Suppressive effect of predators wolf spider, Pardosa astrigera, on the population density of onion thrips, Thrips tabaci, on Welsh onion in laboratory tests

Abstract

The suppressive effect of predators wolf spider, Pardosa astrigera, on the population density of onion thrips, Thrips tabaci, on Welsh onion was investigated in laboratory tests. Test 1: Thirty adult females of T. tabaci and 20 nymphs of P. astrigera were released in 30 Welsh onion seedlings planted in pots. Two weeks after release, the number of T. tabaci and the damage on the Welsh onion were investigated. Our results showed that the number of T. tabaci and the damage caused by the release of P. astrigera were less than that of the no-release. Test 2: Thirty adult females of T. tabaci and five nymphs of P. astrigera were released in 3 Welsh onion seedlings planted in pots. In order to confirm the effect for a longer period, the number of T. tabaci and P. astrigera were investigated until 4 weeks after release, and as a result of releasing P. astrigera, the number of T. tabaci was less than the no-release on 16 to 28 days after release.