TY  - BOOK
AU  - Ashish V V
AU  - Haseena Bhaskar (Guide)
TI  - Bioefficacy of Tagetes minuta L. against Teranychus truncatus ehara (Prostigmata: Tetranychidae) and Aphis craccivora koch (Hemiptera: Aphididae)
U1  - 632.6 
PY  - 2023///
CY  - Vellanikkara
PB  - Department of Agricultural Entomology, College of Agriculture
KW  - Agricultural entomology
KW  - Tagetes minuta L
KW  - Teranychus truncatus
KW  - Aphis craccivora
N1  - MSc
N2  - The spider mite, Tetranychus truncatus Ehara and the black cowpea aphid, Aphis 
craccivora Koch are two predominant sucking pests infesting several vegetable crops 
in Kerala. Farmers depend heavily on chemical pesticides for the management of these 
pests. However, due to the adverse effects of synthetic pesticides on environment and 
non-target organisms, there is a growing need for environmentally benign alternatives.
This has generated interest in the development of biopesticides, based on botanicals.
Tagetes minuta L., commonly known as Mexican marigold or wild marigold or 
southern cone marigold is a plant whose pesticidal properties have been well 
documented.
 The study was carried out in the Department of Agricultural Entomology, College 
of Agriculture, KAU, Vellanikkara during 2020-2022. The objectives of the study were 
to identify the bioactive fractions of T. minuta and to evaluate the bioefficacy of the 
solvent fractions against T. truncatus and A. craccivora. Tagetes minuta plants 
cultivated in the Department of Floriculture and Landscaping, were harvested at the 
flowering stage followed by shade drying and grinding. The powdered botanical was 
extracted sequentially using hexane (non-polar), chloroform (medium polar) and water 
(highly polar) as solvents. The hexane, chloroform and aqueous fractions of T. minuta
were evaluated for their efficacy against T. truncatus and A. craccivora in the laboratory
at five different concentrations viz., 0.025, 0.05, 0.1, 0.15 and 0.2 %. 
The ovicidal and adulticidal effects of the solvent fractions were evaluated 
against T. truncatus by topical application method. Considerable ovicidal action was 
exhibited only by hexane fraction at higher concentrations (0.1, 0.15 and 0.2 %), with 
cent per cent egg mortality at 0.2 %, after 120 h of treatment. However, all the three 
solvent fractions caused appreciable mortality of adult mites, in a concentration 
dependent manner. The hexane fraction at 0.2 % and 0.15 % were significantly superior, 
causing 91.67 and 90.00 per cent mortality, respectively, followed by 0.2 % chloroform 
(66.67), 0.15 and 0.10% (56.67), and 0.2 % aqueous fraction (53.33), after 120 h of 
treatment. 
 The efficacy of the solvent fractions (0.025, 0.05, 0.1, 0.15 and 0.2 %) against A.
craccivora was evaluated in the laboratory on cowpea seedlings grown in paper cups.
Though the highest reduction in aphid count after 120 h of treatment was recorded in
hexane fraction at 0.2 % (90.00 per cent), chloroform (86.67) and aqueous fraction 
(85.00) also recorded reduction in aphid count on par with it, at the same concentration. 
 Qualitative phytochemical analysis of the hexane and chloroform fractions was 
carried out by GC-MS/MS to identify the major bio- active constituents. The two 
compounds, 4-o-methylphorbol 12, 13- didecanoate and milbemycin b were found in 
both the fractions, while 4α-phorbol 12,13-didecanoate was found in hexane fraction 
only.
 The best concentrations of the three botanical fractions of T. minuta were tested 
for efficacy against T. truncatus on potted plants of amaranthus along with neem oil 
emulsion (2%) and horticultural mineral oil (2.5%). After 14 days of treatment, the 
hexane fraction recorded the highest reduction in mite population (88.78 %) followed 
by chloroform and aqueous fractions which were on par with each other (77.97 and 
76.96 %, respectively). Hexane fraction was superior to neem oil emulsion, while 
chloroform and aqueous fractions were found to be on par with neem oil emulsion 
(76.44), which is a widely recommended botanical preparation for mite pest
management in different crops. 
 The best concentrations of the three solvent fractions of T. minuta identified 
in the laboratory study were evaluated against A. craccivora on cowpea, in a pot culture 
experiment. By 10th day of treatment, the field efficacy of hexane fraction (78.95 % 
reduction) was comparable with that of neem oil emulsion (87.59 %), while chloroform 
(72.43 %) and aqueous fractions (68.20 %) were comparable with azadirachtin 1 EC 
(67.97 %).
The results of the study indicate that Mexican marigold possess excellent 
acaricidal and insecticidal properties and that the plant can be explored further, for 
utilization in the management of spider mites as well as aphids
ER  -