Disease Control

Purchase disease-free seed. Use resistant varieties where feasible. Promptly remove any stock plants that are diseased or low in vigor. Use separate greenhouses for herb production and keep stock plants separate from production areas. There are few fungicides or bactericides registered for herbs.

NOTE:  For the products for disease control listed below, one product trade name and formulation is provided for each active ingredient (common name) as an example of rates, days to harvest (dh), REI, and special instructions. In many cases there are other products available with the same active ingredient. Please see Table 22 and Alphabetical Listing by Trade Name for more information on products with the same active ingredients.

Bacterial Leaf Spot (Pseudomonas)

Disinfect all benches, equipment, and pots. Purchase culture-indexed plants and disease-free seed. Avoid overhead irrigation. Discard infected plants. Clean production areas thoroughly after harvest as bacteria can survive in dead leaves.

Botrytis blight and stem canker (Botrytis cinera)

Management of environmental conditions such as temperature, relative humidity and duration of leaf wetness is vital to Botrytis control. Control weeds and remove plant debris between crops and during production. Provide good air circulation and reduce humidity within the plant canopy by proper plant spacing, plant height, and fertility. Water in the morning, never late in the day.

cyprodinil plus fludioxonil (Switch 62.5 WG): 11-14 oz/A. (7 dh, REI 12h, Groups 9 & 12).Do not make more than two consecutive applications.

 Damping-off, Crown and Root Rot (Pythium, Rhizoctonia, & Phytophthora)

Use pasteurized soil or soil-less mixes for transplant production. Disinfect all flats, pots, and tools. Use bottom heat to promote rapid seed germination. Avoid over-watering, over-fertilizing, and overcrowding. Promptly rogue out infected plants. Manage fungus gnats and shoreflies. 

Downy Mildew (Peronospora species)

Downy Mildew of basil is rapidly becoming a major production problem. Start with certified, disease-free seed. Promptly remove and destroy infected plants. Reduce leaf wetness periods by plant spacing, improving air circulation, and watering when plants will dry quickly.

potassium bicarbonate (MilStop): 2.0 to 3.0 lb/A. (0 dh, REI 1 h, Group M1).Uniform and complete coverage is essential for effective results. Do not store unused spray solution.

Fusarium Wilt (Fusarium oxysporum f.sp. basilici)

Fusarium wilt is very difficult to manage as it can persist in the soil or hydroponic system for many years. Practice strict sanitation. Begin with disease-free seed or treat seed with hot water or dilute chlorox. The basil varieties Nufar and Aroma 2 have resistance to Fusarium wilt. Fusarium is a soil inhabitant that can become established in the field. Promptly remove and destry all infected plants, infested soil, and plant debris. Rotate crops, excluding members of the mint family, which can be symptomless carriers of Fusarium.