SCA Efficacy Trial 21 DAT Counts & SCA 2nd Treatment Decision Options
Before we started our counts today, we discussed the validity of these 21 DAT counts. We knew that the untreated check would have fewer aphids due to the overall plant health and predation (although the predators are so far outpaced by the sugarcane aphids that this is not a control option alone). We also suspected that most treatments would be losing control altogether this far out past treatment.
If both of those factors are true, these results would be skewed with heavier aphid numbers on treated plots. We also knew that we did not get good control on the lower leaves in this trial. To counter this potential affect, we are including a plant damage rating. These were collected at 15 DAT and again today at 21 DAT. This rating system is based on a 0-10 scale where 0 = no aphid damage and 10 = dead plants. All graphs and statistics are shared below. This rating system is new for the SCA and is only ready to evaluate damage and cannot be utilized as a threshold marker… yet.
The take home message from the researchers involved in this trial today and gathering from our field experience these past few weeks is this: If you got good control with your first SCA treatment, you MIGHT be able to hold off on the next treatment until 17-21 DAT for the next(assuming aphids are still an issue; I have seen no field where they were not). If you did not get good control, it is VERY LIKELY your next treatment needs to fall 10-14 DAT. If and when a second, or even third treatments become necessary, remember we need to rotate chemistry between Tranform and Sivanto to prevent resistance from this aphid.
I feel the majority of treatments in this trial fall into the second category. If these plots were in a field situation, they would have required a second treatment 5 – 7 days ago. Neither of these situations are what we want but that looks like what the situation is with even more aphids moving in to re-infest and / or populations recovering. Both of these situations need to fall into considerations about how far out harvest is.
We would certainly prefer the next treatment, likely the third treatment if needed, would be the one that cleans the aphids for the combine in conjunction with a sorghum harvest aid. We are so far out from a freeze at this point and these SCA still have a ballooning population that can stay in-field until and after harvest, I do not envision the possibility of being able to wait for a freeze to finish these aphids off so we can harvest.