Let Beneficial Insects Work for You

Beneficial insects include numerous lady beetle species, green and dusty lacewings, minute pirate bug, assassin bugs, predatory mites, and wasp and fly parasites. Some of them, such as many spiders, are generalists that feed on any insect they can catch, including other predators and pollinators. It is a sign of a healthy landscape to have spiders and other generalist predators present, but specialist feeders such as the twice-stabbed lady beetle, which feeds on the crawlers of euonymus, pine needle, and other scale species, are more likely to impact plant-feeding pests.

Why should beneficial insects matter to you? Numerous studies have documented the effectiveness of specific beneficial species against certain plant-feeding pests. It makes sense to maximize the impact these naturally occurring "workers" have on a client's property. Also, they are important for resistance management – over-spraying with pesticides that have the same mode of action can lead to resistant pest populations.

It is extremely important to learn how to correctly identify all the life stages of the most common beneficials. For some predators, the immature and pupal stages look nothing like the adults. Lady beetles are a great example. The adults of many species are easily recognizable, but the larval and pupal stages are rather odd-looking and often mistaken for a pest. Incorrectly identifying one of these beneficial insect life stages as a plant pest and then applying an insecticide negates the positive impact they have in that landscape.

Conserving beneficial insects can yield long-lasting, positive results. For conservation to work, a greater focus on plant scouting is needed. A few key insecticides to consider for this conservation role include ultrafine (all-season) horticultural oil, insecticidal soap, spinosad, neem products, and Bacillus thuringiensis (BT). Remember that the correct pesticide has to be selected for the corresponding pest(s) problem. Meaning a BT product is going to work on caterpillars, but is not the material of choice for aphids. Some of these products can kill beneficial insects, but they have short residuals. A short residual has a less long-term negative impact on non-target organisms, including valuable beneficial insect populations.

Landscape design can play a major role in successful pest management through beneficial insects. Using plants with different shapes, sizes, and flowering habits can help support useful insects in the landscape. The different plant forms provide refuge for the various beneficials. A landscape planted with both woody and herbaceous plants can provide flower abundance throughout the growing season. Continued bloom from spring through fall provides essential food in the form of pollen and nectar to beneficial insects that utilize plants as a supplemental food source. If possible, incorporate native plants that work for the location. The use of natives can increase the overall wildlife diversity by providing food and shelter to native pollinating insects, caterpillar species, and birds.

If a decision is made to pursue biocontrol as a pest management option, whether through augmentation (purchase and release) or conservation, a number of steps should be followed to increase the likelihood of success.

• First, you have to be able to recognize the pest insects and common beneficial insects so that the correct pest management decision is made. If naturally occurring beneficials are present, are they the correct species to manage the current pest problem? Another example: if a release of beneficials is going to happen, has the pest been identified correctly so that the appropriate beneficial organism is purchased?
• Scouting, the major cornerstone of IPM, becomes even more important if biocontrol is used. Regular monitoring enables you to track both pest populations and the beneficial insects that are feeding on them. If beneficials are not managing pest problem(s) to the desired level, pesticides may be required.
• If a first release attempt is not successful, evaluate what went wrong. Maybe the pest population was too high at the time for the beneficials to succeed as a management option, or if a release was done, the wrong organism and/or rate may have been used. Do not give up. Select another opportunity to try biological control again.

The beneficial insects that inhabit the landscape or nursery can play a major role in the successful management of certain ornamental plant insect pests. Think about these key advantages of biocontrol: no toxicity concerns for the property owner or non-target organisms; no phytotoxicity to treated plants; and treated pest populations will not develop resistance.

An excellent publication that can help with identification:

Natural Enemies Handbook: The illustrated guide to biological pest control. 1998. University of California Agricultural and Natural Resources, Davis, CA.