Studies on potato white grubs and their economic losses in Himachal Pradesh
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Date
2022-12-12
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CSK HPKV, Palampur
Abstract
The survey on potato white grubs was carried out at 19 different locations in Himachal Pradesh, and 13 species of white
grubs were collected. In Chamba district, Brahmina crinicollis was found to be the predominant species comprising 100
per cent population at Salooni and 68.18 per cent at Mani. At Shillaroo, Chidgaon, Matiana, Kufri and Fagu in Shimla
district, only Brahmina coriacea grubs were found to cause damage to potato tubers. Maximum population of white
grubs was recorded at Shillaroo with a mean of 11.45±1.05 grubs/ft2
. At Rohru and Tikkar, B. coriacea comprised 77.38
and 56.20 per cent of total grub count, respectively. Melolontha cuprescens grubs caused damage to potato at Khadrala.
In Mandi district, B. crinicollis accounted for 100.00 and 62.50 per cent of total grub count at Bagsiad and Janjheli. In
Barot area, Polyphylla sikkimensis contributed to about 61.19 per cent, whereas Brahmina flavosericea was collected
from potato fields in Karsog area in Mandi district and Benchi in Kullu district comprising 57.75 per cent of total grub
count, respectively. At Shillaroo, 82.35 per cent of the potato fields were found to be infested with white grubs, and the
plant infestation was recorded to be 65.56 per cent. Maximum tuber damage (45.90%) was recorded at Shillaroo. B.
coriacea, B. flavosericea, B. crinicollis, Holotrichia longipennis and Anomala rufiventris were reared in laboratory till
adult emergence. The head capsule width for third instar grubs of these species was recorded to be 4.02, 3.29, 3.25,
5.09, 4.29 and 3.31 mm, and their body length measured 24.13, 27.38, 26.24, 33.43, 42.06 and 28.98 mm, respectively.
In case of M. cuprescens, Melolontha furcicauda and P. sikkimensis, the mean head capsule width was recorded to be
6.5, 6.89 and 7.6 mm, respectively, and their body length averaged 58.74, 59.03 and 59.8 mm, respectively. The raster
patterns for 13 collected species are described along with suitable pictures. To evaluate farmers’ knowledge about white
grubs, data were collected from 164 farmers through personal survey method. The overall literacy rate of heads of
families was about 97.56 per cent. Farming was the primary occupation of 63.41 per cent of total potato growers. On
overall sample farms, 73.17 per cent of surveyed families fall in APL category. The major portion of total land holding
was rainfed (88.01%) and 44.01 per cent of sample potato growers reared sheeps and goats. The majority of the farmers
seem to be self-motivated to grow potato, and 78.05 per cent of the farmers were producing potato for a period of more
than 20 years. The majority of farmers (35.37%) used their own seed. About 95.73 per cent of farmers were able to
recognize white grubs, and 75.16 per cent reported that they have observed the presence of white grubs and their
infestation at the time of harvesting. Only 21.35 per cent of the farmers had gone for insecticidal treatment against the
white grubs, while 40.24 per cent resorted to picking of grubs and their mechanical destruction. Most of the farmers
(48.89%) did mechanical picking at the time of harvesting and about 79.66 per cent of farmers were using granular
insecticides against white grubs, while 20.34 per cent of farmers used chlorpyriphos. The infestation of white grubs was
relatively higher in un-managed potato fields compared to managed fields. The productivity of potato tubers under white
grub managed conditions was found to be 125.8 q/ha. The overall losses on account of white grub infestation have been
estimated at Rs 53308/ha, under un-managed situations as compared to Rs 27392/ha under managed situation. The
overall losses by taking into account managed and un-managed situation together has been found to range from Rs
24412 to 45869 in sample potato growing districts, maximum being in Shimla. The study reveals that the extent of
losses can be decreased by 50.47 per cent on overall farm situation in the study area.