Pest Prevention

Karen Delahaut, Outreach Specialist, UW-Madison

The first step in any integrated pest management program is to prevent pest problems from occurring in the first place whenever possible. Although this will require a little forethought on your part, in the long run it will save you time and money. Once pest problems appear, your available management tools will become limited, and in some cases, non-existent (e.g. viruses).

There are three primary pest preventative actions: sanitation, use of certified planting stock, and isolation of new plants. If your greenhouse is empty for a period of the year, this is a good time to do a thorough cleaning. Disinfect benches, tools, containers, equipment, and irrigation systems. Keep tools and hose ends off the floor where they can pick up pests or pathogens. Remove any crop debris and old plants from the growing area. Locate outdoor refuse piles and compost bins downwind from the greenhouse to prevent air-borne transfer of pests into the house. If you have an earthen floor, remove weeds as they emerge beneath and between the benches to prevent a harborage for pests; also maintain a vegetation-free barrier outside of the greenhouse as well. This will be less of a problem for greenhouses built on concrete slabs however watch cracks in the concrete as weed seeds need only a little soil to germinate.

When purchasing planting stock, make sure that it is high quality, certified as pest-free, and from a reputable dealer. It’s unwise to purchase plants from growers having a “going out of business” sale. Often these plants haven’t been well cared for nor have they been inspected by the state’s department of agriculture. Although these plants may look like a bargain at the time of purchase, if you are also purchasing pests with the plants, it will cost you more in the long run to manage the pest problem.

Examine the shipment as soon as it arrives and reject any infested or infected plants. When bringing new plant material into the greenhouse, make sure that you quarantine the plants and keep them isolated from stock plants and seedlings so that you don’t inadvertently introduce pests. Along the same line, isolate any stock plants from the main production area and monitor stock plants more closely for pest problems than other plants since you can propagate pests along with the plants. New plants should remain isolated for as long as it takes for the key insect pests for that particular crop to appear and this will vary based on the key pests for that crop. Screening off a portion of the greenhouse with a plastic sheet will provide a quarantine area if your space is limited.

Regardless of the growing media you choose to use, it should be pasteurized before use. This is particularly a good idea if you are using compost or native soil as part of your media. Composting, unless high temperatures are maintained and the pile is turned regularly, often will not destroy fungal pathogens or kill weed seeds. Also, it’s not a good idea to reuse planting media but if you have no alternative, be sure to pasteurize the media before reuse. Keep media covered until use if it’s your practice to mix up large batches at one time to prevent contaminants from blowing in.

By implementing a few simple practices you can greatly reduce your pest problems saving you time and money in the long run.