Integrated management of potato tuber moth, Phthorimaea operculella (Zeller) in storage
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Date
2021-09-26
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Palampur
Abstract
The bioassay studies of novaluron and spinosad were conducted against eggs and larvae of P. operculella at
Palampur. The LC50 values of novaluron and spinosad against eggs were calculated to be 0.003 and 0.004
per cent. Against larvae, both these novel insecticides were evaluated by spraying them on potato leaves.
The LC50 values of novaluron for I-IV instar larvae of P. operculella were calculated to be 0.001, 0.003,
0.009 and 0.01 percent, respectively. In case of spinosad, the LC50 values for I-IV instar larvae were
determined to be 0.0003, 0.0006, 0.001 and 0.002 per cent, respectively. The time-mortality response of
novaluron and spinosad against larvae was worked out at different concentrations. The LT50 values in first,
second, third and fourth instar larvae for novaluron were worked out to be 51.86, 45.03, 43.47 and 42.76
hours, respectively. The LT50 values of spinosad for I-IV instars were calculated to be 33.08, 42.41, 41.99
and 52.43 hours. In the present study four natural products viz; neemastra, agniastra, brahmastra and
dashparni were tested at five different concentrations ranging from 10.0 to 40.0 per cent. Against first instar
larvae, neemastra, brahmastra, agniastra and dashparni at 40.0 per cent concentration registered mortality
ranging from 53.33 to 66.67 per cent, after five days of exposure. In case of second instar, these natural
products produced 56.67 to 63.33 per cent mortality, at 40 per cent concentration. When third instar larvae
were treated with these products at 40 per cent concentration, neemastra and dashparni produced 53.33 per
cent mortality, while brahmastra and agniastra registered 46.67 and 43.33 per cent mortality, respectively.
In case of fourth instar, neemastra, agniastra, brahmastra and dashparni at 40 per cent concentration
produced 46.67, 36.67, 43.33 and 46.67 per cent kill, after five days of exposure, respectively. When
different natural products were tested in different combinations using 10 per cent concentration in 1:1 ratio,
the interaction seems to be of additive type, and no synergistic effect was observed. In storage experiment,
minimum tuber damage (2.63%) was recorded in spinosad (0.01%), and novaluron (0.007%) registered
54.39 per cent tuber infestation, after 30 days of exposure. Among natural products, maximum damage 78.59
and 75.80 per cent was recorded in agniastra and dashparni. There was 70.51 and 73.01 per cent damage in
neemastra and brahmastra treated tubers, respectively after 30 days of exposure. Novaluron and spinosad
also revealed sublethal effects when one-day old eggs were treated. Maximum incubation period of 4.83
days was observed with novaluron (0.0003%), compared to 4.20 days in control. The total larval period was
also recorded to be maximum in novaluron (0.0003%). There was considerable reduction in larval growth
index in spinosad (0.00005%), and the larval growth index was calculated to be 3.42. The adult longevity
was significantly affected, and the male and female longevity in novaluron treatment ranged from 4.73 and
4.64 days. In control, the male and female longevity has been found to range from 6.2 and 5.56 days,
respectively.