Oriental fruit moth
Grapholita molesta
Order Lepidoptera, Family Tortricidae
Host plants
In our country, the species is widespread. It damages shoots and fruits of most fruit crops (except cherry and sour cherry). It prefers peach but can also be harmful to pear, quince, and apricot. During the first half of the growing season, it mainly damages shoots, while in the second half it attacks fruits. At high population density, the pest can hinder crown formation in young peach trees by damaging shoot tips and stopping growth, with damage often exceeding 50–60%. Fruit infestation in August–September may exceed 40–50%. In apricot, shoot damage is less significant, but fruit infestation begins as early as June. In quince, the species develops throughout the entire growing season and can cause 20–40% damage to shoots in June and over 80% damage to fruits in October. In pear, shoot damage is minimal, but infestation of ripening and ripe fruits may exceed 30–40%. In plum and apple, fruit infestation is occasional, but there is a preference for some newer varieties.
Life cycle
The species shows a preference for a subtropical climate but also develops successfully under the temperate conditions in our country. Depending on the region, weather conditions during the year, and host plants, the oriental fruit moth develops 2 to 5 generations annually. It overwinters as a larva in a cocoon located under the bark of trunks, in scaffold branches, plant debris, and in the soil. Pupation in spring begins in March, at the bud break stage of peach.
Egg laying
Egg-laying begins 7 to 12 days after the start of adult flight and coincides with fruit set in peach and the mass flowering of late varieties of pear, plum, sweet cherry, and sour cherry. Females lay their eggs individually on the underside of leaves and on young shoots. The average fecundity of a single female is relatively low, ranging from 5–6 to 15–20 eggs.
Larva
Its color varies from yellowish to pale pink, creamy, and red, depending on the diet. The body length reaches up to 12 mm.
The pupa is brown, 10–12 mm long, and enclosed in a dense whitish silken cocoon. It darkens before adult emergence.
After completing feeding, the larvae pupate in a cocoon in and around the site of damage—within tunnels and galleries, in the fruit calyx, in folded small leaves and stipules, near the entry holes in shoots, etc. The pupal stage lasts 8–15 days.
Damage
Newly hatched larvae bore mainly into the tips of young shoots and feed on the green, non-lignified tissue. The galleries formed in peach and apricot are 3–4 cm to 10–15 cm long, while in apple and pear they are 1–3 cm. Once the larva reaches harder tissue or when heavy gum exudation begins, it moves to a neighboring shoot. A single larva can damage 2–3 up to 6 shoots. Some larvae die due to gummosis. The tips of damaged shoots wilt and later dry out. If the gallery is longer, bending of the shoot may also occur. Growth of these shoots stops, and in some more vigorous varieties “brooming” may be observed—numerous new, weaker, densely clustered shoots develop at the base of the damaged shoot. Larvae of the pest can be found only in shoots whose tips have not yet completely dried. If not removed, the damaged shoots remain in the canopy for a long time.
Larvae of the second generation cause damage similar to the first generation, but toward the end of the period (July), damage to the fleshy part of the fruits becomes increasingly common. In quince, the shoots are mainly affected.
Larvae of the third and fourth generations continue to damage shoots if active growth is present, but increasingly attack the fruits as well. Damaged fruits become deformed or rot, and when the vascular tissue between the stem and the pit is disrupted, they show premature ripening symptoms and fall off.
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