Early season practices for managing plant bugs in cotton can result in significantly higher yields for Mississippi growers, studies have shown.
“There are a lot of things growers and crop consultants can do early season to have an impact on plant bug management,” Jeff Gore, assistant research professor at the Delta Research and Extension Center, Stoneville, Miss., said at the annual meeting of the Mississippi Agricultural Consultants Association at Mississippi State University and a following presentation at the Louisiana Agricultural Consultants Association annual meeting at Alexandria, La.
“Several factors affect earliness: variety selection, planting date, thrips management, weed management — anything that delays the crop can make plant bug control more difficult.
“In our trials, the later the planting date, the more insecticide applications were required and the greater the yield loss from plant bug damage. If we planted mid- to late April and early May, we only had to make three or four applications during the entire season, whereas with mid May-early June plantings we had to spray a lot more.”
Selecting varieties for earliness is also important, Gore says. In studies conducted by graduate student Brian Adams, combining early planting with early maturing varieties resulted in less damage and less yield loss.
Planting early can pay dividends
“The later we planted, the greater the yield loss we had from plant bugs,” Gore says. “So, our bottom line message is that consultants and growers need to be aware that planting early and using an early maturing variety can reduce the impact of plant bugs and reduce the number of insecticide applications.
“If you plant a later-maturing variety, definitely plant that variety first and save the shorter-season varieties for your last plantings.”
Data from work by another Delta Research and Extension Center researcher, Don Cook, show that managing thrips early and getting the crop off to a good start is also important to prevent delays in maturity and improve plant bug management, Gore says.
“We’ve also looked at shortening spray intervals and rotating, as best we can, the few insecticide options we have available. Shortening intervals from 7 days to 5 days can help to maximize plant bug control.”
Over the last couple of years, he says, “We’ve also been looking at timing of applications of Diamond, an insect growth regulator that affects plant bug nymphs. In 2009 tests, we found that adult plant bug populations peaked between the third week of squaring and first week of bloom, and that applying Diamond when the adults first begin migrating into the fields provided a protective barrier as those adults laid eggs and nymphs hatched.
“We saw 150 pound to 300 pound lint increases from one application of Diamond during the window when adult populations peak. Across all treatments where Diamond was applied early, we had a 172 pound yield advantage.”
In 2010, trials were expanded to look at different timings, different numbers of applications, and different combinations.
Diamond applications improve yield
“Any place we applied Diamond, yield was significantly better than where it wasn’t used,” Gore says. “But when we applied it the third week of squaring, yields were significantly better than for all of the other later treatments.”
Second and third applications of Diamond later in the year didn’t add much in terms of yield, he notes. “But that’s not to say applications later in the season can’t be useful in terms of protecting the crop that’s left — we just didn’t see much additional impact from a yield standpoint.
“Applying Diamond during that early season window when adult plant bug numbers peak appears to provide the best control and best yield benefit. Gordon Snodgrass (USDA-ARS) showed that second, third, and fourth instar nymphs are as much as 10 times more tolerant of Diamond than first instar nymphs. By getting Diamond out early, as nymphs hatch they will be exposed to the material, even if at a low level, and control will be more effective.”
Also, research by Fred Musser at Mississippi State University showed that when adults had been exposed to Diamond, a very low percentage of their eggs actually hatched.
Some “new” versions of earlier materials that are effective for plant bug control, Gore says, include:
• Fyfanon plus ULV from Cheminova, is labeled on cotton at 8 to 16 ounces, and in studies “has shown a sharp decline in both nymph and adult numbers.” This material is currently available.
• Brigadier from FMC, is currently labeled on cotton, soybeans, and peanuts, with broad spectrum activity on bugs and caterpillars
• Belay from Valent, a neonicotinoid labeled on cotton and soybeans, “looks pretty good on plant bugs.”
• Bidrin XPII from Amvac, should be available this season as a premix for bugs only in cotton. “It’s no longer a co-pack, which should make it more convenient to use and still provide good control of plant bugs.”
New materials pipeline
In the new materials pipeline, Gore says, “there is a lot of excitement” about sulfoxaflor (Transform 50WG), a new insecticide from Dow AgroSciences, expected to be labeled in 2012.
“It’s a new class of chemistry that has good activity on both tarnished plant bugs, and cotton aphids that have become resistant to neonicotinoids. It will be offered in a 50 percent WG formulation.
“In our work, we’ve looked at a broad range of rates, and the 2.14 ounce rate has consistently given us better control of plant bugs than lower rates, with the benefit of added residual. For aerial applications particularly, I think the higher rate will be more effective than the 1.45 ounce rate. Transform can also be mixed at the lower rate with a pyrethroid for increased plant bug control.”
“Where we see the greatest benefit from Transform is when it is applied at 1.45 oz per acre during the pre-flowering period to control both plant bugs and cotton aphids. As we move into the flowering period, the 2.14 oz per acre rate will be provide more consistent control of plant bugs.”
“We are increasingly seeing that standard insecticides don’t provide the level of control they once did, and we continue to encourage producers to promote earliness in their crop and to use different chemistries in an integrated program in order to achieve the best control and minimize losses.”