Disease activity was fairly pedestrian over the month of June and looks to pick up now that July has arrived. The main problem we were continually hearing this spring and until the last week has been the amount of rainfall and lack of sunlight we are receiving the Northeast. On the disease front, we have seen quite a bit of dollar spot in the Pioneer Valley and have been able to begin all of our summer research trials earlier than years past. Dollar spot infection has not been overwhelming, but there has been consistent pressure throughout June. One trial we are currently conducting is averaging 30 infection centers in the untreated plots (3 x 6 foot plots). We are beginning to hear more reports from the field of dollar spot and the next ten days should continue this trend. The forecast predicts temperatures will be quite favorable and just enough moisture in the mix from late afternoon thunderstorms.
Depending on moisture, conditions should be favorable for brown patch as well. We observed a healthy amount of brown patch at the Joseph Troll Research Center last Wednesday (June 28th) on creeping bentgrass (L-93) a putting green (Fig. 1) and colonial bentgrass fairway (Fig. 2). A week later there are still some symptoms from infection, however new infection was minimal the last few days. Anthracnose seems to be relatively quiet thus far in the season. Low amounts of anthracnose have been observed in the fungicide trial we are conducting and we have not heard of any major outbreaks in the field. As temperatures rise and cool season putting greens incur more summer stress, anthracnose will be more likely occur.
We were able to make our first site visit (Fig. 3) to collect samples for fungicide resistance screening of Sclerotinia homoeocarpa (the pathogen that causes dollar spot). If you believe you are seeing reduced fungicide control (benzimidazole, demethylation inhibitor, dicarboximide, and carboximide fungicides) and are not sure which fungicides will provide the longest control interval at your golf course, this service should be considered. Learn more information about the fungicide resistance assay.
Submitted by: Dr. Geunhwa Jung and James Popko