1. Exploitation Spiders Predators In Corn In Biological Control
Of Invasive Species Diabrotica Virgifera LC (Coleoptera: Chrysomelidae)
Ioana Grozea*, Horgos Horatiu, Ramona Stef, Ana Maria Virteiu, Alin Carabet, Levente Molnar
Department of Biology and Plant Protection, Banat’s University of Agricultural Sciences and Veterinary Medicine “King Michael I of Romania” Timisoara, Romania
Population level from the adults of Diabrotica virgifera virgifera LeConte (1868), a serious pest of corn, may be reduced by exploitation of predator spiders existing in corn crops. About 20 years after their introduction in Romania, acreage treated for adults of this pest was substantially reduced by using different non-chemical methods.
A less common method is classical biological method using natural enemies, especially predator spiders. Few studies have tackled in this direction, in many cases without success.
In our study, developed over two years (2014, 2015), during five weeks in July and August, we considered abundant species of spiders predators in the west of the country (Timis county). Researches were held both in the natural life of spiders and laboratory, in 4 cages and 4 terrariums specially arranged. In each cage (in field) were placed about 50 predator spiders and 40 beetles of Diabrotica. In each terrarium (in laboratory) were introduced 5 spiders and 10 beetles.
The most aggressive proved to be spiders of the genus Argiope and Xysticus who consumed between 6.8 and 7.5 Diabrotica beetles, weekly, in their living habitat. No beetles have been consumed by spiders in the laboratory.
Predator-prey interaction efficiency in biological control
Predator
species
Years
Variants
(cages
in crop field)
Total no. of predator spiders (placed/cage)
No. of beetles Diabrotica (alive- in analysis momment)
No. of beetles Diabrotica (weekly dead-assuming that they were devoured)
The percentage efficacy (%)
Argiope b.
2014
Cage 1 40
12.5
7.5 15
Araneus d.
Cage 2
33.5
3.3
6.6
Xysticus sp.
Cage 3
16.0
6.8
13.6
Theridion c.
Cage 4 48
0.4
0.8
2015
17.5
6.5 13
39.5
2.1
4.2
20.0
6.0 12 41
1.8
3.6
Experimental field from Sag
(Timis County)
Xysticus k. spider despoiling a female of Diabrotica
Argiope b. spider preparing for attack
Argiope b. spider despoiling beetle of Diabrotica
Emergence cage placed in corn crop
Terrariums laboratory for growth and maintenance beetles and spiders
Future, consideration of the protection and exploitation of crop predator spiders can be a way to reduce polluting methods using in pest control.
They were seen preying only spiders who weave cloth (Araneae: Argiopinae, Araneidae, Theridiidae) and those who are hiding in the silks of directly attacking prey (Thomisidae). Thus were revealed following species: Argiope bruennichi S., Araneus diadematus C., Xysticus kochi T.,Xysticus cristatus C. and Theridion cinereum T.
References (selective)
Altieri, M. A., 1999, The ecological role of biodiversity in agroecosystems. Agriculture, Ecosystems and Environment. 74:
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Hoffmann, M.P. and Frodsham, A.C., 1993, Natural Enemies of Vegetable Insect Pests. Cooperative Extension, Cornell Univ., Ithaca, NY. 63 pp.
Marc, P., Canard, A., Ysnel, F., 1999, Spiders (Araneae) useful for pest limitation and bioindication. Agriculture, Ecosystems & Environment. 74: