Many people don't realize that nature has the ability to maintain 'biological' controls in which one group of organisms suppress destructive organisms from overpopulating the environment. People can implement physical and cultural practices in order to encourage these natural controls. One example of this is the conservation of beneficial insects.
There are hundreds of species of beneficial insects available in nature that can help control insect problems in your vegetable and flower gardens. Many beneficial insects are predators that prey on destructive insects. The others are parasites, which lay their eggs in or on another species of insect. This balance between insect predators or parasites and their pest prey can be encouraged and maintained by:
A) providing suitable habitat for predators and parasites
B) avoiding insecticides that harm these beneficial insects
Let's find out more about these conservation measures for beneficial insects.
A.) Providing Habitat
Beneficial insects can be attracted to your garden with your help. To attract beneficials, water, food and shelter must be provided.
Water can be provided in shallow trays filled with sand or gravel, or birdbaths with a few stones added to provide foothold for the insects. (Be sure to empty these out and replenish with fresh water to keep mosquitoes out!)
Food can be provided in two forms: naturally occurring pest insects, and pollens and nectars provided by flowering plants. Usually, providing pests takes care of itself! Nectar serves as an energy source for the foraging predators and parasites as they look for insect prey ("meat"!).
Pollen is an additional source of protein for these creatures.
Permanent plants in the landscape such as perennials (shrubs, trees and herbaceous plants) of different sizes and shapes can provide hiding places from birds and other predators, shelter from storms and over wintering protection.
B.) Avoiding insecticides harmful to beneficials
Reliance on spraying should be minimized when possible since fewer than 3% of all insects are actually destructive. Use of broad-spectrum insecticides destroys many forms of insect life; beneficial insect populations as well as pest populations. Also, predators and parasites have a slower rate of reproduction than pests, so you may actually be helping the pests in the long run! If a spray must be used, choose chemicals carefully to pick those that are "softer", that is, they do not kill as many different kinds of insects or are not very toxic or poisonous. One can also pay attention to when and where pesticides are applied to try not to impact beneficials as much. For example, many beneficials are active during the hot part of the day and are attracted to flowers, so don't spray flowers nor spray during that time of day in areas where you see lots of beneficials at work. Remember, if you kill them, you inherit their jobs!
Building the ABC Tub
In this exercise, students will have the opportunity to get hands-on experience with creating an environment that is suitable for attracting beneficial insects. Students will construct a tub filled with plants, that when flowering, will attract beneficial insects (and maybe some pests as well!). This project can be conducted in school or at home. Anyplace outside with plenty of sunlight will do (courtyard, roof, walkway, lawn, garden). Observations and group discussions can be held, or the students may write a report on beneficial insects and how to attract them.
- Learn about beneficial insects and their importance.
- Learn about ways to attract beneficial insects
- Recognize some beneficial insects
- Discover that indiscriminant spraying of insecticides can destroy beneficial insects
- Discuss other creative options for attracting beneficial insects
- 18 gallon planter tub
- a drill
- potting soil
- fish emulsion or other organic fertilizer
- variety of flowering plants to fill tub
- identification guide/pictures of beneficial insects (see poster provided)
- Obtain an 18-gallon galvanized tub or a similar sized lightweight container.
- Drill 10 holes in container bottom to provide drainage.
- Fill planter with potting soil.
- Transplant plants that will flower; rich in pollen and nectar to attract insects. (see list provided)
- Provide full sun, good drainage, water several times per week, and feed weekly with fish emulsion or other organic fertilizer.
- Observe every week to see which insects you have attracted.
- Sit very still and count how many of what different kinds of insects come to which flowers. Students can keep a journal of "visitors" to their tubs.
Also make observations on feeding habits and life cycles of your insects for added discussion.
Preparation: Plants take time lots of time to grow from seedlings. Instructors may decide that it is more prudent to use plants that are already established so that time to flowering will be 2-3 weeks. This project could potentially last for half of the academic year depending on the age of the plants used in the project. If you have a greenhouse, students might work in teams to order seeds in advance, based on their research, and propagate their own plants from seed.
- Set-up tubs in classroom & outdoors: 30-40 minutes.
Once plants are transplanted into tubs and flowers are appearing:
- Observation over time: 15 minutes each observation. Number of observations will vary according to age group and lesson scheduled.
- Discussion time: Variable, depending on how lesson is used.
This is a useful and fun project for students of most ages. Making observations can add to the intensity of learning for the older student. Also, observe what types of flowers attract which types of insects. This could lead to lessons on recognizing the different insects and what classes of plants attract these insects. For older students discussing pesticide issues, this activity could lead to discussion of choice and timing of pesticide applications according to the life cycle, activity times and feeding habits of beneficial insects.
Species diversity: Discuss importance of having diverse plants to attract different insects.
Natural insect management: Brainstorm on different ways to attract beneficial insects and learn who eats who.
Life cycles and timing: Using observation that will be made by class, prompt students into thinking about what role insect life cycles can play in pest management.
Native vs. exotic plants: Discuss the importance of planting species that are native to the area. Native plants tend to be well-adapted to the local environment and resist insects and disease better than non-native, or exotic plants. That means less problems with pest management for you!
When PA IPM staff provide on site teacher training, these materials will be provided for this Exercise:
Poster: "10 Most Wanted Insects"
Insect info sheet: Common beneficial insects
Brochure: "Native Plants"
Plant Lists: 2 lists of plants that attract beneficial insects
List of Pesticides: List of insecticides and which are most or least toxic to beneficials
Best Easy to Use References:
1. Natural Enemies in Your Garden: A Homeowner's Guide to Biological Control (2000)
Michigan State University Extension, Bulletin 2719, 60 pages $6.25; (517)-355-0240
Well-written with simple but accurate explanations of the major beneficials and how to "use" them.
2. The Good Guys: Natural Enemies of Insects
30 color laminated cards with pictures of beneficials on one side and facts on the other; $8.50, available from Illinois Natural History Survey, 607 E. Peabody Drive, Champaign, IL 61820 217-333-6880.
Excellent classroom resource. This card set is part of a series that includes "The Bad Guys, Set 1 Garden Pests" "The Bad Guys, Set 2 Landscape Pests" and "The Ugly Guys, Household Pests"
1. "Pests Have Enemies Too: Teaching Young Scientist about Biological Control" (1995)
M. R. Jeffords & A. S. Hodgins, 64 pages worth of interesting information and activities for grades 5-10. from Illinois Natural History Survey Special Publication 18, $10 contact as above.