South Plains IPM Report

June 26, 2017

Tyler Mays, Texas A&M AgriLife Agent, IPM

General Conditions

Hot, dry, and wind has been the story of the last 7-10 days, and this weather pattern that we are in has been harsh to crops in Gaines, Terry, and Yoakum Counties. This weather has negatively affected our cotton from getting a stand. Cotton in the scouting program is ranging from just emerging to the 4-true leaf stage. Thrips are still present in local cotton and peanut fields, but none of the fields in the scouting program have reached threshold. Earlier this week we were seeing wind damage to young cotton plants that was mimicking thrips damage, more on this will be in the cotton section of the newsletter.

Some areas in Terry County this week received some rain, however, like any storm around this time of year high winds and hail accompanied it. There are reports of fields being lost due to hail damage around the FM211 and FM168 intersection. I am not aware of how wide spread this damage is, but it does not appear to be South of Highway 380 and West of Highway 385, as I drove around trying to see the extent of the damage.

Peanuts are starting to bloom, and if you have not evaluated your field(s) inoculation program, now is the time. Evaluating our nodulation on a field by field basis helps to determine which fields could benefit from mid-season Nitrogen applications. We have not observed diseases in peanuts yet this year, but soil inhabiting insects, such as wireworms and grub worms are being found more often.

Cotton

Thrips are still a concern for most of the cotton fields in the area, but are still staying below threshold. Thrips are only an economic pest until the 5-true leaf or once the plant begins to square. At our current situation, our irrigated cotton will reach this stage in a very short time. Cotton needs between 50 and 60 Growing Degree Day 60 (DD60s) to emerge after planting, and need another 425 to 475 DD60s to reach squaring.

Based on the DD60s shown, cotton planted before May 10th, bearing inadequate weather conditions should be squaring within the next 7 to 10 days.

On Monday of this week, I walked into a cotton field that is in the scouting program, and saw what I thought to be thrips damage. At first, I was afraid my field scouts and I missed a heavy population of thrips. Once I checked about 20 plants within the field it was apparent to me that this was not actually thrips damage, but instead wind damage from the high winds that have plagued most of the area.

This damage was caused by our soil getting hot during the afternoon, and then when the wind picks up, the hot blowing sand hits the tender cotton leaves, and desiccates the leaf margins causing the leaves to curl and pucker as they continue to gain size. If you see this damage in the fields, it is best to check to make sure thrips are not the true cause of the cupped or puckered leaves. This can be done by looking at the underside of the leaves to check for thrips feeding damage, and check the terminal and unfurled leaves for actual thrips. Thrips damage appears as sunken silver tissues that is caused when the thrips use their piercing/rasping mouthparts to rupture the plant’s cell so they can feed on the plant fluids.

Peanuts

Peanuts are progressing nicely, and fields in Gaines County have started to bloom this week. If it has not been done yet, now is the time we need to be checking on the amount of root nodules per plant. Ideally, we would like to see 15 or more nodules per plant. To inspect peanut nodulation, one should dig up 3 row feet of peanuts and count the number of nodules on the plant at each site and the number of plants at each site. You can average these for each site and average out these averages, or you can keep a running total for the whole field and calculate the average once finished with the field. If a field averages less than 15 nodules per plant, the field will need some Nitrogen, but still at a slightly reduced rate. If a field averages less than 6 nodules per plant, one should also try to figure out what happened with their inoculant.

Diseases have not been observed in the peanut fields the IPM program is scouting this year, but as we start irrigating our peanuts more we should really keep an eye out for leafspot diseases.

Common leaf spot diseases of peanuts for our area include early and late leaf spot. Both leaf spot diseases can look similar on the upper leaf surface, however early leaf spot typically has a yellow halo around the lesion where this is inconspicuous to absent around late leafspot lesions.

Spores of early leafspot are typically produced on the upper leaf surface, where late leaf spot usually produces it spores on the lower leaf surface. Use of preventative fungicides around 60-70 days after planting usually provides good management of these diseases, however late in the season another foliar fungicide may be needed if conditions favor disease development.

Wireworms and white grubs are still being found in area fields, and in some fields are becoming more common. These insects right now are feeding on secondary roots of the plant which will decrease the amount of water and nutrients taken up by the plant. Later in the season when we start setting pods, they will be feeding on both the pods and roots of the plant.

Control options are minimal as there are no insecticides that effectively control these insects. An application of Lorsban has shown to suppress the damage caused by these insects, and depending on the fate of Lorsban with the EPA may be applied if populations are high enough. Foliar feeding worms are still being found, but are very sparse, find no more than one worm per a single field. If these insects begin to increase and reach numbers of 8 to 10 per foot in runner type peanuts and 6-8 in Spanish type peanuts, insecticide applications may be warranted.

Share on FacebookTweet about this on TwitterShare on LinkedInPin on PinterestShare on Google+Email this to someone

Category: Agriculture