Basil Plant Damage

Diseases

• Fungal and bacterial diseases plague basil plants. Fusarium wilt is a fungal disease found in poorly spaced plants. The fungus damages leaves and stems causing the plant to wilt, grow poorly and ultimately die. Gray mold is another fungus found growing on basil stems and on ground litter. High heat and humidity contribute to fungal growth. This fungal infestation is found in greenhouse crops but also outdoors when conditions are right. Basil plants sited in wet areas develop root rot and experience a disease called damping off. Saturated root systems fail to provide plants with nutrients. Plants wilt and die.

Foliage Damage

• Aphid-infected plants display puckered, wilted leaves streaked with a shiny substance. Ladybugs naturally control aphid populations and are helpful when introduced to your garden. The leafhopper is another harmful insect that not only leaves spots on basil leaves but also spreads viral diseases. Control aphids and leafhoppers with horticultural oil, botanical sprays and insecticidal soaps. Chemicals such as rotenone and pyrethrum are also used, but chemical sprays may be harmful if ingested so read labels with caution.

  Slugs chomp holes in foliage but their damage is controlled by limited overhead irrigation. Keep crop rows clear of debris as this limits potential slug living areas. Mature Japanese beetles are another insect responsible for chewing holes in tender foliage, an action that renders basil leaves useless. Japanese beetles stay in a grub stage for years. These grubs live in garden soil and infest crops once they mature. Control and prevent Japanese beetle damage by planting your basil crop in a different garden area each growing season.

Root Damage

• Root knot nematodes attack basil plant roots causing plant discoloration. Nematodes damage root tissue, and plants are unable to absorb needed nutrients. Over time, basil plants turn yellow and grow limp from malnutrition. Fortunately, simple preventive measures such as amending garden soil with mulch and compost or tilling soil and exposing it to bright sunlight for a few days diminish the presence of a root knot nematodes.

Prevention

• Healthy plants are less susceptible to insect infestation and disease, the major causes of basil plant damage. Plant your basil in an area that receives six hours of bright sunlight each day of the growing season. Soil should be moist and well-drained. Basil will not tolerate saturated soil and will develop fungal infections and diseases when left in saturated areas. Thin basil seedlings six to 12 inches apart. This allows air circulation, which will help prevent the spread of insects and disease.