Abstract:
During present investigation experiments were conducted on the
pest phenology on tomato crop for three years (1989-91), at
Pes t
Peshawar.
Institute,
Tarnab,
Research
Agricultural
pehnological studies comprised egg, larval population dynamics,
spatial distribution analysis and development of larval time
sequential sampling plan. On population dynamics, the regression
equation for egg and/or larval population development showed feeble
negative p values during 1989 and 1991, and positive p values
All equations showed poor correlation
during the year 1990.
coefficient. The sequent ional sampling programme data showed two
distinct population configurations i.e. outbreak and endemic. The
differences in growth rates between types were small at first. ,
A total of ca . 6 samples
reached to its peak and then declined.
(each week) would be adequate to detect type of configuration in
any one year. Spatial pattern of H. armigera Hb . egg distribution
during the study revealed that index of dispersion (I.D.) values
were more than 1 in 1990 and 1991.
However, in 1989 the l.D.
values oscillated around 1. Moreover, most of the green's index
(G.I.) values were positive which confirm the negative binomial
The I.D. values of the
distribution of Hÿ_ armigera Hb. eggs.
spatial pattern of H. armigera Hb. larval distribution were mostly
higher than 1. Therefore, larval distribution also fits negative
binomial distribution.
The results of discriminating doses of potassium fertilizer on
egg and larval population, and the fruit infestation showed that
there was no significant effect of fertilizer on the uptake of
tomato plants, on egg and larval population, and on the infestation
of tomato.
To compare relative efficacy of nine insecticides, one
application was done during the year (1989), and three during each
remaining two years of study i.e. 1990 and 1991.
All the
insecticides were found successful in keeping the larval population
below outbreak configuration level upto 15 days after spray.
( viii )
S
!
Consolidation of study data over a period of three years revealed
that Thiodon was statistically the most effective wiLh 77.88
percent larval mortality, followed by Folidol M (75.96%), Sevin
(69.32%), Thuricide (67.12%), Dimilin (66.38%), Edcidin (65.32%)
and Atabron (59.85%). Permasect and Azodrin were significantly the
mortality
larval
and
54.66%
58.55%
with
effective
least
level).
The resulLs also
respectively (cdii = 17.03 at 0.05
indicated a tendency in the reduction of effectiveness of Folidol
M, Azodrin, Dimilin and Thuricide over a period of three years
which might probably be due to enhancement in the degree of
tolerance developing in H. armiqera Hb .
Cluster analysis on the interactions of eggs and larval per
plant, percent fruit damage and yield in Kg per plant of 65 toniaLo
cultivars gave five cluster groups.
Frequency-wise cluster
analysis showed two varieties in group A (3.08%), two in B (3.08%),
one in C (1.53%), fifty nine in D (90.78%) and one in E (1.53%).
In the regression analysis of correlation between characteristics
of 65 varieties and H- armiqera Hb. infestation, step-wise model
was fitted, the correlation between infestion gave negative
dependence larval infestation (-0.3251) with poor correlation
(-0.2558) .
Similar
coefficient
results were obtained for
correlation between yield and number of larvae per plant (b=0.4Q04,
r=0 . 0893 )
The step-wise model correlation between larval
chemical/physical
population
and
parameters
gave
negative
dependence on trichome length (-0.0100) and iron content (-15494E-
04) and positive dependence on zinc (0.0028) and vitamin C
(0.0279). Cluster analysis on the interaction of larval duration,
pupal duration, adult longevity, duration of life cycle, larval and
pupal weight and survival to adult stage also gave five cluster
groups .
Frequency-wise cluster analysis showed two varieties in
group A (3.08%), four in B (6.15%), fifty two in C (84.62%), three
in D (4.62%) and one in E (1.53%).
Tiny Tim being moderately
resistant cultivar, was placed in group E.
.
The results indicated that integration of resistant cultivar,
Tiny Tim and Bacillus thurinqiensis had maximum effect on larval
mortality and minimum percent fruit infestation, it was followed by
accession 87-11(1) also a resistant line, while the maximum
infestation was recorded on the most susceptible cultivar, Big
long.
The host range and average number of larvae/plant of H.
armiqera Hb
were recorded on soybean (1.63), gram (4.80), tomato
(0.31), tobacco (1.64), maize (0.81), sunflower (0.07), okra
(0.67), potato (1.92) and burseem (0.90). Gram was observed to be
the most favourable host plant of this pest