Dr. Camp Hand:
“The glaring difference in the past two weeks is going to be the chances of rainfall this week. Below you will find the Defoliation Handout that myself and Dr. Snider put together, which contains rainfree periods for some of the more common defoliants used. The one that sticks out is going to be your thidiazuron products (Dropp, Freefall, Klean-Pik, etc.), with a 24 hour rainfree period. Thidiazuron is your regrowth inhibitor that also helps with juvenile leaf removal.
Now, does this mean that if you apply Dropp and it rains 12 hours later that it isn’t going to work at all? I don’t think so. But it could reduce effectiveness compared to if it got 24 hours of dry time. One thing that could improve uptake in a situation like this week is adding an adjuvant (COC, NIS, MSO, etc.) to the tank. However, it should also be noted that an adjuvant could also increase the risk of sticking leaves. Last week I got a call from an agent that said a grower was sticking leaves, but the mix was fairly normal (3.2 oz Dropp, 8 oz Folex, 32 oz Ethephon). With those rates, and the conditions we had last week, I wouldn’t expect to see stuck leaves. But the grower also included an adjuvant in that mix, which I believe was the causal agent of his stuck leaves. So it is quite the balancing act, but this week I would consider using an adjuvant just because of the uncertainty surrounding rainfall.”
