Investigations on cotton Mealybug, Phenacoccus Solenopsis Tinsley on Bt Cotton Under South Gujarat Condition
Loading...
Date
2011-07
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Agricultural Entomology Department, N. M. College of Agriculture, Gujarat Agricultural University
Abstract
The studies on "Investigations on cotton mealybug,
Phenacoccus solenopsis Tinsley on BI cotton under South Gujarat
condition" were carried out during 2010-11. Biology of P. soienopsis
was studied in P. G. Research Laboratory, Department of Agricultural
Entomology, N. M. College of Agriculture, Navsari during September
to November 2010. The studies on population dynamics of mealybug
and its natural enemies and assessment of crop loss due to P.
so/enopsis on BI cotton (cv. VICH 5 Bt) were carried out at the Main
Cotton Research Station, Surat during kharif 2010-11. Development
and parasitizing potential of Aenasius bambawaiei Hayat on P.
soienopsis was studied during January to February 2011 in bio-control
laboratory of Main Cotton Research Station, Surat.
In the study of biology of P. so/enopsis on Bt cotton,
whitish yellow eggs were laid in groups within the white cottony
ovisac underneath the body. Egg measured on an average 0.35 ± 0.02
•mm in length and 0.20 ± 0.01 mm in breadth, with an average
incubation period of 42.04 ± 7.81 minutes. The nymphs of female
moulted three times with an average developmental period of first,
second and third instar nymphs in 7.00 ± 0.92, 7.85 ± 1.04 and 6.45 ±
J.lS days, respectively. Whereas in male, nymphs moulted four times
with an average duration of first, second, third and fourth (cocoon)
instars in 6.40 ± 1.10,8.45 ± 0.82,5.70 ± 1.81 and 5.35 ± 1.18 days,
respectively. Nymphs measured on an average of 0.41 ± 0.01,0.75 ±
0.03, l.ll ± 0.05 and 1.38 ± 0.02 mm in length and 0.13 ± 0.01, 0.34
± 0.01, 0.53 ± 0.02 and 0.54 ± 0.03 mm in breadth corresponding
which the four instars. The female adults of P. solenopsis were
stationary, wingless, soft bodied, oblong in shape with blackish stripes
on the sides of posterior abdominal region along with waxy deposition
on the body and along the margins.
The males were free living,
winged with a pair of delicate 10 segmented antennae, three pairs of
brownish legs, two pairs of terminal filaments and smoky white in
colour. The males on an average measured 1.17 ± 0.06 mm in length
and 2.33 ± 0.07 mm in breadth with expanded wing, whereas the
female adult was 2.53 ± 0.27 in length and 0.92 ± 0.07 mm in breadth.
Prior to egg laying, the female measured was 3.86 ± 0.48 mm in length
and 1.66 ± 0.28 mm in breadth. The fecundity, on an average, was
328.7 ± 120.07 eggs with pre-oviposition, oviposition and post-oviposition periods of 5.90 ± 0.80, 17.60 ± 4.03 and 9.45 ± 1.\ I days,
respectively. Average longevity of male and female was 3.85 ± 0.88
and 32.95 ± 4.56 days, respectively. Whereas, total life cycle was
29.75 ± 2.77 for male and 54.25 ± 4.95 days for female . The sex ratio
of male: female was 1:3.68 and 1:3 .16 in laboratory and field
populations, respectively.
The incidence of mealybug was observed throughout the
th
crop period starting from 38 standard week i.e. third week of
th
September with peak during 5
standard week i.e. first week of
February (21.00 mealybugs/5 cm apical shoot) with average grade of
2.9 and corresponding severity of 72.50 per cent. The observations on
important natural enemies were also recorded. Amongst parasitoid,
st
Aenasius bambawalei Hayat was active from 41 to 8th standard week
with peak activity during fourth week of February (33.71% parasitism).
The correlation between mealybug incidence and parasitoid and
predators studied was positive and highly significant. The activity of
mealybug and its parasitoid was positively correlated with sunshine
hours, whereas temperature (minimum and maximum), relative
humidity (morning and evening), rainfall and rainy days showed
negative correlation.
The studies on assessment of crop loss due to P. solenopsis on
Bt cotton (cv. VICH 5 Bt) indicated 25.02 per cent loss in seed cottonyield worth of
~
26,350 per ha. The cost benefit ratio (CBR) was
estimated to be I: 9.95 in protected plots. The incidence of other
sucking pests and bollworm was found to be non significant.
A study on development and parasitizing potential of A.
bambawalei indicated that the parasitoid preferred 1lI instar nymphs
(av. 51.48 ± 21.55 % parasitism) and adult female mealybugs (av.
38.15 ± 11.81 % parasitism) as compared to II instar nymphs (av. 4.93
± 4.96 % parasitism) for parasitism. The developmental period of A.
bambawalei was 10.29 ± 0.86, 10.49 ± 0.80 and 10.56 ± 0.97 days
when exposed to II Instar nymphs, III instar nymphs and adult
mealybugs, respectively. The single female adult of A. bambawalei
could parasitize on an average of 125 ± 13.2 mealybugs. Maximum
parasitism (60.00 %) was observed by 7-days old age female wasp
when exposed to its preferred host (III instar mealybug). The average
longevity of female and male parasitoids was 13.8 ± 2.17 and 1.20 ±
0.45 days, respectively .
Description
Keywords
null
Citation
SNEHAL RAMESH PAWAR_46346