BIONOMICS, POPULATION DYNAMICS AND MANAGEMENT OF APHID, Hyadaphis coriandri DAS INFESTING FENNEL 2416
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Date
2017-08
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JAU,JUNAGADH
Abstract
Key words: Fennel, aphid, Hyadaphis coriandri, coccinellid predators, bionomics, population dynamics, varietal screening, chemical control.
Investigations on bionomics, population dynamics and management of fennel aphid, H. coriandri were carried out under laboratory condition at Department of Entomology and Instructional farm, College of Agriculture, Junagadh Agricultural University, Junagadh during Rabi 2015-16. For the management of aphid, different nine varieties /genotypes were screened and different nine insecticides were evaluated against the pest.
The aphid nymphs were moulted four times before attaining the adult stage. Average body length, width, antennal length & cornicle length of first, second, third and fourth instar nymphs were 0.51 + 0.02, 0.30 + 0.01, 0.24 + 0.01 & 0.03 + 0.01 mm; 0.69 + 0.02, 0.36 + 0.02, 0.34 + 0.01 & 0.05 + 0.01 mm; 0.92 + 0.03, 0.45 + 0.02, 0.46 + 0.02 & 0.10 + 0.01 mm and 1.13 + 0.03, 0.60 + 0.06, 0.54 + 0.02 & 0.15 + 0.01 mm, respectively. Average body length, width, antennal length and cornicle length of adult aphid were 1.41 + 0.02, 0.67 + 0.03, 0.68 + 0.02 and 0.21 + 0.01 mm, respectively. The average developmental period of first, second, third and fourth nymphal instar nymphs were 1.44 + 0.51, 2.44 + 0.51, 2.48 + 0.51 and 1.48 + 0.51 days, respectively. The total nymphal duration was 7.19 + 1.60 days. The mean longevity of adult aphid was observed to be 10.14 + 1.49 days with an entire life span of 17.33 + 1.91 days.
The pre-reproductive, reproductive and post-productive periods were found to be 1.33 + 0.48, 6.95 + 1.36 and 1.86 + 0.73 days, respectively. The fecundity was observed to be 30.67 + 8.41 nymphs per female and the intrinsic rate of single female per day was an average of 4.41 + 1.61 nymphs /day.
The activity of aphid, H. coriandri was commenced from 2nd week of February and remained up to 3rd week of March having peak during 4th week of February in fennel crop. Simultaneously, higher population of coccinellids was observed during 4th week of January to 3rd week of March and showed significantly highly positive correlation with aphid population.
The lowest aphid incidence was recorded in GF-2 (0.87 A.I. /plant) variety of fennel and was categorized as highly resistant variety. Genotype RF-125 (1.73) found to be highly susceptible (HS) against aphid incidence. The highest coccinellids (5.87 coccinellids /plant) and seed yield (985.19 kg/ha) were recorded from the variety GF-2.
The results of nine tested insecticides on aphid, H. coriandri can be effectively managed by spray application of dimethoate 0.003%, flonicamid 0.015% and clothianidin 0.025%. Acetamiprid 0.008%, imidacloprid 0.005% and thiamethoxam 0.01% could also be exhibited satisfactory protection but only up to 50 per cent reduction over control. Thiacloprid 0.021%, difenthiuron 0.05% and dinotefuran 0.01% did not provide satisfactory protection against aphid to fennel crop. Among the different insecticides, dinotefuran 0.01% was found the safer treatment against coccinellid predators as highest number of coccinellids (7.35) was recorded in this treatment. Dimethoate recorded more than 75 per cent reduction in coccinellids population over control and such it was categorized as “harmful”.
The per cent increase over control was recorded maximum seed yield loss could be avoided with spray application of flonicamid 0.015% followed by dimethoate 0.03%, clothianidin 0.025%, acetamiprid 0.008%, imidacloprid 0.005% and thiamethoxam 0.01%. Even though the yield and yield increase over control was very low in the treatments i.e., dinotefuran, difenthiuron and thiacloprid, they increased the yield in the range of 24.08 to 33.15 per cent.
The highest Incremental Cost Benefit Ratio (ICBR) was calculated from the plots treated with dimethoate (1:54.64). In overall effectiveness of insecticides, flonicamid 50 WG @ 0.015% found most effective (first rank) followed by dimethoate > imidacloprid > acetamiprid > clothianidin > difenthiuron > dinotefuran > thiamethoxam > thiacloprid against H. coriandri.
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ENTOMOLOGY