Management of defoliator's pests in litchi (Litchi chinensis Sonn.)

Authors: Kuldeep Srivastava, Vishal Nath, R. K. Patel, Devinder Sharma* and AKD Anal
NRC on Litchi, Mushahari, Muzaffarpur, Bihar

*SKUAST-J, Chatha, Jammu, J&K

Litchi (Litchi chinensis Sonn.) is one of the most important subtropical fruit trees of the family Sapindaceae, which includes longan and rambutan. Insect pests are the major constraints in healthy litchi production, in terms of quality as well as quantity. Litchi fruit borer, shoot borer, bark eating caterpillar, litchi mite, litchi bug, mango mealy bug, leaf roller, semilooper, bag worms and leaf cutting weevil have been considered as major pest of litchi. On the basis of nature of damage and/or mode of feeding, litchi pests can be grouped in to three different categories viz., borer complex, sap suckers and defoliators and obviously needs different management strategies. In this article we have summarized defoliators of litchi and their management strategies.

1. Leaf roller (Pletypeplus aprobola Meyer; Tortricidae : Lepidoptera)

It is a cosmopolitan pest and besides India, has been reported on various fruits in Hawaii, South Africa, Australia and China. Besides litchi, longan, rambutan, rose, kaith, jamun, chhota amaltas are the other plants damaged by this pest. The symptoms of leaf injury by the larvae are manifested through rolling of tender leaves and feeding inside. The incidence of leaf roller can be observed on litchi trees throughout the year. However, severe infestation can be observed on new flushes. Mating and oviposition, took place during night. The female moth laid 150-200 creamy white eggs under the surface of newly emerged tender leaves. Incubation period varies from 2-8 days as per environmental conditions. The larval period varied from 7-14 days and pupal period 7-24 days and pupates within the clipped piece of the leaf. The adult emerged within 7-10 days after pupation.



2. Semilooper (Perixera illepidaria; Geometridae : Lepidoptera)

Pest has been reported from China, USA, Australia, Thailand and India. Attacks tender leaves in mass and defoliate the new shoots. In severe form it's completely defoliate the newly emerged flush. Incidence of this pest has been observed from July to December however, highest population in September- October completely defoliate the new flush.

3. Bag worm (Eumeta crameri Westwood; Psychidae: Lepidoptera)

It occurs in all litchi growing areas of India. Bag worm larvae infest the older leaves and bark. Young caterpillars construct silken bags covering with bark and dry twigs and by living inside scrap the leaf surface. Coffee, tea, maize, pomegranate, tamarind, castor, sandal, casuarina, cinnamon, Shorea robusta, etc are the host trees of this pest. Incidence of this pest has been noticed throughout the year on litchi. Maximum population can be seen in the month of September-October. Females remain in their bag within their pupal case and release a sex pheromone to attract males. After mating female laid eggs on pupal case. Newly emerged larva initially feed on dead mother, then construct their own cage. Life cycle is completed around 3 months and usually 4 generations are completed in a year.

4. Leaf cutting weevil (Myllocerus undecimpustulatusn Faust; Curculionidae: Coleoptera)

This pest has been reported from Sri Lanka, India, Pakistan and U.S.A. In India weevil occurs in all litchi growing areas. It attacks on leaves, shoot and flower. Adult weevils congregate on the tender leaves and nibble irregular holes on the leaves and sometimes consume the entire leaf leaving the midrib only. The damage is more severe at the time of shoot emergence as it prefers newly leaves therefore; newly established orchard/nurseries are more vulnerable for the attack of leaf cutting weevil. Pest can be observed throughout the year on litchi trees, however, maximum population build up may be observed in rainy season. Commonly found on several plants including longan, rambutan, pigeonpea, cowpea, sorghum, maize, rice, cotton, jute, sunflower, mango, sisoo, etc. Adult has long snout with grey colour. Though, it is poor flier but very active feeder on the leaves of litchi. Female of Myllocerus spp. lay up to 360 eggs over a period of 24 days, and grub emerge in 3-5 days. Eggs are laid directly on organic material at the soil surface, which is common for most Myllocerus spp. Eggs are less than 0.5 mm, ovoid and usually laid in clusters of 3-5. The eggs are white or cream-colored at first, then gradually turn brown when they are close to hatching. Larvae burrow into the soil where they feed on plant roots for approximately one to two months. The larvae pupate in the soil for approximately one week.

Management strategy

Summer ploughing to remove possible pupae in the field. Additionally, grubs of weevils feed on organic matter in the soil below the canopy; hence, ploughing exposed these grubs and reduces the problem.

Hand picking of the adult weevils reduces their incidence to some extent. The rolled leaves that contain larvae may be removed manually during light infestations to check further infestation. Silken bags can be removed as easily seen on the surface of leaf. Semiloopers pupate at the leaf surface and can be seen easily therefore, may also be removed manually at the same time.

Adult weevils can also be removed from plants by vigorously shaking a branch over an open, inverted umbrella. The collected weevils can then be dumped into a container of soapy water.

Foliar spray of imidacloprid 17.8 SL 0.5 ml/l or chlorpyriphos 20 EC 2ml/l may be done when 20 per cent of leaf flushes are infested with these pests to minimize damage to young trees or at critical periods of leaf growth in older trees.

Removal of affected flush, summer ploughing, spray of chemicals can be much effective than alone chemical spray.

About Author / Additional Info:
Sr Scientist, Horticulture (Fruit Science)