Home & Garden

Friend or foe? Not all garden bugs are bad

Both the larva and the adult of the convergent lady beetle eat large quantities of aphids.
Both the larva and the adult of the convergent lady beetle eat large quantities of aphids. Jack Kelly Clark

Q: “I’m trying to be more sustainable in my garden, but there seem to be too many bugs on my plants. What should I do?” - Charlotte Henry, Templeton

A: To many gardeners, the sight of an insect crawling on a plant means that it’s time to whip out the bug spray! However, of the millions of insect species, few are truly harmful. Many of the others are beneficials, meaning that they are natural enemies of the pests that damage or kill plants. Most beneficials are insects, but spiders, some mites, some reptiles and several microorganisms can also eradicate pests by killing them or interfering with their ability to reproduce.

It is difficult to tell friend from foe when observing creatures in the garden. This is another case when you “can’t judge a book — or a bug — by its cover.” Lady bugs — correctly known as lady beetles or ladybird beetles — are cute and colorful and obvious “good guys,” but their larvae, on the other hand, are extremely homely. Even the furriest, most cuddly-looking caterpillar can cause havoc in the garden. Ideally, every gardener would research and identify every organism in the garden, its life cycle and common prey. Clearly this is not a realistic goal, but there are some basic principles to maximize the ability for beneficials to thrive in your garden.

1. Avoid indiscriminate insecticide use because you’re sure to wipe out the “good guys” with the bad. Be cautious about combination products that feed the plant and fight pests. These systemic pesticides may kill the aphids that feed on the plant, but can then kill the ladybird beetle that feeds on the aphid — and a dead ladybug is a very sad sight.

2. Tolerate a low level of plant feeding insects and mites to provide food for the beneficials. This may mean living with slight damage to plants.

3. Plant a wide variety of plants to provide food and shelter for beneficials, then stand back and let the bugs duke it out!

4. Eradicate ants using traps and stakes, because they actively farm and protect aphids and scale.

5. If, as a last resort, spraying is necessary, use the least toxic preparation — starting with a strong spray of water.

The Master Gardeners are happy to address your specific questions, and the UC Davis website http://www.ipm.ucdavis.edu has a wealth of information.