IPM control measures for Citrus Fruit Fly

Citrus Fruit Fly (Bactrocera minax Enderlein)

Bactrocera minax Enderlein is a tephritid citrus pest. It is locally known as fruit fly or citrus fly (Refer to Fig 1). Female files have long and exposed ovipositor. It is brownish in colour with yellow spots. It is wasp-like with dark bands along the outline of the wings. Maggots have creamy white appearance with black mouth parts. Matured maggots are 12 mm- 15 mm long and yellow puparia are 8– 11 mm long.

Citrus fruit fly oviposits in citrus fruits causing premature fruit drop. In Bhutan, the fly causes 30-80% fruit drop in middle-altitude mandarin (Citrus reticulata Blanco) orchards. There is emergence of files from puparia in the soil around April. As soon as fruits reach 11 mm diameter, flies colonize citrus fruits extensively. From mid-June onwards, some brownish, round spots of 1- 2 mm appear. Eggs hatch within the citrus fruits from September and prematurely ripen. They drop in October (Refer to Fig 3) and maggots’ development continues. Maggots feed inside, making the fruits useless. Fruits turn yellow and soon maggots become easily noticeable (Refer to Fig 2). Soon they leave for pupation in the soil. Later dropped fruits rot and become dry.

Some of the Integrated Pest Management Control Measures for citrus fruit fly are;

1.      Cultural control:

1.1. Extensive hygienic campaigns are organized and orchards are cleaned from oviposition signs.

1.2. Tilling orchards to kill remaining puparia by exposing them to natural predators.

1.3. Infested orchards are ploughed and intercropped with annual crops to change the pupal environment and enhance the effectiveness of natural enemies (Yang et al., 2015).  It is feasible for controlling the fly.

2.      Mechanical control

2.1. Maggot-loaded mandarin fruits are collected and disposed in pits of 1 m to 2 m depth. Maggots died of suffocation. It considerably reduces puparia densities in autumn.

3.      Biological control

3.1. Natural enemies such as ants, hens and rats grazed spots where puparia are  concentrated and preyed on over 90 % of the puparia population (Schoubroeck, 2019).

4.      Chemical control

4.1. Insecticides can be used to manage adult fruit fly populations. It is done by luring female files with proteinaceous bait sprays. Bait spray will attract and kill the fruit fly. Bait sprays are applied as spot treatments.

5.      References

National Plant Protection Centre. (2017). Citrus Pests and Diseases Management Manual. Semtokha, Bhutan. Ministry of Agriculture and Forestry.

Schoubroeck, V. F. (1999).  Learning to fight a fly: developing citrus IPM in Bhutan. Den Haag, Netherlands. Thesis Wageningen University and Research Centre.

Schoubroeck, V. F. (2019). IPM for Chinese fruit fly. II Can hygienic measures control a univoltine tephritid fly? Wageningen, The Netherlands. Wageningen Agricultural University.

1.      Annexures

Figure 1: Chinese Fruit Fly

Figure 3: Dropped fruits

Figure 2: Maggots