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June 5, 2014 Cotton Scouting Report

Thrip Damage to Cotton

Thrip Damage to Cotton

Thrip management and weed control continues this week. The thrip population has been especially severe given the continued hot, dry weather. Note the continued distorted growth of newly expanding leaf indicated continued thrip feeding in the image to the left. Fortunately, many areas received rainfall between 0.5-1.5 inches on Friday, June 6th. Rapid growth of cotton should eliminate the need for continued thrip management for most fields. However, growers should scout fields carefully and apply remedial insecticide treatments for later planted cotton that is not at or approaching the 5th leaf stage if the newly expanding leaf shows signs of feeding and live thrips are found. If herbicides are to be included in the tank mix, be aware that some stunting may results. (See articles, Cotton Thrips Management- Focus on Tank Mixes With Herbicides and Keep Cotton Safe From Thrips Until Five Leaves)

If one has not been recently applied, now is time to consider application of a herbicide with preemergence activity to control herbicide resistant palmer amaranth. It should be noted that research surveys indicate both ALS and glyphosate resistant palmer amaranth within Craven County. Potential tank mixes and comments are provided below.

Tank Mixes with Glyphosate Applied Over the Top of Round-up Ready Flex Varieties

Pyrimax or Staple LX may be tank mixed with glyphosate and applied until 60 days prior to harvest. Rates range from 1.3-3.8 oz depending upon product and weed size. This tank mix offers improved control of hemp sesbania, morgningglories (except tall), spreading dayflower and glyphosate resistant palmer amaranth. This tank mix may also temporarily injure cotton if applied when cotton is stressed from cooler temperatures, wet weather/soils, thrips or seedling diseases. Additions of insecticides, adjuvants or foliar fertilizers may increase the likeliness of injury.

Envoke may be tank mixed with glyphosate and applied from the 5th to 12th leaf stage. The rate ranges from 0.1-0.25 oz/ac. This tank mix provides greater control of nutsedge, morningglories and smartweed. This tank mix may cause some yellowing in the cotton terminal and shorten internode length. Note the label requires the use of a non-ionic surfactant only (1 qt/100 gallons). Additions of liquid fertilizer, boron or other additives will stunt cotton.

S-metolachlor products may be applied over cotton that is at least 3 inches tall until 100 days prior to harvest. Minor necrotic speckling of leaves may occur but no yield loss has been noted unless additional surfactants, adjuvants or insecticides are also included. If insecticides are added, injury is worse when applied to wet cotton (dew or rain) or when the weather is extremely hot and dry.

A pre-packaged mixture of the potassium salt of glyphosate plus S-metolachlor is available (Sequence) to supply 0.7 pounds a.e of glyphosate plus 1.0 pt of S-metolachlor when applied at 2.5 pts/acre.

It should be noted that metolachlor products are also available. These products should provide similar control as S-metolachlor products if applied at equivalent rates. A metolachlor product would require 50% more than a product containing S-metolacholor to get the same activity.

Warrant herbicide can be tank mixed with glyphosate and applied after cotton emergence but before first bloom. It has been noted to provide similar preemergence weed as S-metolachlor products. The addition of surfactants or insecticides has shown to increase the probability of crop injury, especially during periods of stress.

Do NOT mix either S-metolachlor or Warrant with pyrithiobac products.

Clethodim, fluazifop, quizafop and sethoxydim products can be mixed with glyphosate to control volunteer Round-up Ready Corn.

Tank Mixes with Glufosinate Applied Over the Top of LibertyLlink Cotton

Tank mixes for over the top applications of glufosniate and other products are similar to that of glyphosate with the following exception:

1. Do NOT mix glufosinate and postemergence grass control herbicides. Reduced grass control will occur. Either apply the grass control herbicide first and the glufosiante application at least 3 days later OR apply the glufosninate first and the grass herbicide application 7 days later.

The use of brand names and any mention or listing of commercial products or services in this publication does not imply endorsement by the N.C. Cooperative Extension Service nor discrimination against similar products or services not mentioned. Individuals who use agricultural chemicals are responsible for ensuring that the intended use complies with current regulations and conform to the product label. Be sure to examine a current product label before applying any product.