Alabama Peanuts: Caterpillar Pests – What Can You Expect?

Corn earworms, bollworms. Photo: Bob Griffin, University of Arkansas

There have been several reports of armyworms and loopers over the past few weeks. Below is a brief discussion of the seasonal fluctuations in major caterpillar pests based on moth catches from sticky wing pheromone traps that have also been summarized in the graphs.

Number on the graph indicates our best estimate for the number of generations and season fluctuations. For detailed peanut insect pest recommendations, please refer to the Alabama Peanut IPM Guide.

Corn earworms and tobacco budworms:  A slightly higher activity of tobacco budworm was noted this year (with perhaps 3-4 overlapping generations) compared to the corn earworms. The average moth numbers were close overall for both species with 2 to 3 moths per trap per week. The caterpillars will probably continue to build in numbers very gradually in various row crops. Tobacco budworm numbers were high in some northern counties that were in the insect monitoring project in 2016.

Loopers:  As usual, cabbage looper activity preceded soybean loopers this year. Cabbage looper numbers ranged from 6 to 14 moths per trap in August, with the average being 10 per trap. Recently, we have noticed a spike in soybean looper moths with average numbers exceeding 21 moths per trap (range 15 to 28). Such sudden spike (10X) in moth activity can results in large populations of soybean loopers in row crop fields and extensive feeding on the terminal leaves.

Peanuts may look ‘grazed’ from the top when looper numbers exceed 4 to 5 per row foot. It is best to use a beat sheet across several scouting locations to accurately access looper numbers in the peanut canopy.

Armyworms:  It appears that beet armyworms have completed about five generations with the average trap counts of 21 moths per trap. In comparison, fall armyworms appear to be in their third generation with 18 moths per trap – these moths are highly migratory in search of row or horticultural crops. In July, beet and fall armyworm moths averaged about 10 and 6 moths per trap, respectively.

In other words, moth activity has increased two to three times within a month. So watch out for armyworms – there are more to come! There has been an extraordinarily high activity of armyworms in hay, pasture, and home lawns.

Lesser cornstalk borer:  Based on the most recent U.S. Drought map, it appears that most of the southern (peanut producing) counties of Alabama are not in the drought zone after the steady rainfall. There have not been very many calls about the lesser cornstalk borer this year which is a good sign.

The truth is that moth activity is still pretty high and steady at 133 moths per trap – almost the double the numbers from July 2016. So, this insect is a ‘hidden pest’ that takes advantage of dry weather and lays low during unfavorable soil conditions. Threat to the peanut crop is not over till peanuts are out of the ground. So watch out and keep scouting the pods directly.

moth activity graph8-30-2016.jpg

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