Garden dectective: holes in green tomatoes

Published: Saturday, Jun. 22, 2013 - 12:00 am | Page 8CALIFORNIA LIFE
Last Modified: Saturday, Jun. 22, 2013 - 8:32 am

I live in El Dorado Hills and use a planter box to grow tomatoes. Something is eating good-sized holes into the green tomatoes. In the past, I have had problems with birds pecking holes in them but this damage does not look the same.

One difference is I have noticed some lizards have taken up residence in the planter box. Could they be the culprits?

– Carl Epple, El Dorado Hills

According to UC Master Gardener Carol Rogala, lizards likely are not your tomato tasters. Although some lizards eat plants, most feed on insects. In California, the most common types feed on beetles, ants, wasps, aphids, grasshoppers and spiders.

Lizards cause no measurable damage to plants in gardens and should be left alone.

Holes in fruit are more than likely caused by a worm of some type or slugs.

One possible pest is the armyworm. Armyworm larvae feed in groups, which distinguishes them from other vegetable pests such as corn earworms and loopers. Markings on newly hatched armyworms are usually hard to distinguish from those of other caterpillars; older larvae have distinct lengthwise stripes.

Armyworms may feed on the crowns of seedlings. On larger plants, armyworm caterpillars skeletonize leaves. In tomatoes, strawberries and cucurbits (such as squash), they make shallow (occasionally deeper) gouges in fruit.

The solutions for armyworms? Hand-pick and dispose of them.

Virus diseases, parasites (such as hyposoter and trichogramma) and general predators may be effective to combat these caterpillars. Eggs are protected from parasites by fluff. Bacillus thuringiensis, a biological insecticide, or other insecticides such as Spinosad may be used against young caterpillars but are needed only when numbers are high on seedlings. Ignore armyworms in sweet corn, where they do not usually cause major damage.

Another pest is the corn earworm: The corn earworm (also known as the tomato fruitworm) can cause holes in fruit. The color of this species varies and is not reliable for identification. Older larvae have distinct stripes along the sides and many short, whiskerlike spines over their body surface.

Earworms destroy lettuce seedlings and bore into heads, feeding on leaves, buds, flowers and pods of beans. They also eat through kernels of corn and leave deep, watery cavities in fruit.

Solutions for earworms? Hand-pick those, too. Avoid spraying with insecticides. Bacillus thuringiensis may kill 40 to 60 percent of the population but must be applied just after eggs hatch and before caterpillars enter fruit. Spinosad may also be effective.

Important natural enemies of the earworms include hyposoter and trichogramma parasites. General predators also feed on eggs and larvae.

How to outwit these bugs? Plant early and harvest before late August. Disc or rototill plants immediately after harvest to reduce over wintering populations and prevent migration to neighboring crops.

Now for other culprits. Snails and slugs are among the most bothersome pests in many gardens and landscapes. They feed on a variety of living plants and on decaying plant matter. They chew irregular holes with smooth edges in leaves and flowers and can clip succulent plant parts. They also can chew fruit and young plant bark.

A good snail and slug management program relies on a combination of methods.

Locate vegetable gardens or susceptible plants as far away from snail and slug hiding places as possible. Eliminate snails and slugs, as much as possible, from all places where they can hide during the day.

Hand-picking can be very effective if done thoroughly on a regular basis. You can trap snails and slugs as well as setting up barriers to keep them out of the beds.

Other possibilities for holes in tomatoes are birds, rats and squirrels.

For more detailed information on these pests, click on, the university's Integrated Pest Management website.


Questions are answered by master gardeners at the UC Cooperative Extension services in Sacramento and Placer counties.

Send questions to Garden Detective, P.O. Box 15779, Sacramento, CA 95852. Send email to h& Please put "Garden Detective" in the subject field and include your postal address. To contact your UC Extension directly, call:

• Sacramento: (916) 875-6913; 9 a.m.-noon and 1-4 p.m. weekdays

• Amador: (209) 223-6838; 10 a.m.-noon Monday through Thursday; email

• Butte: (530) 538-7201; 8 a.m.-noon and 1-5 p.m. weekdays

• El Dorado: (530) 621-5512; 9 a.m.-noon weekdays

• Placer: (530) 889-7388; 9 a.m.-noon on Tuesdays, Wednesday and Thursdays or leave a message and calls will be returned

• Nevada: (530) 273-0919; 9 a.m.-noon Tuesdays through Thursday or leave a message

• Shasta, Tehama, Trinity: (530) 225-4605

• Solano: (707) 784-1322; leave a message and calls will be returned

• Sutter, Yuba: (530) 822-7515; 9 a.m.-noon Mondays and Tuesdays and 1-4 p.m. Thursdays

• Yolo: (530) 666-8737; 9-11 a.m. Tuesdays and Fridays, or leave a message and calls will be returned

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