The weather has been just what the doctor ordered for cotton this past week. Heat units are pilling in and the generally ‘late’ or ‘rank’ cotton is responding well while fields that have been cut-out on ‘schedule’ are starting to pop bolls. In fact, most producers are pondering irrigation and economic viability this late in the season as leaves wilt during the heat of the day.
Believe it or not, our large plants have already gone through most if not all the rains from August. We are finding for some fields, those cut-out with large bolls up top, the answer is yes, some light ‘boll fill’ irrigations through drip or pivot should be a great management choice to shore up yield and fiber quality.
In other cotton fields, those just cut-out or even not yet, a touch more heat stress would a good thing. In many of those we should reevaluate these fields once we are certain irrigation inputs will not cause vegetative growth and then consider some light irrigations. How long that would be depend full upon each individual field.
On the pest side, even though fall is in the heated air, someone forgot to tell the insects in our Plains Pest Management scouting program. Our bollworm adult moth trap numbers remain high, egg lay in sorghum, corn, and cotton remains noticeable to dangerously threatening.
Our sugarcane aphid populations, unless controlled by good treatment applications, are playing their heavy reproduction and repeat game while swarms of sorghum midge are out desperately looking for blooming sorghum.
In our Plains Pest Management scouting program cotton, we still have one field not cut-out. This field was still averaging 4 NAWF. The rest were at least reaching cut-out with about 15% sporting some open bolls. Only a few were at 1% open boll or more.
Many of these fields are apparently still attractive to bollworms. We are still finding fresh egg lay in about 45% of our fields. We are finally at a point for most fields that I feel they are past economic bollworm damage, regardless how the moths feel about the fields.
Either fields, non-Bt and Bt alike, are sporting large bolls up top that will be next to impossible for worms to establish on or fields are so lush with junk up top that worms will stay on that fruit and not bother anything economic.
There are a few fields still out there that I will view as a priority for scouting next week. These fields have enough ‘junk’ to establish one but can move onto harvestable bolls. These handful of fields aside, my cotton scouting focus moves over exclusively to cotton aphids.
Cotton aphids resurged this week with our fields ranging from about 2 per leaf up to 52 per leaf. I am suggesting on our acres that we give the beneficials as much leeway as possible in controlling these aphids.
The ET for cotton aphids should be between 50-90 per leaf. In this situation while we are not actively setting harvestable fruit, I will lean toward that upper level with my recommendations. However, once we regularly start seeing open bolls, that number should drop to 12 per leaf to prevent sticky cotton.
So, what is ‘regularly seeing open bolls’? I generally utilize a 20-25% level. With current heat unit accumulation and fruit set pattern this year, once bolls start popping regularly, it will not take long to reach that level.
The new cotton aphid management guide can be found here, complete with a list of suggested control products if needed.
Sorghum remains where all the ‘excitement’ remains. Our fields ranged between grain in the bin back to early dough. Of the later fields, sugarcane aphids (SCA) remain the primary pest of note.
Several fields are reaching the best hoped for extended range of residual control of the first SCA treatment. These fields are experiencing serious population increases again.
For these fields, which are starting to show color on their grain, making use of our research proven second treatment threshold for fields in this situation. Simply it is, protect the upper ½ of the plants. IF SCA colonies reach this upper half, then a second treatment should be justified.
All of our few late sorghum fields except one has been treated for headworms successfully. The worms have not really found the only untreated one for some reason. This field only averaged 0.4 small worms and 0.083 large worms per head with none of the worms being fall armyworms.
I have reports from the area of headworms as high as 4 per head, but many reports of them over ET. Midge are still out and desperately looking for blooming sorghum. I checked a ‘sucker’ head in one of our plots today and found 34 midge.
Our late corn field is entering dent stage and had no pest of note. Bollworms (corn earworms) were still prominent but cycling out with only larger worms remaining on about 30% of the ears. No fall armyworms, western bean cutworms, or spider mites were found this week. With higher temperatures and less humidity, corn diseases stopped increasing.