New threats of insect pests and disease in litchi (Litchi chinensis Sonn.) in India

Abstract

In India, litchi is grown mainly in the eastern part of the country and Bihar Province contributes nearly 74% of the total production. Between July 2011 to June 2012, some new threats of pests and diseases were observed during scouting and fixed plot surveys of litchi orchards in Bihar that were hitherto either unnoticed or of minor importance. Studies were conducted to assess the occurrence and level of damage by these pests and diseases. Ten trees in an orchard were randomly selected and observations recorded in three branches having approximately 200 leaflets. Pests were reared in the laboratory for identification and study of their biology. The symptoms of damage were described. Three insect pests viz., red weevil (Apoderus blandus), semilooper (Anisodes illepidaria) and bagworm (Eumeta crameri) and one disease viz., leaf and twig blight (Colletotrichum gloeosporioides and Gloeosporium sp.) were identified. While red weevil and semilooper damaged young leaves, bagworm preferred older leaves. Temperature fluctuations, particularly during peak summer and winter, negatively affected the activity of red weevil and semilooper while bagworm was affected by high temperature during summer. The results indicated that trees having highly damaged canopies (>50% foliage) by these pests represented as much as 40.0% while partially damaged (10-30% foliage) plants represented were up to 20.8%. The incidence of leaf and twig blight disease was from 28.1 to 66.3%. The percentage infected leaflets in a tree varied from 21.0 to 37.0, whereas disease severity index was 3.7 to 47.8%. The disease manifested itself from the beginning of August to the end of February. The occurrence of A. illepidaria and E. crameri is being reported on litchi for the first time from India. The emerging insect pests and diseases may become a limiting factor to litchi cultivation and will have a socio-economic impact for litchi growing areas.