1

Downy Mildew

Downy or fluffy growth of pathogen (sporangia/spores) on lower surface of leaves.

Plasmopara viticola on grapevine.

2

Powdery Mildew

White or grayish powdery growth on upper leaf surface (conidia of fungus).

Erysiphe cichoracearum on cucurbits.

3

Rust

Rusty or orange pustules of spores appear on leaves/stems.
➡️ Autoecious rust: Life cycle on one host (Melampsora lini – Linseed rust).
➡️ Heteroecious rust: Requires alternate host (Puccinia graminis – Wheat rust).

Puccinia spp. on wheat.

4

Anthracnose

Dark, sunken, ulcer-like lesions on fruits, pods, or stems.

Colletotrichum lindemuthianum on beans.

5

Smut

Black, sooty or charcoal-like powder of fungal spores, especially in grains or floral organs.

Ustilago maydis on maize.

6

White Blisters / White Rust

Numerous white pustules on leaves; burst open releasing white powdery spores.

Albugo candida on crucifers.

7

Scab

Roughened, crust-like or scurfy lesions on fruits, leaves or tubers.

Venturia inaequalis on apple.

8

Sclerotia Formation

Formation of hard, black, compact masses of dormant mycelium (resting body).

Sclerotium rolfsii on groundnut.

9

Phyllody

Transformation of floral parts into green leafy structures.

Phyllody of sesame (caused by phytoplasma).

10

Etiolation

Excessive elongation and pale colour due to growth in darkness.

Seedlings grown in dark.

11

Exudation / Ooze

Bacterial masses ooze out from infected tissues as sticky drops or streaks.

Xanthomonas oryzae on rice.

12

Chlorosis

Yellowing of leaves due to loss or reduction of chlorophyll.

Nutrient deficiency or virus infection.

13

Necrosis

Death of tissues resulting in brown or black patches.

Alternaria leaf spot on crucifers.

14

Hyperplasia

Abnormal increase in number of cells (due to excessive cell division).

Crown gall (Agrobacterium tumefaciens).

15

Hypertrophy

Abnormal increase in size of cells (due to nucleus division).

Gall formation, root-knot nematode.

16

Leaf Curl

Twisting, rolling or curling of leaves.

Leaf curl virus in chilli.

17

Wilt

Drooping and drying of leaves due to loss of turgidity.

Fusarium oxysporum on tomato.

18

Damping-off

Seedling disease; stem rots near soil line → collapse and death.

Pythium spp., Rhizoctonia solani.

19

Blight

Rapid death of tissue giving burnt appearance.

Phytophthora infestans (late blight of potato).

20

Canker

Dead, sunken, cracked areas on bark/stems of woody plants.

Xanthomonas citri (Citrus canker).

21

Die-Back

Drying of twigs or branches from tip backwards.

Colletotrichum gloeosporioides (Mango).