Corn Leafhoppers. Photo by S. Biles

There are several growers who have planted corn crops for fall production. Much of the fall corn is sweet corn crops but other purposes exist as well including tourism. Insect issues can be more severe for fall planted corn and the crops should be monitored for pest insects.

The three more likely insect pests that may develop into problems include fall armyworms, corn leaf aphids and corn leafhoppers. The corn leafhopper is the insect of greatest concern; not just because of what it can do to the current crop, but we also need to be thinking about the overwintering populations.

Corn Leafhoppers were also an unusual insect pest for 2024. The added challenge to the corn leafhoppers is the primary issue is corn plant disease so developing an economic threshold may not be viable.

Corn Leafhopper Damage. Photo by D. Kerns

Corn Leafhopper Damage. Photo by D. Kerns

Two weeks ago, I visited a corn field near College Station that was planted late in the spring. This field had heavily diseased plants and was not going to produce any grain.

The challenge with providing solutions to this pest is there are some things we do not know. If corn leafhoppers are vectoring the diseases responsible for corn stunt, you do not want any of them in the field. The problem is there is no way to know if they are vectoring the disease.

Management suggestions from South America include:

1. Control leafhoppers found prior to V9, treatment may be prevent yield losses.
2. Eliminate volunteer corn plants for at least 90 days prior to planting the spring crop. This is because the insect requires corn for reproduction and the insect does not live longer than 90 days.

Insecticidal seed treatments are expected to manage aphids and leafhoppers for three weeks post-planting. It is advisable to scout corn fields in South Texas for insect pests such as the fall armyworm, corn leaf aphid, and corn leafhopper.  Insecticides labeled for control of leafhoppers in corn include: Sivanto, Pyrethroids, Azadirachtin, Carbaryl, and Malathion.

Corn Leaf Aphids. Photo by S. Biles

Corn leaf aphids are found every year in corn and sorghum fields without becoming a yield limiting pest. This year, in April and May, we saw aphid numbers rise to alarming levels, likely resulting in yield losses.

Fall armyworm is usually managed by growing a Bt corn hybrid. The fall armyworms tend to be effectively controlled with the Bt corn. If a Bt hybrid has not been planted, control is possible with several insecticides including those containing Chlorantraniliprole (Vantacor or Beseige) and pyrethroid insecticides.

The 2024 MidCoast IPM corn leafhopper summary can be found at the two links below:

Corn Leafhoppers | Mid-Coast IPM (agrilife.org)

Leafhoppers in Corn: Update | Mid-Coast IPM (agrilife.org)

Corn leaf aphid was discussed here: Corn Leaf Aphids in Corn | Mid-Coast IPM (agrilife.org)