ISHS Acta Horticulturae 696: VII International Symposium on Temperate Zone Fruits in the Tropics and Subtropics - Part Two
DISTRIBUTION AND ACTIVITY OF GRUBS AND ADULTS OF APPLE ROOT BORER DORYSTHENES HUGELII REDT. |
| Authors: | J.P. Sharma, D.R. Khajuria |
| Keywords: | apple root borer, Dorysthenes hugelii, grubs, distribution |
| Abstract:
Apple root borer infests all commercial cultivars and age groups of plants. The present studies were conducted during 1997-2003 to know precisely when the adults of this pest emerge and lay eggs and which area of tree basin in the infested tree harbours the maximum population of the grubs. The distribution of grubs in tree basins was studied by exposing the roots of infested apple trees raised on M-7 and seedling rootstocks in winter to record the distance of each grub from the trunk and depth to which it was found feeding. Adults start emerging with the onset of pre-monsoon rains during the second fortnight of June and majority of the beetles (75-80%) emerge by the first week of July but the emergence continues up to second week of August depending upon the frequency of rainfall. A light trap with largest diameter (45 cm) and having maximum distance between upper and lower cones (20 cm) was the most effective for mass trapping of the beetles. Rainfall was found as a pre requisite for the emergence of adults. The data on the larval distribution indicated that 98.56 and 71.26 per cent grubs were present within 90 cm radius and 30 cm depth, repectively, of apple tree basins. In trees raised on seedling rootstock having an average diameter of tree as 2.15 cm, the maximum number of grubs (98.34% and 95.94%) was recorded within 90 cm radius of tree basin and up to 30 cm depth of the soil, respectively. Thus, the control measures against the adults and eggs must be initiated with the emergence of adults in June- July. Similarly for the control of grubs, the area up to one meter from the trunk and to a depth of 30 cm is the most important where control measures should be directed. | |
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