Tag Archives: predator insects

Mantises in the Greenhouse

Posted on by Katie Schmidt

In our greenhouse and nursery, I work very hard to create a hospitable environment for pollinators and wildlife. This means limited use of pesticides and herbicides. Unfortunately, greenhouse pests flourish when uncontrolled and can lead to devastating crop losses. They affect the appearance of our plants, which in turn affects how well they sell. This year, to minimize my use of insecticidal soap spray, I tried using Mantises as greenhouse predators instead.

I can tell by the shape of the egg case that these mantises are not our native species, but likely the chinese mantis, Tenodera sinensis.

Finding and Identifying Egg Cases

While cleaning garden beds this spring, I found many mantis ootheca (egg cases) hanging on branches of shrubs and trees. The egg cases can easily be spotted in areas of dense vegetation that stay standing through the fall and winter. Non-native mantis ootheca are round and bulbous, but native North American mantises (Stagmomantis carolina) have a long, flat egg case resembling a tiny trillobite.

I carefully cut the cases away from the parent plant, leaving the egg sac attached to its branch. I then placed those egg sacs in our unheated greenhouse, sticking the end of their twig into potted plants that often get pest problems in early spring.

This mantis nymph is freshly hatched and just a little bit bigger than an eyelash. At his feet are the white skins of aphids that molt as they grow.

For two months, nothing happened. But in mid April when the days were consistently sunny and warm, they finally hatched out in a giant wriggling mass!

They were fun to watch, and they dispersed themselves all across the greenhouse. But when it comes to aphid control, they were not voracious enough. In the past I used lady bugs and parasitic wasps as predators, both of which preyed on more aphids and at a faster rate than the mantises.

Do Not Order or Buy Mantises

I would not recommend ordering mantises from any garden center or organic pest control website — often they send the non-native type that are more likely to cause problems than solve them. Mantises are indiscriminate, and eat beneficial insects like bees, caterpillars, and even prey on hummingbirds.

I had fun experimenting with them because they were readily available to me on our grounds, but I would otherwise be cautious of using a nonnative insect for pest control. The best pest control method for residential gardens is a diverse planting that attract lots of pollinators and predators. These insects will find a balance amongst themselves!

Predator Gardens

Posted on by Katie Schmidt

Pollinator gardens are the current craze, and rightly so! Pollinators of all shapes and sizes are desperately in need of good quality habitat. But it’s not all beautiful butterflies and buzzing bees – there are predator insects on the loose, patrolling your flowerbed for their next meal. These helpful arthropods can reduce the weeds in your garden and put a stop to those leaf eating larvae. Inviting certain predator insects to your yard can benefit your flowers and keep your little slice of the ecosystem in balance. Following are a few ways to start a predator garden and how it can benefit the rest of your landscape.

Beetle Banks

Photo from http://www.projectnoah.org/spottings/995056020.
The Pennsylvania ground beetle (Harpalus pennsylcanica) is found all over North America. It feeds on the seeds of ragweed and giant foxtail as well as the larvae of Colorado potato borer. What more could you want?

A great way to start a predator garden is by creating ‘beetle banks’. We all love the aphid eating lady beetle, but there are thousands of less charismatic species to be thankful for as well. Ground dwelling beetles can be a gardeners best friend by eating weed seeds, preying on slugs, snails, mites, and much more. You might not see them in action since many species are nocturnal. Planting raised berms/mounds of clump and tuft forming grasses such as Panicum, Tripsacum, or Sprobolous, invites ground-dwelling beetles to stick around. The uncut grasses keep them cozy during winter and the raised area helps keep them dry. I learned all about this technique at a Xerxes Society training day for farmers interested in beneficial insects. Beetle banks are being tested on the agricultural scale, but it works on the small scale too.

While this Panicum virgatum planting is wild and natural looking, a few clumps of an upright variety in your garden can be beneficial and still look groomed. Wikicommons public domain image at https://commons.wikimedia.org/wiki/File%3AUSDA_switchgrass.jpg

Don’t Swat the Wasps

Your first instinct might be to knock down that wasp nest, but not so fast! Wasps are excellent predators who can rid your garden of hornworms, army worms, flies and crickets. Paper wasps and yellow jackets will package up the remains of these little pests and feed them to their young. Some wasps are so small they resemble a fly or mosquito, and these are likely a species of parasitoid wasp. These helpful friends lay their eggs inside tomato hornworms and aphids, immobilizing and eventually killing them. In fact, the University of Maryland extension called parasitoid wasps “the single most important biological control method gardeners have”. Adult wasps of all kinds mostly feed on nectar and can easily be attracted the same way as any other pollinator – by having season long nectar available in your native flower bed. Just be careful not to get too close to their nest, we all know how a wasp sting can smart!

Above, a paper wasp (Poliste fuscatus) feeds on horsetail milkweed nectar/pollen.

A Home For All Seasons

Depending on the size of garden/field you are trying to pest control, it can take years to establish a reliable predator population. Pollen/nectar producing flowers are the first part of attracting these helpers, but creating habitat is crucial to keeping them around. Along with beetle banks, blooming hedgerows or shrubby borders will provide summer nectar and winter shelter. Leaving your garden uncut through winter will make sure there are plenty of pithy stems where insects can overwinter. Reduce the amount of tilling every year to ensure that ground dwelling beetle populations aren’t decimated. And lastly, try to avoid the use of prophylactic pesticides such as treated seeds or broadcast/non-selective application. This will also kill the non-target species, such as the predator insects that might save you the cost of pesticide next season!