Bloggin About Basil: What's Botherin My Basil??

Below are a few of the diseases that you may come across when growing your basil.

however, this information does not cover every problem that can occur with basil. If you notice a problem in your field or greenhouse, you can contact your local cooperative extension or agricultural agency and arrange to have the affected plants tested. Testing is the only sure way to diagnose the cause of a pest or disease problem. Very few chemical pesticides and fungicides are registered for use on basil, therefore, good cultural practices are important in preventing the onset of problems. For the best chance of having a successful basil crop, use the following guidelines:

Use quality seed that has been tested for the presence of fusarium wilt fungus.
Grow your crop in disease-tested soil or sanitized greenhouse conditions.
Do not grow consecutive basil crops in the same soil.
Inspect growing areas frequently, and remove any diseased plants immediately.
Limit overhead irrigation, which can spread disease through the stand of plants.
Create good air movement by increasing the spacing between plants or using fans.
Increase the organic matter in the soil, which favors pathogen reduction.

Please share with others through our blog, any issues that you have experienced!

Fusarium Wilt

Pathogen - Fusarium oxysporum, a soil-borne fungus that can last in the soil for 8-12 years.

Host - Only sweet basils; specialty basils seem resistant.

Environment – Soils with high moisture and poor drainage have higher rates of presence.

Signs & Symptoms - Typical plant growth until 6-12 inches, then stunted growth, followed by wilting, brown streaks on stem, discoloration of internal stem tissue, crooked stems, and sudden leaf drop.

Controls - Buy disease-tested seed or resistant varieties. If soil is contaminated, avoid planting any members of the mint family in that plot for 8-12 years - mints will not display symptoms of disease, but will carry over the inoculum. Also spread through contaminated plant material, so careful handling and destruction (by burning) of the plants is necessary.

Basil Downy Mildew

A relatively new disease affecting the leaves of basil, making it unmarketable.

Pathogen - Peronospora belbahrii, a fungal-like pathogen spread from infected seed or wind-dispersed spores with high travel capabilities.

Host – Basil and other Lamiaceae family plants, including crops and ornamentals

Environment – Carried in by wind.

Signs & Symptoms – Slight yellowing of leaves, similar to nutrient deficiency or water stress, dark-grey fuzziness on underside of leaves.

Controls – Use disease-free certified seed or disease-resistant varieties. Several OMRI certified fungicides exist, but are most beneficial when applied before the disease shows up and will need to be applied to the underside of leaves, which can be difficult. Affected plants should be removed from the area to reduce the chance of spreading. Till in diseased plants or lay out on a sunny day for the pathogen to be killed by UV radiation.

Yellowing of the upper surface of affected basil leaves often occurs in sections of the leaf delineated by veins because the downy mildew pathogen cannot grow past major veins in leaves.

Bacterial Leaf Spot

Pathogen - Pseudomonas cichorii, a bacteria spread by water splash or handling or by contaminated seed.

Host – wide host range

Environment – Thrives in hot, wet/humid conditions.

Signs & Symptoms – Blackening of leaves.

Controls – Use certified disease-free seed. Plant crop at a wider spacing to increase air circulation. Avoid the use of overhead watering systems. Remove diseased leaves to reduce spread.