Botrytis Blight

  • Symptoms

  • Trigger

  • Biological Control

  • Chemical Control

  • Preventive Measures

Botrytis Blight

Botrytis cinerea

Fungus


In a Nutshell

  • Profuse gray mold can be observed on leaves, fruits or pods, giving them a fuzzy appearance.
  • Plant parts or the plant as a whole may wilt, turn brown and die (damping-off).
  • Occasionally, dieback of branches and canker formation have been observed on woody crops.

Hosts

Almond

Apple

Bean

Cabbage

Canola

Capsicum & Chili

Carrots

Cherry

Chickpea, Gram

Citrus

Cucumber

Currant

Eggplant

Grape

Lentil

Mango

Onion

Pea

Peanut

Plum

Potato

Pumpkin

Red gram, Pigeonpea

Strawberry

Sugar beet

Tomato

Zucchini

Symptoms

The profuse growth of mold on leaves, shoots, pods or fruits is the most striking symptom. Initially, sparse, tan or brown and water-soaked lesions appear on plant parts that are in contact with the soil or that have been injured. Profuse, hairy and gray to brown patches of fungal growth develop on these tissues. Later on, the mold grows on younger fruits and pods, giving them a fuzzy appearance. Alternatively, the symptoms appear during storage. In both cases, severe losses can be expected. Basal leaf and stem rots cause a total crop failure in the case of susceptible varieties of horticultural crops (damping-off). Occasionally, dieback of branches and canker formation have been observed on woody crops.

Trigger

The symptoms are caused by the soil-borne fungus Botrytis cinerea, which can grow and infect all plant parts. Moist weather, with frequent rainfall and cool temperatures favors the appearance of the symptoms. The reported optimal temperature range for the development of the fungus, the colonization of the plant and the progression of the disease is 15 to 20°C. Symptoms first appear on leaves or plant parts that have been injured mechanically during field work or through hail or frost. Lower leaves are most vulnerable. Excessive irrigation and dense canopy may increase the level of the disease by providing a humid, dense environment that is favorable for fungal growth.

Biological Control

Biofungicides containing the competitive fungus Trichoderma harzianum are effective against gray mold on a wide range of crops. Products based on Streptomyces griseovirides are also available for use on lettuce.

Chemical Control

Always consider a integrated approach with preventive measures and biological treatments, if available. Control is difficult to achieve because the fungus may colonize the host plants close to harvest time, thus preventing the application of chemicals that leave toxic residues. In case of early infections, foliar sprays with chlorothalonil can be applied to control its spread. Other fungicides based on fluazinam, and thiophante-methyl can also work. The development of resistance is common when fungicides are used intensively.

Preventive Measures

Use healthy planting material from certified sources.,Plant resistant or tolerant varieties of the crops.,Plant early or early-maturing varieties.,Keep a reasonable distance between the plants.,Ensure an adequate row orientation and upright plants.,Ensure good drainage of the location and avoid inappropriate irrigation.,Do not overfertilize the crops.,Take great care not to injure the plants when working in the field.,Monitor the field and remove the decaying plant tissues.,Use mulch to impair the life cycle of the fungus and reduce the inoculum.