Pigeonpea Cyst Nematode

📖 Description

Pigeonpea Cyst Nematode (Heterodera cajani), also called Pigeonpea Cyst Nematode or Cajanus Cyst Nematode, is an important soil-borne microscopic nematode pest of pigeonpea and other pulses across the Indian subcontinent, particularly severe in the major pigeonpea-growing belts of Maharashtra (Latur, Osmanabad, Nanded, Parbhani, Aurangabad, Solapur — India’s largest pigeonpea-producing state), Karnataka (Gadag, Bijapur, Bagalkot, Kalaburagi, Bidar, Raichur), Andhra Pradesh (Kurnool, Anantapur, Prakasam, Guntur), Telangana (Mahabubnagar, Nalgonda, Adilabad), Uttar Pradesh (Banda, Chitrakoot, Jhansi, Hamirpur), Madhya Pradesh (Sagar, Jabalpur, Rewa, Damoh), Gujarat (Vadodara, Panchmahal, Dahod) and Tamil Nadu (Tirunelveli, Ramanathapuram, Sivaganga) where India is the world’s largest producer of pigeonpea (over 5 million hectares cultivated, producing over 4 million tonnes annually — pigeonpea (tur/arhar) is the most important pulse crop in India by both area and production, providing the primary source of protein for the Indian vegetarian diet, with India producing over 70% of the world’s pigeonpea and consuming nearly all of it domestically). The pest is unusual among pigeonpea pests because (a) it is a cyst nematode — adult females swell up, die and form protective cysts that contain 100-300 eggs and can survive in soil for 3-5 years without a host — making this one of the most difficult soil pests to control, (b) the cysts are spread primarily in soil on equipment, footwear and irrigation water — making sanitation between fields essential, (c) the pest has a relatively narrow host range (essentially pulses and legumes — pigeonpea, cowpea, greengram, blackgram, soybean, sesbania) — meaning that crop rotation with non-host cereals can effectively suppress populations over 1-2 years, (d) the pest is essentially invisible (microscopic juveniles and adult females inside roots) until severe damage is done — by the time patchy stunting is visible the nematode population is already well-established, (e) the pest has a relatively long life cycle (30-45 days) — only 2-3 generations per crop season — but populations build up over multiple seasons, especially in continuous pigeonpea cropping, (f) the pest directly affects the nitrogen-fixing Rhizobium nodules — reducing the plant’s ability to fix nitrogen and thereby compounding the direct feeding damage, and (g) the cysts protect eggs from nematicides and natural enemies — only systemic nematicides or soil fumigation are effective, and even these provide only partial control. IPM with soil testing for nematode presence before planting (most critical preventive measure), resistant pigeonpea varieties (ICPL 88063, ICPL 87119, BDN 2, Asha show tolerance), 1-2 year crop rotation with non-host cereals (maize, sorghum, pearl millet), marigold intercropping or rotation (roots release alpha-terthienyl toxic to nematodes), biological control (Pochonia chlamydosporia and Paecilomyces lilacinus egg-parasitic fungi destroy eggs inside cysts), organic amendments (neem cake, mustard cake, farmyard manure), seed treatment with Trichoderma viride or Pseudomonas fluorescens (protects roots from nematode-associated fungal pathogens), and need-based nematicide rotation provides effective and sustainable control. The pest is a particular concern for Indian pigeonpea growers because the long survival of cysts (3-5 years) and the buildup under continuous pigeonpea cropping mean that once a field is infested it requires multi-year management to bring the population below damaging levels — making prevention through soil testing and crop rotation absolutely critical. The pest is most severe in the deep black soils (Vertisols) of Maharashtra, Karnataka and Andhra Pradesh pigeonpea belts where continuous pigeonpea cropping has allowed populations to build up to damaging levels. Climate change with warmer winters is allowing the pest to expand its range and severity in northern India.