Root rot

Casual Agent:Phytophthora cinammomi

Symptoms and Damage

• Tree infected with root rot have small, fibrous feeder rots which are black, brittle which later die from the infection.
• Avocado tree exhibits small, chlorotic or pale green leaves when infected with root rot.
• Leaves later wilt, develop necrotic lesions. Branches on the top of the tree die back, resulting to fruits being exposed to sun scald.
• There is reduction in fruit production as a result of root rot. The tree may die slowly or rapidly depending with the infection rate.

Solution

Anthracnose

Casual Agent:Colletotrichum gloeosporioides

Symptoms and Damage

• It’s a fungal disease that affect the fruit mostly severe after post-harvest.
• Under heavy attack, young fruits drop off from the tree.
• The disease manifest itself as a dry spot with dark to brown colour on the skin of the fruit, which may cause abnormal development.

Solution

Cercospora Fruit Spot

Casual Agent:Pseudocercospora purpurea

Symptoms and Damage

• It’s a fungal disease that affects the quality of the fruits.
• The lesions on the fruits appears as a small pale yellow spot that advances to hard reddish brown spots which eventually cracks.
The infected leaves become brittle and thin leading to the affected tissues dropping off leaving a ragged shaped holes on the leaf.

Solution

Scab

Casual Agent:Sphaceloma perseae

Symptoms and Damage

• It’s a fungal disease common in humid areas.
• It affects the young tissues of twigs, leaves and fruits.
• The disease manifest itself as a small dark spot which is oval to elongated in shape.
• The spots may merge forming corky texture on the surface/skin of the fruit but the fresh of the fruit remains intact.

Solution

Bacterial soft rot

Casual Agent:Erwinia carotovora var. aroideae

Symptoms and Damage

• It is a bacterial infection which manifest as soft, dark in colour and flat spot.
• The spots may merge and cover the entire fruit.
• Under the skin, a sunken, concave in shape and dark-brown depression appears.
• A putrid smell emanates from the infected fruits.

Solution

Rust

Casual Agent:Uromyces appenduculatus

Symptoms and Damage

• The disease is caused by a fungus Uromyces appenduculatus.
• Characterised by rust-spots surrounded by a yellow area/halo.
• As the disease progress, the spots becomes larger and spores turn black.
• Rust can affect all the above ground parts of the plants.
• Under severe attack, the leaves fall off the plant and the pods get deep dark pits.

Solution

Angular leaf spots

Casual Agent:Phaeoisariopsis griseola

Symptoms and Damage

• The disease is caused by a fungus.
• It affects all above ground parts of the plant; leave, stems, pods, and petioles.
• Lesions appears on the leaves as brown spots that are confined between the major veins, giving it an angular shape.
• As the disease progress, the leaves turn yellow in colour, necrotic and later fall off from the plant.
• Grey mould appears on the affected pods.

Solution

Fusarium root rot

Casual Agents:Fusarium solani

Other Agents:Pythium spp, Macrophomina phaseolina, Fusarium oxysporum f. sp. phaseoli

Symptoms and Damage

• The disease is caused by a fungus, Fusarium solani which is a soil borne disease.
• The infected seedlings become stunted.
• The leaves turn yellow and the plant wilts.
• The vascular tissue appears red-brown in the affected plants and the adventitious roots fail to develop.

Solution

Anthracnose

Casual Agent:Colletotrichum lindemuthianum

Symptoms and Damage

• The disease is caused by a fungus.
• The disease can affect stems, leaves, pods, petioles and seeds.
• On the leaf surface, the veins show dark streaks and angular reddish to brown spots.
• Dark brown, circular to elliptical, sunken lesions appear on the stems and petiole.
• Small reddish to brown, sunken circular spots forms on the pods, as the disease progress, they become large, turn dark and sunken lesions which distort the shape of the pod.
• Yellow to brown lesions develop on the seeds which affect seed development and later germination.

