The first symptom is the appearance of water-soaked brown lesions in the spear leaves of root-wilt affected palms. Gradually these spots enlarge and coalesce resulting in extensive rotting.As the leaf unfurls the rotten portions of the lamina dry and get blown off in wind, giving a ‘fan’ shape to the leaves. Sometimes, the symptom becomes very acute and the spear fails to unfurl.
- Remove and destroy severely affected / senile and uneconomic palms.
- Replant with healthy seedlings from elite palms and hybrid varieties tolerant to the leaf rot – root (wilt) disease complex. CGD and hybrids of CGD X WCT are tolerant under field conditions.
- Adopt all recommended practices viz agronomic, cultural, plant protection etc as applicable to root (wilt) disease endemic region.
- Clean the crown in general during pre-monsoon period.
- Remove and destroy the rotten portions from the spear leaf and the 2-3 adjacent leaves.
- Pour 300 -1000 ml of fungicidal solution of 3g mancozeb in 300ml water at the base of spear.
- Spray crowns and leaves with 1% Bordeaux mixture or 0.5% Copper oxychloride formulation (5g/L) or 0.4% Mancozeb (4g/L) in January, April-May and September. While spraying, care should be taken to spray the spindle leaf and 2-3 adjacent leaves.
The adult beetle bores into the unopened fronds and spathes. Damage by the pest leads to 10 to 15% loss in yield. The attacked frond when fully opened shows characteristic triangular cuts.. Central spindle appears cut or toppled. Fully opened fronds showing characteristic diamond shaped cuttings. Holes with chewed fibre sticking out at the base of central spindle.
Natural enemies of rhinoceros beetle:
Predator: Reduviid bug
Red palm weevil
Red palm weevil is one of the most destructive pests of coconut, oil palms and ornamental palms. The hole can be seen on the stem with chewed up fibres protruding out. Many times reddish brown liquid can be seen oozing out from the hole. The grubs cause damage inside the stem or crown by feeding on soft tissues and often cause severe damage especially when a large number of them bore into the soft, growing parts. In case of severe infestation the inside portion of trunk is completely eaten and become full of rotting fibres. In case of young palms the top withers while in older palms the top portion of trunk bends and ultimately breaks at the bend (wilting). Sometimes the gnawing sound produced by the feeding grubs inside will also be audible. In the advanced stage of infestation yellowing of the inner whorl of leaves occur. The crowns falls down or dry up later when palm is dead.
Black headed caterpillar
The coconut trees of all ages are attacked. Dried up patches on leaflets of the lower leaves, only three or four youngest leaves at the center of the grown remain green. Galleries of silk and frass on underside of leaflets. In case of severe infestation the whole plantations present a scorched appearance.
Natural enemies of black headed caterpillars:
Parasitiods: Bracon spp., Ichneumon spp., Goniozus nephantidis, Brachymeria spp. etc. Predators: Reduviid bug, spider, red ant, earwig, ground beetle etc.
Coconut eriophyid mite
The earliest symptom on 2-3 month old buttons is pale yellow triangular patches seen below the perianth.Later, these patches become brown. Severely affected buttons may fall. As the buttons grow, brown patches lead to black necrotic lesions with longitudinal fissures on the husk.Oozing of the gummy exudation from the affected surface of the nuts.Uneven growth results in distortion and stunting of nuts leading to reduction in copra yield. In severe cases, the nuts are malformed with cracks and hardened husk.
Natural enemies of coconut eriophyid mite:
Predators: Phytoseiid mites, ladybug beetles, syrphid flies, minute pirate bug, Oligota spp., lacewing
Termites are likely to cause damage to transplanted seedlings particularly in the earlier stage (wilting of seedlings). Base of trunks plastered with runways made of soil and fibers.
Biological control of termites through EPNs:
EPNs seeks out and kills all stages of harmful soil-dwelling insects. They can be used to control a broad range of soil-inhabiting insects and above-ground insects in their soil-inhabiting stage of life. The IJs emerge from cadaver, search for termites, infect, kill and again multiply and remain in the moist soil. Termites which are major pests in sugarcane can be managed by using EPNs effectively. EPN can be produced even at farmer level using either Galleria or Corcyra as a host.
Harvesting of Coconut:
There are different ways of Harvesting
- The climber often uses a small ladder. After climbing top of the ladder he uses a rope ring round the feet for climbing the rest of the tree. On reaching the crown he harvest matures nuts.
- Harvesting is done from the ground with the help of a knife attached to a long bamboo pole.
- Trained monkeys are also used for harvesting.
- Nuts are allowed to fall from bunches.
The average yield per ha varies from 10,000 to 14,000 nuts per annum. From a well maintained garden an annual yield of 25,000 nuts / ha per5 year can be obtained.