10. Control of Wireworms - 1998
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10. CONTROL OF WIREWORMS - 1998 Back to contents 10.1 SUMMARY 10.2 DAMAGE CAUSED BY WIREWORMS 10.3 CULTIVAR SUSCEPTIBILITY 10.4 POTENTIAL FOR USE OF FOOD BAITS FOR DETECTION OF WIREWORMS 10.5 CONTROL OF WIREWORMS CONTROL OF WIREWORMS 10.1 Summary Wireworms may cause direct damage to potato tubers and may also provide entry holes for other pests. Potential damage may increase with later dates of harvest. Cultivars may differ in susceptibility to wireworms but there are few data available. Traps may provide some indication of the potential problem from wireworms but the traps need to be buried in soil. 10.2 Damage caused by wireworms Wireworms are larvae of click beetle, of which there are 60 species in the U.K. The three major species causing damage are Agriotes lineatus, A. obscurus and A. sputator. Other damaging species are Athous haemorrhoidalis and Ctenicera spp. Wireworms are particularly abundant in grassland but will also attack cereals and root crops. The wireworm lifecycle lasts for four years, including larval stages in each year and infestations may therefore persist in crops following grassland (Jones and Jones 1977, Pests of Field Crops). Wireworms damage potatoes by making deep tunnels into tubers and leaving small round holes on the surface. These provide access holes for other pests such as slugs and cutworms. There are indications that later the time of harvest, particularly after September, the greater is the potential for damage. 10.3 Cultivar susceptibility It has been suggested that cultivars differ in susceptibility to attack by wireworms but only very limited data are available (Table 1). It was also suggested that cultivars with a high glycoalkaloid content may be more likely to be resistant, while those with a low glycoalkaloid content may be more likely to be susceptible. The glycoalkaloid content of tubers from a number of cultivars is shown in Table 2. Table 1. Susceptibility of potato tubers to wireworms Cultivar Resistance ? Glycoalkaloid content Rosamunda Susceptible moderate Maris Bard Susceptible low Silla Resistant moderate Ulster Chieftain Resistant high Jonasson and Olsson (1994) Table 2. Glycoalkaloid content of whole potato tubers of various cultivars. Cultivar Glycoalkaloid content (mg / 100 g fresh weight) Bintje 6.2 Cara 4.6 Desiree 6.6 Diana 5.5 Foxton 5.9 King Edward 5.2 Maris Piper 4.2 Pentland Crown 5.9 Pentland Dell 10.3 Pentland Ivory 7.5 Pentland Squire 6.0 Record 6.2 10.4 Potential for use of food baits for detection of wireworms Traps are an accepted method for estimating the potential slug problem within a field. Experiments have attempted to assess the potential of traps for detecting wireworms (Parker 1994). Three methods of detecting wireworms were investigated: soil cores, holes dug in soil and sealed, baited traps. Soil cores were found to be an inefficient method of detecting wireworms and accounted for only 8 % of the total number captured. Holes in soil were approximately 10 cm square and were dug to a depth of 30 cm. The holes were then baited with various materials but were found to be less effective than were baited traps. The sealed, baited traps comprised 350 ml plastic beakers with lids attached. Twenty four 4 mm holes drilled in the side and six in the bottom of each beaker. The beakers were then baited with the same materials as the soil holes and were buried to a depth of 30 cm. The baited traps captured the highest numbers of wireworms but baits differed in efficacy. Approximately 70 % of the total number of wireworms were captured in holes or traps using cereal baits of wheat and barley or wheat and maize mixtures. Only 20% were captured with vegetable baits of carrot or potato, the remainder being from soil cores. Unfortunately trap and hole catches cannot be used to calculate the density of wireworms per unit area and not all wireworms will be recovered by these methods. However, traps may provide a better presence or absence test or a better indication of numbers than do soil tests. 10.5 Control of wireworms The only chemicals recommended for control of wireworms in potato crops are ethoprophos and phorate. Ethoprophos should be incorporated into soil to a depth of 10 - 15 cm depth before planting, while phorate may be incorporated into soil or applied as a foliar treatment. Back to top Back to contents.