Early Armyworm and Thrip Control

Armyworms, either true or fall, in whorl of knee high corn in Mobile County. Pyrethroid is suggested for control.

Cotton planted April 10-12 at Prattville, Alabama is putting on first true leaf bud this week. Remember thrips control with seed treatments drop sharply at 21 days after planting (which with the cool nights in 2013) is about the time that thrips control is really needed.

The best timing for foliar thrips control is when plants are putting on the first true leaf bud. Acephate (Orthene or generic) is one of the most effective treatments.

Our objective should be to push the plant to about the 5^th true leaf stage as fast as possible. We want the largest and healthiest plant possible when we reach the 5^th true leaf. For that reason, the timing of a foliar spray is more effective at the 1^st true leaf than a spray at the 3^rd, 4^th or 5^th true leaf.

Just remember that what we see as far as thrips injury above ground is also happening below ground with the root system. We don’t want these plants, with 1000-1500 lb. yield potential, to start off with a stunted root system.

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Grasshopper Control with Winter Weed Burn Down

Several calls have been received from consultants, advisors and Extension agents this week concerning grasshopper control. Reports indicate that numerous early instar grasshoppers and nymphs are present in reduced tillage fields that are receiving burn down herbicides. There are also reports of large adult grasshoppers present in wheat in the southern area of the state.

Based on experiences during the past 10 or so years, it is suggested that where grasshoppers have been a concern in reduced tillage fields of seedling cotton, the best time to control is when applying winter weed burn down.

 Grasshoppers are a “risk” insect when cotton is in the seedling stage. With today’s seed and technology costs at planting, we must manage this risk just as we manage our in-season insects. I do not know of any established thresholds. This problem is much greater in reduced tillage in the central and southern areas of Alabama. The immature stage of grass hoppers are much easier to control in March and April than the adults will be in May. Most all labeled cotton insecticides, at the lower labeled rates, give good control of immature grasshoppers. Control can be achieved for as little as 50 cents to $1.00 per acre with some chemistries by mixing with the burn down herbicides. If that window is missed, broadcast applications behind the planter would not be too late if planting in April.

The addition of Dimilin, at 2 oz. per acre, would give residual control when applications are made in March or early April. Dimilin would provide control of later emerging grasshoppers or those that might migrate from field borders.

No highly effective controls have been found for adult grasshoppers that may be present in May. Cotton is susceptible to grasshopper chewing on the stalk, just above the soil line, until plants reach the fifth to seventh true leaf stage.

More comments about early season thrips control will follow in a week or so.

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