Wireworms

True wireworms Aeolus spp., Conoderus spp., Limonius spp.,
Hemicrepidus spp., Agriotes spp., Melanotus spp. and
False wireworms Eleodes spp., Blapstinus spp.

Wireworms (click beetle larvae) and false wireworms (darkling beetle larvae) are cotton pests in the Texas High Plains (Figs. 10 and 11).

The larvae of these species are very similar, and it is difficult to distinguish wireworms from false wireworms. They are hard-bodied, smooth-skinned, elongated, cylindrical, and up to 1¼ inches long.

Creamy white to yellow or light brown, their heads are typically darker with small true legs clustered near the head and no abdominal prolegs (Fig. 12). They move by slowly pulling themselves with their legs while dragging their bodies. Wireworm larvae are soil-dwellers, and you will not see them unless you remove them from the soil. They feed on decaying vegetation, roots, seeds, and other subsurface plant parts.

Wireworm attacks on cotton (including wireworms and false wireworms) tend to be most severe following grain crops (especially sorghum), in fallow or weedy ground, or in reduced-tillage systems. Overwintering larvae inflict the most damage as they become active in the spring. However, darkling beetle adults have been known to girdle or clip seedling cotton off at the soil surface much like a cutworm (Fig. 13).

The larvae damage cotton by feeding on the root, hypocotyl, and cotyledon of plants before the plants emerge from the soil. Root feeding can kill plants but usually results in stunting. The most severe damage occurs when the hypoco- tyl is severed, killing the plant and

reducing the stand. Larvae also feed on the growing point of the plant, causing a loss of apical dominance. These plants often have a Christmas tree appearance after they emerge (Fig. 14).

Management and Decision Making

In the spring, growers, scouts, and consultants should look for darkling beetles and their damage from planting to the four- to five- leaf stage. Darkling beetle adults can enter cotton fields from corn, pastures, sorghum stubble, or weedy areas. These beetles are a threat only if they cut off the seedling plants, reducing the stand (Fig. 15).

Chemical Control and Action Thresholds

Minimize wireworm infestations through clean cultivation and clean fallowing. Infestations are most severe in no-tillage or reduced-tillage situations, particularly following alfalfa, cover crops, or grain. Planting shallow and under warm conditions often allows cotton seeds to germinate quickly so plants can outgrow wireworm injury potential rapidly.

Treat wireworm larvae preventively. Insecticidal seed treatments are the most effective way to prevent wireworm damage. Treat for darkling beetle adults only when they are present in large numbers, plant clipping is evident, and unacceptable stand reduction is probable.

 

Suggested Insecticides and Rates for Managing Wireworms in Cotton
Insecticide (Trade name)	Lb active ingredient per acre	Amount of formulated per acre	Acres treated per gal or lb of formulated	Mode of Action Group (IRAC)
Foliar sprays for wireworm adults
Pyrethroids—see individual labels for information				3A
Seed treatments for wireworm larvae
Clothiadan/Bacillus firmus I-1582 (Poncho/Votivo	—	10.7 fl oz/100cwt	—	4A, NA
Imidacloprid (Gaucho 600, generics)	—	0.375 mg AI/seed	—	4A
Thiamethoxam (Cruiser 5, Avicta Complete)	—	0.34 mg AI/seed	—	4A
Imidacloprid, Thiodicarb (Aeris)	—	ea. at 0.375 mg AI/seed	—	4A, 1A