Wireworm populations in relation to crop production: I. A large‐scale flotation method for extracting wireworms from soil samples and results from a survey of 600 fields

Abstract

The wireworm survey in the Eastern Counties revealed many cases where the observed wireworm damage failed to correspond with the estimated field population. A possible explanation for this was the inaccuracy of counts made by picking wireworms out of the soil samples by hand. Tests showed that such methods recovered an extremely variable proportion of the wireworms in the‐ samples and, on the average, only two‐fifths of the larvae were obtained. A modified form of the washing and flotation technique used by Salt & Hollick (1944) was introduced for large‐scale work and is described. By this method, ten samples of soil (4 in. diam. and 6 in. deep) bulked together are examined at a time and can be dealt with at the rate of 13 samples per man per hour with an efficiency of 95‐100% in the extraction of wireworms. The populations estimated on 600 fields sampled between December 1942 and May 1943 have thrown more light on the size and composition of the wireworm population in grass and arable fields. Inspection of the crop results on fields tested by the washing process showed a much closer relationship between wireworm population and wireworm damage than had been obtained by the hand‐sorting method in the previous year.

The biology and management of wireworms (Agriotes spp.) on potato with particular reference to the U.K.

“…The conclusion was that sampling based on 20 Q 10 cm diameter cores for a 4±10 ha ®eld was the most ef®cient method for estimating wireworm abundance (Anon, 1948). This technique, allied with devices for extracting invertebrates from soil bȳ otation (Salt & Hollick, 1944;Cockbill et al, 1945), was widely used during the extensive wireworm surveys done in the U.K. in the 1940s. However, this technique is subject to signi®cant sampling errors (Yates & Finney, 1942), particularly when wireworm abundance is low.…”

Chemical Control of Leatherjackets (Diptera: Tipulidae) in Grassland

“…In most trials leatherjackets were extracted from soil cores using the same method for pre-and post-treatment samples. For many sites extraction was hy washing, using either the modified Salt and Hollick method {Cockbill et al, 1945) or the Bristol method (Mayor and Browne, 1964). At Cwmbelan, Cilcennin andPonterwyd, 1974/75, andat Cwmbelan, Monknash andSwyncombe, 1975/ 76, samples were hand-sorted and checked; at Monknash, 1974/75, leatherjackets were extracted by applying heat from below; and at Hexham, 1975/76, the Biasdale heat extraction method was used (Blasdale, 1974).…”

Wireworm Distribution in East Anglia

“…Samples, usually twenty in number, were taken from each field with a 4-inch diameter soil corer (Anon, 1944), either before or after ploughmg. The depth ot each sample was normally six inches in unploughed grassland, and where already ploughed to just below the depth of ploughing-usually about mne inches The wireworms were extracted from the soil by the flotation process, which has been fully described by Cockbill, Henderson, Ross and Stapley (1945). Most of the samphng was done during the autumn and winter, and the samplmg year started in September.…”