Texas: Cotton, Grain Pests More Apparent In Lower Rio Grande Valley

Cotton fleahopper. Photo: Danielle Sekula

This week across the Valley we are seeing more insect pest activity in both cotton and grain. In all 3 counties, dryland fields are certainly struggling to continue to grow as there is very little to no moisture available. However, we are seeing large parts of land in Willacy County that remain extremely dry and just failed to receive rain in time to produce a stand. Those fields that failed to make a stand are being adjusted out as the drought continues to loom on.

Many fields around the Valley have uneven stands and have taken a beating from all the sandblasting from the constant dry wind, plus the heat we’ve continued to have since the growing season began. Every year is different and growers remain positive, hoping for rain in the near future for our crops.

Cotton: Certain Pests More Apparent Now

The majority of our cotton is squaring. Some late-planted fields came up this week in the cotyledon stage. Any growers with cotyledon cotton might want to check for thrips. This week they have become very abundant in cotton across Hidalgo and Cameron counties, but the majority of cotton is past early growing stages were thrips can cause the most damage. But it’s the cotton fields that just came up that will need to be on top of monitoring for thrip activity.

Cotton aphids seemed to calm down this week in cotton as we noticed several natural enemies of aphids feeding on them in the cotton keeping populations in check. I only came across a few fields where there were too many cotton aphids feeding on the stem and growing point that warranted treatment.

In several fields we also noticed an increase in red spidermite activity. Cotton is most susceptible to injury from spider mites during fruiting periods (squaring) and when the crop suffers water-deficit stress which is what many are experiencing now. Spider mites infest the underside of leaves and feed causing the leaves to dry out and fall.

We noticed fleahopper adults and nymphs in cotton this week from fields in McCook all the way to fields in the Rio Hondo area and fields in-between the mid Valley.

The majority of cotton fields have around 5% – 10% fleahoppers where they are beginning to increase as squaring continues. I was in a handful of fields this week that were on their 2nd, and 3rd week of squaring and those cotton fields had fleahopper activity at around 20% to 30%.

I saw some blasted squares in those fields so it will be very important to monitor fleahopper populations in cotton right now during squaring to protect potential yield as research shows that as many as 85% of total bolls harvested come from squares set during this time period.

Again, when scouting for fleahoppers, each time you sample (weekly is good) check 25 terminals in at least 4 locations of a field starting when the first squares are appearing.

If you notice anywhere from 15 to 25 fleahoppers per 100 terminals with squares being lost (rule of thumb: 10% the first week of squaring, 15% the second week of squaring, and 25% the third week of squaring, with treatment rarely needed after first bloom) treatment is justified.

Grain Sorghum: Sugarcane Aphid Populations Bear Checking

This week was our first sighting of high populations of sugarcane aphids in Cameron County in the Rio Hondo, Bayview and San Benito areas. These particular fields I came across were either just headed out or one was in the flowering stage that had sugarcane aphid consistently throughout the fields in moderate to high populations that warranted spray treatment.

Along Military Highway from Pharr to the Olmitto area, we have been monitoring several sorghum fields and have yet to see any sugarcane aphid populations that warrant treatment. The most we have seen in those areas including mid-Valley through to Lyford area is a few alates (winged) and maybe 5 to 10 nymphs at the most but only on a couple of leaves and certainly Not throughout the entire field.

More on Cotton


I have been seeing ladybugs, syrphids, and some parasitism going on to control SCA populations so please monitor your field and see if it is even necessary to spray.

Corn, Sesame, and Sunflowers

Corn continues to have no pest activity to warrant treatment that I have come across yet. Dryland corn however is struggling to grow as the lack of rain has stunted some corn growth in Willacy County.

Some sesame has been planted in the McCook and Rio Hondo areas and has gotten off to a good stand with no insect pressure yet of any kind. Out in Edinburg and McCook area oilseed sunflowers are standing tall as fields will likely start to bloom within the next two weeks.


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