Common Insect Problems in Vegetable Gardens

Stink Bug

These insects are commonly found in vegetable gardens that include tomatoes, squash and beans. They are distinctly shield shaped and are brown or green. Small bundles of barrel shaped white eggs may be spotted on leaves. Insecticidal soaps are effective against sub-adults. Handpicking adults is recommended. Controlling weeds where the bugs overwinter is also a good idea.

Cucumber Beetle

Cucumber beetles like shady cool places such as leaf and melon undersides. Keep leaves dry and raise fruits to keep the underside dry. There are no effective sprays for the beetles. The adult beetles overwinter in weedy area. Keep weeds cut down all year. Completely cover emerging seedlings with row cover, fine screen or paper cup until the plant is large enough to tolerate some damage. Zucchini squash is a favorite plant, followed by crookneck squash, melons and beans. Hand picking is recommended.

Squash Bug

These bugs are about ½ long, brownish yellow and flattened like a stink bug. Zucchini is a favorite plant. Leaves will blacken and drop as they dry. The bugs can difficult to control. Placing row cover over young plants helps prevent infestation. These bugs also overwinter in nearby weeds.

Common Tomato Insects/Diseases

Tomato Russet Mite

The most common and probably least recognized tomato problem is the tomato russet mite that appears as dead leaves starting at the bottom of the plant and moving upwards. The stem takes on a bronzy appearance. It can be controlled with an application of wettable sulfur mixed in a pump sprayer with a spreader-sticker and applied to the entire plant including undersides of leaves and deep into the interior of the plant. Sulfur should not be applied if temperature is expected to be above 90 degrees F. Refer to the UC Pest Note for more information.

Verticillium Wilt

The first symptom is yellowing of the older leaves at the bottom and a slight wilting of the tips of the shoots during the day. The yellowed leaves dry and fall off and eventually the whole plant is affected. The leaves higher up will be dull looking and the new leaves will tend to curl upward. All the branches are uniformly affected. You will still get tomatoes, but they will be stunted. The fruit is exposed to the sun without leaf protection and most of the crop will be lost to sunscald. This also affects potatoes, peppers, eggplants, strawberries and raspberries. Refer to the UC Pest Note for more information

Fusarium Wilt

This is the most prevalent and damaging tomato disease. It also starts with the yellowing of lower leaves, but the yellowing may be only on one side (stopping at midrib) of the leaf or just one branch or one side of the plant. The older leaves will droop and curve downward. The yellow leaves wilt and die, gradually killing the whole plant. Sometimes a single shoot is killed before the rest of the plant shows any damage. There are a few additional details in the UC Pest Note on tomato fusarium wilt.

Wilt Control

There is really no point to trying to save plants with wilt problems. Many times there is a combination of the above diseases. Look for seed packets and plant tags that have “VF” on them as these are resistant varieties. Soil diseases can last for years. Do not plant tomatoes in the same spot every year. Use crop rotation. Soil solarization is a good way to control both wilts.

Hornworm

If you have a hornworm, you will know it. You will look at your plant and a good portion of it will be missing, eaten by the hornworm. All that is left are some large black droppings, the remains of your leaves. You may see this first, because they are the same color as the leaf and are hard to see. They are the largest caterpillars you will see in the garden, as long as four inches, with a distinctive horn or thorn on the rear end. They are beautiful, with white striping and little round circles. The amount of damage they do is unbelievable. Hand pick to control or use Bacillus thuringiensis (BT).

Other tomato problems:

• Stress - Irregular watering can cause blossom-end rot (see below). High temperatures can affect the coloring process. Give the tomato deep watering, once or twice a week is more than enough. Fertilize only if plant has yellow or purpling (indicating a nutritional deficiency) with small amount of sulfate of ammonia or fish emulsion. Too much nitrogen will give you a lush beautiful plant and few fruits. Mulching would be very beneficial.
• Blossom drop - Night time temperatures too cool (below 55). Also a sustained heatwave can cause blossom drop.
• Blossom-End Rot - This is one of our most asked questions. There is nothing like watching your first tomato of the season ripen. You can hardly wait to eat it, it looks great from the side and top. You finally pick your tomato only to find that the blossom end is sunken and dark brown. The first tomatoes are usually growing low on the vine and that's why you don't see the bottom. Blossom-end rot is caused by inconsistent soil moisture or a calcium deficiency. Try to be more consistent about irrigation. Water during dry periods. Mulch to prevent moisture loss. Use lime or calcium fertilizers before planting to prevent calcium deficiency.
• Catfacing - Cool cloudy weather during bloom may cause the blossom to stick to the small fruits resulting in malformation of the fruit. The blossom end of the fruit is puckered, with scars. It usually occurs on the early fruit of large fruiting varieties.
• Fruit cracks - Rain or too much water during high temperatures (above 90), followed by a dry period, causes rapid growth. This is worse on ripening or fully ripe fruit. Again, irregular watering could be the problem.
• Leaf roll - This is different than leaf roll caused by disease. This is caused by prolonged rains or too much moisture in the soil. Some varieties are more prone to rolling than others. The lower leaves roll first and continues. Leaves may cup and overlap, feel firm and leathery. Regular watering and mulching is the best control. This is not a serious problem.
• Misshapen fruit - Bulges, pointed, puffy, abnormal, not round and smooth. This happens when young plants are exposed to temperatures of 55F or lower and usually affects the first tomatoes. The low temperatures interfere with the growth process.
• Sun scald - Poor foliage cover causes a yellow or white patch to form on green tomatoes. As the fruit ripens, it shrinks, forming a large flat grayish white spot with a paper feel. Caging helps to concentrate foliage and protect fruit.
• Anthracnose - This is prevalent on overly ripe fruit at the end of the season. Small sunken circular spots that increase in size, with the center turning black. Wet weather promotes disease development.
• Graywall or Blotchy Ripening - Yellowish blotches or internal browning on otherwise ripe fruit. This disorder has been associated with environmental factors and possibly bacteria. Its cause is not clearly understood. Low light intensity (dense vines), low temperatures, excessive soil moisture, soil compaction, high nitrogen, or low potassium may promote Graywall.

