2. INTRODUCTION
•First discovered infecting citrus in California
(Thomas 1913).
•Nathan Cobb(1912) described this nematode as a new
species Tylenchulus semipenetrans as a causal agent of
slow decline in citrus.
•In India it was first reported by Siddiqi (1961) from
Aligarh (Uttar Pradesh).
•Globally it causes 8.7 to 12.2% loss in citrus yield
annually.
3. SYMPTOMS –
•Above ground symptoms:
•Sparse foliage, exposure of bare crown limbs.
•Dull gray-green leaves smaller than normal
•Upright and cupped, drop early
•Trees wilt often during mid-day
•Reduction in number and size of fruits
•Below ground symptoms:
•Small feeder roots do not develop properly causing slow
decline.
•Infested roots appear dark while healthy roots are
creamish.
4. Sparse foliage and bare limb
Dull grey green leaves
Wilting during mid-day
and reduction in size of
fruit Below ground symptoms
Cupped leaves
Normal plant
5. ETIOLOGY
Kingdom –Animalia
Phylum –Nematoda
Class –Secernentea
Order –Tylenchida
Sub order –Tylenchina
Family –Tylenchulidae
Genus –Tylenchulus
Species -semipenetrans
•Tylenchulus genera has got stronger stylet ,more of
posterior excretory pores, a hyaline band corresponding to
the copulatory system in posterior portion of body
•Semipenetrans shows nematode’s semi-endoparasitic
nature
• Citrus nematode signifies the host specificity
6. EPIDEMIOLOGY
Primary source of inoculum
•Soil
•Nematode infected propagative
planting material
•Finely textured soils or sandy soils with high organic matter
will support high nematode population
•Increase in soil salinity will hinder the population
•Other host – Trifoliate orange, Grapevine, Lilac and Olive
Secondary source of inoculum
•Irrigation water
7. EGG and J₁
Sedentary adult
Grafting
J₂-stage
Female feeding on nurse cells
On Roots of healthy plants
Disorganization
and break-down
of surrounding
cells
Symptom development
8. MANAGEMENT
•Nursery should be raised in a nematode free soil
•Treatment of basin area by carbofuran @4 kg a.i./ha of
soil just before flowering.
•Pulverize the soil with nematicide
•Fenamiphos (Nemacur) 10.8-21.6 kg a.i./ha
• Aldicarb (Temik) 5.5-11.0kg a.i./ha followed by light
irrigation.
•Interculture of onion, garlic or marigold in citrus
orchard.
9. •Use of resistant root-stock like swingle citrumelo and
Poncirus trifoliata with certified propagative citrus
planting material.
•The egg-parasitic fungus, Paecilomyces lilacinus,
reduced T. semipenetrans densities
•Incorporation of Neem cake @1kg per tree along with
carbofuran@ 2kg a.i./ ha in basin area.