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
Comments
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
Comments
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
Blackened and shriveled roots due to black rot infection
Clusters of fungal fruiting bodies on peanut stem
Rotting caused by Cylindrocladium black rot on peanut
Plants yellowing and wilting
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
Comments
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
Close-up image of an early leaf spot lesion on peanut
Symptoms of early leaf spot on peanut leaves
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
Comments
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
Severe defoliation in peanut field infected with Cercospora
Peanut plant infected with Cercospora fungus
Cercospora lesions on peanut
Cercospora infected peanut leaves
Peanut plant infected with Cercospora fungus
Defoliation due to Cercospora infection
Peanut plant infected with Cercospora fungus
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
Comments
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
Circular lesions with red-brown margins and light brown or tan centers on leaves
Symptoms of Phyllostica leaf spot on peanut leaves
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
Comments
Management
Disease is held in check by fungicides applied to control early or late leaf spot.
Rust
Puccinia arachidis
Rust symptoms on peanut
Symptoms of rust on peanut leaves
Rust symptoms on peanut
Symptoms of rust on peanut leaves
Rust symptoms on peanut
Rust symptoms on peanut
Symptoms of rust on peanut leaves
Rust symptoms on peanut
Symptoms of rust on peanut leaves
Symptoms of rust on peanut leaves
Symptoms
Characteristic orange pustules on undersides of leaves which become covered in masses of red-brown spores; pustules may form on pods.
Cause
Fungus
Comments
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
Severe Sclerotinia blight on peanut
Sclerotia of Sclerotinia minor inside peanut pod
Early infection of Sclerotinia minor on peanut
Stem shredding by Sclerotinia minor on peanut
Hard black sclerotia on infected peanut stems
Sclerotia, stem bleaching and shredding by Sclerotinia minor on peanut
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
Comments
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
Below-ground symptoms of southern stem rot.
Dense white mycelial growth and brown sclerotia of Sclerotium rolfsii, causing southern stem rot of peanut
White fungal mat developing on the stem close to the soil line
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
Comments
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.
Verticillium wilt
Verticillium spp.
Symptoms
Chlorosis of leaf margins; curling leaves; loss of leaf turgor; plants wilt and become stunted as the disease progresses; plants wilt rapidly during periods of water stress; vascular system becomes dicolored.
Cause
Fungi
Comments
Management
Irrigate plants frequently to reduce wilting of infected plants and allow them to reach maturity; eliminate weeds int he plantation which may allow inoculum to build up in the soil; remove and destroy infected crop residue after harvest to reduce inoculum in the field.
Web blotch (Phoma leaf spot)
Phoma arachidicola
Web blotch infected leaves
Symptoms
Circular, brown-black lesions on the upper surfaces of the leave; web or net-like brown lesions on leaves may form on leaves during periods of high humidity; as sisease progresses, lesions darken and develop a rough texture; lesions may cover entire leaf surface.
Cause
Fungus
Comments
Management
Remove and destroy infested crop debris to prevent build up of inoculum in soil; rotate crops away from peanut; foliar fungicide applications are largely ineffective if conditions are favorable for the disease.