More July Tips

Watering

When is it enough? Whether you are using drip or sprinklers or hand watering, measuring how much water is actually getting down to the plant’s roots is important so you don’t under or overwater. At your local garden center, there is a tool called a moisture meter that can help determine the proper amount to apply. It sells for less than $10 and has a metal probe and a simple needle dial on top that tells you if the soil is dry, moist or wet. The moist reading is recommended. Great for using in pots or on vegetables. One caution, pull the meter out of the soil using the probe rather than the plastic housing on top as the meter can pull apart.

Winter Vegetables

Late July is the time to start seeding your winter vegetables. They need the heat to germinate and then the long cool, wet winter to slowly grow for harvest in the spring. Review our cool season vegetable chart for what and when to plant. Quickly growing summer vegetables may also be planted now such as bush beans, radishes, lettuce and peas.

Spinach Leafminer

Adults are small black to gray flies with yellow markings. Females puncture leaves to feed on plant sap and lay eggs within the leaf tissues. After 2 to 4 days, eggs hatch. Larvae feed between the upper and lower surface of the leaves, making distinctive winding, whitish tunnels or mines that are often the first clue that leafminers are present in spinach or chard. Larvae emerge from the mines and pupate on the leaf surface or, more commonly, in cracks in the soil. Many generations occur each year and the entire life cycle can be completed in less than 3 weeks when the weather is warm. The simplest control is removal and disposal of every affected leaf. Check very early leaves and remove at first sign. See the UC Pest Note for more information.

Butterfly Gardens

To attract a variety of butterflies and moths to your garden you need a mixture of spring and summer nectar producing flowers for them to feed on. Butterflies lay their eggs on plants that the newly hatched caterpillars will eat. Here are some of the plants that butterflies and moths like.

• Herbs: Sage, Hyssop, Thyme, Dill*, Catnip, Lavender, Parsley*, and Common Rue*.
• Wildflowers: Queen Anne's Lace*, Bee Balm, Goldenrod, Red Clover*, Milkweed*, Purple Coneflower, and Butterfly Weed*
• Vegetables (let flower): Cabbage*, Kale*, and Broccoli*
• Misc. plants: Globe thistle, Yarrow, French Marigolds, Sunset Cosmos, Mexican Sunflowers, Phlox, and Alfalfa*. (*especially good)
  

Cantaloupe Melons

By this time the vines have spread out and there are flowers everywhere. A foliar spray of a water-soluble fertilizer will give them a boost now. Keep the water flowing as they are one of the thirstiest plants you can grow. You can set young melons on the top of inverted cans (coffee cans, tuna cans, etc.) to warm them faster and more evenly. Punch a hole in the bottom of the can so water won't puddle and rot the melon. Melons will begin ripening in August. How will you know when it's ripe? The background color behind the netting will turn from green to tan. The stem will slip right off with just a light touch. Last but not least. let your nose tell you if it's ripe. Smell the stem end; it should have a wonderful melon aroma. The color and smell test also works well in the grocery store.

Tomatillo (Physalis philadelphica)

Tomatillos still to this day is a truly wild plant. Attempts to hybridize them have failed. The plant is native to Mexico and was brought to the U.S. by Mexican Indian immigrants. It has a tart green apple taste and is the main ingredient in green salsas. It is also used in soups, stews, and guacamole. It is a member of the Solanaceae (nightshade) family as is the tomato and will grow any place a tomato will. It is fairly drought tolerant. Being a wild plant, there is a great deal of variability in plant habit, fruit size, etc. It is an annual, a low growing, sprawling plant usually not more than 2 feet high. The tomatillo has small, sticky, tomato-like fruits enclosed in papery husks. They are 1 to 3 inches in diameter and green or purplish in color. Culture is very similar to that for tomatoes or peppers. Plantings are generally direct seeded. The first harvest is ready in 70 - 80 days. They are not ripe until the fruit begins to break through the husk.

Geranium (Tobacco) Budworm

Watch for budworms feeding on the buds of geraniums, roses and petunias. It is closely related to the corn earworm. Both 'worms' are the larvae of a dull gray-colored, night-flying moth. Mating is after the full moon. By the new moon the larvae are numerous and each cycle brings a bigger and bigger population. The pupae overwinter in the soil and emerge as moths in April or May. It lays one egg per bud and the hatched larvae feed on it as it grows, eventually moving on to the rest of the plant. It takes on the color of the plant it is eating. For heavy infestation try spraying with Bacillus thuringiensis. Repeat weekly until no more damage is being done.