Common Vegetable Garden Problems and Pests

Every region has its own set of common vegetable garden pests and diseases. The UC Master Gardener Program encourages home gardeners to manage pests by using Integrated Pest Management (IPM), a science-based strategy to manage the damage pests (insects, diseases, vertebrates, and weeds) cause in the garden.

UC ANR's statewide UC IPM Program provides detailed home garden pest information and management techniques. The table below lists general problems and symptoms typical of many vegetables grown in home gardens in California.

General Problem Diagnosis for Vegetables
What the problem looks like	Probable cause	Controls and comments
poor fruit yield; small fruit with poor taste	uneven moisture poor soil fertility improper temperature	Supply moisture during dry periods. Add compost or well-composted manure. Plant at right time of year.
plants grow slowly; light green leaves	insufficient light cool weather improper pH excess water	Thin plants; do not plant in shade. Provide hot caps, floating row cover. Test for pH. If alkaline, add soil sulfur, aluminum sulfate, and peat moss. Do not overwater. Improve drainage by adding amendments and/or building raised beds.
seedlings do not emerge	insufficient soil moisture soil crusting damping-off (fungal problem) incorrect planting depth or seeds washed away slow germination due to weather root maggots old seed	Supply water. Apply light mulch to soil surface or water often enough to keep surface moist. Do not overwater. Use treated seed. Use gentler watering technique. In spring or fall, cover bed with clear plastic to increase soil temperature. Use registered soil insecticide. Use floating row cover as exclusion. Use registered soil insecticide. Use floating row cover as exclusion. Use current season seed.
seedlings wilt and fall over	dry soil damping-off (fungal disease) cutworms root maggots old seed	Supply water. Do not overwater. Treat with fungicide. Destroy crop residues; keep garden weed-free. Use cardboard collars, floating row covers. Use floating row cover as exclusion; use soil insecticide. Use current season seed.
chewed seedlings, plants, fruit	birds, rodents, rabbits	Place fence around garden; cover with netting, floating row cover.
leaves stippled with tiny white spots	spider mites air pollution (ozone)	Treat with registered miticide or insecticidal soap spray. Wash off foliage.
wilted plants	root rot (fungal disease) vascular wilt (fungal disease mainly affect-ing tomato, potato, eggplant, pepper) root knot nematodes various root-feeding nematodes waterlogged soil	Do not overwater. Remove old plant debris. Rotate crops. Use resistant varieties. Use soil solarization techniques. Rotate crops. Use resistant varieties. Use soil solarization techniques. Rotate crops. Submit soil sample for nematode analysis. Use soil solarization or fumigation. Improve drainage.
general leaf yellowing; no wilting	nutrient or mineral deficiency insufficient light	Test soil for deficiencies. Add complete fertilizer. Thin plants to reduce shading. Move to sunnier garden location.
leaf margins turn brown and shrivel	dry soil salt damage fertilizer burn potassium deficiency cold injury	Supply water. Do not place garden where de-icing salt may have been applied on nearby concrete. Keep salty water off foliage. Leach with good-quality water. Do not overapply fertilizer. Flush soil with water. Test soil for soluble salts level. Test soil for deficiency. Apply potassium fertilizer, compost, or manure. Protect from cold with hot caps, floating row cover.
discrete brown spots on leaves	chemical injury due to local application or drift	Do not apply chemicals that are not registered for use on the plant. Apply chemicals at registered rate.
white powdery growth on upper leaf surface	powdery mildew (fungal disease)	Choose resistant varieties. Use Safer’s sulfur with surfactant.
leaves shredded or stripped from plant	rodents, deer, hail damage, or slugs	Place fence around garden. Use slug bait.
leaves with yellow and green mosaic or mottle pattern; puckered leaves; stunted plants	virus disease	Use resistant varieties if possible. Remove infected plants. Remove old plant debris. Practice insect and weed control.
curled, puckered or distorted leaves	herbicide injury virus disease aphids	If you use lawn herbicides, apply after wind has died down. Do not apply herbicides in the heat of the day. Use resistant varieties if possible. Remove infected plants. Remove old plant debris. Practice insect and weed control. Use soap-based spray, floating row cover.

Source: California Master Gardener Handbook, Table 13.5.

Comprehensive information about managing vegetable pests, weeds, diseases, insects, mites, snails, slugs, and nematodes in California is available in Pests of the Garden and Small Farm (Flint 2018), which is recommended as a resource and reference book for UC Master Gardeners.