Texas High Plains Cotton: More High Winds and Hail, Still Dry

Cotton field hit by hail. Photo: Jourdan Bell, Texas A&M AgriLife Extension Entomologist

General Status

For another week, our fields were windblown and dry, unless hail stones fell. Although we did have a few days without constant high winds allowing some area fields to make strides in recovery, beneficial rains eluded all of us. Instead, we received extreme winds that came with a few area night storms.

For the third straight week at least, if any appreciable rains fell from these storms, it came with hail that destroyed even more crops. Weed pressure renews again this week, pest populations linger opportunistically, while some cotton and grain fields develop with fertilizer and possibly PGR needs.

Cotton

Our PPM scouting program cotton ranged in stage from wildcat replanted emergence up to large match head square stage. Most fields fell between large pin head squares to match head. Only a handful of fields were still susceptible to thrips damage with no fields at ET (economic threshold) for this pest.

Our per true leaf thrips counts ranged from 0.02 up to about 0.8 with the thrips starting to tapper off behind treatments, finding better host plants, or with cotton developing past economic thrips damage.

Plant bugs are our next pest of note. On cue, fleahoppers are showing up in our data sets. No field was at threshold this week, but about 1/4 to 1/3 of our fields had some fleahoppers found. Most of our fields are still too young and small for drop cloth or sweep net collection and whole plant inspection re-mains our only method of plant bug detection for these fields.

Our highest whole plant inspection fleahopper population came in at 25% terminals infested with 9.94% square drop, most of which was determined to be weather related.

In our more advanced fields where drop cloths could be utilized along side plant inspections, our highest fleahopper population was 1 fleahopper / 11.2 row feet with 9.82% square drop, also mostly due to weather. The majority of fields held no fleahoppers and 2-7% square drop, all of which was weather related.

On an ‘average’ season, about 25% of our fields will reach ET for plant bugs before 1st bloom. While we have not found any Lygus in our fields yet, this year’s plant data already looks in line with our ‘average’ treatment need based upon our early fleahopper numbers assuming the population continues to advance without beneficial intervention.

It will take diligent field scouting to identify which fields will require treatment and which ones will not. Our ET for fleahoppers for this stage of cotton remains 35% terminal infestation with about 10% plant bug caused square drop or 1 fleahopper / 1.5-2 row feet with the same 10% square drop (or 90% retention conversely).

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This amount of fruit loss is cumulative up to bloom stage to about 25% drop due to the plants ability to replace some of the earliest lost squares.

Some of our older fields are starting to show a quick increase in predator populations. This was a distinct concern of mine following our widespread treatment of wheat for cutworms in early spring/late winter and our need for multiple thrips treatments early in our cotton’s development this season.

While later fields have few if any beneficials in-field, our older fields are starting to host notable minute pirate bugs, big-eyed bugs, increased spiders, and ladybugs. All are good fleahopper predators.

Corn and Sorghum

Our scouting program corn ranges in stage from still to be planted seed up to V12 (or possibly VX with weather damage on lower leaves adding difficulties in stage determination). Our youngest corn we have actively growing is V2 stage.

Our sorghum ranges in stage from seed to V8 stage with the youngest established field at V4. We still have no pests of note in either crop.

We did find one lone fall armyworm whorl feeding site in our older seed milo field and some corn leaf aphids. Do not mistake these aphids for the infamous sugarcane aphid. In addition to several dichotomously noted differences, the corn leaf aphid will typically be found feeding near, in, or around the whorl while the sugarcane aphid will establish much lower on the plant.

We actually like to see the corn leaf aphid this early in either sorghum or corn as beneficial populations will build on them without any economic damage accumulating. It takes about 1,500 corn leaf aphids per leaf to reach ET.

While this is no problem for the sugarcane aphid, the corn leaf aphid cannot reproduce anywhere near that rate, nor is their feeding nearly as severe. Any economic situation from the corn leaf aphid would come from the honeydew accumulation in the whorl physically ‘gluing’ the whorl together preventing new leaf establishment. This is very, very rare.

While we view the establishment of corn leaf populations as a great food source for predators that we will need later for more damaging pests, seeing them this early is an indication that any insecticidal seed treatment used for the early control of aphids is paying out.

We should now be on the lookout for greenbugs, yellow sugarcane aphids, and even the sugarcane aphid itself (although none have been spotted near us so far).

Our bollworm moth trap catches have been miniscule so far in 2020 with less than 5 moths per week. We are also having trouble keeping the traps in good shape due to weather and possibly even some human tampering. For the first 4 weeks of trapping, our Hale trap has 2 weeks with missing data.

Dr. Porter’s fall armyworm traps in Lubbock were very high most of this week, indicating we could see a sharp increase in fall armyworms in our sorghum and non-Bt corn over the coming weeks. For whorl stage sorghum or corn, it takes 25-35% foliage loss be-fore the damage becomes economic.




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