IF YOU SEE: Leathery skin on fruit and a dark or water soaked area on the blossom end (opposite the stem) of the fruit that eventually enlarges, turns brown or black, and becomes sunken and flat …
This might be BLOSSOM END ROT, which is often caused by fluctuating soil moisture such as occurs when a dry period is followed by lots of rain. This is evidence of a calcium deficiency in the fruit. Too much nitrogen, high salt levels in the soil, or root damage can also contribute. Note: Fruit does not rot unless secondary organisms invade. Tomatoes grow slowly and may ripen prematurely.
To avoid: Prepare deep, well-drained soil. Apply lime if calcium is low. Plant in warm soil. Water uniformly and regularly; provide mulch. Cultivate shallowly. Avoid overfertilizing; use nitrogen forms that do not contain ammonia, which inhibits calcium uptake. Stake plants when young.
To control: Remove affected fruit.
IF YOU SEE: Misshapen fruit with scars at the blossom end …
This is CATFACING, which is caused by prolonged cool weather during flowering. Poor pollination or high nitrogen levels may also be a factor.
To avoid: Transplant during warm weather. Provide row covers when nights are below 55[degrees]F.
IF YOU SEE: Radial cracks from the stem end of fruit and concentric cracks around the shoulders of the fruit …
This is CRACKING, which results from rapid fruit development and fluctuating soil moisture (such as a dry spell followed by warm, rainy weather while fruit develops).
To avoid: Choose resistant varieties. Water regularly and evenly; provide mulch. Do not overfertilize with nitrogen.
IF YOU SEE: Few or no flowers or blossoms dropping without setting fruit …
This is POOR FRUIT SET, or POOR FLOWERING, which results from too much nitrogen or too much shade. Too little water or temperatures above 90[degrees]F during the day or below 55[degrees]F at night during flowering may cause blossoms to drop. Pests and diseases or lack of pollination may also contribute.
To avoid: Grow early-maturing varieties. Choose a site that receives at least 6 hours of sun per day. Set plants out when night temperatures are consistently above 55[degrees]F or protect with row covers at night. Do not overfertilize with nitrogen. Provide even moisture.
FUNGAL AND VIRAL DISEASES
IF YOU SEE: Sunken spots that darken and develop rings on ripe fruit …
This is ANTHRACNOSE, which is prevalent in warm, wet conditions.
To avoid: Provide well-drained soil.
To control: Destroy infected fruit. Spray plants with a copper-based fungicide to prevent spread.
To avoid next time: Destroy infected plants after harvest. Use a 3- to 4-year crop rotation.
IF YOU SEE: Concentric, dark rings on older leaves and stems and dark, concentrically ringed, sunken areas near the stems of green fruit …
This is EARLY BLIGHT, or ALTERNARIA BLIGHT, which thrives in warm, humid weather. It can be present in seeds.
To avoid: Choose resistant varieties. Allow enough space between plants to provide good air circulation. Do not wet plants unnecessarily. Weed regularly (some weeds serve as hosts to this disease).
To control: Remove infected leaves. Spray with a copper-based fungicide or sulfur dust to deter spread. Pick fruit promptly.
To avoid next time: Destroy infected plants after harvest; do not compost (fungus can overwinter in diseased plant debris). Practice crop rotation.
IF YOU SEE: Yellowing and wilting lower leaves and/or stunted plant growth …
This is FUSARIUM WILT or VERTICILLIUM WILT, which enter plants through their roots. Fusarium wilt occurs frequently in 80[degrees] to 90[degrees]F temperatures and survives best in sandy, dry soils. It may attack one shoot or side of the plant first; shoots or the whole plant may wilt and not recover after watering. Look for dark streaks in the stem when cut lengthwise. Verticillium wilt prefers 65[degrees] to 75[degrees]F and is present in many soils. It shows up as V-shape, yellow-to-brown areas on lower leaves; affected foliage wilts and may drop off; the stem may be light brown inside up to about a foot above soil level; top leaves remain green; fruit are small.
To avoid: Choose resistant varieties. Soak seeds in a 10 percent bleach solution before planting.
To control: Place tools in boiling water for 5 minutes and then wash with detergent.
To avoid next time: Destroy infected plants after harvest; do not compost. Practice crop rotation.
IF YOU SEE: Mottled and yellowed leaves and twisted or deformed young growth …
This is TOBACCO MOSAIC VIRUS, which spreads through seeds and direct contact.
To avoid: Grow resistant varieties. Soak seeds in a 10 percent bleach solution before planting. Avoid handling tobacco near plants.
To control: Destroy infected plants; do not compost. Disinfect gardening tools.
IF YOU SEE: Twisted, puckered, yellow leaves and distorted buds and flowers and/or honeydew (clear, sticky liquid), sometimes accompanied by sooty mold …
You have APHIDS, which are pearshape green, black, pink, gray, or cottony white soft-bodied insects with long antennae; sometimes winged; and less than 1/8-inch long at maturity. The nymph is similar to the adult. Aphids are often present in large numbers. Adults and nymphs suck plant sap.
To control: Knock the insects off with a strong spray of water. Attract beneficials such as lacewings or lady beetles. Repeatedly spray insecticidal soap.
IF YOU SEE: Dropped buds, deformed young fruit, and shallow, yellow-white, corky spots on fruit (called cloudy spot) …
You have STINK BUGS, which are shield-shape green or brown insects that are about 1/2-inch long and emit a disagreeable odor when handled. The nymph is wingless. Adults and nymphs suck sap from all parts of the plants.
To control: Eliminate surrounding weeds where adults overwinter. Encourage native parasitic wasps. Spray with insecticidal soap or dust with sabadilla, if a heavy infestation occurs.
IF YOU SEE: Holes in leaves and stalks and distorted young leaves; a hole near the stem of green fruit; and/or rotted, hollow fruit that may collapse …
You have TOMATO FRUITWORMS, aka CORN EARWORMS, which are 1 1/2 inches long at maturity. The larvae are light yellow with a brown head; the color can darken and change to green, red, or brown as they mature; stripes might appear. A single larva may be inside fruit.
To control: Destroy infested fruit. Spray larvae on leaves with BTK (Bacillus thuringiensis ssp. kurstaki). Cover plants with row covers to keep adult moths from laying eggs.
IF YOU SEE: Leaves with large holes and severe defoliation in heavy infestations; devoured flowers; and/or scarring on fruit surfaces …
You have TOMATO HORNWORMS, which are 3 to 4 inches long at maturity and have a black horn on their hind end. (The tobacco hornworm is similar, with a red horn.) The caterpillar has eight V-shape stripes on its green body.
To control: Handpick, if there is a minor infestation. Encourage natural predators such as the braconid parasitic wasp. Introduce Trichogramma parasitic wasps or spray with BTK when caterpillars are small.