Abstract
The research work was carried out in the litchi orchard of Gopalpur upazila under
Tangail district during 2014 to 2017 fruiting seasons. Farmer's perceptions of
insecticide usage to manage litchi fruit borer, C. sinensis in three litchi growing
districts, efficacy of some traditional and new generation insecticides against the insect
were conducted during 2014 to 2015 experiment years. A demographic survey showed
that almost all the farmers know the infestation symptoms of fruit borer and its control.
Insecticide was found as a common control practice where twelve brands were in use
maximum twenty times in a fruit season with incorrect dose. Farmers were in the
opinion that controls of internal feeder litchi fruit borer with traditional insecticides
were quite difficult who spraying insecticide to control fruit borer with a little idea on
the negative effect of environment and health. Advices of insecticide use are mainly
from pesticide dealers or retailers and a few farmers contact extension worker for this
purpose. Both the visual and mechanical tactics which applied five to ten days after
fruit set were observed dropping and harvested litchi, fruit borer its activity begun ten
to fifteen days after fruit set and increasing advance fruiting season with peak period
in the month of May and infestation decreased in matured fruit. Four types namely
three mechanical, four botanical with two combinations, twelve foliar spraying
different form with four combinations and three soil dressing granular insecticides
were tested on fruit trees to evaluate for their efficacy against C. sinensis. The
mechanical tactic butter paper bagging at ten days within or after fruit set showed
better performance in respect of benefit cost ratio 5.55:1 and the reduction of fruit
infestation was 100 percent with significantly higher healthy fruit 62.71 percent. Neem
leaf extract 20 ml/L of water spraying showed comparatively better performance in the
reduction of 80.30 percent fruit infestation, 71.87 percent fresh yield increased and
benefit cost ratio of 9.03:1. New chemical insecticide Novastar 56 EC (Biphanthrin+
Abamectin) @ of 1ml/L of water on the basis of benefit cost ratio 5.75:1, it gave the
maximum reduction of fruit infestation 98.08 percent and increased yield 51.51
percent over control. Application of granular insecticides with mixing at root zone
soil of litchi tree beginning at inflorescence stage before flower open Furadan 5G
(Carbofuran) @ 200g/tree of four times at interval of 20 days gave better protection
63.38 percent and fresh fruit increased 67.38 percent over control and benefit cost
ratio was 4.48:1. Application of spraying insecticides and botanicals in different
frequencies and times in the fruiting season showed that all the spray materials
were found effective at inflorescence stage once including with thrice on fruit at 15
days interval spraying started within ten days after formation of fruit but varied
among benefit cost ratio. Insecticides showed the highest persistence effect up to 7
days after spraying and then after certain time the reduction capabilities of
infestation exhausted. Among the tactics on the basis of infestation reduced, fresh
yield increased, long persistence effect and least harmful effect from the residual
point of view showing ranking order mechanical > foliar insecticide > botanical >
granular. Therefore, white color butter paper bagging, Novastar 56 EC, Neem leaf
extract and Furadan 5G could be recommended to protect litchi fruit from the
attack of C. sinensis and ensure the highest number of fresh litchi fruit.