MSc

The study entitled ‘Management of phytophagous ants in vegetable crops
under homestead cultivation’ was carried out at Department of Agricultural
Entomology, College of Agriculture, Vellayani during the period 2021-2022. The
main objectives of the study were to document the phytophagous ants infesting
vegetables, to assess the extent of damage and to develop effective management
practices against them.
Fourteen phytophagous ant species were identified from various vegetable
crops viz., Myrmicaria brunnea Saunders from cowpea, Anoplolepis gracilipes
Smith, Meranoplus bicolor Guerin-Meneville, Camponotus mendax Forel,
Camponotus rufoglaucus Jerdon, Tetramorium smithi Mayr, Carebara diversa
Jerdon, Solenopsis geminata Fabricius, Trichomyrmex destructor Jerdon,
Diacamma assamense Emery, Monomorium sagei Forel, Nylanderia yerburyi Forel,
Tapinoma melanocephalum Fabricius from okra and Camponotus compressus
Fabricius from brinjal during the purposive survey conducted among ten farmers
each of two districts viz., Kozhikode and Thiruvananthapuram. Study revealed that
okra was the most preferred crop with 35 per cent infestation followed by brinjal
(18.18%) and cowpea (14.28%).
Based on the results of the survey, C. diversa, S. geminata and T. destructor
were identified as the most destructive phytophagous ant species owing to their
regular feeding behavior and preference for both flowers and fruits. From the study
on assessment of extent of damage, the most preferred part in okra for attack of S.
geminata was flower bud (11.82%), followed by flower (9.56%) and fruit (6.67%)
respectively. Flowerbuds, fruits and flowers were equally susceptible to the attack of
T. destructor, while in case of C. diversa preference was for fruits (6.45%) rather than
flowers (3.54%) and flower buds (4.34%). Biochemical analysis was conducted to
quantify the sugars (glucose, fructose and sucrose) in different plant parts of okra viz.,
flowers, fruits, leaves, stem and tender shoots which revealed that concentration of all
the sugars was the highest in fruits followed by leaves and flowers.
Field experiment to test the attractiveness of traps proved that greater
attractiveness was shown towards sugar based liquid baits. Accordingly, more number
of ants were attracted towards sugar 25% + boric acid (0.5%) (7.60), sugar 25% +
thiamethoxam(0.0001%) (7.63) and sugar 25% (control)). In the laboratory
experiment to test the efficacy of traps, the highest ant mortality was recorded in
sugar + rava + fipronil (1:1:0.3) where 100 per cent mortality was obtained in 24 h. In
case of sugar 25% + boric acid (0.5%) and sugar 25% + thiamethoxam 0.0001%, a
steady hike in mortality due to delayed action of toxic materials in which 65.11 and
52.58 per cent mortality was recorded respectively on 19th day after placement of
traps. In field experiment on management of phytophagous ants by the application of
various treatments, up to fifth day after treatment, no phytophagous ants was observed
in okra plants treated with ethion 40% + cypermethrin 5% EC. Ant population on
plants treated with Neem oil + garlic emulsion, turmeric powder, lemon garlic extract,
talc based formulation of B.bassiana, H. indica were 77.55, 72.05, 69.56, 65.54 and
82.91 respectively and were significantly on par. Harvest time residues of insecticides
(ethion, cypermethrin, fipronil, thiamethoxam) applied in different treatments in okra
fruits were less than Limit of Quantification (LOQ for ethion and cypermethrin was
0.05 mg kg-1
and for fipronil and thiamethoxam LOQ was 0.01mg kg-1
).
To conclude, fourteen phytophagous ant species were identified during
the survey conducted at Kozhikode and Thiruvananthapuram districts. The most
preferred crop for phytophagous ants was okra and the most destructive phytophagous
ant species on vegetables were identified as C. diversa, S. geminata and T.
destructor. The most susceptible stage to S. geminata attack was flower bud (11.82
%), while in T. destructor, flower bud, flower and fruit were equally susceptible to
attack. In case of C. diversa, the most susceptible stage to attack was fruit (6.45% ). In
the laboratory experiment on ant mortality the best results were obtained in sugar +
rava + fipronil (1:1:0.3) with 100 per cent mortality followed by sugar 25% + boric
acid(0.5%) and sugar 25% + thiamethoxam (0.0001%) with 65.11 per cent and 52.58
per cent mortality respectively. In the field experiment on testing the attractiveness of
traps greater preference of ants was observed in sugar 25% + boric acid (0.5 %) and
sugar 25% + thiamethoxam (0.0001%). In field experiment on management of
phytophagous ants by the application of various treatments, up to fifth day after
treatment, no phytophagous ants was observed in okra plants treated with ethion 40%
+ cypermethrin 5% EC.