Guava is commonly called a poor man`s apple in the tropics and known for its delicious, pleasant aroma and outstanding nutritional values throughout the world.
It is an excellent source of pectin, phosphorus, calcium, iron, potassium, and sodium with a pleasant aroma. The guava fruit is having a medicinal property and a good source of antioxidant and also having the anticarcinogenic property.
Due to various constraints, guava production is severely affected. Among all the known factors, insect pests are of prime importance. The guava is subjected to attack by several kinds of pests and about 80 species of insects have been recorded on guava, but only a few of them have been recognized as a pest of regular occurrence and causing significant damage.
Among insect pest, the fruit fly is the major limiting factor in obtaining a good quality of fruits and vegetable and known to cause considerable losses. Fruit flies are one of the most diversified and noxious pests on a wide range of tropical and sub-tropical fruits and vegetables. Fruit flies are considered as a highly destructive pest of guava fruit production causing yield losses and quality degradation of the produce. It is recorded, that crop losses caused by fruit fly ranging from 20-80 percent usually depend upon the crop locality, season and variety.
Nature of damage:
The infestations caused by fruit fly often spread quickly in guava trees which produce sweet-smelling with an edible rind and creamy white, yellow or pink flesh. On the ripening stage of fruit, emit a pungent, musky odor that attracts fruit flies. Adult female fruit flies have a needle-like ovipositor with which they puncture the skin of fruits to lay their eggs in the flesh.
Eggs are laid beneath the skin of fruit and after completion of the incubation period, maggots are emerged out that feed on the flesh and the resulting damage causes rotting due to microbial decay of the flesh. When the guava fruit is squeezed, the tiny punctures that leak juice from surface indicate the infestation. At first, the oviposition marks are difficult to detect but as within one to two days the eggs hatch, oviposition marks appear as a distinct spot with a brownish patch around the puncture site.
Biology:
Biology of fruit flies differs on the climatic condition, availability of preferred host and natural bioagents. The life cycle of fruit fly especially B. dorsalis consists of three distinct larval instars. Larvae have got a characteristic jumping pattern of movement which serves as a defense mechanism. Adults generally mate at dusk.
Egg:
The adult females lay their eggs after searching for the suitable soft tissue of fruit. Females of B. dorsalis lay eggs in batches beneath the skin of the ripened or ripening host fruits 5-10 days after mating using her needle-like sharp ovipositor. A female can lay 10–30 eggs during each oviposition and can lay more than 1200 eggs during its lifespan. The egg is creamy white, spindle-shaped and measuring about 1 mm in length.
Maggot:
The maggot is a creamy white that caused damage to fruits by tunneling and feeding on pulpy content of the fruits. The maggots feed on the decaying fruit tissue. There are three larval stages and period ranged from 10-14 days.
Pupae:
Upon completion of larval feeding, the third instar larvae burrow into the soil and pupate inside a puparium at a depth of 6 cm. This transition from feeding to wandering occurred when the larva attained a critical nutritional or developmental status.
Adult:
After 8-10 days, adult flies emerge from the puparium and dig their way out of soil or debris. Adults fed on the host plants to obtain nutrient materials from nectar, dew, and fruit. By feeding on the host plants, the flies attain sexual maturity within 10-20 days and mate together to start a new cycle of damage.
Total developmental period:
Total life cycle ranged about 1-2 months. Being facultative breeders and having a short life cycle, fruit flies are multivoltine in nature having more than one generation per year. B. dorsalis can complete 3-5 generations per year. It completes 5-10 generations in a year in tropical areas and less than 4 in subtropical areas.
Management:
The management of fruit flies is challenging because third-instar larvae leave decaying fruits and drop to the ground to pupate in the soil; consequently, both larvae and pupae in fruits and soils are just like shelter that prevents reach of applied insecticides against target stages of a fruit fly.
Nowadays Entomologists and Ecologist focus on the adoption of Integrated pest management (IPM) as IPM is an eco-friendly approach for bringing down pest population before reaching economic injury level and emphasize on the growth of healthy crop without disruption of agro-ecosystem. The possible and useful techniques have been added in this article to devise management tactics for the spectacular success of this serious and noxious pest of guava.
Cultural control:
Manipulation of farming practices for reducing or preventing pest damage to crops is known as cultural control.
Early harvesting:
Early harvesting of fruits may avoid infestations, i.e., afore the attack of fruit fly on fruits that infest almost-ripe fruits but not for species that attack small, green and un-harvestable fruits. Avoidance of fruit fly infestation is possible by harvesting crops at a stage of maturity when the fruit or vegetable is not susceptible to fruit fly attack.
Crop Sanitation:
Cleaning and maintenance of hygiene are essential around fruit trees significantly contribute to the reduction of fruit fly population in the orchard. The collection and destruction of fallen, infested and overripe fruits are strongly recommended to reduce the resident population of fruit flies.
Soil raking:
Raking of soil around the guava trees can be done for effective destruction of pupal inoculation during the summer season. The residual pupae are the major source of the infestation.
Bagging of fruits:
Bagging of fruits during development can reduce the chances of physical damage, improve color at harvest. Wrapping of individual fruits with transparent polypropylene (20μ gauge) bag and paper piece within the polypropylene bag for partial cover to sunlight’ was the best option for guava fruit fly management.
Sterile Insect Technique (SIT):
Sterile males are released in a large number to mate with wild females. Sterilization is accomplished through irradiation, chemo-sterilization, or by genetic manipulation in selected males of fruit flies. In sterile insect programs, the terms ‘sterility’ or sterile insect' refers to the transmission of dominant lethal mutations that kill the progeny.
Trapping:
The management of fruit flies at the destructive larval stage is difficult because insecticides in the form of dust or sprays cannot reach till target maggots. The ways to deal with them is to target adult flies before they start laying eggs by trapping them or using insecticides to control their populations.
MAT (Male annihilation technique):
Male annihilation technique (MAT) is a widely used and it is one of the most outstanding alternatives for the management of fruit fly that kill male flies and reduce the insect’s chances of mating. Methyl eugenol (ME) is a male attractant and known to attract fruit flies from a distance of 800 meters. The use of parapheromon like methyl eugenol along with appropriate trapping technique has also been found successful in monitoring, suppressing fruit flies on large areas by male annihilation technique (MAT) and even complete eradication of various fruit flies.
BAT (Bait annihilation technique):
Bait annihilation technique (BAT) is gaining importance because it is one of the successful components for the suppression of female fruit fly as they are the principal factor for multiplication. Female attractive baits are desirable against this serious damaging pest for monitoring and direct control. Female fruit flies need a protein source to their gonads development and also eggs. Protein hydrolysate was identified as an efficient attractant for female fruit flies.
Quarantine significant:
Movement of materials may spread the chance of infestation from infested countries to non-infested countries, where pest does not exist. Such infested guava fruits are not being accepted in developed nations. Quarantine restrictions imposed by importing countries to avoid entry and establishment of the fruit fly. Many species of fruit flies are considered as high priority quarantine pests in various countries.
Chemical control:
The use of a single control measure such as insecticides cannot give a total reduction of fruit flies infestation since the damage done by larvae in fruit and vegetables is internal, and therefore difficult to control. Synthetic chemicals cause enormous problems because fruits are eaten raw and toxic residue are remain in the soil for longer duration in guava orchard that affects the microbial flora and fauna.
Authors
Irsad and Parvez Qamar Rizvi
Department of Plant Protection
Faculty of Agricultural Sciences A.M.U., Aligarh
mohdirshad060@gmail.com