Category : Fungal
Botrytis blight (Botrytis cinerea)
Symptoms
Numerous spots on upper surface of leaflets; entire plant or discrete parts may wilt and die; pods and stems become covered in fungal sclerotia.
Cause
Fungus
Management
Avoiding frost damage by planting early peanut varieties can help protect the plant from fungal colonization; application of appropriate foliar fungicides (e.g. benomyl), where available, can help to control the disease.
Charcoal rot (Macrophomina phaseolina)
Symptoms
Water soaked lesions on stems of seedlings close to soil line; lesions girdle stem and kill seedlings; lesions in similar area may be present in older plants; lesions are initially water-soaked but turn brown; if lesions girdle the stem, plant wilts and branches die; infections beginning in the roots cause leaves to turn yellow and wilt and causes stems to be blighted.
Cause
Fugnus
Management
Rotating crop with rice for a period of 3-4 years can reduce the level of oioculum in the soil; providing the plants with adequate irrigation and fertilization reduces susceptibility to the disease; there are currently no resistant varieties of peanut; frequent irrigation to wet soil reduces the incidence of the disease.
Cylindrocladium black rot (Cylindrocladium crotalariae)
Symptoms
Leaves on main stem turning chlorotic and wilting; entire plant wilts very rapidly when there is a period of water stress following high moisture; clusters of red-brown fungal bodies occur on on stems, pegs and pods; roots destroyed; roots blackened and shriveled.
Cause
Fungus
Management
The most effective method to control the disease is to plant peanut varieties that have some resistance to the disease; rotation of crop with nonhost such as corn , cotton or tobacco may help to reduce inoculum in the soil; application of appropriate soil fumigants in heavily infested fields can help to control the disease.
Early leaf spot(Cercospora arachidicola)
Symptoms
Small chlorotic flecks on leaf petioles, stems and pegs which enlarge and turn dark in color; lesions on upper surface of leaves usually possess a yellow halo and are reddish brown on the underside of leaves.
Cause
Fungus
Management
If disease is present, a rotation away from peanut for a period of 2-3 years is advised but is insufficient to control the disease completely; peanut crop debris should be plowed into soil after harvest and any volunteers removed from the nonhost crop; fungicides should be applied with caution as they can exacerbate other foliar diseases where they are present.
Late leaf spot (Cercospora personatum)
Symptoms
Small chlorotic flecks on leaf petioles, stems and pegs which enlarge and turn dark in color; symptoms may be very similar or identical to early leaf spot and can only be differentiated by examination of conidia under a microscope.
Cause
Fungus
Management
If disease is present, a rotation away from peanut for a period of 2-3 years is advised but is insufficient to control the disease completely; peanut crop depris should be plowed into soil after harvest and any volunteers removed from the nonhost crop; fungicides should be applied with caution as they can exacerbate other foliar diseases where they are present.
Phyllostica leaf spot (Phyllostica arachidis-hypogaea)
Symptoms
Circular lesions with red-brown margins and light brown or tan centers on leaves; centers of lesions may dry out and drop from leaf resulting in a “shot-hole” appearance.
Cause
Fungus
Management
Disease is held in check by fungicides applied to control early or late leaf spot.
Rust (Puccinia arachidis)
Symptoms
Characteristic orange pustules on undersides of leaves which become covered in masses of red-brown spores; pustules may form on pods.
Cause
Fungus
Management
Allow field to fallow for at least one month between successive peanut plantings; remove any volunteer peanut plants during fallowing to reduce inoculum; sprays of appropriate fungicides such as Bordeaux mixture can effectively control the disease; such fungicides are often also effective at controlling leaf spot.
Sclerotinia blight(Sclerotinia minor)
Symptoms
Tips of infected branches wilt or flag rapidly; early signs of infection include the presence of small water-soaked lesions at the base of the stems which turn yellow or bleached; leaves on infected branches turn chlorotic and then wither; fluffy white fungal growth may appear on infected tissues during periods of high humidity.
Cause
Fungus
Management
Plant seeds which are coated with protectants; avoid injuring plants with tools and/or machinery; application of appropriate fungicides can reduce crop losses when disease is present; avoid excessive irrigation during cool weather.
Southern stem rot (Sclerotium rolfsii)
Symptoms
Lateral branches or main stem yellowing and wilting; white fungal mat developing on the stem close to the soil line; white to brown spore containing structures developing from the fungal mats.
Cause
Fungus
Management
Plow crop debris deeply into soil after harvest of crop; crop rotation of 3-4 years are very effective at reducing soil inoculum in the case of severe infestations; applications of appropriate fungicides can help suppress stem rot but care should be taken with selection as some pesticides (e.g. benomyl) are known to increase the severity of the the disease.
