The majority of our program sorghum fields are in a milky dough stage to coloring dough. I can make note of a few area fields with combines starting to make their first turns all the way back to some area sorghum still in whorl stages. It is clear that all area fields have been hit by the sugarcane aphid to some extent.
Sugarcane Aphid (SCA)
We are seeing some very interesting things re-garding the SCA this week. As we watched field after field rebuild with damaging populations following treatment, we braced for another round of SCA treatments in those same fields this week.
Even in fields where we felt we had supe-rior control with our first treatment we were still seeing populations building back up last week. In many of these fields, we were delighted to find the SCA population far below what we were expecting. In others, it was exactly what we expected and additional treatments were triggered.
As myself, Dr. Pat Porter, District 2 Entomologist, and Dr. Ed Bynum, District 1 Entomologist, put our heads together to see what was causing this distinction there were two common themes. First, the fields that did not require retreatment as expected this week did have what we felt was superior control from the first treatment. Secondly, the predator population (the highest I have seen in my career) continues to grow rapidly.
What we suspect is happening is this: In sorghum fields where we have gotten really good control from our treatments, whether it be first or second, the preda-tors have finally reached a high enough level to have a major impact. In essence, we may have lowered the SCA populations in these good control fields to a point that the predators can clean them up. However, be fare warned because: In fields where our level of control was marginal, we still have SCA increasing despite the same level of predators. These lesser control level fields still required additional treatment for SCA.
This does provide me with some cautious optimism to a hope that we will not be forced into treating repeatedly up until the point where the combine leaves the field. There is a chance, now that the predators appear to be at a high enough level to be a of major assistance behind a good treatment, that with one good hit on these SCA could carry us to black line stage. It also underscores the need to make each SCA treatment count by utilizing proven rates, plenty of water, and silicone based surfactants.
While the shock of SCA has gotten most of the attention as the invasive pest, the battle in many corn fields with mites has been just as serious. In our program, we have treated 90% of our mid-maturity stage corn this season but did not add any new fields to this total this week. Predators, environmental conditions, and good control have caused a BGM in corn crash.
We need to re-main vigilant for BGM in our youngest staged corn fields, just now entering dough stage and what should be the best opportunity for the mites to increase in these fields and cause more problems. However, this is September. The nights are cooler, days shorter, and dew/leaf moisture more prevalent. These are all factors that work against BGM populations and the predator population now is much higher than the older fields in our scouting program had to deal with.
We are still noting mites in sorghum also. We have had no sorghum field in our program require treatment for mites, but they are present alongside SCA in all fields. Thus far, the predators have kept the impact of our mites in check but it is also apparent that spidermites and SCA do not coexist in the same location of a leaf very well.