Introduction
India is the largest producer of mango in the world, contributing 53.63% of total mango production. In spite of its larger coverage the productivity of mango is quite less as compared to other mango producing countries. The probable causes of low productivity are the wide range of the climatic condition, diversity of associated pests and diseases and the management. Among the insect pests, mango leaf webber, Orthaga euadrusalis Hampson, (Pyralidae: Lepidoptera) is one of the major pests responsible for low productivity, heavily infested trees gives a burnt look and severe infestation result in complete failure of flowering (Vergese,1998). It is widely distributed in different agro-climatic zones of India, and gained the status of serious pest in UP, Uttaranchal, and AP. (Singh et. al. 2006). Mango leaf webber infests over wide range of mango varieties and cause damage before mango season.

Some of the mango cultivars have been reported to be resistant to the pest attack (Raddy et al., 2001). Management of mango leaf webber is difficult firstly due to the large size of mango tree secondly micro-ecosystem of the mango orchard in which the pest breeds in active period and remained in the same orchard during off-season (Shukla et al., 2001). General application of insecticide in orchard is hazardous to non-target organisms; therefore it is necessary to have an idea about the host liking and effective eco-friendly methods for its management.

1 Result
1.1 Seasonal activity of the mango leaf webber
The activity of pests in mango orchards was initiated in the month of June and remain active up to the December beyond that sudden decline was observed no further infestation was noticed in the mango orchards .The pest complete several over lapping generation from June to December .The most active period was September to December with mean infestation ranged from 20.00 to 25.00 webbed mass/tree. Weather factors viz. temperature (Maximum and Minimum), rainfall and related humidity had no direct influence on the activity of the pests the correlation was non significant.

1.2 Screening of the mango varieties against the infestation of mango leaf webber
Results indicated that the six varieties of mango namely Chinnarasm (0.22 WM/Tree), Bombay Green (0.41 WM/tree), Malda (0.43 WM/Tree), Piddarasm (0.50 WM/Tree), Sindhuri (0.54 WM/Tree) and Alphanjo (0.59 WM/Tree) were the least susceptible varieties with minimum the infestation range 0.0 to 1.25, WM/Tree respectively. These varieties were statistically at par with Totapari (2.63 WM/Tree), Safeda (3.63 WM/Tree), HathiJhool (2.51 WM/Tree), Karela (3.71 WM/Tree), Local collection (2.68 WM/Tree), Bangalora (2.09 WM/Tree), Bombay Yellow (3.18 WM/Tree), Mallika (4.2 WM/Tree) and lalpari (2.95 WM/Tree). Varieties like Gulab khas, Swarn Rekha, Malgoha, Dasheri, Hapus and Fajali were received moderate infestation, but the level of infestation were found consistent throughout the observation period. Most susceptible varieties were Langrah (15.57 WM/Tree), Temuria (15.23 WM/Tree), Dahiyar (10.83 WM/Tree) and Mango Glass (9.87 WM/Tree). Singh et al. 2006 reported dasheri cultivar was the most susceptible and Mallika received low incidence and Amrapalli cultivar was completely free from infestation (Table 1).  
 

Table 1 Screening of mango varieties against of mango leaf webber

1.3 Influence of tree canopy on the infestation of mango leaf webber
Significant and positive correlation (r value = 0.838) was observed between the tree canopy type and the extent of infestation level. It was observed that the mango varieties were not entirely responsible for the different infestation level of the pest but tree canopy also play an important role in determining the pest infestation. The least susceptible varieties of mango was having canopy of type 1 and type 3-recorded 1.99 (Safeda, Malda, Bombay yellow, Sinduri, Bombay green, Alphanjo, Lalpari and Sapia) and 1.13 (Chinnarasam, Piddarasam and Mallika) mean infestation of mango webber per tree respectively. The most susceptible cultivar was Dahiyar, Fajli and Temuria possessing canopy type-7 (10.86 mean infestation) (Table 2). 
 