Solution

Powdery Mildew

Casual Agent:Erysiphe polygoni

Solution

Bacterial brown spots/Halo blight

Casual Agent:Pseudomonas syringae pv. phaseolicola

Solution

Common Bacterial blight

Casual Agent:Xanthomonas axonopodis pv. phaseoli

Solution

Bean Common Mosaic Virus

Transmitted: Aphids and through seeds

Solution

Anthracnose

Casual Agent:Colletotrichum gloeosporioides

Symptoms and Damage

• It is a fungal disease caused by Colletotrichum gloeosporioides which is an important disease in mango production.
• The symptoms can occur on flowers clusters, petiole, leaves, twigs and fruits.
• Anthracnose on the leaves start as a small lesion, angular in shape, brown to black in colour. The spots can merge to form an extensive necrotic/dead area. In dry weather, the necrotic part may drop off from the leaves.
• On the flowers and the petiole, anthracnose appears as dark to grey elongated lesions.
• On the emerging fruits, it causes abortion while on large fruits dark, depressed and circular spots appear on the skin. In some cases, the spots can merge and affect a large area of the fruit. This affects the marketability of the produce.

Solution

Powdery mildew

Casual Agent:Oidium mangiferae

Symptoms and Damage

• Powdery mildew is characterised by a whitish powdery mycelium growth which can be on flowers, young fruits, panicle’s stalk and leaves.
• When flowers are severely attacked, they turn black or brown and fall off. It may cause severe flower abortion on the affected tree or early fruit drop leading to poor fruit set or complete loss of flowers and fruits.
• The affected leaves become malformed and a necrotic area appear on the upper leaf surface. Eventually, the leaf may fall of from the plant.
• On the fruits, the epidermis cracks and the tissue become corky.

Solution

Die back

Casual Agent:Lasiodiplodia theobromae

Symptoms and Damage

• The disease manifest itself through drying up of twigs from the top to bottom. This lead to tree defoliation and the entire branch or tree dies.

Solution

Early blight

Casual Agent:Alternaria solani

Symptoms and Damage

• Symptoms appear on the leaves, stem.
• The disease appears first on the older, lower leaves as small brown lesions/spots.
• As the disease progresses, irregular concentric rings develop surrounded by chlorotic area.
• Eventually, the whole leaf turns chlorotic and dies off leading to plant defoliation.
• On the tubers, the disease manifest itself as a dark coloured lesion which is sunken with raised borders. In most cases, the tubers don’t rot but deteriorate in terms of appearance and quality.

Condition favouring growth

Solution

Late blight

Casual Agent:Phytophthora infestans

Symptoms and Damage

• On the stem, dark lesion develops at or near the ground level (damping off).
• The disease progress through the petioles and leaflets resulting to brownish foliage.
• Development of dark brown, water soaked lesions with green grey edges that are not confined by the major veins.
• The dark, water soaked lesions develops from the leaf margins infecting the whole leaf.
• White fungal growth appears on the infected surface during high humidity.
• Rapid and extensive foliar damage with favourable weather conditions.
• Affected tubers have a characteristic rot of reddish, tan-brown or purplish color.

Condition favouring growth

Solution

Fusarium wilt

Symptoms and Damage

• First symptom appears on the lower part of the plant or older leaves where they turn yellowish.
• Diurnal wilting (wilting during sunny days) on one side of the branch in the affected plant.
• Brown discolouration of the vascular bundles is evident on the stem when dissected.
• In severe cases, the whole plant wilt and die off.
• The skin of affected tubers develops wrinkles and sink inwards.
• The internal tissues change colour to light brown or black due to fungal growth and infected cells dying.
• Fungal mycelium grows on the infected area; during high humidity, bacteria may invade and cause rotting of the tubers resulting to a foul smell from the rotting tubers.

