Texas Blacklands: Fleahoppers in Cotton, Start Scouting for Sugarcane Aphids

Photo: Stephen Biles, Texas AgriLife Extension

GENERAL

Wheat harvest wraps up for a lot of farms last week, and yields reports have been average to higher, but bushel weights and quality took a hit after all the rain. Corn, Cotton, and Sorghum remain growing under good conditions.

Earworms are starting to show up in corn, and on sorghum heads in some of our earlier planted sorghum fields.

Thrips and fleahoppers are still hanging around area cotton fields in high numbers, as fields became dry enough to run a ground rig last week. The first bollworm eggs were found on Monday (6/17).

COTTON

Cotton is ranging from 1st true leaf to as late as 1/3rd grown square. High populations of thrips have been observed in young cotton, with average thrips per true leaf averaging 1.5 thrips per true leaf across all susceptible fields in the scouting program. Most of our cotton fields have been sprayed at least once for thrips, and thrips will remain a pest until cotton beings to set squares which usually happens around the 5th true leaf stage.

The economic threshold for thrips in Texas is 1 thrips per true leaf, so if you are finding 2 thrips per plant on two leaf cotton, the economic threshold has been reached. Acephate has been the common insecticide applied, but other labeled insecticides include, dicrotophos (Bidrin 8 and generics), Spinetoram (Radiant SC), and dimethoate.

Cotton fleahopper are still being found in area fields that are squaring. Two weeks ago, fleahoppers were found in some earlier planted cotton in the scouting program that was averaging over 1 fleahopper per plant, well above the economic threshold of 10-15 fleahopper per 100 terminals. This past week fleahopper numbers were back at the economic threshold with fields averaging 12 fleahoppers per 100 terminals.

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There are several insecticides labeled for fleahopper control in cotton which includes, acephate (Orthene 97 and generics), acetamiprid (Inturder Max 70WP and generics), flonicamid (Carbin 50WG), thiamethoxam (Centric 40WG), imidacloprid (Alias 4F and generics), and dicrotophos (Bidrin 8 and generics). Fleahoppers will remain an economic pest of cotton until fields start to bloom.

Cotton aphids are hanging around in area fields but remain well below the economic threshold of 40-70 aphids per leaf. Fields that are being sprayed for thrips or fleahoppers should select insecticides based on the number of aphids present in the field.

Fields with aphids present that need to be sprayed for either thrips or fleahoppers should be sprayed with an insecticide that is soft on our beneficial insects. This will preserve our beneficials in the field and help keep our aphid populations below the economic threshold.

Bollworm egg lays in cotton are here, while scouting fields around Whitney eggs I was finding eggs laid in the upper 1/3rd of the plant. These eggs are not very abundant but indicates the start of bollworm scouting in cotton. The fields with eggs present also had a good number of minute pirate bugs that can help control the larvae when they hatch.

SORGHUM

Sorghum growth stages range across the area with the early planted fields starting to head out, while some field fields were planted late to a short maturity hybrid. Sugarcane aphids are present in area sorghum fields but remain well below the economic threshold since finding them in sorghum by the Hillsboro Municipal Airport on May 15th.

I have found sugarcane aphids in fields around the following towns/communities: Lovelace, Milford, Irene, and Abbott. If you are growing sorghum it is time to start checking fields at least weekly until sugarcane aphid populations start increasing. The economic threshold for sugarcane aphids is sorghum is an average of 50 aphids per leaf.

Recommended insecticides include flupyradifurone (Sivanto Prime) and Transform which received a Section 18 label for the 2019 growing season.

CORN

The corn crop around the area is moving along nicely with very few pest issues to date. I am starting to find corn earworm larvae in corn ears around Hill County. They are being seen in both Bt and non-Bt corn ears. It is not surprising to me that I am finding earworm larvae in Bt corn as we have document resistance to a number of Bt toxin used in corn, but if you are seeing large numbers of earworms making through Bt corn please let me know as I would like to at least look at the field.

Some corn disease has been observed in area corn fields as well but are not to a level where we would see an economic loss. I have seen both northern corn leaf blight and common rust in area corn fields, but the severity of both diseases has remained low. Common rust rarely causes an economic loss, but southern rust can cause an economic loss in corn.

I have not seen southern rust in corn fields yet, but infection process could be taking place right now, thanks to the rains received yesterday afternoon.


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