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Where are the Predatory Mites?

Last week a group of us from the lab took a trip to Empire Farm Days, which is a three day event focused on agricultural related topics.  A lot of it is machinery and equipment, but there is a building for the Cornell Cooperative Extension.  We set up a table with information on GPS sensing and grape pests, but unfortunately not too many people stopped to chat with us about these topics.  There were many people from the extension there with booths and information on agriculture, so the attendees did learn something new, even if it wasn’t related to vineyard management.unnamed

On Wednesday I went to a vineyard/hopyard in Pennsylvania with Tim and Luke.  We were only there for about an hour in the morning, but it gave me the opportunity to see an actual production hopyard outside those planted for research and extension.  The hopyard was much bigger than those here and in Geneva, and it was also the shorter production rows, instead of the tall ones.  It was really interesting to see the amount of cones that will be harvested from their plants; they were heavy with them and will be ready to harvest in a couple of weeks.  As we were walking down their rows we did see some TSSM damage though; hopefully they can take the right measures to get rid of them before they infest the conunnamed1es and damage their crop.

The rest of the week I spent counting the mites from the leaf samples I collected Wednesday afternoon.  The TSSM are really starting to spike in some areas of the hopyard, and I am starting to see the bronzing on the leaves that is characteristic damage of TSSM (photo to the left).  However, as I keep mentioning, I am not seeing the numbers of predatory mites I should be.

I had a conference call with Greg about my project and we talked about potential reasons why the predatory mites aren’t there.  Heavy rainfall will cause the mites to wash away from the leaves, which would result in lower numbers following a storm.  Also, predatory mites don’t move with the wind using spinnerets the way TSSM do, sunnamed4o if they don’t have a food source readily available, they will crawl to find a new one; my best guess would be down to the ground where there are other plants and weeds where they can feed on pollen.  I am going to go back and look at the weather, especially rainfall, the day before I collected my leaf samples each week and the day after I released the predatory mites in June to see if that could be the cause.

After our discussion we decided that I should release some more predatory mites into the hopyard.  On Thursday I ordered 20,000 more N. fallacis and had them overnighted so I could release them on Friday.  This time I released them at the opposite end of the hopyard that I released them at in June.  This week will be my last week of counting, but I am hoping to see more predatory mites at the end of the row where I released them.  If I still am not seeing them there will be another interesting project for someone in the future looking at where they might be going!



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