Conditions favouring growth

Solution

Bacterial wilt

Casual Agent:Ralstonia solanacearum

Solution

Rice Blast

Casual Agent:Magnaporthe grisea

Symptoms and Damage

• It is the most destructive fungal diseases of rice.
• The fungus affects the leaves, stem nodes, panicles and the grains.
• It appears as an elongated spot which is light coloured at the centre and reddish on the edges.
• It is severe when it affects the stem node just below the head which causes breakage.

Solution

Bacterial leaf blight

Casual Agent:Xanthomonas oryzae pv. Oryzae

Symptoms and Damage

• It is a destructive bacterial disease of the cultivated rice.
• The symptoms appear first as water soaked lesions along the leaf edges in most cases near the tip of the leaf.
• The lesions enlarge and coalesce, the colour changes to yellowish and as the disease progresses, it turns to greyish-white which eventually leads to the leaf drying up.

Solution

Sheath and leaf blights

Casual Agent:Rhizoctonia solani (teleomorph= Thanatephorus cucumeris)

Symptoms and Damage

• The disease is caused by a fungus.
• The growth of the fungus is favoured by high temperature and humidity.
• The disease affect rice from tillering stage to heading stage.
• It manifests itself first on the leaf sheath near the water level by irregular or oval or elliptical greenish to grey spot.
• As the disease progresses, the spots become greyish/white in colour with a border which is blackish/brown or purple brown in colour.
• The lesions merge and cover the entire tiller, from water level to flag leaf.
• The infection may cause the death of the entire leaf and can extend to the inner sheaths causing the death of the whole plant.

Solution

Brown spots

Casual Agent:Bipolaris oryzae (Helminthosporium oryzae)

Symptoms and Damage

• It is a fungal disease that affect all stages of rice plant.
• The disease appears as brown spots on the leaves and grains.
• Seedlings from infected seeds shows seedlings blight.
• It is severe in soils low in nutrients.

Solution

Brown spots

Casual Agent:Beetles(Chaetocnema pulla, Dicladispa viridicyanea, Sesselia pusilla, Trichispa sericea)

Symptoms and Damage

• It manifests on rice plant by yellowing of the leaves, stunted growth, reduced tillering and affects the fertility of the seeds.
• Other mode of transmission is mechanical transmission and from the soil.

Solution

Early blight

Casual Agent:Alternaria solani

Symptoms and Damage

• Symptoms appear on the leaves, stem and the fruits.
• The disease appears first on the older, lower leaves as small brown lesions/spots.
• As the disease progresses, irregular concentric rings develop surrounded by chlorotic area.
• As the disease progresses, irregular concentric rings develop surrounded by chlorotic area.

Condition favouring growth

Solution

Late blight

Casual Agent:Phytophthora infestans

Symptoms and Damage

• On the stem, dark lesion develops at or near the ground level (damping off).
• The disease progress through the petioles and leaflets resulting to brownish foliage.
• Development of dark brown, water soaked lesions with green grey edges that are not confined by the major veins.
• The dark, water soaked lesions develops from the leaf margins infecting the whole leaf.
• White fungal growth appears on the infected surface during high humidity.
• Rapid and extensive foliar and fruit damage with favourable weather conditions.

Condition favouring growth

Solution

Powdery mildew

Casual Agent:Leveillula taurica

Symptoms and Damage

• Initial symptoms are light green to bright yellow lesion on the upper surface of the leaf.
• Light powdery fungal growth (sporulation) forms on the underside of the leaf.
• White masses of conidia eventually develop on both surfaces of the leaf.
• Leaf becomes necrotic and dies off.
• Disease mostly appear late in the crop cycle or older crop.

Conditions favouring growth

Solution

Fusarium Wilt

Casual Agent:Fusarium oxysporum f.sp. lycopersici

Symptoms and Damage

• First symptom appears on the older leaves or branches where they turn yellowish.
• Diurnal wilting (wilting during sunny days) on one side of the branch in the affected plant.
• Brown discolouration of the vascular bundles is evident on the stem when dissected.
• In severe cases, the whole plant wilt and die off.

