Fasna Sherin, K
Bioefficacy of entomopathogenic fungi against cassava mealybug, phenacoccus manihotti matile-ferrero (Hemiptera: Pseudococcidae) - Vellanikkara Department of Agricultural Entomology, College of Agriculture 2024 - 82,xixp.
MSc
Cassava mealybug (CMB), Phenacoccus manihoti Matile-Ferrero (Hemiptera:
Pseudococcidae) is a major insect pest of cassava. It causes severe damage by stunting the
growth points of cassava plants, sometimes totally defoliating the plants. Level of
infestation and yield loss by cassava mealybug varied from 30 to100 and 30 to 90 per cent
respectively. In India, the occurrence of this pest was first noticed on cassava in Thrissur,
Kerala during April 2020.
Control of mealybugs commonly relies on the use of insecticides. But, it is difficult
to control mealybugs using insecticides, due to their cryptic life cycle, presence of waxy
coating, and formation of dense colonies. Management of insect pests using
entomopathogens has received considerable importance in recent times.
As part of AICRP programme of 2020-22, AICRP on BCCP, Thrissur centre
conducted survey in cassava growing fields of Thrissur and Palakkad district to assess the
species composition of mealybugs, damage intensity and associated natural enemies.
During the survey, mycosed cadavers were collected and seven isolates of
entomopathogenic fungi were obtained. Out of seven, five entomopathogenic fungal
isolates were selected, characterized and evaluated under the present study entitled
“Bioefficacy of entomopathogenic fungi against cassava mealybug, Phenacoccus manihoti
Matile-Ferrero (Hemiptera: Pseudococcidae)”.
The identity of five isolates was confirmed through morphological, cultural and
molecular characterization. The fungal isolates were identified as two isolates of
Simplicillium aogashimaense (EPF 2 and EPF 4), two isolates of Purpureocillium lilacinum
(EPF 3 and EPF 7) and one isolate of Lecanicillium psallioate (EPF 5).
Pathogenicity of these fungal isolates was tested against second instar nymphs of
cassava mealybug, P. manihoti in the laboratory. A preliminary screening bioassay was
carried out initially, and the superior isolates were subjected to dose-response and
exposure-time response bioassay. In the preliminary screening bioassay, P. lilacinum
isolates (EPF 7 and EPF 3) recorded more than 90.0 per cent mortality. S. aogashimaense
(EPF 4) and L. psalliotae (EPF 5) registered mean mortality of 82.5 and 75.0 per cent
respectively. S. aogashimaense (EPF 2) recorded the lowest mortality of 70.0 per cent,
which was significantly lower than all other isolates.
The best four isolates in the pre-screening were subjected to dose-response and
exposure time- response bioassay. Spore suspensions of five different concentrations
ranging from109
to 105
spores ml-1 were tested against mealybug. Ten days after treatment,
two isolates of P. lilacinum (EPF 7 and EPF 3) recorded more than 80.0 per cent reduction
in population of mealybug at the concentration of 109 spores ml-1
. The same isolates showed
low LC50 and LT50 values.
Efficacy of these two superior isolates of P. lilacinum (EPF 7 and EPF 3) at
concentration of 1×108 spores ml-1 was evaluated in a pot culture experiment. The isolates
were compared with a standard biocontrol check, NBAIR isolate of Lecanicillium lecanii
@ 1×108 spores ml-1
, a botanical insecticide (neem oil emulsion @ 2%) and a chemical
insecticide, dimethoate 30 EC @ 1.5 ml L-1
. Maximum reduction in the mealybug
population was observed in dimethoate treated plants (99.86%). Even though, the neem oil
emulsion (2%) showed significant effect on mealybugs, certain signs of phytotoxicity were
observed in treated plants. Among three fungal isolates, significantly higher reduction in
population was observed in P. lilacinum, EPF 7 (78.55%) followed by P. lilacinum, EPF 3
(74.92%), and both being on par with each other.
In conclusion, the present study revealed that biological control of cassava
mealybug, P. manihoti using two promising isolates of P. lilacinum could be a viable
component in the integrated pest management. Two rounds of foliar application of any of
the two isolates of P. lilacinum (EPF 3 and EPF 7), at 15 days interval at the dosage of
1×108 spores ml-1 was found effective against cassava mealybug, P. manihoti.
