Outwitting Plant Bugs

Early Planting Can Help Farmers Avoid Pressure From Plant Bugs

JACKSON, TENN.
   Cotton plant bug control claimed the attention recently of Dr. Scott Stewart, Extension IPM specialist for West Tennessee with responsibilities for all the row crops. He is located here at West Tennessee Research and Education Center.
   “That’s probably the one issue that’s plaguing us the most in cotton,” he said. “When you talk about plant bugs in West Tennessee you have to include stink bugs because they are often in the mix; and plant bugs can cause significant yield losses if we let down our guard.
   “Many of the seed treatments or at-planting treatments for thrips are pretty mature technologies; we know what to expect with them. They do a pretty good job. With the eradication of the boll weevil and the high adoption of Bt cotton, that has left us with live plant bugs and stink bugs as our biggest pest problems. This year on the experiment station we had a lot of plant bugs and stink bugs, at least by our standards. We probably averaged five plant bug applications, and any cotton we left unprotected lost anywhere from 1-2 bales of yield.”
   Luckily that’s not a reflection for what has happened throughout all of West Tennessee.
   “We had a band of plant bugs and stink bugs that went from Madison County, parts of Haywood County, parts of Crocket County, Gibson County; it went up the east side of West Tennessee. Towards the Mississippi River populations were generally low, not showing up in consistently higher numbers until later in the season. Often, it’s just the other way around.”
   Stewart couldn’t pinpoint any one environmental aspect that makes plant bugs worse. However, when they are present like they were in some places this year, good scouting and well timed insecticide applications are needed to keep damage to a minimum.
   “Scouting is really important,” Stewart said. “We have two issues. We have early season populations which are hard to predict. They’re sporadic, they can do a lot of damage in a short period of time, but fortunately it’s a relatively rare occurrence.
   “Once it gets later in the season, mid July though early August, a lot of our acres will be infested with plant bugs or stink bugs. A lot of years we may be able to clean those up with one or two insecticide applications.”
   However, this is not always the case. In some locations this year, insecticide applications were made every week for 4-5 weeks in a row.
   “That runs up the insecticide bill quite a bit,” he said. “We still have some acres that aren’t being scouted as intensively as they should be, so you get damage as well as increased insect control costs.
   “We’ve done a lot of work throughout the region in recent years to determine what our treatment thresholds for plant bugs should be, and we are continually evaluating which insecticide treatments are best. Unfortunately, we are heavily reliant on insecticides to control these pests. Relying on pesticides is not necessarily the best paradigm, but that’s the only option when plant bugs are in the field in high numbers.”
   He recommends that farmers plant early and try to avoid the plant bugs. Early planting can help avoid late season plant bugs and stink bugs. Of course, the best laid plans to plant early can be foiled because of weather, flooding and other interferences.
   “In West Tennessee we typically plant early maturing varieties because we’re in a northern climate,” he added. “That helps us to avoid late season bug problems to some extent, but it’s not going to eliminate the problem.”
   “That’s probably a good take home point,” Stewart said. “If you have some later maturing cotton, it needs to be watched especially closely for plant bugs and other pests; toward the end of the season insects will often concentrate in late maturing fields as earlier fields become less attractive. As I said, there has been quite a bit of work done to evaluate our sampling techniques and our thresholds, and these thresholds and sampling techniques work well. But you still have to grind it out. Good scouting can pay for itself tenfold.” Δ
   BETTY VALLE GEGG-NAEGER: Senior Staff Writer, MidAmerica Farmer Grower 

Dr. Scott Stewart, Extension IPM Specialist for West Tennessee, explains that the plant bugs and stink bugs are the number one issue plaguing cotton. Photo by John LaRose