Conditions favouring growth

Solution

Damping off

Casual Agent:Pythium spp, Phytophthora spp, Rhizoctonia solani

Solution

Botrytis

Casual Agent:Botrytis cinerea

Solution

Septoria leaf spot

Casual Agent:Septoria lycopersici

Solution

Athracnose (fruit rot)

Casual Agent:Colletotrichum spp.

Solution

Buckeye rot (on the fruit)

Casual Agent:Phytophthora parasitica

Solution

Stem rust

Casual Agent:Puccinia graminis

Symptoms and Damage

• The disease is caused by a fungus Puccinia graminis.
• It affects the leaves, leaf sheath, stem and glumes.
• It is characterised by oblong pustules which are reddish-brown in colour and powdery.
• The pustules have unique torn-like margin that can appear on the stem, both side of the leaves and on the glume.
• As the crop matures, the pustules on the stem and leaf sheaths produces black spores (teliospores).

Solution

Brown rust/Leaf rust

Casual Agent:Puccinia triticina

Symptoms and Damage

• The disease is caused by the fungus Puccinia triticina.
• It affects the leaves of wheat and barley.
• Brown rust has pustules that are orange-brown in colour, round to oval in shape and mainly on the upper side of the leaves.
• The spores are small and round in shape.
• Severe infection affects the rate of photosynthesis on the leaf surface reducing the grain fill as well as it increases transpiration rate causing the crop to be more susceptible to drought.
• There is yield loss, both quality and quantity due to shrived.

Solution

Stripe rust/Yellow rust

Casual Agent:Puccinia striiformis f. sp. tritici

Symptoms and Damage

• Yellow rust is caused by a fungus Puccinia striiformis f. sp. tritici.
• The diseases infect the leaf, leaf sheath and the glumes.
• Yellow rust is characterised by symmetrical lesions running along the leaves.
• The pustules are orange to yellow in colour which releases yellow- orange masses (Urediniospores) when they break open after maturation.
• Under heavy infection, the plant become stunted.

Solution

Septoria disease

Casual Agent:Septoria tritici

Symptoms and Damage

• Septoria is caused by fungus Septoria tritici.
• The diseases affect the leaves and the heads.
• The disease is characterised by pale brown or greenish-grey pustules that are oval to stripe in shape.
• The lesions coalesce to cover a large area on the leaf.
• Heavy infection causes the kernels to shrivel.

Solution

Septoria glume blotch

Casual Agent:Parastagonospora nodorum (Stagonospora nodorum)

Symptoms and Damage

• It is a fungal disease caused by fungus Parastagonospora nodorum.
• It affects leaf sheath, leaves, glume and the stem.
• Seedlings from infected seeds become distorted and have stunted growth.
• The disease appears as small dark-brown lesions with a halo on the leaves close to the ground level.
• As the disease progress, the lesion become oval in shape with a dark-brown centre which eventually turns to greyish-white at the middle with dark brown margins.
• Under heavy infection, the lesions merge to cover the entire leaf causing the death of the leaf tissue.
• Infection on the glume can be identified by a lesion brown in colour which start from the tip and progressing downwards.
• When the infection is on the stem and the node, it is characterised by dark-brown lesions.
• Infection on the glume causes the kernels to shrivel affecting the quality and quantity of the grains.

Solution

Ear disease/Fusarium head blight/Scab

Casual Agent:Fusarium spp.

Symptoms and Damage

• It is a soil borne fungal disease of wheat and barley caused by Fusarium spp.
• It affects the head, grain and the neck.
• The disease is characterised by water-soaked lesion at the glume which is brown in colour.
• As the disease progress, the glume become bleached in colour.
• The disease can also be identified by unfilled spikelets from the point of infection due to premature bleaching.
• The grain will become sterile or shrivelled due to the infection.

Solution