STUDIES ON DIVERSITY, POPULATION DYNAMICS AND PREDATORY POTENTIAL OF SYRPHIDS AGAINST Brevicoryne brassicae (L.) INFESTING CRUCIFEROUS CROPS IN HIMACHAL PRADESH
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Date
2023-03
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UHF,NAUNI
Abstract
ABSTRACT
The present study entitled “Studies on diversity, population dynamics and predatory
Pradesh” conducted during 2019-2022 at Department of Entomology, Dr. Y. S. Parmar University of
Horticulture and Forestry, Nauni, Solan, Himachal Pradesh. A total 27 species of syrphids belonging
to 12 genera were recorded from the four agroclimatic zones of Himachal Pradesh. The maximum
number of syrphids were found in Zone-II (23) followed by Zone-I (17), Zone-III (13) and Zone-IV
(11). The syrphid population appeared on the crop during 3rd-4th standard meteorological week which
coincided with the appearance of cabbage aphid population in the field condition and the peak was
recorded in the mid of March during both the cropping seasons. The population of E. balteatus, E.
corollae, E. pseudonitens, I. scutellaris and S. indiana showed the significant and positive correlation
with cabbage aphid and with maximum and minimum temperature except for S. pyrastri and B. isaaci
whose population remained low during both the cropping seasons while non-significant correlation
was observed with the relative humidity and total rainfall. The first, second and third instar larvae of
E. balteatus, E. corollae, E. pseudonitens, I. scutellaris, S. indiana, S. pyrastri consumed on an
average 21.70, 21.15, 24.2 , 11.84 , 9.10 and 12.70, 97.21, 71.70, 95.60, 46.75 and 81.53, 278.56,
287.10, 327.0, 272.17, 217.56 and 328.70 aphids, respectively. The maximum value of net predation
rate (Co) was recorded for E. pseudonitens (430.14 aphids) whereas the gross reproductive rate (33.18
offspring/ individual), net reproductive rate (29.20 offspring/individual), intrinsic rate of increase
(r=0.132), finite rate of increase (λ= 1.141), stable host- kill rate (ψ =18.63) and finite host- kill rate
(ω =21.07) were recorded for E. corollae. Logistic regression analysis on the proportion of aphids
consumed and the initial density of aphids confirmed the Type-II functional response for all the larval
stages of syrphids. The third instar larva of syrphids was the most voracious feeder with the highest
attack rate, shortest handling and highest prey consumption. Hence, among dominant syrphid
predators, E. corollae is the potential predator against the cabbage aphid, B. brassicae and can be used
in the integrated pest management program