Nematode Pests of Horticultural Crops and their Management (1+1)

Introduction to Symptology (Contd.)

Foliage distortion in chrysanthemum is caused by Aphelenchoides ritzemabosi.

A. Crinkled or distorted foliage: Foliage distortion in onions, strawberry, lucerne and red clover is due to infestation of D. dipsaci. This nematode has so far not been reported authentically from India.

Garlic distorted by Ditylenchus dipsaci Photoby :G Caubel,Nemapix Vol.2

Crinkling of wheat ear is due to attack of Angunia tritici and of Paddy ear is due to Aphelenchoides besseyi and Ditylenchus angustus

Crinkling of wheat ear by A . tritici Photo by: Jonathan D Eisenback,Nemapix

B. Seed Galls: Black shrunken galls at the place of normal wheat grains are produced in presence of Anguina tritici.

Healthy wheat grains and Black shrunken galls(due to Anguina tritici) Photo by: Ulriche Zunke Nemapix

C. Leaf galls: Anguina graminis and Ditylenchus graminophilus produce leaf galls in many grasses. Anguina balsamophilla produces similar galls on balsam leaves

Leaf galls produced by Anguina balsamophilla

D. Spikkles: Ditylenchus dipsaci causes light yellow, raised pimple-like structures called spikkles on narcissus and daffodil leaves.

Spikkles on daffodil leaves caused by Ditylenchus dipsaci

Daffodils infected by stem and bulb nematode Photoby :G Caubel,Nemapix Vol.2

E. Leaf spots and lesions: Nematodes sometimes enter through stomatal opening and produce water soaked areas which later turn brown. Such leaf lesions are produced by A. ritzemabosi on its host plants.

F. Dead or devitalized buds: Many Aphelenchoides spp. which attack the growing points of the host plant cause ‘blind’ i.e., no production of flower primordia as it attacks buds.

Dead and devitalized buds due to Aphelenchoides spp.

G. Aerial necrosis: Red ring nematode of Coconut, Bursaphelenchus (=Rhadinaphelenchus) cocophilus causes necrotic banding on the trunk of coconut plants.

T.S. of coconut trunk showing band of necrotic red ring, Photo by: W F Mai

H. Toppling Disease – Burrowing nematodes causes ‘toppling’ of banana plant. Banana roots are so severely affected that they cannot hold the tree upright once the extra weight of the developing fruit is added and the whole plant topples down

Toppling of banana plantation due to Radopholus root rot, Photo: D J Hooper

V. Temporary wilting
Wilting though an above ground symptom is a result of root damage caused by the nematodes. The plants attacked by nematodes show a tendency of temporary wilting in hot weather (although enough moisture may be present in soil) and may recover during cooler hours. Wilting is more pronounced on broad leaved plants.

• Heterodera schachtii causes wilting on sugar beet.
• Globodera rostochiensis causes wilting on potato
• Meloidogyne incognita causes wilting on tobacco and many vegetable crops like tomato, capsicum, cucurbits etc.

Wilting in tomato and capsicum (under protected cultivation) due to root-knot nematode