TY  - BOOK
AU  - Mithra Mohan
AU  - N Anitha (Guide)
TI  - Mealybugs of vegetable ecosystems and tritrophic interactions of brinjal mealybugs
U1  - 632.6 
PY  - 2022///
CY  - Vellayani
PB  - Department of Agricultural Entomology, College of Agriculture
KW  - Agricultural Entomology
KW  - Brinjal
KW  - Mealybugs
N1  - PhD
N2  - The study on “Mealybugs of vegetable ecosystems and tritrophic 
interactions of brinjal mealybugs” was conducted at College of Agriculture, 
Vellayani during 2017 to 2020 with the objectives to identify mealybugs and their 
natural enemy fauna in solanaceous and cucurbitaceous vegetables, to carry out 
the molecular characterization of mealy bugs in solanaceous and cucurbitaceous 
vegetables and to find out the tritrophic interactions of mealybugs infesting 
brinjal.
An investigation on mealybug diversity in solanaceous and cucurbitaceous 
crops of Kerala revealed a total of six mealybug species viz., Coccidohystrix 
insolita, Ferrisia virgata, Paracoccus marginatus, Phenacoccus solenopsis, 
Planococcus citri and Pseudococcus jackbeardsleyi. Besides, four mealybugs viz.,
Crisicoccus hirsutus, Maconellicoccus hirsutus, Planococcus lilacinus and 
Rastrococcus iceryoides infesting other vegetable crops were also recorded from 
Kerala. The study also revealed that the population of mealybug, C. insolita
collected from different regions of Kerala exhibited significant morphological 
variation. The molecular characterization studies proved that the population 
belongs to C. insolita and the variations may be environmental induced.
An exploration of the host range of mealybugs infesting solanaceous and 
cucurbitaceous vegetables in Kerala revealed a total of 113 plants under 73 genera 
belonging to 31 families, out of which 14 plants were recorded as new host 
reports. A rich natural enemy fauna on mealybugs belongs to five orders viz.,
Coleoptera, Lepidoptera, Diptera, Neuroptera and Hymenoptera were documented 
from Kerala. Twenty species of mealybug predators from five different families 
were recorded, among which the predominant family was Coccinellidae with 16 
species under six genera. Among the various predators collected, Cacoxenus sp. 
was recorded for the first time as a predator of P. jackbeardsleyi. 
Eleven hymenopteran parasitoids belonging to five families were 
documented from mealybugs, of which the majority belongs to the family 
Encyrtidae. Four new host-parasitoid associations were also recorded for the first 
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time. The study also identified six hyperparasitoids under the family Encyrtidae, 
of which two species were recorded as new report which includes Cheiloneurus
sp. and Prochilonerus sp. associated with the mealybug P. solenopsis.
The ants associated with mealybugs in different agroecosystems were also 
investigated and a total of 14 species of ants belonging to nine genera under three 
subfamilies were recorded, of which the most dominant subfamily was 
Formicinae followed by Myrmicinae and Dolichoderinae. The present study also 
revealed 15 new ant-mealybug associations for the first time.
The molecular characterization of eight mealybug species was carried out 
that complemented the morphological identification of species. A total of eight 
nucleotide sequences were submitted to NCBI GenBank and accession numbers 
were generated. The sequences were also submitted to BOLD and illustrative 
barcodes were generated. The barcodes of C. insolita, C. hirsutus and 
P. jackbeardsleyi were generated for the first time. The diversity of 
endosymbionts of the mealybug C. insolita was carried out for the first time. The 
study revealed a total of 15 phyla of endosymbionts on C. insolita, of which 
Proteobacteria was the predominant one.
An experiment was conducted at Instructional Farm, Vellayani to identify the 
tritrophic interaction in brinjal, C. insolita and its natural enemies. The study 
revealed that out of the ten brinjal cultivars evaluated, the lowest mean population 
of mealybugs was observed in Pusa Uttam whereas the hybrid cultivar, Udit 
recorded the highest number of mealybugs. The lowest mean per cent leaf 
infestation was recorded in Pusa Purple Long which was statistically on par with 
Pusa Uttam whereas the hybrid cultivar, Udit was severely damaged by the 
mealybugs. Among the tested cultivars, Pusa Purple Long was recorded under the 
group resistant whereas Udit and Haritha were included under the highly 
susceptible group based on the mean per cent leaf infestation caused by 
C. insolita. The cultivar Haritha attracted the highest number of predators whereas 
the maximum mean population of spiders were observed in Pusa Purple Long.
