Some common agricultural pests can be problematic in a greenhouse, and may be particularly troublesome because use of pesticides and insecticides in a covered, controlled environment is discouraged for both health and safety reasons. The truth is that it's impossible not to have pests in a greenhouse, but it is possible to prevent them from damaging your plants. Constant monitoring of plant condition is required, and the use of sticky cards is recommended as an early warning system. Common greenhouse pests include caterpillars and slugs, sap-feeding insects and pollen feeders. They can be difficult to control, and growers should constantly be on the lookout for evidence of pests. Examine plant leaves, top and bottom, and look for pollen spread and droppings. Many common pests are tiny. Aphids, mealybugs, mites and whiteflies proliferate in the warm, humid environment of a greenhouse and can lead to devastating crop loss if not treated quickly and effectively. Some pests feed on leaves and mature plants, while others attack root systems and tender shoots.
Many pests, including thrips, which feed on flowers and spread pollen, and the tiny flies that become extreme nuisance pests, can be killed with regular spraying of insecticidal soap or repeated applications of Neem oil. Treatments should be applied every five to seven days or until all evidence of the pests disappears. A bucket of soapy water should be a greenhouse staple, allowing growers to hand pick caterpillars and slugs from existing plants and surfaces. They will die when thrown into the bucket, and controlling them in this way requires nothing more than routine and regular plant inspection. Some greenhouse growers purchase and release beneficial ladybugs as pest-hunters. They can consume large numbers of aphids, and they will not harm growing plants. Another effective pest control strategy is the use of diatomaceous earth, a natural silica powder, spread around the greenhouse perimeter. It discourages ants and other crawlers from entering the greenhouse. Intermixing natural pest-repellent flowers and herbs, such as nasturtiums, marigolds, bay leaves or basil, and catnip, with your vegetables is another natural way to discourage damaging pest infestation.
