We had some promising results from the 2005 study on whether habitat attracts and retains diverse populations of beneficial insects in greenhouses states Glenister. Greenhouses are often extremely vulnerable to pest attack because natural enemies of pests have a hard time getting into the greenhouses, and once in, it is hard for them to find suitable food and shelter. I wanted to present our results to this working group because our study fit perfectly with the theme of this years conference. A central question for the working group was whether or not natural control increased with biodiversity. Although there were several examples to show it can, there were also several examples to show that the opposite could occur: sometimes pests can increase with biodiversity. Glenister was interested in the practical aspects of biological control and landscape management. She brought a broader question to the group: How do we assess the pest levels and then decide whether a) nature is going to handle the pests, or b) we need to give nature some help. Glenister was especially curious to see what techniques the scientists were using to measure the impact of other plants on the natural control of pests, because our project evaluates the impact of habitat plants.
There is a new movement in the scientific community to investigate the influence of non-crop plants on the natural control of pests, says Glenister. Non-crop plants, like naturally occurring plants in weedy strips, can support natural enemies by offering pollen and nectar.
According to Glenister, habitat management is essential to maintaining low pest levels in crops. There are efforts in both the United States and in Europe to better understand and use plant services to support pest control. We can only expect natural enemies to occur where there is habitat to support them. Habitat supplies food (pollen, nectar, or prey) and/or shelter. If we can retain the natural enemies and support their reproduction, the natural enemies will be there to keep pest numbers below damaging levels, she adds. When asked how the scientists responded to her results Glenister said they were very interested to learn about the various plants being explored in the United States. They have not yet begun to investigate using Marigolds and Lantana, two plants that turned out to play significant roles in our trials. Sweet Alyssum, which we also used, was already included in their studies.
Glenisters 2005 study, funded by NeSARE (Northeast SARE), documented the effectiveness of habitat plants in attracting and retaining natural enemies in greenhouses. Whitefly, aphid, and spider mite numbers remained at acceptable levels throughout the season. Before that trial there were little-to-no reports on demonstrations of biological control in herbs; all reports were anecdotal. But the system used in that trial did not keep thrips numbers at acceptable levels. In the 2006 trial we are adjusting the thrips management strategy to keep their numbers down. IPM Laboratories, Inc., Locke, New York, produces and distributes beneficial insects, mites and nematodes for the biological control of greenhouse pests.
For more information contact Carol Glenister
Phone: carolg@ipmlabs.com
http://www.iobc-wprs.org/