Journal of Tea Science Research. 2015, Vol. 5, No. 6, 1-7
4
Bower (
Clerodendron infortunatum
). It kills mites by
direct contact and disturbs the life cycle by anti
oviposition & feeding deterrence. Rescue is effective
against mites, aphids & jassids etc. It gives prolonged
control against all mites. The efficacy of rescue is not
affected by high temperature. Rescue is safe for
natural predators & parasitoids. It is compatible with
other chemical pesticides but not with foliar nutrients
& copper fungicides (Anonymous, 2011).
T
orpedo (
Sophora alopecuroides
+
Stemona sessilifolia
)
Torpedo is a broad spectrum pest control weapon of
plant origin of Pea flower tree (
Sophora alopecuroides
)
& Wild asparagus (
Stemona sessilifolia
). Torpedo can
give fast & fantastic relief from vulnerable pest attack.
It is an ultimate trendsetter for the control of red
spider mites and loopers. It can kill the pest by contact
as well as by stomach poison. This formulation
also interferes with the life cycle of the mites and
thus gives a prolonged control of mites. These are eco-
friendly, economic, target-specific & biodegradable.
Torpedo is very effective against mites, loopers,
caterpillars, aphids, jassids etc. These are safe for
natural predators & parasites. It is compatible with other
insecticides but not with foliar fertilizers, copper
fungicides & plant growth regulators (Anonymous,
2011).
Laboratory bioassay of commercial biopesticides
against red spidermite in tea
For laboratory evaluation of plant extracts, 30 healthy
adult female of red spider mites were released on a
healthy detached tea leaf of BT2 in the laboratory. The
selected biopesticides viz. Bio-Cawach, Karanza,
Miticon, Neemakar, Rescue and Torpedo were used @
0.8 mL, 1.0 mL, 1.0 mL, 1.0 mL, 0.5 mL and 0.5 mL,
respectively. Each treatment was replicated thrice.
Direct toxicity test was done in complete randomized
design under laboratory. Each product was sprayed on
the both surfaces of leaf using glass atomizer. The
number of live red spider mite was counted by a
magnifying glass at 24, 48 and 72 hours after treatment.
Each treatment was replicated thrice. Original data were
corrected by Abbott’s (1987) formula: Percentage of
corrected mortality=(Observed mortality-Control
mortality/100-control mortality)×100
Field evaluation of commercial biopesticides
against red spider mite in tea
A field trial was conducted to evaluate the efficacy of
different commercial plant products against red spider
mite in tea fields at BTRI main farm. The experiment
was laid out in RCBD with seven treatments including
control each having three replications. The plot size
was kept as 5 x 5 m
2
having 30 tea bushes. Each plot
in the experiment was separated by two buffer rows of
non-experimental tea. Thirty bushes per replication
were considered for each treatment along with
unsprayed control. Sections with heavy infestation of
red spider mite were chosen for this study. After
selection of the plots, pretreatment count was taken in
the respective plots and two rounds of foliar spray
were given at 15 days interval with hand operated
Knapsack sprayer with water volume of 1000 litres/ha.
Post treatment observations were taken at weekly
interval for four weeks after treatment. Observations
on mite population were made on both adaxial and
abaxial side of the ten randomly collected mature leaves
per replication for each treatment of different plant
extracts along with unsprayed control using mite
brushing machine (Model-Leedom Engineering, USA)
and a compound microscope. Field performance of
tested biopesticides against red spider mites in tea was
calculated by using Henderson &Tilton (1955) formula.
Effect of biopesticides on natural enemies i.e.
Stethorus gilvifrons
and
Oxyopes
sp.
The biopesticdes were also tested for its effect on the
mortality of two important predators of red spider
mite i.e.
Stethorus gilvifrons
and
Oxyopes
sp. in the
laboratory condition. Ten adult predators were placed
in rectangular jars (9.5 cm×7.5 cm×20 cm) with mite
infested tea leaves. Approved concentration of tested
biopesticides were sprayed directly onto adults of
Stethorus gilvifrons
and
Oxyopes
sp. Spraying was
performed as described for the laboratory bioassay
and observed everyday for mortality.
Organoleptic test in respect of quality
A field experiment was also conducted to study
whether tested biopesticides have imparted any taint
to black tea. Tea shoots were harvested on 7
th
day after
spraying of selected biopesticides at app roved
