Garden & Greenhouse


Natural Pest Control for the Greenhouse and Garden

Posted December 1st, 2007 by Garden & Greenhouse in

Many gardeners would rather use natural products to control pests, but are confused about developing an overall strategy for natural pest control. The best offense is a good defense and the easiest way to prevent insect damage is to discourage them from coming in to the garden in the first place. The following steps will help:

  • Avoid Weak Plants Find a local planting calendar by doing an internet search on the county in questions name and the words “planting calendar”. Make sure to only plant annuals during their proper planting season. This will help to assure healthy plants that can better combat minor infestation. Remove plants that clearly are doing poorly; they may already be infected. If not, they will attract pests. Pull the weak plants and dispose of them away from the garden area, and do not attempt to compost them.
  • Build Healthy, Organic Soil – Natural composting methods, mulching and top-dressing your soil with compost or natural fertilizer is the best way to develop strong, vigorous plants. Get an inexpensive soil testing kit and follow the instructions to amend soil pH and other problems as necessary.
  • Use Seaweed and Fish Fertilizer Seaweed contains trace elements such as iron, zinc, barium, calcium, sulfur and magnesium, and fish emulsion contains primary nutrients which promote healthy development in plants. Seaweed and Fish fertilizer are a great organic alternative and will enhance growth and give plants the strength to better withstand disease.
  • Clean Gardening PracticesClean the garden area of debris and weeds which are breeding places for insects. Buy quality mulch and keep a thin layer on top of the soil. The mulch will discourage weeds, keep plant leaves out of the soil and hold in moisture.
  • Interplant and Rotate Crops Insect pests are often plant specific. When plantings are mixed, pests are less likely to spread throughout a crop. It also helps to plant aromatic flowers like marigolds between vegetables to discourage insects and inhibit their spread. Rotating crops each year is a common method to avoid re-infestation of pests which have over-wintered in the ground. In some cases where soil bound pests are abundant it may be necessary to undertake off-season soil sterilization procedures.
  • Keep Foliage Dry Water early so foliage will be dry for most of the day. Wet foliage encourages insect and fungal damage. Trim lower leaves so they are not on the ground and keep mulch around the base of all plants.
  • Keep Tools Clean It is a good idea to clean tools before moving from one garden area to another. This will reduce the speed of invading insects. Clean tools with warm soapy water every couple weeks during the growing season.

Diligent application of these clean gardening practices is the first line of defense. Another beneficial practice for natural pest control is the planting of host plants to attract beneficial insects. Beneficial insects are insects which can be attracted to the garden, or bought from catalogues, which prey on harmful insects or their larvae. These are the most common: Nematodes; Ladybugs; Lacewings; Hover-Flies; Praying Mantis; Brachonids; Chalcids; and Ichneumon Wasps. The following are plants that can be helpful in attracting beneficial insects: Carrots; Celery; Parsley; Caraway; Queen Anne’s lace; Daisies; Tansy; Yarrow; Goldenrod; Black-Eyed Susans; and Asters.

When beneficial insects are being used to combat pests in the garden, even natural pesticides should be used sparingly and only on infected plants because they will have an adverse impact on the beneficial insects as well as the unwanted ones. Many natural sprays for a variety of pest problems can be made at home and complete lists of various recipes for different problems can be found online.

By applying these natural pest control techniques it is possible to stay one step ahead of the pests and be ready for them when they arrive.

Dr. Christopher J. Kline is a master gardener and writer living in Paradise Valley Arizona.

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