vegetable crops, but not other berries. Both have shown excellent activity against strawberry anthracnose in research trials—better than captan plus Benlate, which was the best we could do before. However, these fungicides are expected to be very prone to fungicide-resistant pathogens. Therefore, they must be used sparingly and in alternation with unrelated fungicides. So, if a strawberry field has a history of anthracnose, and warm, wet weather prevails as fruit are sizing and ripening, alternate a strobilurin with captan + Topsin-M. Of course, make sure there’s clean straw between the rows and no standing water. Anthracnose spores can bounce off puddles and spread great distances, whereas straw absorbs the impact. Cabrio and Quadris can be applied up to the day of harvest. On raspberry, Cabrio is effective against many important diseases, including rusts, leaf spots, and cane blight.

For more details on these and other products for disease control, see UW Extension bulletin A1934, Strawberry and Raspberry Pest Management in Wisconsin, and of course, read and follow directions on product labels.