Agricultural Entomology
Cassava
Entomopathogenic fungi
Phenacoccus manihotti
Hemiptera: Pseudococcidae
632.6 / FAS/BI PG
Bioefficacy of entomopathogenic fungi against cassava mealybug, phenacoccus manihotti matile-ferrero (Hemiptera: Pseudococcidae) - Vellanikkara Department of Agricultural Entomology, College of Agriculture 2024 - 82,xixp.
MSc
Cassava mealybug (CMB), Phenacoccus manihoti Matile-Ferrero (Hemiptera:
Pseudococcidae) is a major insect pest of cassava. It causes severe damage by stunting the
growth points of cassava plants, sometimes totally defoliating the plants. Level of
infestation and yield loss by cassava mealybug varied from 30 to100 and 30 to 90 per cent
respectively. In India, the occurrence of this pest was first noticed on cassava in Thrissur,
Kerala during April 2020.
Control of mealybugs commonly relies on the use of insecticides. But, it is difficult
to control mealybugs using insecticides, due to their cryptic life cycle, presence of waxy
coating, and formation of dense colonies. Management of insect pests using
entomopathogens has received considerable importance in recent times.
As part of AICRP programme of 2020-22, AICRP on BCCP, Thrissur centre
conducted survey in cassava growing fields of Thrissur and Palakkad district to assess the
species composition of mealybugs, damage intensity and associated natural enemies.
During the survey, mycosed cadavers were collected and seven isolates of
entomopathogenic fungi were obtained. Out of seven, five entomopathogenic fungal
isolates were selected, characterized and evaluated under the present study entitled
“Bioefficacy of entomopathogenic fungi against cassava mealybug, Phenacoccus manihoti
Matile-Ferrero (Hemiptera: Pseudococcidae)”.
The identity of five isolates was confirmed through morphological, cultural and
molecular characterization. The fungal isolates were identified as two isolates of
Simplicillium aogashimaense (EPF 2 and EPF 4), two isolates of Purpureocillium lilacinum
(EPF 3 and EPF 7) and one isolate of Lecanicillium psallioate (EPF 5).
Pathogenicity of these fungal isolates was tested against second instar nymphs of
cassava mealybug, P. manihoti in the laboratory. A preliminary screening bioassay was
carried out initially, and the superior isolates were subjected to dose-response and
exposure-time response bioassay. In the preliminary screening bioassay, P. lilacinum
isolates (EPF 7 and EPF 3) recorded more than 90.0 per cent mortality. S. aogashimaense
(EPF 4) and L. psalliotae (EPF 5) registered mean mortality of 82.5 and 75.0 per cent
respectively. S. aogashimaense (EPF 2) recorded the lowest mortality of 70.0 per cent,
which was significantly lower than all other isolates.
The best four isolates in the pre-screening were subjected to dose-response and
exposure time- response bioassay. Spore suspensions of five different concentrations
ranging from109
to 105
spores ml-1 were tested against mealybug. Ten days after treatment,
two isolates of P. lilacinum (EPF 7 and EPF 3) recorded more than 80.0 per cent reduction
in population of mealybug at the concentration of 109 spores ml-1
. The same isolates showed
low LC50 and LT50 values.
Efficacy of these two superior isolates of P. lilacinum (EPF 7 and EPF 3) at
concentration of 1×108 spores ml-1 was evaluated in a pot culture experiment. The isolates
were compared with a standard biocontrol check, NBAIR isolate of Lecanicillium lecanii
@ 1×108 spores ml-1
, a botanical insecticide (neem oil emulsion @ 2%) and a chemical
insecticide, dimethoate 30 EC @ 1.5 ml L-1
. Maximum reduction in the mealybug
population was observed in dimethoate treated plants (99.86%). Even though, the neem oil
emulsion (2%) showed significant effect on mealybugs, certain signs of phytotoxicity were
observed in treated plants. Among three fungal isolates, significantly higher reduction in
population was observed in P. lilacinum, EPF 7 (78.55%) followed by P. lilacinum, EPF 3
(74.92%), and both being on par with each other.
In conclusion, the present study revealed that biological control of cassava
mealybug, P. manihoti using two promising isolates of P. lilacinum could be a viable
component in the integrated pest management. Two rounds of foliar application of any of
the two isolates of P. lilacinum (EPF 3 and EPF 7), at 15 days interval at the dosage of
1×108 spores ml-1 was found effective against cassava mealybug, P. manihoti.
Agricultural Entomology
Cassava
Entomopathogenic fungi
Phenacoccus manihotti
Hemiptera: Pseudococcidae
632.6 / FAS/BI PG