Regional Gardening Reports :: National Gardening Association

In the Garden:
Southern California Coastal & Inland Valleys
August, 2011
Regional Report

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Lush tomato plants but no blossoms? Too much water, or too hot temperatures!

Tomato Problems #1: General Growing Issues

Tomatoes are the reason that many folks garden. Their luscious ripeness, especially when greedily gulped just-picked, warm and juicy, is the beginning of an enveloping change in lifestyle. Playing with your food by growing your own starts here!

But there can be problems that foil our enjoyment and sustenance. The plants don't grow well, or don't produce fruit. Here are some of the most common tomato problems, their symptoms, and solutions. This column covers many of the general growth issues. The next column will deal with the fruit.

Symptom: Deformed growth or wilt.
Problem: Numerous insects sucking sap. Aphids found on undersides of leaves or clustered on new growth. Whitefly larvae on underside of leaves; adults fly up when foliage is disturbed.
Solution: A few insects won't hurt production. Crush them onto leaves or stem. Spray with soapy water. Natural enemies of aphids include ladybug larvae and adults, syrphid fly larvae, lacewing larvae, and parasitic wasps.

Symptom: Slow growth. Leaves paling from top of plant down. Leaves small and thin, with purple veins. Stems yellow and rigid. Flower buds yellow and drop off.
Problem: Nitrogen deficiency.
Solution: Apply nitrogen and compost.

Symptom: Leaves roll upward and are firm and leathery, but show no yellowing or stunting. Leaves on the sunny side of staked plants may often curl, while those on the shady side do not.
Problem: Curling leaves don't harm plant development or fruit production. Too much leaf pruning, sucker removal, or overly wet soil may promote leaf curl.
Solution: Plant on well-drained soil. Do not cultivate deeply near the plants, and avoid extremely close pruning.

Symptom: Yellow and green mottling on foliage; leaves crinkled and smaller than normal, with a shoestring appearance.
Problem: Mosaic viruses. Transmitted from weeds and flowers, aphids, cucumber beetles.
Solution: Wash hands with soap and water before handling plants. Do not smoke or handle tobacco before or while handling plants. Remove and destroy infected plants.

Symptom: Yellowing, wilting, dying of lower leaves progressively up the plant. Initially, often affects only one side of the plant. Brown streaks in tissue of lower stem when split lengthwise. Plants produce few fruits, which usually decay and drop before ripening.
Problem: Verticillium or fusarium wilts.
Solution: Plant resistant varieties. Use clean soil. Avoid areas previously planted with tomatoes, peppers, eggplant, potatoes, or cucurbits. Destroy infected plants.

Symptom: Foliage is distorted, cupped, or curled, ragged at edges, curved downward. Light- colored veins appear parallel.
Problem: Exposure to hormone-type herbicides.
Solution: Use extreme care when using herbicides. Plants may outgrow damage if given good cultural care.

Symptom: Irregular greenish-black water-soaked patches on older leaves that enlarge and may show a white, downy growth on surface. Fruits develop gray, green spots that becomes brown and wrinkled or corrugated; may become mushy.
Problem: Late blight fungus. Prevalent in mild, moist weather.
Solution: Hot, dry weather will slow or stop advance of disease.

Symptom: Dark areas of dead tissue surrounded by yellow on oldest leaves.
Problem: Anthracnose, a soil-borne fungus disease.
Solution: Avoid handling wet plants or planting in poorly-drained soil. Rotate to new soil each year. Remove and destroy infected plants or plant parts after harvest.

Symptom: Many tiny round holes; leaves may be so riddled that they turn brown and wilt.
Problem: Flea beetles.
Solution: A few holes are not damaging. Most damage occurs during the first warm weather of spring, when plants are small. Apply garlic spray.

Symptom: Leaves are eaten or chewed, partially or entirely.
Problem: Hornworm.
Solution: If the worm is carrying white pupae that look like grains of rice, let it be -- it's the victim of a parasitic braconid wasp and should be left to nurture a new brood of these beneficial insects. Remove worms by hand and destroy; sprinkling water on plant will make them wriggle, making them more visible and easy to pick. Spray with Bt. Release trichogramma wasps. Grow dill or four-o'clocks as a trap crop.

Symptom: Foliage has a greasy appearance, becoming bronzed and stippled; webbing and "moving dust" on undersides of leaves or in leaf axils. Plant appears to dry out from the ground up. Leaves turn brown and paper-like but do not wilt.
Problem: Mites.
Solution: Thrive in hot, dry weather. Wash down plant, especially undersides of leaves. Use garden sulfur according to label directions.

Symptom: Blossom drop.
Problem: Plant is stressed due to cool night temperatures (below 58 degrees) or high daytime temperatures (over 90 degrees), unusually heavy fruit set, lack of moisture, poor soil fertility, too much shade, certain diseases, excessive nitrogen fertilizer, insufficient potassium or phosphorous, or an aphid infestation.
Solution: Plant in full sun. Large-sized fruit varieties are very susceptible where summers are hot and dry. Choose varieties which produce small or medium-sized fruits. Cherry tomatoes tolerate cooler weather and set fruit better when air temperatures are in the low 50's. Blossom set will resume approximately seven to ten days after temperatures return to cooler levels. Readjust irrigation schedule.

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