Crop Diseases and Insect Pests
Crop Diseases and Insect Pests
Crop Diseases and Insect Pests
Pictorial Illustration
By Nwagu Chiamaka
@ St Cyprian’s Special Science School, Nsukka
Intended for Teaching and Instruction of Agricultural Science in SS2 Classrooms
MAIZE SMUT
Caused by Fungi (Ustilago zea)
Symptoms
• Grains are converted to
large mass of spores
RICE BLAST
Caused by Fungi (Piricularia oryzea)
Symptoms
• Long red spots which
turn grey or brown
appear on leaves
• stem collapse
MAIZE RUST
Caused by Fungi (Puccinia polysora)
Symptoms
• Certain portions of the
leaf turn deep brown
and later die
MAIZE STREAK
Caused by Virus
Symptoms
• Chlorotic streaks
parallel to the veins of
the leaf
DOWNY MILDEW
Caused by Fungi (Peronosclerospora sorghi)
Symptoms
• Dwarfing of plant
• Pale chlorotic patches on the
leaves
• Leaves become twisted and
shredded
• White spores appear
underneath the leaves
• Deformation of floral
structures
CERCOSPORA LEAF SPOT
Caused by Fungi (Mycosphaerella spp)
Symptoms
• Lesions appear on the
upper surface of leaves
which turns dark brown
to black as they mature
ROSSETTE
Caused by Virus
Symptoms
• Stunting
• Chlorosis on leaves
BLACK POD
Caused by Fungi (Phytophthora palmivora)
Symptoms
• Brown spores soon
covered with soaky
powdery spores
• The whole pod gradually
gets black and rotten
COFFEE LEAF RUST
Caused by Fungi (Hemileia vastatrix)
Symptoms
• Yellow circular lesions
develop under the leaves
and later cover the whole
undersurface
• This gradually leads to
the death of the leaves,
branches and the whole
plant.
SWOLLEN SHOOT
Caused by Cocoa Swollen Shoot Virus
Symptoms
• Chlorosis between
leaf veins only
• Vein clearing of
non green veins
• Swollen stems
and/or roots
CASSAVA MOSAIC
Caused by Begomo Virus
Symptoms
• Vein clearing,
• Distortion of the
leaves and
• Stunted plant
BACTERIAL LEAF BLIGHT
Caused by Bacteria
Symptoms
• Spot appears on the
leaves which later
become bigger and join
to form blight
• Leaves drop
• Plant wilts and later dies
DRY ROT
Caused by Nematodes
Symptoms
• Browning of yam
tissues which later
becomes soft
CITRUS GUMMOSIS
Caused by Fungi (Phytophtora citrophtora)
Symptoms
• Sap oozing from
small cracks in
infected barks
Symptoms
• die back of the plant
• slow stunted growth
• low vigor and yield
CITRUS SCAB
Caused by Fungi (Sphaceloma fawcetti)
Symptoms
• Young leaves and
stem are attacked
especially in the
nursery
• Raised scabs on
leaves, fruits
and twigs
TRISTEVA
Caused by Virus
Symptoms
• Branches die at
their tips
• yield is greatly
reduced
ROOT KNOT
Caused by Nematodes
Symptoms
• Unusual
enlargement/knotting of
certain cells of the
roots resulting in
growth retardation and
wilting of the plant
DAMPING OFF
Caused by Fungi
Symptoms
• Retarded growth
• Cells become water
logged
• Gradual wilting of plants
• Death of plant
ONION TWISTER
Caused by Fungi
Symptoms
• Twisting of leaves
• Grey patches on leaves
• Reduction in yield
• Death of plant
BACTERIAL WILT
Caused by Bacillus Bacteria
Symptoms
• Rapid wilting
• slimy exudates from the
cross section of stem
cut near soil level
• death of the plant
TOMATO LEAF CURL
Caused by Virus
Symptoms
• Leaves curl upwards
and become rolled
BLACK ARM
Caused by Bacteria (Xanthomonas malvaceanum)
Symptoms
• Angular spots on leaves
and branches
• dead branches
• Boll rot
BUNCH TOP
Caused by Virus
Symptoms
• Stunted plants
• leaves crowded and
having curl edges
STORE PRODUCE MOULD
Caused by Fungi
Symptoms
• Wooly moulds on the
seeds or material
• bad odour
• sour taste
• Rottening
AND THAT’S IT!
FOR THIS TOPIC