The fruit fly larva, commonly known as the mandarin duck fly, belongs to the family Tephritidae. It primarily infests a citrus variety called ponkan, causing significant damage to the fruit.
1. **Symptoms of Infestation**: Adult fruit flies lay their eggs inside young ponkan fruits. Once hatched, the larvae feed on the fruit's flesh, leading to discoloration—starting with an unripe yellow color, then turning yellow with red spots, and eventually rotting off the tree.
2. **Morphological Features**: The adult fruit fly measures between 12 to 13 mm in length, with a wingspan of 20 to 24 mm. Its body is generally brownish, with darker markings on the front part of the thorax. The eggs are milky white, long-oval in shape, slightly curved in the middle, and measure about 1.4 to 1.5 mm in length. The pupae are yellow-brown, measuring around 9 to 10 mm.
3. **Life Habits**: This species completes one generation per year. The adults overwinter in the soil and emerge in late April. They begin mating in early May and enter orchards for egg-laying from June to mid-July. Peak activity occurs in mid-June, with eggs hatching from July to September. Infested fruits fall from late September to late October. After falling, the larvae burrow into the soil, where they pupate. Adults typically emerge at noon on sunny days. They lay eggs in the navel of the fruit, creating small holes that cause the skin to change from green to yellow. Orchards with high humidity or those with honey-like secretions suffer more severe infestations.
4. **Prevention and Control Methods**: First, strict quarantine measures should be enforced to prevent the import of infected fruits or soil from affected areas. Second, remove young fruits and boil them thoroughly to kill any larvae inside. Third, deep plowing of the soil in winter can help destroy overwintering pupae and larvae. Fourth, when larvae are active or adults emerge, spray the ground with a 65% phoxim solution diluted 1000 times to kill adults. Apply this every 7 to 10 days for two consecutive applications. When adults begin laying eggs in the orchard, use a mixture of 2.5% deltamethrin or 20% West Insectamethrin diluted 3000–4000 times, combined with a 3% sugar solution. Spray one-third of the tree canopy, repeating every 7 to 10 days for 2 to 3 times. Lastly, consider using sterile insect technique: male fruit flies are exposed to gamma radiation indoors and released into the field. These males mate with wild females, but the eggs laid do not hatch, effectively reducing the population over time.
Respiratory Infectious
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