Effect of intraguild predation between two species of wolf spiders on the biological control of cotton bollworm Helicoverpa armigera

Intraguild predation between wolf spiders has the potential to interfere with biological control in cotton crops, as spiders may attack each other instead of hunting the bollworm Helicoverpa armigera, a main pest. Here we study the predator-prey interactions between the spiders Tasmanicosa leuckartii and Hogna crispipes, and the effect of these interactions on the control of H. armigera. The proportion of H. armigera larvae killed in laboratory trials did not differ when paired with one T. leuckartii, one H. crispipes, or one T. leuckartii together with one H. crispipes. When both spiders are present, H. crispipes was more likely than T. leuckartii to kill H. armigera. Additionally, H. crispipes preferred to attack H. armigera than to attack T. leuckartii, while T. leuckartii did not show a difference in preference between attacking H. armigera or H. crispipes. In glasshouse enclosures, there was no difference in the number of H. armigera larvae that survived to pupation when either one or two spiders of the same species were present. However, the presence of T. leuckartii and H. crispipes together significantly reduced number of surviving H. armigera pupae, compared to T. leuckartii alone. Our results show that despite the presence of T. leuckartii, H. crispipes was still an efficient predator of H. armigera. However, the presence of two spiders in cotton microcosms did not result in an additive effect on pest control, suggesting that intraguild predation does interfere with the potential of several spiders to control H. armigera.