During field inspections, the first insect activity that stood out was the presence of numerous Blapstinus beetles (Fig. 1). These darkling beetles are about 1/4 inch long, dull brown to black in color, and flightless. They are commonly found moving across the soil surface or hiding beneath soil crusts near the base of cotton plants. Blapstinus beetles feed on young cotton seedlings, typically slightly below or at the soil surface (Fig. 2), and can occasionally contribute to stand loss when populations are high.
 |
| Fig. 1 Blapstinus darkling beetle |
 |
| Fig. 2. Chewing injury to cotton seedling |
We dug around affected plants to assess below-ground injury and recovered several false wireworms from the soil (Fig. 3). Although false wireworm larvae can be difficult to identify morphologically, previous work in Martin County, where similar larvae were reared to adults, suggests these specimens were likely larvae of sand darkling beetles in the genus Eussatus (Fig. 4). These are among the most common false wireworms in the Texas South Plains and are frequently associated with seedling injury, particularly in dryland cotton. The larvae feed below ground on germinating seed, roots, and hypocotyl tissue, resulting in reduced vigor, and skippy stands.
 |
| Fig. 3. False wireworm larva |
 |
| Fig. 4. Sand darkling beetle (photo: Pat Porter) |
When asked about the insecticide seed treatment, the grower indicated that the seed had a "premium" treatment package but was unsure of the specific active ingredients and application rates.
This highlights an important point. Growers should not assume that a premium or elite seed treatment package automatically provides adequate protection against early-season insect pests. Seed treatment trade names often do not always reveal which insecticides are included or the rates at which they are applied. For example, imidacloprid may be included in a package, but the rate can vary considerably. Some treatments contain only storage rates intended to protect seed quality during storage, while others contain field-use rates designed to suppress early-season insect pests. These details are often difficult to find, so growers should verify the active ingredients and application rates with their seed company representative before planting. If stand establishment issues arise, it is also worthwhile to verify exactly what seed treatment package and rates were applied.
There are no effective rescue treatments for wireworms or false wireworms. However, if the observed injury is being caused by Blapstinus beetles, a timely foliar application of pyrethroid insecticide will help minimize additional damage. Foliar applications of systemic insecticides such as imidacloprid will not provide significant benefit against Blapstinus beetles or against below-ground wireworms and false wireworms.
For fields that require replanting, make sure the selected seed treatment package includes a full field-use rate of insecticide. Although imidacloprid seed treatments are primarily intended for thrips management, they may provide some suppression of wireworms and false wireworms and are recommended over no insecticide seed treatment. Additionally, if beetles or wireworm larvae are active in field, an in-furrow application of imidacloprid plus pyrethroid insecticide should be considered.
