Landscape - Natural Enemies are Key Players in Pest Management

It is critical to understand how natural controls affect pest populations in the landscape. The following is the first in a series on this subject.

Natural enemies are predators, parasitoids, and pathogens that attack and kill pests. Common predators include lady beetles and assassin bugs, parasitoids are often tiny wasps or flies, and pathogens that kill insects include specific species of nematodes, bacteria, or fungi. Natural enemies are ubiquitous in our natural and managed ecosystems. There is an abundance of data that demonstrate natural enemies are very important in preventing plant feeding insects (herbivores) from reaching population densities that cause aesthetic and/or economic damage to plants in our landscape and production systems. In managed systems we often implement practices that eliminate or reduce the populations of natural enemies so they no longer can keep herbivore populations from reaching pest outbreak levels. As plant managers the best way to prevents pests from damaging our plants is to avoid practices that are harmful to natural enemies and implement practices that will attract and/or retain natural enemies into our landscapes and production systems. This includes the wise use of pesticides: selecting products that have the least toxic effect on natural enemies, and applying pesticides at a time or by a method that reduces the likelihood of exposure of natural enemies to pesticides. Also maintain managed systems that provide natural enemies with: refuge from unfavorable environmental conditions and hiding places from their natural enemies, and an abundance of food resources (nectar, pollen, and alternative prey). This includes adding flowering plants that provide season long floral resources and adding structural complexity such as plants at varying vegetational strata (ex. over and under story trees, shrubs, herbaceous plants, and ground covers).

Extracted from "Natural Enemies are Key Players in Pest Management" by Paula Shrewsbury, Extension IPM Specialist with the University of Maryland in the March 30, 2007 edition of the TPM/IPM Weekly Report for Arborists, Landscape Managers & Nursery Managers, University of Maryland Cooperative Extension