Botrytis Stem and Pod Rot
Botrytis stem and pod rot of lentil is caused by the fungus Botrytis cinerea. This fungus is a common pathogen of many crops including peas, beans, sunflowers and buckwheat and is also a widespread saprophyte on dead and dying plant material. The disease is most severe when moist conditions persist during and after flowering. Yield losses are usually higher in crops with dense or weedy stands or in irrigated crops.
Appearance: Symptoms can be observed on seedlings and mature plants. Seedling blight may occur if infected seed is planted. The stem completely rots at the soil line and the seedling becomes stunted, turns yellow, then dries up and dies. A higher percentage of seedling death than of infected seed planted can occur because the fungus spreads from diseased to healthy seedlings along rows. Infections on the lower stem later in the growing season can result in premature ripening. The infected portion of the stem is light brown or bleached and covered with a gray moldy growth. Infected pods fail to fill properly, rot, turn brown, and are also covered with mold. Infected seeds may be discoloured and shriveled.
Disease cycle: The disease is both seed and stubble-borne. The amount of seed infection is an important factor determining the severity of seedling blight. The severity of the disease on mature plants is dependent mainly on weather conditions during the growing season.
Spores of Botrytis are spread from plant to plant by wind and rain-splash. Wet weather contributes to disease epidemics by providing suitable conditions for spore production and plant infection.
Disease Control: Use disease-free seed or the best seed available to reduce seedling blight. Seed treatments can be used to control seedling blights/seed rots caused by Botrytis and other pathogens.
Botrytis and Gray Mold
Gray mold, caused by the fungus Botrytis cinerea, can cause serious yield losses of peas growing in humid conditions. The fungus is a common pathogen of many crops including lentils, beans, sunflowers and buckwheat. It can also function efficiently as a saprophyte on dead and dying plant material.
Appearance: The first symptoms usually observed are on the lower leaves during or after flowering. Under humid conditions the leaves appear fuzzy because of the masses of spores produced. As infection progresses, infected leaves become dry, gray, and shriveled and eventually fall off.
Pod damage is the main cause of economic loss. Small, oval, tan, water-soaked spots develop on pods often at sites where petals have fallen. Senescent petals provide a food source for the fungus and also help to maintain humidity. Mature spots are grayish, slightly sunken, and sometimes include small black specks.
Disease Cycle: Botrytis over-winters in infected seed or on debris of numerous host plants. Spores of Botrytis move in splashing water, in air, in irrigation water, and on farm machinery. The severity of the disease is dependent mainly on weather conditions during the growing season. Wet weather contributes to disease build-up by providing suitable conditions for spore production and plant infection.
a) Use disease-free or lightly infected seed.
b) Potassium should be applied if this nutrient is deficient in the soil. Potassium deficiencies have been reported to make pods more susceptible to gray mold.