It has been a while since we last discussed or posted concerning the Alabama cotton and row crop insect situation. So what has been going on? No one insect has been overwhelming but treatment decisions have had to be made on a diverse array of insects and mites on all of our row crops (cotton, soybeans, peanuts and grain sorghum).
Most of the attention on cotton has been directed towards plant bugs during the past two weeks. Economic numbers of nymphs have appeared in fields that had adults in late June and early July. Where the population was detected by fieldmen, controls were applied. All recommended insecticides seemed to do a good job. One point I will make here is that some inexperienced fieldmen may have not picked up the just hatched immature plant bugs, which are very small at that stage. There seems to be a gap of time between when we stop seeing adults and when we find the small nymphs. The egg stage of plant bugs lasts from 7 to 14 days.
Aphids have been hit or miss this season. Some fields never had any aphids appear. Other fields saw a buildup sometime from mid-June to mid-July. Aphids were crashing from the fungus on July 24 while other fields were just experiencing their first aphid buildup. Where treatments were applied, insecticides were effective.
The most difficult to control pest on cotton in July was spider mites. Here is my take. We are waiting too late to find mite infestations and as a result populations are high and have been present for several weeks. Therefore, heavy damage has occurred in select fields before controls were applied. Many growers are just not tuned in to mites and are not recognizing their damage until too late. We just don’t have enough experience on when to pull the trigger on mites. I feel that weather may play a big role here. When in a period, such as early-to-mid-July, of high temp and droughty conditions we have to take a more rapid and aggressive approach to mite control.
Most of our fields are now into the 3rd or 4th week of bloom. Some fields much further along than that. This means that we are entering, or are well into, the most critical window for stink bug damage. The population has been predominantly brown up to this point. I expect the southern greens to increase the remainder of the season. Just remember that weeks 3-6 or 7 of bloom is when we need to focus on stink bug numbers and damage. For those who are just going by observations of adults, you usually have a much higher number of stink bugs than what you are visibly seeing. Crushing 10-12 day old bolls and observing for the internal injury is the most accurate way to make stink bug treatment decisions. Most fields are at the stage now that we want to use a 10% internal injury treatment threshold.
On other row crops here are pests that have occurred at damaging levels: soybeans – kudzu bugs and fall armyworms; peanuts – spider mites, lesser corn stalk borers, fall armyworms, beet armyworms and corn earworms; grain sorghum – aphids, fall armyworms and corn earworms. A new species of aphid, the green sugarcane aphid, has been reported on sorghum in both Escambia and Chilton counties. This species has done heavy damage in Texas, Louisiana and Mississippi already this season.
Moth traps in central Alabama indicate that tobacco budworm numbers are down, but bollworm numbers increased tremendously last week. A high level of budworms occurred on tobacco planted as a sentinel crop at Headland during the past two weeks.
With these comments we will close today. Remember that despite our best efforts we cannot always alert you on all pests on all crops from here in Auburn. All crops, including hay, must be scouted regularly for insect pests if they are being grown for economic returns.