Overcoming Barriers to Predation: Effect of Alternative Management Practices on Predator-Herbivore Dynamics in Production Nurseries

Abstract

Alternative pest management tactics were compared to conventional tactics for their affect on pest and beneficial arthropods in production nurseries. Alternatives included habitat manipulations and augmentative releases of predators. Groundcover (weed cloth and hard wood mulch) and container position (pots placed above the ground and pots sunken into the ground [pot-in-pot]) were manipulated in nursery beds. Generally, wood mulch enhanced the abundance of alternative prey and natural enemies at the ground level but not at the soil level within the containers or on plant foliage. The pot-in-pot method strongly increased abundance of both groups at the ground level and the soil level within the containers, whereas pots above ground had a greater abundance of predators on the foliage. Habitat manipulations differentially affected mortality of soil versus foliar herbivores. However, herbivores on the soil in containers suffered greater mortality than those on the foliage, regardless of groundcover or pot position. Day and night differences in herbivore mortality and predator taxa were also examined.

Predatory mites were released on Ilex at two predator: prey ratios to examine their ability to suppress Oligonychus illicis. Generally, release of predators did not reduce abundance of O. illicis compared to the control. Miticide treated plants had consistently lower O. illicis populations. Leaf damage was less on miticide treated plants. Possible explanations for the ineffectiveness of augmentative release are discussed.