Tylenchulus

learn about symptoms, life stages and characteristics of citrus nematode and their control measures

1. Tylenchulus semipenetrans Citrus nematode Prepared by R MOHANAPRIYA Assisstant Professor (Plant Pathology) JSA College of Agriculture and Technology, Ma. Podaiyur , Cuddalore district, Tamilnadu

2. Nematode : Citrus nematode (causal agent of slow decline of citrus) First discovered in California in 1913 by J.R. Hodges and was later described and named by Nathan Cobb India – 1 st reported by Siddiqi 1961, Aligarh (UP) Systematic position Phylum : Nematoda Class : Secernentea Order : Tylenchida Suborder : Tylenchina Super family : Criconematoidea Family : Tylenchulidae Sub-family : Tylenchulinae Genus : Tylenchulus (Latin. Tylos - knob & enchos –spear) Species : semipenetrans (semi endoparasitic ) Major hosts : Citrus (host specific) Type of parasitism : Semi endoparasite

3. Immature female Vermiform , small (<0.5 mm) Head - continuous, round, sclerotization weak Stylet – medium with round basal knob.

4. Mature female 0.35 – 0.4 mm long, neck elongate, irregular Anterior part – slender, irregular with thin cuticle Posterior part – swollen with thick cuticle and projecting tail tapering,blunt , ventrally arcuate Vulva and excretory pore – very posterior; ovary – monodelphic , anterior, convoluted; no anus or rectum.

5. Male Vermiform , short,straight and slender Cephalic sclerotization Stylet and oesophagus reduced Spicule slightly curved No bursa Tail – conical, pointed.

6. Second Juvenile Vermiform Tail – long, pointed Excretory pore at 50-60% of body length Oesophagus as in females Genital primordium differently shaped in male and female juveniles.

7. Biology & Life Cycle Sedentary semi endo parasite Second stage juveniles cause infection of the fine feeder roots Life cycle - 6-8 weeks (eggs hatch out – 12-14days at24 o C) Freshly hatched female juveniles start feeding on epidermal cells of young feeder roots. They penetrate the root tissues and initiate nurse cell feeding sites deep in the cortex. When the females mature, their posterior part enlarges and extends out from the root surface.

8. Single female lays 40-60 eggs Approximately 100 eggs are deposited in a gelatinous matrix. Males and females undergo four moults, but the males remain outside of the root and do not feed. North india – population peak at April-October Coarse textured soils are not favourable for nematode reproduction

9. Symptoms Citrus trees more than 7-8 years old exhibit decline symptoms causes slow decline Which are manifested by yellowing of leaves, defoliation, Premature shedding of fruits, reduction in the number and size of fruits, Increasing number of dead twigs from top and weak seasonal flushes Infested roots appear dark, heavily infected roots are covered with soil particles which do not go inspite of washing

10. Interaction with other pathogens The incidence of fungal pathogens Fusarium solani & Fusarium oxysporum is enhanced in the presence of citrus nematode resulting in root decay and lowering the tree cavity

11. Control Nursery should be raised in nematode free soil (fumigated), or away from the established citrus orhards . Treat the basin area with carbofuran @ 4kg a.i ./ha just before flowering. Pulverise the nematicide in the soil followed by light irrigation. Intetculture of onion, garlic or marigold in the citrus orchards not only reduces the nematode population but also provides additional income. Incorporation of neem cake @ 1kg/tree along with carbofuran @2kg a.i ./ha in the basin area helps in economizing nematicidal use. Some clones and hybrids of trifoliate orange, Poncirus trifoliata are resistant to citrus nematode and can be used as root stock.