True wireworms Aeolus spp., Conoderus spp., Limonius spp.,
Hemicrepidus spp., Agriotes spp., Melanotus spp. and
False wireworms Eleodes spp., Blapstinus spp.
Description. Wireworms and false wireworms are primarily a pest of cotton in the Texas High Plains. There are two types of wireworms found in cotton, true wireworms and false wireworms. True wireworms are commonly called click beetles from the family Elateridae while the false wireworms are termed darkling beetles from the family Tenebrionidae. True wireworm adults vary greatly in size but are usually about ½ inch in length. They are a very hard bodied, elongated beetles that are somewhat rounded towards the head and have a tappered abdomen. When placed on their backs, they will right itself by performing a rapid flexing motion that propels the insect vertically along with a clicking sound. True wireworm adults are usually brownish, grayish or nearly black in color.
False wireworm adults vary greatly in size and shape and are extremely hard bodied. The Eleodes spp. is about 1 ½ inch in length, black and has grooves along its elytra. When disturbed this beetle will often raise its abdomen and appear to be standing on its head. Additionally they may squirt a foul smelling substance to deter predators. These beetles are often referred to as stink beetles. The Blapstinus spp are most common of the wireworm pests infesting Texas cotton. This insect is about ¼ inch in length and about half as wide. They are dull black to reddish-brown in color. The adults are long lived insects able to survive as long as 3 years.
The adults become active in early spring and lay their eggs in the soil in clusters of 10-60. Egg laying continues throughout the summer and into the fall. Larvae produced from the late summer and fall eggs lays overwinter in the soil as well as the adults in leaf litter, stubble or other suitable habitats. True wireworm adults prefer to lay their eggs in moist soil while false wireworms prefer drier soils with some sort of plant cover. Wireworms attacking cotton tend to be most severe following grains crops, especially sorghum, fallow or weedy ground, or in reduced tillage systems.
The larvae of these species are similar in appearance and difficult to distinguish. They are smooth skinned, elongated, cylindrical in shape and measure up to 1 ¼ inch n length. They are creamy white to yellow or light brown in color. Their heads are typically darker in color and they have small true legs clustered near the head and no prolegs. They move by slowly pulling themselves with their leg, dragging their bodies. Wireworm larvae are strictly soil dwelling and will not be seen unless removed from the soil. They feed on decaying vegetation, seeds, roots and other subsurface plant parts. Larval development requires 100-140 days to complete, and pupation another 10 to 25 days.
Damage. Most damage is inflicted by overwintering larvae as they become active in the spring, although adult
Blapstinus spp have been known to girdle or clip seedling cotton off at the soil surface much like a cutworm. The larvae damage cotton by feeding on the root, hypocotyl and cotyledon of plants prior to emergence from the soil. Root feeding can kill plants, but usually results in stunting. The most severe damage occurs when the hypocotyl is severed resulting in plant death and stand reduction. Larvae will also feed on the growing point of the plant causing a loss of apical dominance; these plants often take on a “Christmas tree” appearance after emergence.
Management and decision making.
Cultural management. Wireworm infestations can be minimized through clean cultivation and fallowing. Infestations are most severe in no tillage or reduced tillage situations, particularly following grain crops. Planting shallow and under warm conditions often will allow cotton seeds to germinate rapidly and for plants to outgrow wireworms.
Biological control. There are a number of biological organisms including birds, parasitic nematodes and fungal pathogens that prey on wireworms. The impact of these organisms is not fully understood but undoubtedly important in overall population suppression. Some attempts have been made to utilize commercially available parasitic nematodes for wireworm control in other crops, but success has been inconsistent.
Scouting. In the spring from planting to 4-5 leaf cotton, darkling beetle adults should be watched for invading cotton from pastures, weedy areas, and corn and sorghum stubble. These beetles are only a threat if they cut off the seedling plants resulting in stand reduction.
Scouting for larvae is more difficult and involves bait trapping when the soil is at least 45º F, and at least 3 weeks before planting. A 50:50 mixture of untreated corn and wheat seed should be soaked in water for 24 hours. Approximately 1-2 cups of this mixture should be buried in a 10 inch diameter hole about 6 inches deep. The hole should be back filled with loose soil in a mound, and covered with clear plastic to warm the soil. Stake or cover the edges of the plastic with soil to prevent it from blowing away. Use 8 or more locations per field and mark each sample site with a flag to aid in finding. After 1-2 weeks, each hole should be dug up and inspected for wireworm larvae.
Chemical Control and Action Thresholds. Treat for adult Blapstinus spp only when encountered in large numbers, plant clipping is evident and unacceptable stand reduction probable. Wireworm larvae must be treated preventively. Although there is no recognized threshold for wireworm larvae in cotton, 1 or more larvae per bait trap should raise concern. Seed treatments are the most effective means of preventing wireworm damage.
|Suggested Insecticides and Rates for Managing Wireworms in Cotton
ingredient per acre
|Acres treated per gal or lb of
|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
|—||10.7 fl oz/100cwt||—||4A, NA|
(Gaucho 600, generics)
|—||0.375 mg AI/seed||—||4A|
(Cruiser 5, Avicta Complete)
|—||0.34 mg AI/seed||—||4A|
0.375 mg AI/seed