A fruit fly called Spotted Wing Drosophila lays eggs in fruit as it ripens on the plant. Spraying with products that include the insecticide spinosad is the best defense against these troublemakers.

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In the Garden

Q: For the first time, I’m finding tiny worms in some of my strawberries. Is there anything I can do to prevent this?

A: The worms in your strawberries are the offspring of a fruit fly called Spotted Wing Drosophila, a new arrival to our region. Most fruit flies lay their eggs only in overripe or rotting fruit, but this troublemaker lays eggs in fruit as it ripens on the plant.

If you don’t want to enjoy extra protein when you eat your strawberries, look closely before you take a bite. There is a tiny scar on the skin where the egg was laid, which soon collapses and becomes moldy. The worm feeds in the fruit for around a week before pupating inside the fruit. Each female fly can lay up to 350 eggs and there are several generations per season, so as you can see, this pest can ruin an entire harvest.

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Strawberries are not the only fruit that can be ruined by this pest. They also attack raspberry, blueberry, plum, peach, cherry and grape. You can minimize infestation by harvesting fruit as soon as it ripens and by destroying any fruit with worms in them (stomping works well).

 

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Products with spinosad, a natural substance made of a soil bacterium, have been found to be highly effective against a number of insect pests, including fruit flies. Available at most nurseries and garden centers, used as directed, these products are purported to be nontoxic to humans and pets. Spinosad, however, is harmful to bees and other pollinators if they visit the flowers soon after application, so apply only in the evening hours after the bees have stopped foraging. Spinosad is effective only against the adults and will not control worms inside the fruit.

This is likely to be an ongoing problem, so spray on a yearly basis.

Q: A rose in my garden has yellow zigzag patterns on the leaves. I’ve been told it is a virus and I should remove it or it will spread the disease to my other roses. Is this true?

A: Your rose most likely has rose mosaic virus. Symptoms show up on the leaves and can appear as yellow wavy lines, yellow bands along the veins, or yellow splotching, but the most common pattern is the yellow zigzag lines. The symptoms are most noticeable in spring because the leaf patterns are more evident on spring growth than on leaves that emerge later in summer.

The good news is that research has found that this disease does not spread from one rose to another in a garden setting. Insects and/or pruning shears do not transmit this disease, and even the soil where an infected rose is growing is unaffected by the virus. The only way roses become diseased is through grafting the top section of a desired rose onto an infected rootstock. Grafting is the typical way roses are propagated in the industry, and evidently infected rootstocks somehow got into the system.

The bad news is that although growers are now aware of the problem and have taken steps to prevent it, a fair number of infected roses ended up in our gardens. Unfortunately, roses infected with the virus usually have reduced flowering. Growth is often stunted, and they often have shorter life spans than healthy, virus-free roses.

So even though you don’t have to worry about the disease spreading to other roses, you’re better off replacing your infected rose. Just make sure the replacement you buy is certified virus-free.