Nitrogen and water limitations in tomato plants trigger negative bottom-up effects on the omnivorous predator Macrolophus pygmaeus

Abstract

Omnivorous Heteroptera predators play important roles in biological control of a wide range of pest insects. Their predation could be influenced by various biotic or abiotic factors. Here we examined the effects of nitrogen and water inputs to tomato plants (Solanum lycopersicum L.) on the predation strength of the omnivore Macrolophus pygmaeus Wagner (Hemiptera: Miridae) on eggs of Ephestia kuehniella Zeller (Lepidoptera: Pyralidae). We tested the hypothesis that a change in plant status, manipulated by sub-optimal nutrients and water inputs, may influence predation on E. kuehniella by the predator M. pygmaeus. Nitrogen and water restrictions depressed the predation of E. kuehniella eggs by M. pygmaeus. Moreover, we observed a 30 % reduction in predator longevity on plants under low water inputs. Therefore, the negative bottom-up effect of nitrogen and water limitations (in tomato plants) toward M. pygmaeus may be detrimental for mirid predator-based IPM programs in tomato crops.