Ginger soft rot

One of the serious disease of ginger.

1. Diseases Of Field & Horticultural Crops And Their Management-1 Topic - Ginger Soft Rot Submitted by – Sweta Pattanaik

2. CONTENT Introduction Impact Taxonomy Symptom Favourable condition Etiology Disease cycle Management

3. Introduction Caused by Pythium species. Ginger soft rot is common in all zinger growing areas. This is worldwide. In the tropics & subtropis. Pythium myriotylum is most serious species. It is recorded from Fiji,Australia,New zealand,and Solomon island. Impact It causes loss from 30-100%. The water mould can destroy rhizomes in 1-2weeks. Impact of the disease is reduced if the crop grown for immature ginger and harvested early. Losses still occur in the crop remaining in the field for “seed”, that is, planting material next crop.

4. Taxonomy Kingdom – Chromista Phylum- Oomycota Sub division - Mystigomycotina Class - Oomycetes Order - Perenosporales Family - Pythiaceae Genus - Pythium Species - Aphanidermatum

5. Symptoms When infection takes place through contaminated seed rhizomes, sprouts fail to grow resulting in pre-emergence damping off. If the disease strikes after sprouting it manifests as a translucent brown lesion at collar region and later becomes water soaked and soft, extends to whole shoots. Infected plants can be easily pulled out. Leaves turn to pale yellow wither and dry up. The spear leaf and young upper leaves also wither and the entire plant dies. Soft rot extends from collar region to rhizomes which initially become discoloured and gradually decompose, forming a watery mass of putrifying tissues enclosed by tough skin. The fibrovascular strands are rarely affected. Roots arising from affected rhizome rot and soften. Rotting is also noticed in rhizomes collected from infected crop during storage.

6. Favourable condition Infected rhizomes. Low lying fields, high soil moisture and high humidity. Monoculture of turmeric or zinger in the same field. Rainy weather. Mimegrella flies play a role in the spread of the pathogen and aggravation of diseas. Etiology M y c e l ium - b r a n c h e d , hyaline , A s e p t a t e o r C o e n o c y t i c . S p o r a n g i o s p o r e - s i m p l e l i k e m y c e lium , b e a r s i n g l e s p o r a n g i a . S p o r a n g i a - g l o b o s e w i t h o u t p a p i l l a e O o s p o r e - s p h e r i cal , d o u ble t h i c k w a l l e d .

7. Disease cycle The disease is soil borne. Fungus can survive in two ways- In disease rhizomes kept for seed, Through resting structures like chlamydo spores & oospores that reach the soil from infected rhizomes.

8. Disease cycle .

9. Management Crop rotation with non-hosts. Grow turmeric in light soils with good drainage. Use disease free rhizomes for planting Rhizomes should be dipped in Metalaxyl + Mancozeb (Ridomil MZ 72) 2.5g/l for 40 minutes before planting to reduce seed rhizome borne infection . Drench the soil at root region with Bordeaux mixture 1% or Copper oxychloride 0.5% g or Metalaxyl + Mancozeb (Ridomil MZ 72) 2.5g/l in the initial stages of the disease. Control the Mimegralla insects by insecticide application as spray and baits.