The yield potential of some of the newer cotton varieties should give growers the opportunity to fine-tune their insect programs to help make the most of those years when conditions are favorable, says Ron Smith, Auburn University Extension entomologist.
The first pest of the season on most growers’ minds is thrips, says Smith, and it has become apparent in recent years that a foliar over-spray is needed.
“It’s influenced by planting date, primarily, but also to some degree by nighttime temperatures and overall growing conditions,” said Smith at the recent East-Central Alabama Row Crops Workshop held in Shorter.
“We’re on the same page as Georgia as far as this is concerned. The seed treatments that are planted in the earlier or mid-season window, from early April until about May 10, would benefit from a foliar over-spray in most years.
“The seed treatments last about 21 days from the date of planting, and that’s often about 10 days short of what we need for thrips control. Temik would last 28-plus days, so we’ve lost about 10 days there,” he says.
What is seen with thrips injury above the ground is also reflective of what is seen underground in the root mass, says Smith.
“We have good research data now that indicates there is a direct correlation to what is growing above ground and what is happening with the root system. That could be where our yield increases are coming from with better thrips control.”
The results of multi-state research projects, says Smith, show that over-sprays are most effective during the plant’s first true leaf, which is about the size of a small fingernail.
“This is much earlier than we would normally spray if we were just going out and looking. You really can’t see the injury at the time you need to make the spray. Cotton with four or more true leaves typically does not benefit from these over-sprays,” he says.
Either Orthene or the generic products provide the best results, says Smith.
Pyrethroids were shown to be less effective, and some were no better than the untreated control, he adds.
Hold Bidrin in reserve
While Bidrin was shown to be effective, Smith says this product is best held in reserve for possible stink bug infestations later in the growing season, especially considering the current label restrictions, Smith says.
Over-sprays provided added protection during seven critical days in early season when the plants are vulnerable to thrips, he says.
“Two new products, Benevia and Radiant, developed by Dupont and Dow, respectively, also appear to be highly effective on thips. However, there is still some uncertainty about when they will be registered and their cost.”
The supply of Temik is basically non-existent in the market this year, Smith reminds growers.
“The product Meymik has been approved by EPA, but there will be no supplies in 2012. They’ll hopefully have supplies next year. We won’t have any for research purposes this year.”
Plant bugs are another concern for cotton producers, says Smith.
“We get a movement of plant bugs from wild hosts to cotton in the spring, and that movement is influenced by weather conditions. You typically get really sharp spikes of plant bug movement during hot, dry springs, although this doesn’t last very long,” he says, adding that the bug’s movement tends to be less intense during cool, wet springs, even though it lasts longer.
“In some fields in central Alabama, around June 20, we picked up a movement of plant bugs. After those were taken out, there wasn’t a problem with plant bugs for the remainder of the season,” he says.
The most effective insecticides for plant bugs include Acephate, either Orthene or the generic brands, says Smith.
Other options include Bidrin, although it is labeled only for the post-bloom period. Centric, while effective, also suppresses beneficial species, including fire ants.
“Pyrethroids are effective, although they can flare spider mites,” he says. “Diamond has been shown to be effective on the bugs during their post-bloom immature stage, especially when it is tank-mixed with one of the previously mentioned products.”
Single applications of Intruder, Carbine, imidaclorprid (AdmirePro), Belay and Vydate have been shown to be less effective than the others.
During July, as plant bugs linger and aphid populations build, Smith recommends using products effective against both species.
Intruder, Carbine, imadacloprid and Centric are most effective, particularly as an aphid material, while Diamond can be used with any of these, Smith says. “If moisture conditions are good, we ride the aphids out until they crash from natural diseases.”
Beneficial pests, such as fire ants, continue to play an important role in cotton production, he says.
“We know that some materials are harder on fire ants than others. Fire ants are by far the most dominant beneficial in Alabama cotton today. They’re critically important in conventional systems, but they also will reduce the number of escapes in Bollgard and Widestrike.”
Tests have shown a lot less damage in both conventional and genetic cotton when fire ants were in a system as opposed to there being no fire ants in a system.
“You can see a trend in the genetic cotton, but it’s even more obvious in conventional cotton. Last year, there were practically no bollworms in the system. In a normal year, we think the effect of fire ants would be magnified. Fireants play a big role in minimizing escaped worms in cotton.”
Fall armyworm situation
Turning to fall armyworms, in both 2010 and 2011, there were widespread outbreaks of the grass or rice strain of this insect pest, although this strain primarily attacks pastures, hay, grass and peanuts, says Smith.
“Fortunately, this strain is easy to control with insecticides, including pyrethroids. This strain does not prefer to feed on cotton, and that explains why we haven’t seen any fall armyworms on our cotton in the past couple of years, even though they’ve been in the environment.”
The most damaging cotton insect pest in the Southeast remains stink bugs, and Smith doesn’t see this changing anytime soon.
Scouting is a critical safeguard against these bugs, he says.
“The most effective way to scout for stink bugs is examine 10- to 12-day-old bolls for signs of internal injury. The difference in managing stink bugs could pay for a scout and a consultant itself because we’re talking about $6 to $9 in application costs.”
A laminated card has been developed to better ensure growers inspect the right-sized boll and is available from the Alabama Cooperative Extension System.
“We have a dynamic or sliding threshold for stink bugs, and it represents the number of bolls at risk at a certain time of the season. I believe this is the best threshold we’ve ever had for cotton insects.
“We go by the week of bloom. At week two of bloom, for example, we really wouldn’t have many bolls out there that would be large enough to be damaged by stink bugs, so we can go with a higher threshold. As cotton cuts out, the susceptible bolls would be fewer and fewer. We know that the benefit of spraying for stink bugs comes in week three or week six of bloom.”
Stink bug pressure was low last year for a couple of reasons, says Smith.
“Last year, the winter temperatures were much colder than this year. We also had a hot, dry spring, and when stink bugs were reproducing, the immature ones didn’t fare well. Based on our most recent winter, we’ll probably be back to more normal stink bug pressure in 2012.
Looking at cotton insect pests that may be on the horizon, Smith says the kudzu bug, while not threatening to cotton, has emerged as a serious soybean pest and already is entrenched in neighboring Georgia.
“You can kill them with a pyrethroid, but their numbers come back very quickly,” he says.
Another species new to the region, the red-banded stink bug, is also primarily a soybean pest. One especially serious threat is the brown marmorated stink bug, which is moving from Pennsylvania into the Appalachian region and is threatening the fruit- and apple-growing regions of the Carolinas, according to Smith.