Population dynamics of aphids in Wheat under conventional and natural farming
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Date
2021-11-08
Authors
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Palampur
Abstract
The present investigations entitled “Population dynamics of aphids in Wheat under conventional and
natural farming” were undertaken at Holta Farm of Department of Organic Agriculture and Natural
Farming, CSK HPKV Palampur during Rabi 2019-20 and 2020-21. Two species of aphids viz.,
Rhopalosiphum padi (Linnaeus) and Sitobion avenae (Fabricius) were found infesting wheat. The activity
of aphids commenced from last week of January during both the years of study in all the farming systems.
The peak population was observed in the 3
rd and 4
th week of March in all the farming systems in 2019-20
and 2020-21, respectively. Maximum population of adult coccinellids was recorded during the 3
rd week of
March in conventional and organic farming and a week later in natural farming during 2019-20. During
the second year of study, the peak was observed during the 1st week of April in conventional and natural
farming and during 2
nd week in organic farming. The peak population of grubs and pupae was observed
during the 4th week of March in conventional and organic farming, and a week later in natural farming in
the year 2019-20. In the second year the peak of grub population was observed during the 4th week in
conventional and natural farming, and week later in organic farming. The population of pupae was highest
during the 1st week of April in all the farming systems. The adult syrphids reached to their peak levels
during the 2nd week of April in all the farming systems in 2019-20 and during the 3rd week of April in
2020-21. The maggots and pupae of syrphids reached their peak population during the 4th week of March
in 2019-20 in all the farming systems. In 2020-21, the peak population of maggots was observed during
the 4
th week of March, whereas the pupae reached their peak levels around the 1st week of April. The peak
population of lacewings was recorded during the 4th week of March during both the years of study. The
activity of parasitoids of aphids reached to its maximum around the 4
th week of March during both the
years of study. However, higher per cent parasitization was observed in conventional and organic farming
as compared to organic farming. Lacewings and Diaretiella sp. showed positive and significant
correlation with aphid population in both the years of study, whereas coccinellids showed positive
correlation during both the years and was significant during the first year. The duration of the 1st, 2nd, 3rd
,
4
th larval stages, pupae and adult of C. septempunctata was 2.0±0.71, 4.60±0.55, 4.80±0.84, 6.00±1.58,
4.20±0.84 and 38.80±1.66 days, respectively and it showed a great predation potential by consuming
16.0, 16.19, 21.44, 18.55 and 36.80 aphids per day during 1st, 2nd, 3rd, 4th larval stages and adult,
respectively. Total aphids consumed during the 1st, 2nd, 3rd, 4th larval stages and adult were 33.6, 72.6,
103.0, 112.0 and 1424.6 aphids, respectively.