Current situation in cotton

We are going to see a few planters with cotton seed running for a few more days, but cotton is mostly planted. The last rain has allowed for some dryland to come to a stand. Maybe not a great stand, but possibly a keeper. Here are my stand numbers:

1. Ideally, I like to see 43,000 cotton plants/acre on irrigated, with the bottom side being around 26,000/acre.

2. On dryland I like to shoot for 23,000/acre, with the bottom side being around 19,000/acre.

3. Consistency, consistency, and consistency are key in all situations though.

This cotton needs to root down and take full advantage of moisture present before we start watering. This will allow the root system to develop as extensively as possible to take advantage of moisture now and capture moisture later if from rainfall or irrigation. Plus, a better developed root system will gather nutrients from a larger volume of soil as well.

So, cotton ranges from just emerging to near 7.5 true leaves. I have not seen squaring cotton yet but do anticipate by mid-week next seeing very small squares. I know this is a very small percentage of the cotton out there, but it these sentinel fields which often give a heads up about the next pest which should be on your radar. Right now, thrips are low to moderate in their presence and damage. This heat and hopefully your field moisture should allow the cotton to make relatively good progress through the emergence to 4 true leaf stage avoiding much damage from thrips. But do scout. As we begin to square my attention will turn to fleahoppers. I am seeing the normal silverleaf nightshade (a.k.a. whiteweed) pressure which is a great host for fleahoppers. Plus, rains have brought with it more weed pressure as hosts for fleahoppers and other cotton pests to multiple. Any preventative weed control now goes along ways in limiting some insect pests as well. Last year was a prime example of the relationship between weeds and insect pests. Fortunately, last year’s weeds stayed abundant and healthy most of the growing season and held the attention of the insect as their primary host most of the season with few exceptions.

Cotton Fleahopper

The nest potential insect pest could be the cotton fleahopper. Though I do not anticipate wholesale problems with this pest I think it is important that we cover some of the biology and management here. Adult fleahoppers are about 1/8 inch long and pale green. Nymphs resemble adults but lack wings and are light green. They move very rapidly when disturbed. Adults move into cotton from weed hosts when cotton begins to square. Both adults and nymphs suck sap from the tender portion of the plant, including small squares. Pinhead size and smaller squares are most susceptible to damage.

Management and decision making. The decision to apply insecticide should be based on the number of fleahoppers present, the squaring rate and the percent square set. If conditions are conducive to the rapid build-up of cotton fleahoppers in alternate hosts, scouting intervals should be shortened (i.e., monitor fields every 3 to 4 days).

During the first week of squaring, the economic threshold is 25 to 30 cotton fleahoppers per 100 terminals combined with less than 90 percent square set. In the second week of squaring, the economic threshold is 25 to 30 cotton fleahoppers per 100 terminals combined with less than 85 percent square set. Starting with the third week of squaring up to first bloom, the economic threshold is 25 to 30 cotton fleahoppers per 100 terminals combined with less than 75 percent square set.

As plants increase in size and fruit load, larger fleahopper populations can be tolerated without yield reduction. In most years treatment is rarely justified after first bloom. However, occasionally, when cotton plants do not set an adequate square load during the first 3 weeks of squaring, fleahoppers can prevent the square set that is needed for an adequate crop.

My priority list for the next couple of weeks:

‘ Fertility -where are you at in reaching your realistic yield goal? Be prepared to seize the moment to fertilize.

‘ Irrigation -most plants still need to root down. But make sure not to allow undo stress on irrigated cotton plants as they move into squaring, you can induce square shed. So, irrigate if you do not receive a rain.

‘ Weed control – hopefully you have a good at-plant burndown and residual in place. I am seeing quite a bit of pigweed emergence and volunteer milo. This hot weather may not be very conducive for Liberty. Roundup applications are doing a good job of catching most everything besides the pigweed, and marestail.

‘ Plant map - what is the plant telling you? I doubt this is the case, but stranger things have happened: Will it need a plant growth regulator with good moisture, heat, and fertility? Call if you have questions on this.

‘ Insect scouting - never let your guard down, watch the thrips, wireworms, Lygus and fleahoppers in cotton. If you see something unusual, please give me a call.

West Plains IPM Update is a publication of the Texas A&M AgriLife Extension Service IPM Program in Hockley, Cochran, and Lamb Counties.

Editor: Kerry Siders, Extension Agent-IPM

Contact information: 1212 Houston St., Suite 2, Levelland, TX 79336, (806) 894-3150 (office), 638-5635 (mobile), or 897-3104 (Fax),ksiders@tamu.edu(E-mail)