Real Estate

Beneficial bugs

Fruit trees and insects can co-exist. Can you?

If you are blessed with fruit trees in your yard but are less comfortable about the bugs that might also be enjoying your harvest, relax.

"A lot of it has to do with how squeamish people are," said University of California Master Gardener Candace Simpson, who teaches an annual class on beneficial garden bugs in Palo Alto.

Apple trees, for example, attract codling moths, who lay their eggs on tiny developing apples. As soon as the apple has formed and the egg hatches, the worm tunnels into the apple somewhere near the stem and heads down to the core.

If you've read this far, you are probably brave enough to take Simpson's next piece of advice: When the apple is mature enough to pick, now that you are prepared for what to expect, cut into it, leaving a decent margin around the stem and core, and use the clean parts you've cut off for eating, baking or cider. There may or may not still be a worm inside, or it may have exited out the "blossom" end of the apple, leaving some brown stuff behind. It's now heading to its next developmental phase, making a cocoon on the trunk of the tree and turning into a tiny moth.

"So this is the good news about codling moths: You can cut off what I call the cheeks of the apple," she said.

Apples can also be hand-thinned, once they start to grow. If you see two apples growing in a pair, remove one so that all of the apples on the tree are no more than about five inches apart. This allows the remaining apples to grow larger and prevents moths from burrowing into the apples in the weak spots where they are touching each other.

Stone-fruit trees like apricot or peach or cherry don't have problems with codling moths. Instead, peach trees can be afflicted with "peach leaf curl," which is a fungus that affects nectarine as well as peach trees. This can be prevented in the fall after the fruit tree's leaves have fallen, by spraying a copper-based fungicide which is OK even for organic farms. It's always important to pick up all fallen fruit and pick old fruit off your trees so as not to attract the wrong pests, including rodents. If you don't pick up fallen apples, for example, you could be supplying three more generations of codling moths with homes.

If your stone-fruit tree already has peach-leaf curl, it will still produce a harvest. It's really important, Simpson said, not to remove the affected leaves but instead to leave them. It's a "stressor" on the tree to take those leaves off and the trees have evolved to cope with the fungus while they're growing fruit. Plum trees get a similar affliction caused by a specific type of aphid.

"A lot of people get distressed because of the plum aphid," Simpson said, because it causes the tree's leaves to roll up tightly. But, she said, not to worry. "Those aren't harmful to the tree. The tree has evolved" to be able to cope.

If you want to supply your yard with ladybugs, a predator of aphids, that can help, especially if you have small blooming flowers like yarrow or alyssum for the ladybugs to thrive on in between aphid fests. But ladybugs need prey or they won't stick around.

Another solution is to remove excess debris and fruit on the ground underneath the trees so as not to attract ants, which actually protect and nurture aphids. Ladybugs won't help with plum aphids, by the way, since there is no way for them to get at the bugs rolled tightly in the leaves.

If fruit trees are not allowed to grow too big it's easier to manage the harvest, and the trees might produce higher quality, if fewer, individual pieces of fruit.

Apricot and cherry trees get another fungal disease which can actually be mistakenly spread by pruning shears. The general advice is not to prune these until July, when there is generally a six-week rain-free period to allow the fungus (called Eutypa) to spread.

Earwigs are great for eating up and shredding things that fall and need to decompose in the garden. They also eat some species of aphids. Their ferocious-looking pincers really are not harmful, and if you don't like them, the Old Farmer's Almanac advises to lay one-foot sections of garden hose in your garden overnight and dump out the earwigs that crawl into the hose pieces into a bucket of soapy water. You can spread petroleum jelly around plant stems to keep earwigs from feasting on them.

According to the University of California's Integrated Pest Management agency, you can attract beneficial predators to keep things like aphids in check. Bugs like lady beetles (ladybugs), lacewings, paper wasps and soldier beetles often pollinate flowers as well as eating pests. One note: praying mantids eat good bugs as well as bad, so adding them to your yard may not be a great option for pest management.

"It's a balance," Simpson said. "You have to tolerate some (pests) in order to have a system where they don't get out of control."

Elizabeth Lorenz is the Home and Real Estate Editor at the Palo Alto Weekly. She can be emailed at

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