Oriental Fruit Fly, Bactrocera dorsalis

**The oriental fruit fly, Bactrocera dorsalis, is a serious pest of mangoes and other tropical fruits such as papaya.**

Originating in the Asiatic region, the oriental fruit fly is now found in approximately 65 countries, including parts of America and Oceania, and most of sub-Saharan Africa.

Russell IPM manufacture and supply pheromone lures, traps and complete monitoring systems for Bactrocera dorsalis, the Oriental fruit fly. Accurate monitoring is essential to minimise damage and protect crops. Therefore, installation of pheromone traps will alert to the presence of unwanted pests at an early stage, detecting the insects before they become a major problem and enabling timely and effective treatment.

The fruit fly is a very destructive pest that is well established in Asia: Bangladesh, Bhutan, Cambodia, China, India, Indonesia, Japan, Laos, Malaysia, Myanmar, Nepal, Ogasawara Islands, Pakistan, Philippines, Sri Lanka, Taiwan, Thailand and also Vietnam. B. dorsalis can be found in the United States, particularly Hawaii, California and Florida where reocurring infestations are common) Bactrocera dorsalis can fly 50-100km and has up to 10 generations of offspring per year.

Russell IPM offer Zonatrac against this pest – an innovative system that utilises an attract and kill technique against the males of the Bactrocera species.

Biology

Development of Bactrocera dorsalis from egg to adult requires about 16 days in warm temperate conditions. The mature larva emerges from the fruit, drops to the ground and forms a tan to dark brown puparium. Pupation occurs in the soil. About nine days are required for attainment of sexual maturity after the adult fly emerges.

The developmental periods of the oriental fruit fly may be extended considerably by cooler temperatures. Under optimum conditions, a female can lay more than 3,000 eggs during her lifetime, but under field conditions it is more common to observe appriximately 1,200 to 1,500 eggs per female. Ripe fruit are preferred for viposition, but immature ones may be attacked also.

Nature of Damage

Larval feeding of B. dorsalis in fruits is the most damaging to the plant. Damage usually consists of the breakdown of tissues and internal rotting associated with maggot infestation, but this varies with the type of fruit attacked. Infested young fruit becomes distorted, callused and usually drops. Mature attacked fruits develop a water soaked appearance.

The larval tunnels provide entry points for bacteria and fungi that cause the fruit to rot. When only a few larvae develop, damage consists of an unsightly appearance and reduced marketability because of the egg-laying punctures or tissue breakdown due to decay.

Monitoring

These notes are guidelines of general nature and meant to give the user a head start in implementing pheromone monitoring program. Local conditions and practices can vary and can lead to customization of the program.

Application Guidelines

The following notes are guidelines of general nature and meant to give the user a head start in implementing pheromone monitoring programme. Local conditions and practices can vary and can lead to customisation of the programme.

Lures
Lures can be changed every 4-6 weeks to get the most accurate results.

Lures Handling
Pheromone lures are a very sensitive tool. They can be affected by exposure to high heat and direct sunlight. Direct contact with the hand may cause cross contamination leading to mixed catches in the trap. Some pollutants such as nicotine may have repellent effect of reducing trap catch.

Lure Storage
Store the pheromone in a cool, dry place. Service life may vary from 3-36 months depending on the storage temperature. See data sheet for details.

Trap Selection

The FlyCatcher is most sensitive trap to use for monitoring Bactrocera dorsalis. This trap and others should be used in conjunction with pheromone lures to increase catch rate and enhance specifity of the trap.

Trap Density

Two traps per hectare (2 traps/ha) for small holdings and in field of uneven topography. One trap for every two hectares for large scale fields within homogeneous lands.

Trap Position

Place trap near to the highest point of the plant using supporting posts approximately 1 meter high from the ground.

Data and Interpretation

Collect data weekly from the start of the flight of the over wintering generation. During the height of the population more frequent reading may be needed. Decisions on pesticide application should not be taken solely on the trap catch data. Climatic and biological considerations should be taken in account.

Korsch, M. N. (2013) Piecing together an integrative taxonomic puzzle: microsatellite, wing shape and aedeagus length analyses of Bactrocera dorsalis. Royal Entomological Society.

Bactrocera dorsalis (Hendel) and B. papayae represent a closely related sibling species pair for which the biological species limits are unclear; i.e. it is uncertain if they are truely two biological species, or one biological species which has been incorrectly split taxonomically. The geographical ranges of the two taxa are thought to abut or overlap on or around the Isthmus of Kra, a recognised biogeographic barrier located on the narrowest portion of the Thai Peninsula. Morphological datasets showed consistent, clinal variation along the transect, without disjunction. Within and across the area of range overlap or abutment between the two species, only continuous morphological and genetic variation was recorded. Recognition that morphological traits previously used to separate these taxa are continuous, and that there is no genetic evidence for population segregation in the region of suspected species overlap, is consistent with a growing body of literature that reports no evidence of biological differentiation between these taxa.

Aketarawong, N et al., (2014) Bactrocera dorsalis s.s. in East Asia: disentangling the different forces promoting the invasion and shaping the genetic make-up of populations. Springer 2014.

The Oriental fruit fly, Bactrocera dorsalis, is one of the most economically destructive pests of fruits and vegetables especially in East Asia. Based on its phytophagous life style, this species dispersed with the diffusion and implementation of agriculture, while globalization allowed it to establish adventive populations in different tropical and subtropical areas of the world. The data suggests that the considered samples probably represent well established populations in terms of genetic variability and population structuring. The human influence on the genetic shape of populations and diffusion is evident, but factors such as breeding/habitat size and life history traits of the species may have determined the post introduction phases and expansion. In East Asia the origin of diffusion can most probably be allocated in the oriental coastal provinces of China, from where this fruit fly spread into Southeast Asia. The spread of this species deserves attention for the development and implementation of risk assessment and control measures.