citrus slow decline

This presentation is about the etiology, epidemiology and management of citrus slow decline

1. Citrus slow decline Presented by ANKITA UGS12AGR 6056

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 Soil Irrigation 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.

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