Critically import now to scout peanuts for insects
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Author: John Hart, Southeast Farm Press (7/22/15)
University of Georgia Extension Entomologist Mark Abney characterizes 2014 as a “very buggy year” in Georgia with a great deal of insect pressure and he says last year can provide a number of lessons on peanut insect management this year.
The most important lesson learned, according to Abney, is the critical importance of scouting for insects in peanuts. He is urging growers to actively scout this year.
“Even though we don’t have economic thresholds for all of our pests, we really need to scout,” Abney stressed. “While the increased populations of certain pests in peanut in 2014 were unavoidable, inadequate scouting probably resulted in preventable losses.”
In a paper presented to the 47th annual meeting of the American Peanut Research and Education Society in Charleston, S.C. July 15, Abney said there are two completely different worlds in pest management in Georgia: irrigated and non-irrigated.
“The first thing I ask when I get a call about insects in peanuts, is it watered or not,” Abney said. “Our irrigated crop in 2014 looked good. Pest pressure really wasn’t that bad. It was bad in the non-irrigated peanuts.”
Last year was the “perfect peanut pest storm,” Abney said. “It was hot; it was dry. Most of our most serious pests love it hot and dry. The pest pressure was there and we experienced a lot of losses.”
Abney said insect and mite pest pressure was abnormally high in Georgia’s peanut crop in 2014 and caused significant losses.
“Tobacco thrips, were abundant in seedling peanut for the second year in a row and economically damaging populations of lesser cornstalk borer and two spotted spider mite, were prevalent in non-irrigated fields. The peanut burrower bug caused significant losses in 2014 after two years of relative obscurity,” Abney said.
“Hot, dry conditions favored the development of pest populations and the use of broad spectrum insecticides such as rganophosphates and pyrethroids contributed to the overall severity of pest pressure by flaring two spotted spider mite infestations,” he added.
Lesser corn stalk borer is a sporadic pest in Georgia. The southwestern part of the state sees the insect every year while it is less of a problem for the rest of Georgia most years, Abney said. Last year, however, there was an outbreak of lesser corn stalk borer in Georgia peanuts.
“It thrives in hot, dry conditions, so there’s our non-irrigated issue. Last year it was hot and dry. It feeds inside the plant, either below ground or inside the stems where we have a very difficult time getting insecticides to it, therefore it is very difficult to control with insecticides.”
Abney said the ripple effects of lesser corn stalk borer in 2014 are being felt this year. “There’s a lot of apprehension in Georgia this year because it ate our lunch last year,” he said. “They may or may not have had lesser corn stalk borer last year, but everyone is worried.”
In the meantime, in another paper presented at the APRES meeting, Brian Hayes, University of Georgia Extension agent in Grady County, said the biggest challenge is there are very limited chemical control options for lesser corn stalk borer in peanuts. Grady County is in southwest corner of Georgia and is a hot spot for the pest.
“Granular chlorpyrifos, a broad spectrum organophosphate, is currently the only insecticide recommended for use against lesser corn stalk borer by the University of Georgia,” Hayes said. “Nevertheless, growers commonly target lesser corn stalk borer with foliar insecticide applications. The effectiveness of these applications has not been proven in university research trials.”
The problem with granular chlorpyrifos or Lorsban is that it cannot be applied by air and it must have rainfall or irrigation to be activated which presents a problem in dryland peanuts, Hayes stressed.
“If you have an outbreak of lesser cornstalk borer, and you go through the time and money to apply Lorsban, if it doesn’t rain for three weeks, it doesn’t get activated. It’s also an organophosphate chemistry which greatly increases the outbreaks of caterpillars and spider mites which are also a big problem for us,” Hayes explained.
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