Effects of selected pesticides on web building behaviour of Larinioides sclopetarius (Clerck) (Araneae, Araneidae)
1994
Lengwiler, U. (Swiss Federal Institute of Technology, Zurich (Switzerland). Entomological Inst.) | Benz, G.
Sublethal effects of four pesticides (Pirimor(R), active ingredient (a.i.); pirimacarb Decis(R), a.i. deltamethrin; Alaxon(R) D, a.i. diazinon; Kelthane(R) EC, a.i. dicofol) on the web building behaviour of the common gray cross spider Larinioides sclopetarius (Clerck) were investigated with the spider test of Witt and Peters. Pirimicarb applied in a dose of 0.64 mig/mg (corresponding to the application of 1.28 mig/mg Pirimor(R)) caused neither mortality nor aberrations in web geometry. Alaxon(R) D led in a dose of 5 center dot 10(-4) mig/mg to a mortality rate of 17.6 %. Web building activity was only slightly affected. The webs themselves showed some changes. The area of the webs was reduced to 62 % of the original size. The regularity of the catching spiral and the median angles of the radii were also affected but in a lesser degree. Decis(R) applied in a low dose of 5 center dot 10(-5) mig/mg caused 10 % mortality. Web building activity was affected (average delay in web building was 2.32 days). The area of the webs was reduced to 72 %, the number of radii was reduced by 17 %, the median angle of the radii was enlarged by 21 % and the regularity of the angles was reduced by 36 %. Kelthane(R) EC, in a high dose of 9.6 center dot 10(-3) mig/mg, resulted in 10 % mortality. No negative influence on web building activity was recorded. The webs themselves were hardly affected: only the number of radii was reduced by 5 %. The efficiency of the various pesticides can be ranked as follows: Decis(R) (deltamethrin) much greater than Alaxon(R) D (diazinon) over Kelthane(R) EC (dicofol) equal to Pirimor(R) (pirimicarb). Substance specific differences of the effects are discussed
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