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Sclerotium Rot

Sclerotium Rot

Athelia rolfsii

fungi

In a Nutshell

    The fungus forms a white, fluffy mat with roundish, tan to brown structures on the stem and surrounding groundThe base of the stem turn pale brown and soft, but not wateryLeaves start to wilt and become chloroticPlant can lodge or die, and entire rows or large patches of dead plants are observed in the field

Hosts: %1$s

· Bean · Capsicum & Chili · Eggplant · Carrots · Turnip · Pea · Cucumber · Pumpkin · Tomato · Cabbage · Potato · Pigeonpea · Chickpea · Soybean · Onion · Maize · Sweet Potato · Melon ·

Symptoms

The fungus primarily attacks the stems, although other plant parts may be affected under favorable conditions. It grows rapidly over the plant tissue and surrounding soil forming a white, fluffy fungal mat with characteristic roundish, tan to brown "seeds" called sclerotia. The stem tissues turn pale brown and soft, but not watery. In some cases, the stem may be completely girdled and leaves gradually start to wilt and become chlorotic. Eventually, the plant can lodge or die, and entire rows or large patches of dead plants can be observed within the field. Seedlings are particularly susceptible and die quickly once they become infected. Occasionally, fruits are also covered with the fungal mat and they rapidly decay.

Trigger

The symptoms are caused by the fungus Athelia rolfsii, also known as Sclerotium rolfsii, thereby the common name of the disease. It overwinters in the soil or associated with plant debris. It causes disease on a wide range of agricultural and horticultural crops (lentil, sweet potato, pumpkin, corn, wheat and peanut, to name a few). In favorable conditions, it has an extremely rapid growth and can colonize plant tissues at or near the soil line in question of days. Low soil pH (3.0 to 5.0), frequent irrigation or rain, dense planting and high temperatures (25 to 35 °C) favor the life cycle of the fungus and the infection process. By contrast, calcareous soils with high pH usually do not cause problems. Dissemination depends on the movement of infested soil and water, contaminated tools and equipment, as well as infected plant and animal material (seeds and manure).

Biological Control

Antagonistic fungi (often in combination with other treatments) can provide some control against this pathogen. Note that results depend greatly on the type of crop and the environmental conditions. Some of the commonly used organisms are Trichoderma harzianum, Trichoderma viride, Bacillus subtilis, Streptomyces philanthisome, Gliocladium virens and some species of Penicillium.

Chemical Control

Always consider an integrated approach with preventive measures together with biological treatments if available. Use of multipurpose soil fumigants before planting provides a good control of the fungus. Products based on metamsodium, methyl bromide, chloropicrin, formalin, or chlorobromopropene can be used for treatment of seed beds or fields for valuable crops.

Preventive Measures

    Make sure to use healthy seeds from certified sourceUse resistant varieties, if availableCheck that seeding rate is not too high and allow for good spacingPlanting late may also help to reduce the incidencePick up any diseased plant or plant part and bury it deep or burn itDo not overwater plants as this favors the fungusProvide the fields with good drainage to prevent excessive soil moistureUse stake to keep the plants upright if necessaryBury debris deep in the soil to impair the growth of the fungus and expose the soil to solar radiationPlan a crop rotation for several years with non-host plantsKeep your tools and equipment disinfected and cleanMake sure not to transport soil between fieldsKeep the fields free of weedsTake care not to injure the plants during field workUse black plastic mulch to cover soil and limit fungal growthAdjust soil pH through limingprovide a good fertilization program to strengthen plants