We are in the middle of our stink bug month, and plenty of stink bugs are in the system.
If you have cotton that has been blooming for several weeks, and you have not made an application for stink bugs, check your fields. If you have treated for stink bugs within the last few days, take a breath, but go back about 7-10 days after the last spray and check for stink bugs and assess boll injury again.
As long as the crop is getting water and doing well, repeat scouting trips and treatments, as needed, through the 7th week of bloom, and then start looking for reasons to shut it down. Determining when to terminate sprays for stink bugs is not an exact science, but there are some data.
Roughly, bolls can be considered safe at about 21 to 25 days after white flower or about 500 to 550 heat units for the boll. Heat units are calculated in cotton by taking the average daily temperature (Fahrenheit) and subtracting 60.
For example, if the high temperature for a day is 95, and the low is 75, heat units calculate to 25 for that day ([95+75]/2 – 60 = 25). If that same pattern happened each day for 21 days, it would calculate to 525 heat units.
So, figure out which flowers you plan to protect until the end, and use all of this information (and other information like yield potential, etc.) to make that termination decision.
How long the fall will keep providing good accumulation of heat units determines when our season winds down and how long we should protect cotton from insects, so pay attention to the long-term forecast. The white flowers in the field now are some of the last ones we need to protect (as bolls) from stink bugs.
Let’s Talk Bollworms
Bollworm is escaping control from some of our 2-gene cotton technology, but no crazy breakthroughs are being reported. Our most recent pheromone trap data indicate an upward trend on captures of bollworm moths, so our next flight has started.
We observed fresh, white eggs in the field today, and easy-to-spot moths were “flushed” as we walked the field.
Continue to check for bollworm escaping control from the Bt toxins.
Meanwhile, In Soybeans…
We have numerous species and insect pressure in soybeans this week. For caterpillar species, we have soybean looper, green cloverworm, velvetbean caterpillar, podworm and a few armyworms in the mix.
Be able to identify the moths and larvae in soybeans, since good control with insecticides depends on accurate identifications. Also, in some soybeans today at the R4/R5 stage of growth, we observed significant numbers of stink bugs, particularly freshly hatched eggs of southern green stink bug.
Around The State
Jay Crouch, county agent covering Newberry, Saluda and Edgefield Counties, noted that the insect complex in beans he’s scouted included “mainly green cloverworm and low levels of kudzu bug adults towards the Piedmont counties.
“The Ridge has a mixture of green cloverworm, velvetbean caterpillar, podworm, and soybean looper, with an occasional stink bug. Levels of soybean looper are approaching threshold and green cloverworm are abundant.
“I suspect producers will start spraying soon. Soybeans are not quite at R3, but levels have them concerned.”
Fleming McMaster, a local crop consultant, reported that he has “hit threshold levels for stink bugs in MG 4 soybeans…both brown and green. I’m also seeing increased levels of green cloverworms and soybean loopers but not at threshold levels. And podworm (corn earworm) is making an appearance.”