Fruit and Shoot Borer (Leucinodes orbonalis) – Symptoms and Damage Prevention
The Fruit and Shoot Borer is a lonely translucent back head caterpillar which attacks bugs, mostly during dry season. It is the type of disease that affects crops like Egg plant.
At the end of larval stage, the caterpillar becomes red and falls on the soil where it will become a nymph. Holes due to caterpillar exit can then be seen on bud.
Leucinodes orbonalis, the eggplant fruit and shoot borer or brinjal fruit and shoot borer, is a moth species in the genus Leucinodes. It is found in the tropics of Asia, and it is a minor pest in the Americas.
Furthermore, it has been intercepted in imports of Solanaceae fruits from Asia and has been taken at light in the UK presumably as an result of such importations. The species was first described by Achille Guenée in 1854.
It is a major pest of eggplant. The adult is a small moth, with a wingspan of 18-24 mm, white in colour with a pink and bluish tinge, and a few brown spots on its wings.
Moths lay creamy white single eggs on leaf undersides, stems, flower buds, or the base of fruits. Upon hatching the caterpillars (white in colour) bore into the top section of fruits and tender shoots.
Caterpillars develop inside fruits and stems reaching a length of 15-18 mm. When fully-grown, caterpillars make a small hole in the fruit or shoot and drop to the soil and pupate among fallen debris.
When plants start bearing fruits, most caterpillars prefer to feed on the tender fruits. The damage to the shoots is not seen until they droop as a result of the caterpillar feeding inside them.
Recently damaged fruits are not easy to detect. The first indication of damage to the fruit is a small hole just below the calyx where the insect has entered. Fruits are filled with frass.
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They change colour and taste; they drop off and are unmarketable. Caterpillars are difficult to control with pesticides. Within hours of hatching from eggs, caterpillars enter the shoots or fruits, and are not reached by contact pesticides.
The primary larval hostplant is eggplant or brinjal, Solanum melongena, where most of the economical impact of this species is reported. Secondary hostplants comprise tomato, potato, nightshade, Sodom apple, Ethiopian nightshade, potatotree, nipplefruit, black nightshade, turkey berry, tropical soda apple, Solanum anguivi, Solanum xanthocarpum, cape gooseberry, and Physalis minima.
Eggs are laid during the night on the lower surface of the young leaves, green stems, flower buds, or calyces of the fruits. Within an hour of hatching, the caterpillar (larva) bores into the nearest tender shoot, flower, or fruit.
Soon after boring into shoots or fruits, they plug the entrance hole with excreta. In young plants, caterpillars are reported to bore inside petioles and midribs of large leaves.
As a result, the affected leaves may drop off. Larval feeding inside shoots results in wilting of the young shoot. The damaged shoots ultimately drop off, disturbing plant growth and reducing fruit number and size.
New shoots may grow but this delays crop maturity. Larval feeding inside the fruit results in the destruction of fruit tissue, making even slightly damaged fruit unfit for marketing.
A genetically modified brinjal, called Bt brinjal, has been developed to fight against L. orbonalis. Several other integrated pest management strategies, for example, sex pheromones, physical and mechanical barriers, cultural practices, use of bio-pesticides and biological agents, botanical pesticides and safer chemical pesticides has been suggested to combat this pest.
Symptoms and Damage
Caterpillars eat the inside part of buds, including abortion. Sometimes, they also attack young fruits, eating the inside part and stopping total development of the fruit.
Damage Prevention Measures of Fruit and Shoot Borer (Leucinodes orbonalis)
Some of the damage preventive measures include the following:
- Regularly check buds before flowering.
- Apply an insecticide (Bacillus thuringiensis).
- Conserve natural enemies. Predatory ants are the main natural enemies of the shoot and fruit borer. Other natural enemies include: ladybird beetles, praying mantis, earwigs, predatory bugs and spiders.
- Destroy old eggplant plants and stubble (burn or bury them) immediately after harvest. Pupae can survive in the stubble for several weeks, infesting the new crop.
- Use healthy, pest-free seedlings. Raise seedlings far away from sources of infestation (old eggplant fields, eggplant stubble).
- Grow seedlings under nylon netting to prevent moths from laying eggs on the plants.
- Remove and destroy infested shoots (readily visible as dry tip of branches). Burn, shred into tiny pieces or bury attacked shoots at least 20 cm in the soil. If this is done by all farmers in a community, especially before fruiting, pest infestation and damage can be drastically reduced. Continue cutting attacked shoots at least once a week until the final harvest.
- Destroy infested fruits found during harvest.
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