This week’s post is written by Jennifer Stotland explores chemical-free pest management – how to identify and encourage insect predators.
It was not long ago that the way of thinking was to eliminate all insects from our gardens with insecticides. In an age more conscious of our own health and the health of the planet we turn to other measures against pests; soil health, vigourous plants, companion planting and the encouragement of a diversity of life to predate on pest insects and keep them under control.
In this article, learn to recognise some of the insects in our garden that are helpful for pest control and how to encourage them.
Ladybugs are a popular solution for aphids. You will probably see them attracted to your aphid situation all by themselves, along with their larvae which look like this:
If it makes you feel better, the aphids on your shrubs are attracting ants that ultimately aerate and contribute fungal health to your soil. Rob Avis at Verge Permaculture had good luck getting rid of aphids by applying a fungally-dominated compost tea, to boost the health of the soil and the shrubs. Mix 1 Tbsp/ gallon water of compost, molasses, and three of oatmeal before aerating and applying the tea to the soil and leaves and stems of your shrubs.
Entomologist Clayton D’Orsay with Parks Canada tells me that many ladybugs, at least in cities, are varieties of an introduced and more abundantly breeding asiatic ladybug, Harmonia axyridis. While in theory these ladybugs would take care of more aphids, they are also more diverse in their diet, sometimes also snacking on the crop plants themselves. If you buy ladybugs from a nursery, make sure they are not Harmonia axyridis, as they can out-compete native ladybugs and may go after your berries and grapes 1 It may be cheaper and more effective to simply encourage predatory insects to arrive on their own.
These are generalist predators that eat only a small amount of plant matter. Centipedes will come out at night to eat slugs, worms, other insects, and anything they can catch. They like to have leaf litter and debris on the ground in which to hide.
Dragonflies and Damselflies
Dragonflies rest with their wings spread out at the side at a 90 degree angle. Damselflies rest with their wings close along their bodies. Both eat a broad variety of flying insects, while their larvae eat aquatic insects. Clearly they need a lake or pond environment, but they are excellent for mosquito control. Edible Forest Gardening says that even a small body of water will attract them.
These eat aphids, mealybugs, caterpillars and mites. They seem to be a sort of holy grail for gardeners.
Red Soldier bug
I have definitely seen these before, mostly in my childhood searches for lightning bugs, which they resemble (they won’t light up though). By the by, fireflies will also prey on slugs, snails and other pests 1.
The earwig we see most commonly in our gardens, Forfucula auricularia, is introduced from Europe. They will eat small insects and their eggs, spiders, dead plants and insects, lichens, algae and other scavenged materials1. I have been pinched by earwigs but not nearly as often as I’ve seen them scurrying away. They like to hide in stalks or crevices and come out at night to feed. Any hollow tube or bundle of stalks left in the garden will be sure to fill with them.
Spiders tend to eat whatever is most abundant, thus preventing pest explosions. 2 They like to have areas with branches in which to build their webs, and hollow stalks in which to spend the winter. Because they have no exoskeletons, their soft bodies are particularly vulnerable to chemical disturbances and to drying out. Provide lots of mulch on the ground for both moisture and habitat, leave some dead stems and other locations for webs.
Virtually all wasps will eat insects, especially when raising their young, and will also need a source of nectar. Some of these are the ones you may have seen in nature documentaries that lay their eggs near or on the prey caterpillar, and whose young then consumes the hapless prey alive. This gruesome solution is exactly the one we want to cultivate. Don’t worry, it’s natural! Some of them are specialist (one species of wasp for one species of caterpillar) and some are generalist (they will collect or prey on many sorts of insect).
The best kind of flowers for encouraging these insects are those with short, flat nectar tubes that don’t require specialized mouth parts to get into them. Umbelliferae like wild carrot and fennel work well, as do the mints, yarrow, borage, alfalfa, mallows, goldenrod, clovers and buckwheat.
Here are some wasps you may see in your garden:
Brachonid and Ichneumonid wasps: superfamily Ichneumonoidea
These solitary wasps are specialists, using their scary looking ovipositors to prey on one sort of caterpillar. Genum Brachonid and Ichneumonid wasps look virtually identical and do roughly the same things. The long tube on the end of this insect is not a stinger but is used to probe into the soil or wood and search for caterpillars and grubs on which to lay eggs. I saw some of these in my garden for the first time this year.
Among the smallest wasps in existence, calcids are easy to overlook (I have never seen one). They include the world’s smallest known insect, Dicopomorpha echmepterygis, which is 0.139 mm from Costa Rica. They are also often blind and sometimes flightless, but exert a great influence over ecosystems over much of the world through their habit of preying on insect eggs 1. Edible Forest Gardening recommends looking for these insects at dawn or dusk, when the slanting light makes them more visible flying over flowers. 2
Hornets (genus Vespa) and yellowjackets (genus Vespula or Dolichovespula)
These are the ones you are most likely to see going after your soft drink. Yellowjackets breed under the ground while hornets do so above ground.
Like bumblebees, these wasps start a new colony every year, when a pregnant female emerges from hibernation to birth workers, queens and males. At the end of summer, impregnated females leave the others to perish and then hibernate anew. Though they are aggressive, they also are generalist consumers of insects, nectar, pollen, fruit and sap. They can be encouraged both by growing fruit and nectar sources, though they might be more suitable for a larger and more remote garden system than a personal backyard vegetable garden.
These wasps prepare a mud pot, paralyse their prey, and then drop them into the pot, where they lay an egg. You guessed it, the prey insects are eaten by the young. Wikipedia states that humans may have learned from this wasp the craft of pottery. They need a source of mud and water, as well as walls or sheltered areas, such as beetle burrows on which to build their pots
They are not aggressive and will only sting if provoked. Wikipedia also states that they have an ability to recognise the faces of their nestmates that is comparable to humans and chimps.
Digger and Dauber Wasps
These wasps also tend to be non-aggressive.
In general, a greater diversity of these insects will control a greater diversity of pests. A very tidy garden is not attractive to insect diversity: design your garden to create a diverse habitat with lots of mulch, stems and texture on the ground, and perhaps a small pile of logs or stones. Some vertical element with bushes and trees, and bright flowers with shallow nectar tubes, should encourage a diversity of meat-eating insects that will keep your garden in natural balance and provide interest and ecological value.
If you liked this blog entry you may want to read more from my blog at http://www.barefootpermaculture.dreamwidth.org
These were also some great blog entries on helper-insects:
2 Edible Forest Gardens by Dave Jacke and Eric Toensmeier
Thank you to Clayton D’Orsay for editorial assistance.