Pests
For controlling pests of bitter gourd, go for mechanical and biological control methods. Chemical control of insect pests should be done only when significant damage occurs. Avoid pesticides that kill or inhibit the development of beneficial organisms especially the pollinators. Choose pesticides that last only a few days.
Fruit flies (Bactocera cucurbitae)
Fruit fly is the most destructive insect pest of bitter gourd. Fruit fly maggots feed on the internal tissues of the fruit causing premature fruit drop and also yellowing and rotting of the affected fruits. This fly is difficult to control because its maggots feed inside the fruits, protected from direct contact with insecticides.
Control: In homestead gardens, covering the fruits in polythene/paper covers help to prevent flies from laying eggs inside the fruits. In large gardens apply malathion 0.15 % suspension containing sugar or jaggery @ 10 g/litre at fortnightly intervals at flowering and fruit initiation. It can also be effectively controlled by the use of banana fruit traps. Spray as coarse droplets on the ventral leaves. Remove and destroy affected and decayed fruits. It can also be effectively controlled by the use of banana fruit traps coupled with the removal and destruction of infected fruits. It is more efficient than two sprayings with insecticide. Traps at 2 m distance after a border row, replenished after 7 to 9 days. Start bait trapping before flowering.
Epilachna beetle (Epilachna spp.)
The yellowish coloured grubs and adults of the beetle feed voraciously on leaves and tender plant parts, and the leaves are completely skeletonized leaving only a network of veins. When in large number, the pest causes serious defoliation and reduces yield.
Control: Remove and destroy egg masses, grubs and adults occurring on leaves.
Pumpkin beetle (Aulacophora fevicolis, A. cincta and A. intermedia)
Adult beetles eat the leaves, makes hole on foliage and causes damage on roots and leaves. Grubs cause damage by feeding on root. It also feeds on flowers and bores into developing fruits.
Control: Spray 2% talc based formulation of Beauvaria bassiana + 0.1% teepol at fortnightly intervals for the management of pumpkin caterpillars, leaf footed bugs and plant lice.
Aphids (Aphis gossypi)
Aphids in large number congregate on tender parts of plant and suck sap resulting in curling and crinkling of leaves. Ants carry aphids from one plant to another.
Control: Apply 1.5% fish oil soap. First dissolve soap in hot water and then make up the volume.
Diseases
Downy mildew (Pseudoperonospora cubensis)
Cottony white mycelial growth is seen on the leaf surface. Chlorotic specks can be seen on the upper surface of the leaves. It is severe during rainy season.
Control: Complete removal and destruction of the affected leaves. Spraying 10 % solution of neem or kiriyath preparation. If the disease incidence is severe, spraying indofil M-45 0.2%, akomin 0.3 % or mancozeb 0.2 % will be useful.
Foliar spraying of combination fungicide Cymoxanil + Mancozeb 2 g/l or 2 sprayings of Pseudomonas fluorescence 2% (20 g/l) thrice at fortnightly interval on the appearance of the symptom.
Powdery mildew (Erysiphe cichoracearum)
The disease appears as small, round, whitish spots on leaves and stems. The spots enlarge and coalesce rapidly and white powdery mass appears on the upper leaf surface. Heavily infected leaves become yellow, and later become dry and brown. Extensive premature defoliation of the older leaves resulting in yield reduction. High humidity and heavy dew increase the severity of the disease.
Control: Control the disease by spraying Dinocap 1 ml/ litre or Trichoderma viridae 2 g/l or neem oil 2% or 3 foliar sprays at 14 days interval on symptom appearance.
Mosaic (Cucumber Mosaic Virus)
Mosaic disease is characterized by vein clearing and chlorosis of leaves. The yellow network of veins is very conspicuous and veins and veinlets are thickened. Growths of plants infected in the early stages remain stunted and yield of the plant get severely reduced. White fly (Bemisia tabaci) is the natural vector of this virus.
Control: Control the vectors by spraying dimethoate 0.05%. Uprooting and destruction of affected plants and collateral hosts should be done. Harvesting can be done only after 10 days (at least) of insecticide/fungicide application. The fruits should be washed thoroughly in water before cooking.