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The correlation analysis on the mean population of mealy bugs with 
biophysical parameters revealed that trichome density, length width ratio of leaf 
and number of branches exhibited a significant positive correlation with mean 
population of mealybugs. Correlation studies on the mean population of natural 
enemies with biophysical parameters revealed that plant height exhibited a 
significant negative correlation whereas leaf thickness and number of branches 
revealed a non-significant negative correlation with the mean population of 
natural enemies. Among the biochemical parameters of brinjal cultivars, total 
phenol content exhibited a significant negative correlation with the mean 
population of mealybugs whereas total chlorophyll content showed a significant 
positive correlation. The correlation between biochemical parameters of brinjal 
cultivars with the mean population of natural enemies revealed that total phenol 
and carotenoid content exhibited a non-significant negative correlation whereas 
total protein content, reducing sugar and total chlorophyll content showed a nonsignificant positive correlation. 
The info-chemical mediated interactions in brinjal cultivars, mealybug and its 
natural enemies were studied using a multi-armed olfactometer and Y-shaped 
olfactometer assay. The results revealed that the cultivar Udit attracted the highest 
number of natural enemy Chrysoperla zastrowii sillemi while the cultivar Pusa 
Uttam attracted the lowest number. The variation in preference shown by the 
natural enemies may be related to the difference in volatile compounds emanating 
from the host cultivar. The GC-MS analysis of the synomonal compounds of the 
cultivar, Udit revealed a total of eleven compounds whereas the cultivar Pusa 
Uttam was recorded with a total of five compounds. The Y shaped olfactometer 
studies revealed that C. zastrowi sillemi adults showed more preference towards 
the synomonal compounds of mealybug infested plants than that of healthy plant 
synomonal extracts. On comparing the volatile profile of synomones of mealybug 
infested and healthy plants revealed that the synomonal extracts of the mealybug 
infested cultivar Udit comprised of 11 compounds whereas healthy plant 
synomonal extracts contained nine compounds. 
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The relative response of C. zastrowi sillemi towards the kairomonal 
compounds of C. insolita was evaluated in a Y tube olfactometer and the results 
revealed that the highest mean number of adult lacewings were attracted to the 
kairomonal compounds of mealybug compared to control. The kairomonal 
extracts of the mealybug comprised of seven compounds and the composition of 
these hydrocarbons may determine the selectivity of natural enemies towards the 
preferred host.
The present study recorded a total of six mealybug species infesting 
solanaceous and cucurbitaceous vegetables and its host range, natural enemies and 
associated ants in different agro ecological regions of Kerala. The molecular 
characterization studies supported the morphological taxonomy and the sequences 
were submitted to NCBI Genbank and BOLD. The study also elucidated the 
interactions mediated by plant traits and info-chemicals in brinjal-mealybugnatural enemy tritrophic systems. The study recorded Pusa Purple Long as 
resistant cultivar and Udit and Haritha as highly susceptible cultivar to C. insolita. 
The plant traits viz., trichome density, length width ratio of leaf, number of 
branches, total phenol content and total chlorophyll content exhibited significant 
correlation with mean population of mealybugs whereas plant height exhibited 
significant correlation with mean population of natural enemies. The study on 
info-chemical mediated tritrophic interactions revealed that the concentration and 
composition of volatile compounds determine the differential selectivity of natural 
enemies. The volatile compounds identified in this study can also be used as a cue 
in moderating the behavior of natural enemies in the ecosystems. So a thorough 
knowledge on the tritrophic relations in the ecosystem will aid in manipulating 
these interactions to devise a better pest management strategy
UR  -  https://krishikosh.egranth.ac.in/handle/1/5810197405
ER  -