The biology of Agriotes sordidus Illiger (Col., Elateridae)

Abstract

This paper describes the life cycle, including adult behaviour, oviposition, larval and pupal development rate of Agriotes sordidus Illiger. Each larva passed through up to eight to 13 instars. The larval size range of each instar was defined. Larvae need live vegetable tissues to survive and grow, otherwise most die within 40 days. Resistance to starvation increases with the age of the larvae (last instars can survive up to 1 year without food at 20°C). Each instar passes through three phases: mandible hardening and darkening, feeding, pre-moulting. The intense feeding (damaging plants) phase lasted <25% of the whole development time. They are poliphagous and the rate of larval development does not vary with host-plant type (maize, alfalfa). Provided sufficient soil moisture and food are present, larval development rate strongly depends on soil temperature. The duration of each instar increased with the age of the larvae. No larval growth was observed below 9°C. Under laboratory conditions the average heat sum (above a base of 9°C) required for development from egg to adult was about 3900 DD. Similar results were found in the rearing cages and in the open field. At the latitudes of the regions where this study was carried out (northern Italy, Veneto between 45°34¢00¢¢N and 45°42¢00¢¢N and central-south Italy, Molise, between 41°49¢720¢¢N and 41°56¢501¢¢N) the 6th instar (which normally is the first one passing 10 mm in length) is attained by September of the same oviposition year. Pupae can be found between the end of May and September mostly in the upper soil layer. Their transformation into adults took about 16 days at 25°C. Larvae of different stages overwintered by burrowing deep into the soil. Vertical migrations during the year are described: they depend mostly on soil temperatures from October to early spring. The adults overwintered and laid eggs in the subsequent spring. At lower latitudes or in warm seasons most of the population completed its life cycle (from egg to egg) in 24 months over three calendar years. At more northern latitudes, part (sometimes most) of the population completed the whole life cycle in about 36 months over four calendar years.

Management of wireworm damage in maize fields using new, landscape-scale strategies

“…Finally, crop damage was estimated for each field. The most problematic click beetle species in maize in France belong to the genera Agriotes, which lay their eggs in clumps in the spring for several months (Furlan 2004;Parker and Howard 2001). Larval populations can be either strongly aggregated or randomly distributed (Cherry and Stansly 2008;Salt and Hollick 1946), possibly in relation to their age (Doane The last column indicates whether the variable was included in the final (best) model according to the employed selection procedure.…”

“…Taken altogether, these results indicate that the longterm effect of the presence of a grass ley in the fields' past was only slightly influenced by the present rotation sequence. This effect can be attributed to the capacity of wireworms to endure long periods of starvation (Furlan 2004) and to feed on a large variety of plants (Traugott et al 2008) or to adapt their diet to available plant diversity (Schallhart et al 2012). Thus, our findings suggest a strong inertia in the distribution of wireworm populations.…”

“…Due to the multiannual biological cycle of wireworms (Furlan 2004;Parker and Howard 2001), crop rotation is considered a good agricultural practice for controlling damage when it includes nonhost plant species. Wireworms preferentially live in grasslands that provide favorable conditions for eggs and larvae in terms of moisture, soil temperature, and nutrient resources (Furlan 2004;Miles 1942;Parker and Howard 2001).…”

“…Wireworms preferentially live in grasslands that provide favorable conditions for eggs and larvae in terms of moisture, soil temperature, and nutrient resources (Furlan 2004;Miles 1942;Parker and Howard 2001). However, when no suitable plant species are present, wireworms can still survive starvation by feeding on organic matter (Gough and Evans 1942).…”

Preventive application of an entomopathogenic fungus in cover crops for wireworm control

“…In many of these crops, wireworms are not necessarily the most destructive insects, but are among the most difficult to control, particularly because of their long life cycle and overlapping generations, their polyphagous nature and their adaption to a wide range of agricultural ecosystems, including grassland and arable crops (Furlan 1998;Ritter and Richter 2013;Sonnemann et al 2014;Sufyan et al 2014;Traugott et al 2013Traugott et al , 2015. Wireworms are also able to react quickly to changes in abiotic conditions with vertical migration to depths of 50 cm or more (Fisher et al 1975;Furlan 1998Furlan , 2004Schaerffenberg 1942). This behaviour often reduces the efficacy of short-term control attempts, which are typically applied to upper soil layers.…”