MSc

The research work entitled “Development of baits for the management of Spodoptera litura
(F.)” was conducted in the Department of Entomology, College of Agriculture, Vellayani,
Thiruvananthapuram, during the year 2020-2022 with an objective to develop and evaluate poison
and NPV baits against Spodoptera litura (F.).
Base matrices were prepared using different food materials viz. Rice bran, wheat bran, deoiled
soybean chunk, chick pea flour, wheat flour, in which jaggery containing corn flour was used as an
attractant. Base matrices were prepared by taking 100 g of base to which 25 g of jaggery and 0.25 g
of corn starch dissolved in 50 mL water was added and mixed thoroughly using an additional 50 mL
of water. After allowing fermentation for 24 hours, it was passed through a steel press which had 3
mm sized holes which forced the bait matrix out as cylindrical granules.
S. litura larvae attracted to different base matrices was studied in a free choice experiment in
which significantly high attraction was elicited by wheat bran (16%) and wheat flour (16.5%)
matrices which was next to the natural food of castor leaves. Among the food matrices significantly
high consumption was for the wheat bran and wheat flour matrices (5.37 g and 3.84 g by 20 larvae
respectively), exposed to fermentation for 24 hours at 48 HAT. Since in no choice experiment also
wheat bran food matrix elicited significantly superior feeding (7.19 mg/g of larvae), it was chosen as
the most suitable fresh bait.
Storable bait matrices which can be rehydrated prior to use was developed by mixing wheat
bran and wheat flour in various proportions as base materials, since they exhibited maximum
attraction and feeding by S. litura. These base matrices were dehydrated by exposing to 450C for 8
hrs in a hot air oven and then rehydrated. Comparison of structural integrity revealed the superiority
of base matrix comprising of wheat bran and wheat flour in 65:35 proportion, which exhibited
structural integrity scores of 3,3,2 before dehydration, after dehydration, and after rehydration
respectively, without any clump formation. This combination matrix also exhibited superior ingestion
by S. litura larvae in a no-choice trial wherein 1.82 and 1.6 g were ingested by 5 larvae at 24 and 48
HAT respectively.
In order to further improve the structural integrity of the combination rehydratable base
matrix, various stickers viz, xanthan gum, acacia gum arabic, agar, carboxy methyl cellulose @ 1%
were tried. Wheat bran + wheat flour food matrix was prepared by mixing 65 and 35 g respectively
along with 25 g of jaggery, 0.25 g of corn flour and 1.3 g of sticker in 100 mL of water.
Though xanthan gum and CMC based combination matrix improved the
structural integrity of the matrix to a score of 1 with less than 5% crumbling the latter
was selected as sticker because of its superior palatability. 1.99 g of the combination
matrix containing CMC as sticker was consumed by 5 nos. of S. litura larvae in 48 hrs
as against 1.34 g of same containing xanthan gum in a no choice experiment.
Insecticides, viz., fipronil (5 SC) @ 0.15%, thiodicarb (75 WP) @ 0.2%,
emamectin benzoate (5 SG) @ 0.004%, novaluron (10 EC) @ 0.015%, flubendiamide
(39.35 SC) @ 0.012%, cyantraniliprole (10.26 OD) @ 0.012%, chlorpyriphos (20 EC)
@ 0.05% and Sl NPV @ 106
OB/g, were evaluated as toxicants in the wheat bran based
and wheat bran + wheat flour based food matrices both as fresh and rehydrated forms.
Cyantraniliprole 0.12% and emamectin benzoate @ 0.004% incorporated fresh baits
exhibited cent per cent mortality of S. litura at 48 HAT and 60 HAT respectively and
were significantly superior to the rest of the treatments. The rehydrated baits containing
the above toxicants though exhibited less mortality when compared to fresh baits at early
intervals they became on par to that of fresh baits at 72 HAT.
Poison baits were evaluated for its efficacy against S. litura in cowpea (var.
Anashwara) in a caged pot culture experiment. Wheat bran based fresh bait and wheat
bran + wheat flour based rehydratable baits were evaluated. Among the baits tried,
cyantraniliprole @ 0.012% containing wheat bran based fresh bait produced 97.5%
mortality of S. litura at 2 DAT, an effect on par with that of foliar application of
insecticides with the least leaf area damage (11.56%) making it the most promising
poison bait. In comparison to the control, Sl NPV baits caused considerable mortality and
reduced leaf area damage.
Storable wheat bran+ wheat flour based bait containing cyantraniliprole @
0.012% and emamectin benzoate @ 0.004% after rehydration produced mortality of 77.5
and 75% respectively which were on par with each other. Leaf area damage was also
significantly low in these treatments compared to control. Hence these baits have the
potential to be developed and used as commercial storable poison baits against S. litura.
Wheat bran based fresh poison baits (100 g wheat bran + 25 g jaggery and 0.25 g corn
starch + 100 mL water) containing cyantraniliprole @ 0.012% can be used for
management of S. litura in cowpea.
A storable dehydrated wheat bran + wheat flour poison bait formulation (65 g wheat bran
+ 35 g wheat flour + 25 g of jaggery+ 0.25 g of corn flour + 1.3 g of CMC) containing
cyantraniliprole @ 0.012% was also developed in the current study, which can be readily
used under field condition after rehydration.