Do I Need to Apply an Insecticide to Manage Early-season Corn Insects? - South

Some insects that injure corn seed or seedlings can be difficult to manage as there are no sampling programs developed and/or no rescue treatments available to respond to economic damage.  As often is the case with these pests, plant injury after the fact is often the only clue of the presence of the pest. The insecticide component of seed treatments available from Acceleron® Seed Applied Solutions can provide excellent control against some early-season pests that feed directly on the seed or seedling, such as seed corn maggot, seed corn beetle, and southern corn rootworm, for which there are no sampling programs or rescue treatments available. 

What insect pests can attack corn seed in my area?

 

While it is difficult to predict which, if any, early-season insect pests will cause economic injury, there are some situations where the risk of injury is increased. For example, fields coming out of sod or grass mixed stands of alfalfa are at higher risk of injury by white grubs, billbugs, sugarcane borer, Japanese beetle grubs, and wireworm.  Fields that are high in organic matter (manure applied or cover crop termination) and were tilled close to planting are at higher risk of injury by seed corn maggot and seed corn beetle. The destination of black cutworm moths, which migrate from Southern Texas and Mexico, is determined by the direction of the wind. So, while winter annual weeds are highly attractive to the females to deposit eggs, if the females are not in the area, a field with these weeds is at low risk as the moth is not present. 

While field history is not always a predictor of future injury, if a field or specific area on the farm has had a history of economic injury by a particular pest, it should be considered in the decision-making process as risk is assessed. 

Can planting time influence the type of insect pest and the pest levels?

 

Planting time can impact both the species of insect as well as the density.  For example, early planting may decrease the risk of injury by black cutworm, billbugs, and chinch bugs but increase the risk of injury by seed corn beetles and wireworms by planting at a time when temperatures are cooler, delaying seedling emergence. 

What other factors can contribute to higher risk of early-season injury?

 

As mentioned above, previous crop and planting date can influence both the species of the insect pest and risk of injury. Other factors include soil type and weather. Sandy or course textured soils are associated with a higher risk of injury by lesser corn stalk borer, particularly under dry conditions and when corn is planted late. Corn produced in reduced tillage systems is more at risk from stink bug and corn flea beetles, but less so from lesser corn stalk borer, seed corn beetle, and seed corn maggot.  

What should I look for when scouting for some of these pests?

 

Often with insect pests of the seed or seedling, the first clue is reduced stand or reduced seedling vigor. Black cutworms hide under clods of dirt or just beneath the soil surface, so gently looking under clods or using a hand rake to “till” the soil can help to find the larvae. A pocket knife is helpful to remove soil near the base of the seedling to look for injury to the stem. On very hot days, stink bugs seek cooler conditions in soil cracks and under debris, making detection difficult. 

Is there a rescue treatment tactic that I can use for the early-season pests?

 

For some insect pests that attack the seedling, such as black cutworm, billbugs, and stink bugs, sampling programs and thresholds are available. Farmers should consult their location extension office for  recommendations. However, for many early-season pests, sampling programs and treatment thresholds have not been developed. Table 1 provides a summary of the major early-season corn insect pests in the southern states. 

For more information on corn cutworms, please read Management of the Most Common Cutworms.

 
Sources:

Reay-Jones, F. 2019. Corn insect control. South Carolina Pest Management Handbook for Field Crops. https://www.clemson.edu/extension/agronomy/pestmanagementhandbook19.pdf/2019_PMH_CornInsectControl.pdf

2 Akin, S. A guide for scouting insects of field corn in the Mid-Southern U.S. University of Arkansas Extension. http://www.utcrops.com/corn/corn_insects/pubs_pdf/CornScoutBooklet-Web.pdf

3 Reisig, D. 2014. Stink bugs in corn. North Carolina State University Extension. https://entomology.ces.ncsu.edu/2014/07/stink-bugs-in-corn/

 

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