No gardener wants bugs eating holes in their plants or destroying their vegetables. Fortunately, for every insect or bug that ruins all your hard work, there are other predatory species that feed on the plant-eaters. So be careful to avoid exterminating these helpful organisms:
Lady beetles (aka ladybugs or ladybirds) are effective against aphids, scale insects, mealybugs, and mites. Though lady beetles are available to purchase in bulk, it is generally not especially helpful to buy them. These are migratory insects, and as soon as they wake from the hibernation they are transported in, most of them are likely to leave.
Green lacewing larvae (aphid lions) combat infestations of spider mites, thrips, leafhoppers, whiteflies, and caterpillar eggs.
Praying mantis in the nymph stage begin preying on insects as small as mosquitoes as soon as they hatch in the spring.
Syrphid flies eat aphids and serve as valuable pollinators.
Ground beetles are sometimes mistaken for cockroaches, but are actually very useful for controlling pest populations. Most of these species are black, green, or bronze, often with metallic iridescence.1 These are the beetles to turn to for gypsy moth outbreaks.
Rove beetles prey on snails and certain types of maggots. You can spot them by looking for the wing covers that are so short they leave most of the abdominal segments visible, and by the way they carry their abdomen pointing upward.2 They love to live in compost piles and mulches.
Spiders may be scary to some, but they eat insects of all kinds, including those that threaten your plants.
There are many different species of predatory mites, but all will help your garden by eating the mites you consider pests. They live in the upper layers of soil where you may not even see them, so be careful about spreading pesticides.
Centipedes can be found hidden under boards or leaves in damp soil. These fast-moving predators control a variety of pests both indoors and outdoors.
Hover flies (syrphids) may look like yellowjackets at first, but they will not sting you. When they are fully mature they eat only nectar and pollen, but in the larva stage they feed on aphids and leafhoppers.
While bees won’t attack any pests, they are still one of the most efficient pollinators in the insect world. Don’t break out the bug spray—instead, welcome them into your garden with flowering plants.
The wasps you want in your garden fall into three categories: social wasps, solitary wasps, and parasitic wasps. You’re probably most familiar with social wasps, which include yellowjackeets, hornets, and paper wasps. Though they are notoriously aggressive, yellowjackets and hornets are beneficial because they will feed on almost any insect, including many common pests.3 Paper wasps are much more docile, and are distinctive because of their thin waists. When starting a new colony, paper wasps are especially effective against pests, killing thousands of caterpillars within a few weeks.4 Solitary predatory wasps hunt pest species almost exclusively.5 Though they are small, parasitic wasps are very effective for controlling unwanted organisms, such as aphids, in your garden.
1 William Olkowski, Sheila Daar, Helga Olkowski, Common-Sense Pest Control, (Newtown, CT: Taunton Press, 1991).