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

Crossandra, Gladiolus

III. Crossandra
Crossandra is commercially grown for flowers in the states of Karnataka, Tamil Nadu, Andhra Pradesh and in a few areas of Rajasthan. Major pests of crossandra are Pratylenchus delattrei, Longidorus africanus, Meloidogyne incognita and Helicotylenchus dihystera .

a. Lesion nematode (Pratylenchus delattrei)
Biology:

• Migratory endo-parasites; all the juvenile and adult stages being infective.
• Eggs are laid inside the roots. Juveniles on hatching move inside the root tissue in cortex both inter as well as intra-cellularly causing extensive damage to the root tissue.
• The nematode takes about 46-55 days to convert from egg to adult.
• Nematode can survive up to eight months in moist soil in absence of the host crop. Survival period is reduced to three months in dry soil.

Symptoms:

• Infested plants are weak and stunted with pinkish to purple and yellow coloured leaves.
• Inflorescence and flower size is reduced. Root system is reduced and roots bear brown to black lesions.

Management:

• Application of FYM and inter-culturing of african marigold reduces the nematode population significantly.
• Carbofuran 3 G @ 1 g per plant is effective.

b. Needle nematode (Longidorus africanus)
The nematode has been reported from crossandra in USA, Italy, Israel and India (Tamil Nadu).
Nature of Damage:

• The nematode is a migratory ectoparasite that penetrates its long stylet in to the parenchymatous cells and initiates hyperplasia of these cells.
• Hyperplasia progresses from periphery to centre thus pushing the meristem laterally which eventually leads to the formation of dark stained cells.

Management:

• Crop rotation with poor hosts like pea, carrot or onion or non-host crops like cabbage, cauliflower and radish reduces the nematode population significantly and improves the flower production.
• Inter-culturing of these crops also helps to reduce the nematode count.

IV. Gladiolus
Though a number of plant parasitic nematodes viz., Meloidogyne spp., Helicotylenchus dihystera, H. varicaudatus, Criconemella xenoplax, Pratylenchus spp. Tylenchorhynchus ewingii, T. mashhoodi, Paratylenchus curvitatus, Quinsulcius indicus and Hoplolaimus indicus have been found to be associated with gladiolus, only root-knot nematode poses a major problem.

a. Root-Knot Nematode (Meloidogyne incognita):
The nematode has been found to be associated with gladiolus in Himachal Pradesh and Karnataka.
The nematode invades roots, daughter corms and cormels which develop after flowering and survives in the corm tissue in the soil as a source of inoculum for the next season.
Symptoms:

• The infested plants are stunted and show a poor plant stand in form of short and thin floral stalks, low leaf count and hampered appearance of florets.
• Leaves of infested plants turn yellow followed by browning of the leaf tip and ultimately whole leaf dries off.
• Infested plants bear reduced number of daughter corms and cormels.
• Infested roots are heavily galled and have reduced root length.
• Gall size is small.

Management:

• Hot water treatment of corms at 57.8^o C for 30 minutes renders them nematode free.
• Corms dip in the organophosphates like fensulfothion or thionazin @ 0.5 g a.i. per litre of water also reduced nematode infection significantly.
• Interculuring and bordering of Tagetes helps to reduce nematode population.