Insecta, Lepidoptera, Plutellidae .
Description, Biology, Life Cycle, Damage, Common Names, Images
- Host plants: mainly leek and onion, but able to develop on all Allium crop species.
- Overwintering: as adult in plant debris; occasionally the pupa will also overwinter, although this is rare.
- Longevity of females: 6 weeks.
- Fecundity: approx. 100 eggs deposited on centre of inflorescences or on the leaves (*) .
- Eggs: time until hatching, 4 to 6 days in spring, and 8 to 11 in October.
- Larva: development duration, 15 days at 25░C; 5 instars.
- Pupa: developmental duration, 10 days at 25░C.
- The 1st generation, derived from overwintered adults, is small in number (especially if the winter was hard) and causes little damage. The summer generations are much more harmful.
- 2 or 3 generations per year in northern countries, and many more in the southern; the polyvoltinism being well adapted to climate.
- 1st generation adult: in winter, activity ceases due to the cold. Resumes (dusk and night) in March/April according to temperature. Egg-laying period lasts 20 days.
- Larva: mines the leaf on hatching (*) . 2 to 5 days later, it leaves the mine and burrows in between the central leaves.
- 2nd generation adult: appears at the beginning of July and oviposition occurs during July and August. Certain individuals emerge in October and give rise to overwintering adults, others remain in diapause until spring.
When the larva develops on 1st-year leek, it is the leaves that suffer. The lacerated appearance makes the leeks unfit for sale and the lesions facilitate rotting in (*) .
In onions, larvae remain in the leaf cone and cause partial desiccation. The damage in itself is of minor importance but, under unfavorable conditions, the onion ages too quickly and the larvae reach the more turgescent bulb and form galleries (*) . Harvested crops containing damaged bulbs will be rejected, because hidden damage cause losses in store and this can be a serious problem.
On seed-crop the larvae feed mainly at the base of the inflorescences and cause the flower stems to fall off in large numbers. Losses frequently reach 70 to 90% of the harvest.
HYPPZ on line : Species (scientific name), Pests (common names), Glossary, Crops.