Regional Gardening Reports :: National Gardening Association

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

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Crimson Carmelo 2 produces beautiful fruit if you can keep it free of insects and other problems.

Problems With Tomato Blossoms and Fruit

When something goes wrong with our tomato plants, we feel threatened; we're in danger of losing the very payoff we're gardening for! In my June 23 column, I dealt with general growth problems. In this column I'll tackle problems with blossoms and fruit.

1. Symptom: Lush foliage, but no blossoms and few fruits
Problem: Too much nitrogen
Solution: Incorporate a balanced fertilizer at planting time. Don't feed more nitrogen during growing season.

2. Symptom: Blossom drop
Problem: Plant could be stressed due to cool night temperatures (below 58 degrees) or high daytime temperatures (over 90 degrees). Other causes could be unusually heavy fruit set, lack of moisture, poor soil fertility, too much shade, certain diseases, excessive nitrogen fertilizer, insufficient potassium or phosphorus, or an aphid infestation.
Solution: Plant in full sun. Large-sized fruit varieties are very susceptible where summers are hot and dry. Choose varieties that produce small or medium-sized fruits. Cherry tomatoes tolerate cooler weather and set fruit better when air temperatures are in the low 50s. Blossom set will resume approximately 7 to 10 days after temperatures return to cooler levels. Readjust irrigation schedule. Control aphids with insecticidal soap or other non-toxic sprays.

1. Symptom: Light-colored, cloudy spots with pithy or corky areas just below the skin
Problem: Stinkbug punctures
Solution: Remove insects by hand and destroy. Spray with insecticidal soap. Keep down weedy areas if bugs have been persistent. Plant smaller sections of crops, rather than large areas.

2. Symptom: Hole at stem end and fruit hollowed out
Problem: Tomato fruitworm
Solution: Remove by hand and destroy. Spray with Bt or onion/garlic solution. Release trichogramma wasps. After harvest, turn soil to kill pupae.

3. Symptom: Large holes or completely hollowed out
Problem: Slugs
Solution: Stake tomatoes and place mulch or boards under fruit to get them off the soil. Harvest frequently.

4. Symptom: Hollow fruit
Problem: Poor pollination caused by low light (dark, cloudy days), too much nitrogen, heavy rainfall, temperatures that are too high (over 90 degrees) or too low (below 58 degrees), or too much hormone fruit-set spray.
Solution: Set tomatoes out later in season and modify environment with hotcaps. Shade in hot weather. Use less fruit-set spray.

5. Symptom: Cracks in concentric circles around stem or in lines radiating from center
Problem: Sudden, rapid growth during high temperatures (over 90 degrees) and high rainfall or heavy irrigation, especially after a dry spell. Ripening fruit and fruit exposed to the sun are most affected.
Solution: Plant less susceptible varieties. Keep soil evenly moist with proper watering techniques and mulch. Don't remove leaves from plants. Don't irrigate just before harvest.

6. Symptom: Black mold along growth cracks
Problem: Damaged, cracked tissue developing under warm, moist conditions.
Solution: Prevent fruit cracking (see #5 above). Handle fruit carefully.

7. Symptom: Misshapen fruit but no scars
Problem: Inadequate moisture, fruit confined in foliage
Solution: Water deeply and more frequently, especially during hot spells. Provide trellising; free fruits from binding.

8. Symptom: Catfacing -- misshapen, puckered, swollen areas; cavities lined with scar tissue
Problem: Incomplete pollination due to 1) weather being too cool or hot, 2) bees not being available, or 3) overhead irrigation during blossoming that makes blossom cling to itself, resulting in abnormal shaping of the fruit. Common on early fruit of varieties that produce large-size fruit.
Solution: Plant less susceptible varieties, including those bearing smaller fruit. Encourage bee activity. Irrigate under foliage.

9. Symptom: Circular sunken spots on skin that enlarge and darken
Problem: Anthracnose.
Solution: Plant in well-drained soil. Destroy plants and fruits (do not place in compost pile).

10. Symptom: Blossom-end rot -- watersoaked area on blossom end that darkens and becomes larger, sunken, and leathery.
Problem: Related to lack of calcium due to inconsistent watering (alternating wet and dry weather); more severe in sandy soils and soils with a high salt content.
Solution: Plant less susceptible varieties. Refrain from planting in very cool soils. Calcium is not available to plants at a low soil pH, so incorporate dolomitic limestone at time of transplanting. The finer the grade of limestone, the faster it breaks down in the soil, and the sooner it raises the pH and enables the calcium to be utilized. Keep soil evenly moist with more thorough irrigation. Stake tomatoes or mulch beneath them to get fruit off ground.

11. Symptom: Brown, slightly sunken spots that enlarge, darken, and break open.
Problem: Soil rot fungus where fruits are allowed to lie on the soil or are repeatedly splashed by rain or overhead irrigation.
Solution: Plant in well-drained soil, stake plants, and mulch beneath them.

12. Symptom: White or yellow patches on parts of green or ripening fruit that face the sun; patches become blisterlike and form large, flattened, grayish white areas with a dry, paperlike surface.
Problem: Sunscald, most frequent during hot dry weather and on plants that have lost foliage from pruning or disease.
Solution: Some varieties with little foliage are more tender and sunscald more easily. Don't remove leaves from plants. Where fruits are exposed, put a light covering over the clusters to diffuse the direct sunlight.

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