Consider using preventative insecticide seed and at-plant treatments to manage wireworms in cotton

Wireworms are a common pests of seedling cotton across the High Plains and Rolling Plains regions of Texas. Increased wireworm abundance over the last decade or so is partly due to reduced use of broad-spectrum insecticides such as aldicarb (currently available under the trade name AgLogic) and to some extent due to the increased adoption of cover crops and conservation tillage practices in the agricultural landscape. All wireworm species, including true (larvae of click beetle) and false (larvae of darkling beetle) wireworms, inflict damage as worms or immature stages that live exclusively underground. One genus of darkling beetles i.e. Blapstinus, however, can also cause damage as an adult. Often, during drier years, these beetles (~1/4 inch long) migrate from nearby grasslands, and fallow fields to cotton and cause damage by chewing on stems of young and tender seedlings at or slightly below the soil surface.

The incidence of wireworm is more severe in fields with known history of its infestation, those followed by grain crops such as sorghum and wheat, and the fields planted with no insecticide seed treatments. In my observation, wireworm infestation and injury level tend to be much higher in fields that are planted with untreated seed consecutively for more than two years. Although there are no insecticide seed treatments that are specifically labeled for wireworms in cotton, those used for other early-season insect pests such as thrips (e.g. neonicotinoids) do offer some level of wireworm suppression.

There are no rescue treatments for wireworms. Therefore, it is critical to make sure that you are getting a seed treatment package that has the full rate of insecticide (e.g. imidacloprid). Although almost all commercially available cotton seeds come treated with fungicide, they would not necessarily be treated with an insecticide. In addition, some companies have insecticides applied to seeds at a very low rate to protect seeds from storage pests. Such treatment at storage rate will not provide any control against pests in field condition. Different companies provide different combinations of fungicide, insecticide and nematicide active ingredients in their seed treatment product portfolio and it is important that you pay close attention to what you are getting when you opt for a certain package. For instance, under Acceleron brand (Bayer CropScience), the basic treatment (Acceleron Basic) comes with no insecticide, while the Acceleron Standard and Acceleron Elite both have imidacloprid (0.375 mg ai/seed) as an insecticide component. Similarly, BASF offers their Core Seed Treatment Package with imidacloprid at only storage rate (4.7 oz/ 100 lbs seed) and to get the full rate of imidacloprid (0.375 mg ai/seed or ~11 to13 oz/100 lbs seed), you need to get their Prime Seed Treatment Package. Whatever brand of seed you choose, if you are considering seed treatments for managing early-season insects, make sure the seed treatment package you select has a full rate of insecticide active ingredient.

In addition to seed treatment, I would also suggest using at-plant treatments such as in-furrow application of Admire Pro, AgLogic, or pyrethroids (e.g. bifenthrin) in fields where wireworms have been an issue in the previous year/s. These products are labeled for use in cotton for early-season insect pests such as thrips and aphids and have wireworm activity. Considering the long life cycle of these worms (3-4 years), it is very likely that they will be there for next season if were present in the past.   

Table. 1. Insecticide ingredients of selected seed treatment packages in cotton.

Company	Cotton Seed Brand	Seed Treatment Product Trade Names	Insecticide Active Ingredient (at standard rate)
Bayer CropScience	DeltaPine	Acceleron Basic	none
		Acceleron Standard	imidacloprid
		Acceleron Elite	imidacloprid
BASF	FiberMax, Stoneville	Core Seed Treatment Package	none*
		Prime Seed Treatment Package	imidacloprid
Corteva AgriScience	PhytoGen	PhytoGen TRiO	imidacloprid
Americot	NexGen	CottolyST Base	none
		CottolyST IMI+	imidacloprid, acephate
		CottolyST Enhanced	imidacloprid, acephate
		CottolyST Premier	imidacloprid
Syngenta		Avicta Elite Cotton	imidacloprid + thiamethoxam
*imidacloprid at storage rate

 

Darkling beetle, Blapstinus sp. (photo: Pat Porter)

Wireworms (photo: Pat Porter)