Bactrocera zonata (Saunders)
Common name: Peach fruit fly (PFF).
Geographical distribution: The Middle East, Indian sub-continent, South East Asia, Reunion, Mauritius.
Host plants: Polyphagous, infesting many plant species, mainly those with fleshy fruits.
Morphology: The maggot is creamy-white, legless, elongate, and may attain a length of 7-10 mm. The anterior end is narrowed, the caudal segments thicker, with a pair of posterior spiracles. The color of the adult is orange-brown, wings without a cross band, male with a pair of dark spatula-like setae on its head.
Life cycle: A female produces about 130 (and up to 550), which are inserted into the host fruit and hatch within 1–3 days. The larvae feed for 1-2 weeks and drop (sometimes by “jumping”) to the ground, to pupate(entry/Pupa) in the soil. They overwinter in the larval or pupal stages. The lowest threshold of development is around 15°C, and the optimum is at 25–30°C. Depending on the climate, PFF may raise several annual generations. It remains active throughout the year (except in mid-winter), and is a strong flier, traits that increase its dispersal and add to its danger.
Economic importance: The PPF attacks many fruit trees and is a major pest of peach, mango and guava. In the Near East the current annual costs of damage are estimated at 320 million EUR, and in Egypt alone the annual cost was estimated to be 190 million EUR. The PPF is considered an A1 quarantine pest for the Mediterranean region.
Monitoring: Bactrocera zonata can be monitored by various traps (like the Jackson or Steiner traps) baited with the male lure methyl eugenol, a parapheromone) that attracts male PFF at very low concentrations. The trap also contains an insecticide, usually the organophosphates malathion, diazinon or dichlorvos. Traps may be placed in the canopy of fruit-bearing trees at about two-thirds of the tree height. Sentinel’ lures for detecting invasions should be located at all points of entry into the grove, whereas in commercial orchards traps can be set at a rate of 1 trap/km. Lures usually remain effective for about one month.
Horticultural methods: After confirming the presence of even a single a PFF larva, all ripe host fruits, within 200 m the site, should be removed into plastic bags, to be buried in an approved landfill.
Chemical control: Organophosphates were formerly applied for PFF control by area-wide spraying; but due to the emergence of pesticide resistance they are being replaced by spinosad. Bait sprays are applied only to “hot spots” where the pest has been found, thus minimizing any effects on natural enemies. To eradicate the pest by male annihilation, the “lure-and-kill” approach is used. Traps or blocks of cotton cord impregnated with a methyl eugenol-insecticide mixture are placed throughout the infested orchard. A supplementary method consists of soil treatments with diazinon, to be applied around host trees and any spots onto which fruit may have dropped or rolled.
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