Eucalyptus tree and pest control , diseases control

Eucalyptus play a key role in provision of fuelwood, timber, cellulose pulp, building materials and energy. Tree growers should be aware of pests and diseases that could reduce productivity of Eucalyptus. The major pests and diseases that are prevalent within the country are:-

Pests

Eucalyptus snout beetle

Also known as eucalyptus weevil.  Adults and larvae chew and feed on the foliage of various Eucalyptus species. Adults chew leaf edges giving then a notched appearance. Older larvae chew entirely through leaves, leaving holes in inner portions and edges of foliage. No insecticide is required for its control as it can be easily controlled by an egg-parasitic wasp, Anaphes nitens.

Blue gum chalcid (BGC) (Leptocybe invasa)

It is a small gall-forming wasp and attacks mostly seedlings and field saplings causing damage by forming massive typical bump-shaped galls on seedlings and sapling canopy, specifically on the leaf midribs, petioles and stems of new growths. Systemic pesticides that have been tested against this pest include Confidor and Methomex. They are effective on nursery seedlings. Another management option includes possible release of biological control agent Selitricoides neseri.

Winter bronzing bug (Thaumastocoris peregrines)

It is a sap-sucking insect that causes the tree foliage to turn reddish-brown. As infestation increases, foliage becomes yellow-brown (winter bronzing). There is no control for the pest currently but progress is being made to release a biological control agent.

Termites

Termites are associated with damage to eucalyptus in the field. Some termite species are able to kill healthy trees and, therefore cause greater losses. Damage includes attacking the bole, ring barking and death of seedlings. A number of chemicals can be used to protect trees against attack by termites such as Gladiator, Confidor, Imaxi among others.

Diseases

Cylindrocladium Leaf Spot (Cylindrocladium scoparium)

The disease is a severe one that affects nurseries. Brown, rounded to irregular patches that begin at the margins are the disease’s symptoms. Larger patches are created as the spots . The spots’ edges are becoming more distinct and extending. The fungal development on spots appears as white mycelium with millions of conidia inside when the temperature is warm and humid. Complete defoliation is the result of its severe illness. Peak time for disease is  wet season.

 Cercospora Leaf Spots (Cercospora eucalypti)

The disease is characterized by pale brown colored round to irregular spots. The center and margins of the spot is chocolate brown with diffusing margins. Peak period Rainy season.

 Pink Leaf Spots (Gleosporium Sp.)

            The spots start as small pin head sized specks scattered all over leaf lamina. Spotting is characterized by purplish margins. The bigger spots become straw brown on both sides of the leaf. Peak Period May- October

     Control for leaf spots :-

1. The planting material should be disease free and from good progeny.
2.  Maintain sanitation by disposing of diseased material.
3.  Maintain high plant vigour through cultural practices.
4.  Three to four sprays with Bavistin 50 WP @ 1 g of formulation per litre of water, starting with the onset of rains in end of June or July controls the cylindrocladium and cercospora leaf spot diseases.

 In case of pink leaf spot disease, the plants should be sprayed with Dithane M-45 @ 3g per litre of water

Eucalyptus stem blight (Cryptosporiopsis eucalypti)

Eucalyptus trees are rendered susceptible due to the infection caused by two leaf spot  fungi viz. Cylindrocladium scoparium and Cercospora eucalypti during rainy season that result in severe leaf defoliation. Subsequently, Cryptosporiopsis eucalypti causes dieback followed by canker on the trunk. Further Colletotrichum spp. and Diplodia spp. have also been found to be associated with these cankers and die back in young plantations.

Control :-

1. Procure the nursery from certified or reputed nursery growers.

2. This problem has been noticed particularly in nursery plants procured by farmers from Uttrakhand and Uttar Pradesh.

3. Procure plants from gall free nursery and preferably from state forest department or Punjab Agricultural University.

4. 2-3 sprays should be given with Bavistin 50 WP (1 g per litre of water) followed by Tilt 25 EC (1 ml per litre of water) at fortnightly interval starting from last week of June to avoid leaf spots.

 5. Drenching with Bavistin 50 WP @ 0.2 per cent should be done using 25 litre of water per tree during second fortnight of August