PhD

Surveys were conducted in 1995-96 among one hundred bitter gourd
farmers in Thiruvananthapuram district. Information on the personal and socio-
economic characteristics of the farmers was gathered. Field visits indicated that
among the pests at flowering, the jassid, H.phycitis and leaf feeder, D. indica
were important. At early harvest, the jassid and fruitfly B. cucurbitae were the
major pests. Among the natural enemies observed, the potential ones were
Cjohnsoni (parasite on Hseptima), I.scutellare, Msexmaculatus and Snubilis .
(predators on A.gossypii).
Mosaic was severe in 12 per cent of the plots. Sixty two per cent of the
farmers used a combination of mechanical, cultural and chemical measures against
pests. Most common pesticides used belonged to the organophosphate group.
Farmers in general adopted injudicious methods of chemical control. Seventy per
cent farmers relied on mass media and interpersonal cosmopolites for information
on plant protection. The most important constraint perceived by farmers was the
high cost of inputs viz., plant protection chemicals, manures and fertilizers.
Monitoring of fruit fly incidence using Biosense stikatrap (lure) indicated
the maximum catch at eleven weeks after sowing. Ten carbofuran smeared banana
fruit traps (in yellow coloured coconut shell) were found to be more efficient than
one Biosense trap in trapping the fruit fly.

2
Studies on seasonal incidence of the pests and their natural enemies from
1995 to 1996 indicated that they were more from November '95 to April '96.
In studies on the assessment of potential natural enemies of pests, the
biology and efficacy of Cjohnsoni against epilachna beetle was observed. Among
the predators viz., Iscutellare, Msexmaculatus and S.nubilis whose biology and
feeding potential was studied, Msexmaculatus was observed as the most efficient
predator of aphids.
In another set of experiments, the effects of botanicals and chemical
pesticides on pests and their natural enemies were studied. The antifeedant effect
of botanicals on third instar Hseptima grubs indicated that neem seed oil (three
per cent) and nimbecidine (0.40 per cent) were effective. Estimation of the
comparative effect of chemical pesticides against the fourth instar Hseptima grubs
showed that carbaryl and dimethoate were more effective than quinalphos and
malathion. Toxicity studies of botanicals and chemical pesticides to
Msexmaculatus grubs and Cjohnsoni adults as well as parasite emergence from
treated larval! pupal Hseptima hosts indicated that botanicals were safe whereas,
the chemicals were toxic to the natural enemies. Based on the above experiments,
the botanicals viz., neem seed oil three per cent, nimbecidine 0.40 per cent and
the chemical pesticides,carbaryl 0.15 per cent and dimethoate 0.05 per cent were
selected for the pest management trial in bitter gourd.
The reaction of five bitter gourd varieties viz., Priya, Arka Harit, Preethi,
Priyanka and local to pests was tested in a field trial. Based on pest infestation
and yield, Preethi was selected for the pest management trial.

3
The pest management trial was conducted for two seasons (January to
April, 1996 and 1997). The results indicated that combination of botanical with
chemical pesticide was the best in pest control. Based on the results the following
recommendations were suggested as part of IPM strategies in bitter gourd.
1. Use variety 'Preethi' (MC-84) for planting
2. Basal drenching of combination of nee m seed oil three per cent soap
emulsion with either dimethoate (0.025 per cent) or carbaryl (0.075
per cent) prior to seeding. This is recommended in areas where pests
like pumpkin beetles are endemic.
3. Need based application of above till fruit set to control pests.
4. Apply fungicide (Mancozeb) to control foliar disease (downy mildew).
5. Monitor fruit fly incidence using lure trap. Set yellow painted coconut
shell trap's containing carbofuran smeared banana (palayankodan)
alternated with carbofuran poisoned ocimum I jaggery (2m spacing)
at flowering till final harvest.
6. After fruit set, use (need based) a combination of neem seed oil three
per cent soap emulsion and dimethoate 0.025 per cent.