In the Garden:
Southern California Coastal & Inland Valleys
June, 2005
Regional Report

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Tomato plants not growing well? There are lots of possible causes.

Tomato Problems

For many of us, tomatoes are why we garden. Other veggies and flowers may bring us pleasure, but tomatoes are what satisfies our yearning. When things go wrong with our tomatoes, we're distraught. Here are some common problems with plant growth, their probable cause, and how to avoid them in the future. In my next column, I'll talk about problems with the blossoms and fruit.

1. Symptom: Tops become weak, pale, dwarfed; plants wilt easily and die prematurely; yield is lessened. Swelling on roots becomes distorted, enlarged, and decayed.
Likely Cause: Root knot nematode
Solution: Plant resistant varieties. Interplant with marigolds (especially dwarfs) or where marigolds were grown and dug into the soil.

2. Symptom: Sudden wilting of plant and rapid rotting of roots.
Likely Cause: Phytophthora root rot, brought on by excessive watering and lack of drainage
Solution: Correct irrigation techniques.

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

4. Symptom: Slow growth; leaves paling from top of plant down; leaves small and thin, with purple veins; stems yellow and rigid. Flower buds turn yellow and drop off.
Likely Cause: Nitrogen deficiency
Solution: Apply nitrogen and compost.

5. Symptom: Slow growth; plants tinged purple; leaves small and fibrous; delayed fruit set.
Likely Cause: Phosphorous deficiency
Solution: Apply bone meal at planting time, and sidedress six weeks later.

6. Symptom: Brittle young leaves that curl up and turn yellow away from stems; green border on yellowed leaves.
Likely Cause: Magnesium deficiency
Solution: Incorporate dolomitic limestone or a handful of Epsom salts at planting time.

7. Symptom: Blackened areas at growing tip of stunted stem. Terminal shoots curl, yellow, and die.
Likely Cause: Boron deficiency
Solution: Apply 1 teaspoon of borax around base of plant.

8. Symptom: Yellowed leaves with green veins
Likely Cause: Iron deficiency
Solution: Add acidic material, such as leaf mold or manure.

9. Symptom: Stunted shoot growth; poor root development; bluish green foliage; leaves flabby and curled upward; few or no blossoms.
Likely Cause: Copper deficiency
Solution: Apply manure.

10. Symptom: Small, narrow leaves colored yellow between veins and mottled with dead areas. Stems may crack.
Likely Cause: Zinc deficiency
Solution: Apply manure.

11. Symptom: Very slow growth; yellowed areas between veins on leaves; few blossoms; no fruit.
Likely Cause: Manganese deficiency
Solution: Apply manure.

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

13. Symptom: Leaves roll upward and twist, become stiff and leathery, yellowed, stunted. Veins on underside turn purple.
Likely Cause: Curly top, western yellow blight. Transmitted by leafhoppers from weeds.
Solution: Use resistant varieties; destroy infected plants.

14. Symptom: Yellow and green mottling; foliage crinkled and smaller than normal with shoestring appearance.
Likely Cause: 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.

15. Symptom: Numerous, small, dark brown circular spots on young leaves; becoming bronzed and withered; older foliage is yellowed. Dark brown spots or streaks on stems near tips.
Likely Cause: Spotted wilt. Spread by thrips from weeds and ornamentals.
Solution: Keep weeds away from vulnerable vegetables (lettuce, celery, spinach, peppers, and potatoes).

16. 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. Few fruit, which usually decay and drop before ripening.
Likely Cause: 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.

17. Symptom: Distorted, cupped, or curled leaves, ragged at edges, curved downward. Light-colored veins appear parallel.
Likely Cause: Hormone-type herbicides
Solution: Use extreme care when using herbicides. Plants may outgrow damage if given good cultural care.

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

19. Symptom: Dark areas of dead tissue surrounded by yellow on oldest leaves.
Likely Cause: 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.

20. Symptom: Many tiny round holes; leaves may be so riddled that they turn brown and wilt.
Likely Cause: 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.

21. Symptom: Leaves eaten or chewed, partially or entirely.
Likely Cause: Hornworms
Solution: If the worm is carrying white pupae, let it be because those are likely pupae of a parasitic braconid wasp that should be left to nurture a new brood of beneficials. Otherwise 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 parasitic trichogramma wasps. Grow dill or four-o'clocks as a trap crop.

22. Symptom: 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.
Likely Cause: Mites
Solution: Mites thrive in hot, dry weather, so wash foliage, especially undersides of leaves. Use garden sulfur according to label directions.


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