MSc

The work entitled "Improved formulation of Lecanicillium lecanii
(Zimmermann) Zare and Gams and its evaluation against sucking pests” was
conducted at College of Agriculture, Vellayani during the period 2013-15 with the
objective to improve the conidial viability and virulence of L. lecanii in
bioformulations and evaluation of their effectiveness in controlling sucking pests.
Pathogenicity studies revealed that the fungus is infective to sucking pests of
cowpea, viz. the aphid, Aphis craccivora Koch, the white fly,
Bemisia tabaci Gennadius, the jassid Amrasca biguttula biguttula Ishida, the mealy
bug, Ferrisia virgata Cockerell, red spider mie Tetranychus sp. and the brinjal scale
Lecanium sp., causing mortality of 90 %, 53.33 %, 26.67 %, 6.67 %, 100 % and 70
%, respectively, five days after treatment. It was not infective to Riptortus pedestris
Fabricius and Anchon pilosum Walker. Observations on symptoms of mycosis did
not exhibit much variation among the test organisms. Lethargic movement followed
by cessation of feeding was noticed in all species. The cadaver was covered with
white mycelia by 72 hours after treatment (HAT) in aphids and mealy bugs, while
mycelia covered the cadaver of whitefly except the wings. In scales, radiating white
mycelial strands were observed from the margins of body. Mites took infection
within 24 HAT and surface of the cadaver was blanketed with white mycelia. The
effective dose of L. lecanii was determined as 107 spores ml-1.
The media supplement to improve viability and sporulation was assessed
based on biomass, number of spore count, colony forming units (cfu) and mortality
caused to A. craccivora. Maximum biomass yield was obtained with PEG 2 %
(2.67g / 100 ml), followed by that of PEG 4 %, crude and extra pure chitosan 5 % and
arachid oil 5 %. Based on number of cfu, arachid oil (1 %), crude and extra pure
chitosan (0.5, 2 and 5 %), crude and extra pure chitin (5 %), and yeast (1, 2 and 3 %)
were found to be superior media supplements with cfu ranging from 1.53 – 1.57 x 105
ml-1. Sporulation was found to be maximum with 5 % chitosan extra pure yielding
9.34 x 108 spores ml-1, followed by chitosan extra pure 2 % (7.83 x 108 spores ml-1).
The spore suspensions from extra pure chitosan 5 %, crude chitin 5 % and arachid oil
5 %, sprayed on A. craccivora resulted in cent per cent mortality within 72 h of
treatment.
Chitin enriched ground nut oil (GNO + Chitin) and chitin enriched sunflower
(SFO + chitin) were the best carriers suitable for formulation. The viability by the
end of three months of storage was 2.27 x 106 ml-1 and 2.20 x 106 ml-1. The
corresponding spore count was 1.67 x 108 spores ml-1 and 1.65 x 108 spores m-1.
PEG 2 %, POX 0.5 %, tween-80 1 % and glycerol 5 % were found to be the
effective adjuvant concentrations. The effective adjuvant combinations were found
to be tween-80 1 % + PEG 2 % + glycerol 5 % + POX 0.5 % (AC1),
tween-80 1 % + Glycerol 5 % (AC2) and tween-80 1 % + glycerol 5 % +
POX 0.5 % (AC3). Among the four materials tried for their UV protectance, boric
acid 1 % was the best.
The three effective formulations, tested under field conditions for
management of sucking pests in cowpea were Formulation I - Chitin enriched
groundnut oil + AC1 + boric acid 1 % ; Formulation II - Chitin enriched groundnut
oil + AC2 + boric acid 1 % and Formulation III - Chitin enriched groundnut oil +
AC3 + boric acid 1 %. Field evaluation revealed that Formulation I was equally
effective as chlorpyriphos 0.05 % resulting in 98.93 % control at 5 %
level of infestation and 96.74 % at fifty per cent infestation levels, seven days after
treatment. The percentage reduction noted in population of mites, jassids and
whiteflies was 92.58 %, 58.81 % and 96.74 %, respectively after seven days of
spraying. Among the bioformulations, Formulation I and II recorded highest yield of
7.03 and 6.74 kg plot-1 respectively which was significantly lower than the yield
obtained from chlorpyriphos 0.05 % treated plots (8.57 kg).
It is concluded that viability and virulence of L. lecanii formulations can be
improved using chitin enriched groundnut oil as carrier and PEG 2 % +
POX 0.5 % + tween-80 1 % + glycerol 5 % as adjuvant. The formulation at 1 %
concentration with boric acid 1 % as UV protectant effectively controlled aphids,
whiteflies, jassids and mites the common sucking pests in cowpea, under field
conditions.