Pests and Diseases
The four main pest diseases’ and pest of ginger in Fiji is rhizome rot, soft rot, root not nematode and rhizome scale.
i) Rhizome Rot
• It is a partly/completely decomposition of rhizome tissue; a root may dry, wet, hard, soft or slimy where the colour of it normally brown to black. This rot is caused by the fungus (Fusanum Oxysporum) which is a problem in the field and also during post-harvesting when ginger is washed dirty (recycled)water, poor aeration and storage in contaminated sheds where rotten piles of reject ginger is allowed to accumulate.
ii) Soft Rot
• Disease which appeared in 1991, in ginger grown at Veikoba is soft rot – the ginger outside looks using fresh and shinny but the pot is in the inside of it. When touched, it is a bit spongy compared to the good quality one. The soft rot is caused by the fungus pythium gracile, either alone or in combination with a bacterium Erwinia sp. The fungus pythium is a water-mound and develops maximally in moist conditions, and when temperatures are favourable. Prolonged wet weather, therefore, creates ideal condition for development of soft-rot disease in ginger.
iii) Root knot Nematode
• Is a disease caused by the nematode (Meloidogyne In cognita) which attacks both the root and the rhizome of the ginger, resulting in warty overgrowth on them. This nematode normally burrows themselves into the soil and form knots on the roots and rhizome. In this way, they attack the plant by feeding on the food and nutrients which should be used by the plant for growth and production. Therefore, because of less/starved with nutrients and food, the plant dies
i) Rhizome Scale
Description – The size and shape of this scale insect is about 0.5mm to 2mm in diameter and usually circular in shape. They normally have a shell colour brown on top which act as coverage and protection.
– The true colour of the insect underneath
– Yellowish in colour.
-It attacks the Rhizome of the plant by sucking out the juice from it.
– Later, wilting of the plant and therefore it dies. * It is hard or difficult to treat this pest (using insect ides or even hot-water treatment because of the shell forming on top which protects the insect from dying.
Apart from these major pest and diseases, other include;
Fungi & Bacteria
Thread Blight – Ceratobasidium sp; Corticium sp
Stem Rot – Athelia rolfsii
Leaf Spot – Magnaporthe Grisea
a) Burrowing Nematode –Radopholus similis (associated with rhizome rot)
b) Reniform Nematode – Rotylenchulus reniformis (yellowing leaf drying and stunting)
Pin Nematode – Criconemoides OnoensisControl
The most recommended method used to control these Pest and diseases is the use of Hot Water Treatment. Hot-Water Treatment Operation
1. Place the tank on level ground in a shaded area.
2. Fill the tank with water to about 15cm (6”) from the top.
3. Heat the water (using gas burner) to 51°C.
At full blow the water should reach this temperature in about 45 min or depends.
Adjust the burner to maintain this temperature.
4. Fill the first basket with ginger seed, and immerse it on the right hand side of the tank (facing the burner).
Adjust (increase) burner to bring the temperature back to51°C and maintain.
5. Move the first basket to the left after 5 minutes and immerse the second basket to the right-hand side.
6. Remove the first basket from the tank after 10 minutes.
Usually healthy, although red spider mite can be an occasional problem. Increasing the humidity by misting plants twice daily with warm water helps discourage these pests.
To control shoot borer and leaf roller, the spray of indoxacarb of 10 ml per 15 litre of water or novaluron of 10 ml per 15 litre of water is very effective if sprayed at 15 days interval.
Rhizome scale insects destroys rhizome and it can be controlled by dipping the seed rhizome in quinalphos by dissolving 1 ml in 1 litre of water.
To avoid rhizome rot, good drainage and treatment of the seed rhizome with dissolving 3 gm of combination of carbendazim and mancozeb (readily available in the market) in 1 litre of water for nearly 30 minutes, before storage should be done. Bacterial wilt which causes milky ooze as gentle pressing of rhizomes and can be effectively controlled by treating the seed rhizome with dissolving 2 gm of streptocycln in 1 litre of water for 30 minutes.