Table 2 Treatment details

1.4 Effect of the treatments
Overall impacts of treatment show that all treatments were found significantly superior over control. The most effective treatments for the management of mango leaf webber were Diflubenzuron 0.01% (1.41 larvae per webbed mass), Trizophos (0.06%) (0.25 larvae per webbed mass), Chlorpyriphos 0.04% (0.66 larvae per webbed mass), Indoxacarb 0.01% (0.83 larvae per webbed mass), Mechanical removal Treatment (0.91 larvae per webbed mass), Spot Treatment (0.33 larvae per webbed mass) with Imidacloprid which were at par with each other.

2 Methods and Materials
Various factor like mango cultivators, seasonal activity and weather factor and tree canopy that influence the infestation of the pests were studied. Screening of thirty mango cultivars were carried out against the infestation of the mango leaf webber. Observations were recorded at fortnightly interval, the sample size was 5 trees per cultivar. Absolute numbers of infested webbed masses were counted in each observation and removed after recording the observation. Seasonal activity of the pests was recorded on Langrah variety of the mango from May to April at fort nightly intervals and incidence of the pests was correlated with weather parameters.

Influence of tree canopy on the pest infestation was studied. Mango cultivars were grouped in seven categories characterized as the tree canopy type (TC1 to TC7) (Figure 1). Canopy type 1, large tree type dence, branches spreading redially towards the ground .The area around the tree trunk is not receiving proper sun light. Canopy type 2, tree type is small and canopy is scattered type, sunlight penetrates in each and every part of the plant. Canopy type 3, medium size tree, branches moves strait up with slight inclination forwards the periphery making oval shaped in appearance.
 

Figure 1 No.1~No.7 various type of mango tree canopy

Canopy type 4, larged size trees, branches dense towards the top, making shaded dense asymmetrical periphery. Canopy type 5, tree typed is erect, well exposed tree, trunk branches are spreading upwards farming scattered tree canopy. 

Canopy type 6, medium trees with dense canopy branches are spreading type. Canopy type 7, very large and spreading type of tree belongs to there category branches emerged just about the ground level. Efficacy of insecticides including bio-insecticide was compared with the mechanical control method. Observations at fortnightly interval were recorded on Dashehari cultivaron. Pre-treatment population was recorded by counting the actual number of webbed mass per tree. Number of larvae per webbed mass was not counted in pre-treatment observation just to avoid the movement of the larvae from webbed masses. To find out the mean number of larvae per bunch on same date fifty infested webbed mass were examined. The post treatment observation was recorded after 1, 3, 7, 15 days after treatments. In post treatment observations only number of live larvae was counted from two bunches per tree to assess the impact of treatments. Spraying was done with the help of foot sprayer. Before spraying to find out the actual quantity of spray solution required for uniform coverage on tree, spraying of water was done on control untreated trees. After calibrating the required quantity of water per tree, spray solution was prepared. To check the drifting of insecticide alternate tree in a row of Dashehari block of mango orchard was selected for the treatment. In mechanical removal treatment, after recording pre-treatment observation all the infested webbed mass were removed mechanically.

References
Kavitha K., Vijaya Lakshmi K., and Anitha V., 2005, Mango leaf webber, Orthaga euadrusalis walker (Pyrallidaea: Lepidoptera) in Andhara Pradesh, Insect Enviroment, 11(1): 39-40

Shukla R.P., Hasseb M., and Padari R.N., 2001, Integrated pest management in mango, Technical Bulletin CISH, Lucknow, pp.9-11

Singh R., Lakhanpal S.C., and B.K. Karkara, 2006, Incidance of mango leaf webber, Orthega euadrusalis (Hampson) in high dencity plantation of mango at Deharadun, Himachal Pradesh, 11(4): 178-179

Singh G., 1998, Effect of plant based pesticides aginst the mango leaf webber, IV International Symposion on Mango, ISHS Acta., pp.509

Vergese A., 1998, Management of mango leaf webber. A vital package for panicle emergence, Insect Enviroment, 4(3): 7

Raddy C., Harihara Prasad, P. Rajendera, and Umamaheshawari, 2001, Screening of Mango Cultivars against the Leaf Webber, Orthaga exvinacea Hampson (Pyralidae: Lepidoptera), Ind. J. Plant Protection, 29(1&2): 118-111