Peanuts have become a good commercial crop for Delta farmers, and Mississippi State University researchers are evaluating the effectiveness of a group of insecticides on hard-to-control pests that impact these little jewels.
“Peanuts are an economically beneficial crop in Mississippi as more farmers are planting them now that the quota system has ended. But these plants are susceptible to pests such as caterpillars, three-cornered alfalfa hoppers and numerous soil insects,” says Jeff Gore, an entomologist with MSU’s Delta Research and Extension Center located in Stoneville.
What Is The Impact?
Caterpillars eat peanut plant leaves and are difficult to control using insecticides. Adults are active at dusk or at night and lay eggs on plants and foliage. Small, green three-cornered alfalfa hoppers insert their beaks into plants to suck juices from the stems, which results in the plants being girdled and weakened.
Soil insects often go unseen, unlike their effects. Soil insects feed on the roots, reducing plant growth and productivity. In worst-case scenarios, these soil insects feed on the developing pods, which reduces yields.
“We are evaluating the potential damage and impact insects cause on peanut yields because we do not know how they have been affecting the state’s crop,” says Don Cook, a research entomologist in Stoneville.
Using insecticides like organophosphates and carbamates, Gore and Cook are applying treatments and counting insect levels to determine effectiveness. These are the same classes of insecticides that have been used in the past in other areas of the country.
Recommendations Of Their Own
“These insecticides have always been effective, but they have not been evaluated in Mississippi,” Gore says.
Currently, most insect control recommendations are based on data derived from other southeastern states or from Texas. Limited data from Mississippi is available.
When used in crop rotation, peanuts also can benefit the Delta’s cotton farmers by replenishing the soil with organic matter and nutrients such as nitrogen. Cotton requires large amounts of nitrogen to achieve good height, color, fruit production and canopy cover.
“Peanuts leave significant amounts of crop residue and biomass to help supplement the soil after harvest,” Cook says.
According to the United States Department of Agriculture’s National Agricultural Statistics Service, Mississippi farmers planted 4,000 acres of peanuts 10 years ago. In 2005, NASS listed Mississippi as one of 10 states that plant peanuts. Last year, state producers planted 21,000 acres in peanuts and produced 64,000 pounds of the legume. PG
Three-cornered alfalfa hoppers have risen to the level of being a key pest in peanuts, says David Adams, University of Georgia Extension entomologist.
Unfortunately, a lack of research data with this problem insect leaves more questions than answers on control. However, Adams says, there are some factors producers should know about this pest.
“We have seen that some peanut varieties are more susceptible than others,” he says. “Expect that TCAH may feed on one variety more than another.”
Unfortunately, says Adams, research is lacking on TCAH and newer varieties.
“They [TCAH] like Georgia Green, but that variety is being grown less and less,” he says. “We don’t have information on varieties like Georgia 06G that I will get calls about now. What we’re doing now will be more of a judgement call.”
Also, Adams says the first phase of TCAH, which usually enter generally in late June to early July, are not the phase that causes significant damage. It is the second and third populations that do more economic damage. However, during that first population of mostly adult pests, which doesn’t cause as much economic damage as the nymphal stage, might be the best time to spray to knock out subsequent populations.
Stealing Sugars From Developing Pods
TCAH feed directly into the food source of the plant and not into the water source.
“They are feeding in the food transport system taking out sugars that are flowing down the plant to the root system, which is critical because it deprives the peanuts of food,” he says. “You can see that stems below the feeding site will be smaller because the sugars going down have been reduced.”
They also lay eggs into the tissue, making it difficult for predators to get to the eggs, as opposed to laying them on the underside of the leaf, which other insect pests do, says Adams.
What’s the bottom line for producers?
“In June and July, be in the field with a consultant or county agent to make an assessment on TCAH, and if there is a level wherein you just can’t find a place where TCAH aren’t flying out in front of you or you look down and see nymphs emerging, then you need to make a decision right then if you want to make an economical spray mixed in with a fungicide to beat down that population,” says Adams. “It’s becoming our chief pest, so keep that in mind.” PG