Texas LRGV: Cotton Blooming; Sugarcane Aphid in Grain Sorghum

Sugarcane aphid colony on underside of sorghum leaf. Photo by Dr. Mo Way

It’s been very hot, dry and windy (at times) across the Lower Rio Grande Valley. Temperatures have been in the high 90s and at night anywhere from 78F to 80F. I noticed many growers irrigating their cotton this week or setting up to do so. Those with dryland cotton are starting to see the effects/stress from the heat on the plants as well as other dryland crops.

Cotton

A lot more cotton is blooming across the Valley this week. Many growers are starting to apply the first round of mepiquat treatments.

Fleahopper adults continue to be persistent in low numbers overall but I did notice new hatch of nymphs in the La Villa and Lyford areas where we were checking. Persistent monitoring and control of fleahoppers is necessary for optimum yield potential.

I received a couple of reports of false chinch bugs causing trouble along field edges in blooming cotton where control was needed. Basically, any pyrethroid labeled for cotton will control false chinch bug populations and usually will need to only apply to field margins where they have migrated in and started feeding. They are easy to spot along a field because they congregate in large groups like a little army taking over. According to my counterparts in Lubbock,  acephate has been proven effective in controlling false chinch bugs even though the pest is not listed on the label.

We are seeing very few whitefly adults in cotton and I have yet to see any nymphs present. For those who are in areas though were whitefly pressure becomes prevalent it’s time to consider starting a preventative spray treatment program to keep populations from developing once whitefly adults are present. A few red spidermites were in a couple of fields this week but nothing worth spraying. Cotton aphids are still present very low numbers from last week to this week. Our usual ladybug and scymus beetle predators are taking care of them.

Bollworm Resistance

In parts of Texas we have found evidence of bollworm resistance to one or more Bt genes in our Bt cotton. Fortunately for South Texas we have not seen or experienced increased bollworm pressure. A couple of consultants have seen one or two bollworms present in cotton this week but nothing out of the ordinary.

If you have a Bt cotton field with bollworm pressure possibly needing to be sprayed, please contact me at 956-968-5581 so we can collect the larvae if need be. We would like to be ahead of any resistance issues and are asking for your cooperation in protecting our cotton crop.

Grain Sorghum

Most grain sorghum is maturing from soft dough to hard dough stage and coloring nicely as the seed matures.

I received reports or this week of  sugarcane aphid infestation in a few grain sorghum fields. Over the last two weeks many sorghum fields were treated for the first time for sugarcane aphid pressure. Sugarcane aphid populations are currently moderate. I do expect another population peak prior to harvest during the third week of June. Please be mindful of this as we make our way to harvest.

Sorghum  in northern Cameron county was sprayed for headworm pressure this week but overall, I have picked up on very little to none headworm pressure across the Valley. I have seen some rice stinkbug adult and nymphs present but nothing that warrants treatment. For those who have flowering sorghum I have yet to see any midge.

Sesame

This week I did find mirids (Nesidiocoris tenuis) in sesame. Mirids are a type of plantbug that suck plant juices and can cause necrotic damage and stunting of growth to the sesame plant.

N. tenuis mirids adults and nymphs are lime green in color measuring no more than 5mm in size so fairly small and the adults when their wings are closed make a heart shape that upon close observation is easy to spot.

Necrotic damage will look like a reddish/brown scaring to the plant tissue along the stem, leaves and on the seed pods. Mirids N. tenuis also can be predators to whiteflies feeding on them sometimes in the lower canopies of the sesame when present. However, mirids can develop successfully on the sesame plant alone and will feed on the plant more when they have depleted their food source (in this case whiteflies) or there is an abundance in populations.

I have noticed some high populations of mirids in sesame along the river in the Donna and Pharr areas. Mainly what I noticed first was the coloration of the sesame plant (yellowing on the leaves and brownish necrotic damage) and the curly under of the leaves which are signs of high mirid pressure feeding on the plants. I have also picked up on light populations in the Weslaco and La Villa areas. You will want to monitor for mirids and treat if necessary since there feeding can hurt yield potential. Products labeled on sesame that control mirids are Transform and Mustang Maxx. Some growers have also had some worm pressure. Prevathon is labeled for use on sesame.


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