leek moth
Beginner
Scientific Name: Acrolepiopsis assectella Zeller
Identification
- Adult leek moth is a small, reddish-brown moth with a white triangular mark on the middle of the its folded wings.
- Larvae are yellowish-green with a pale brown head capsule and 8 small grey spots on each abdominal segment.
- At maturity, larvae reach 13-14 mm in length.
- Pupae are reddish and encased in a loosely netted cocoon. Most cocoons are found on host plants but can be located on decaying plant matter and neighbouring vegetation.
Often Confused with
Leafminer damage
Period of Activity
There are three flight periods of leek moth per season in Ontario. Adults become active and emerge in the spring when temperatures reach 9.5°C, and mate shortly thereafter. The first flight (overwintering population) appears to begin late April ending mid-May. The second flight period (first generation) can begin as early as mid-June but may not begin until the end of June and extends respectively into early to mid-July. If the second flight period started early July, then the last flight (second generation) usually begins late July ending mid-August. If, however, the second flight period starts in mid-July, the last flight period will begin mid-August ending in late-August.
Scouting Notes
Leek moth presence and activity can be monitored using commercially available pheromone trapping systems. In Ontario, research has consistently found that pheromone traps alone can be used to properly time insecticide applications. When insecticides are applied 7-10 days following a peak flight of leek moth adults (as determined through the use of the pheromone trap system previously described), the leek moth population and amount of damage is greatly reduced.
Thresholds
None established in Ontario. In Quebec, a threshold of 5% is recommended.
Advanced
Scientific Name: Acrolepiopsis assectella Zeller
The leek moth (or onion leafminer), Acrolepiopsis assectella Zeller, is an invasive alien species of European origin which damages Allium spp. It was first identified in eastern Ontario in 1993. The leek moth is considered a serious pest in some parts of Europe, with levels of infestation up to 40% in areas where the insect has several generations per year. In areas where generations are limited to 1-2 per year, leek moth is sporadic and causes minor economic damage.
Identification
- Adult leek moth is a small, reddish-brown moth with a white triangular mark on the middle of the its folded wings.
- Larvae are yellowish-green with a pale brown head capsule and 8 small grey spots on each abdominal segment.
- At maturity, larvae reach 13-14 mm in length.
- Pupae are reddish and encased in a loosely netted cocoon. Most cocoons are found on host plants but can be located on decaying plant matter and neighbouring vegetation.
Often Confused with
Leafminer damage
Biology
Adults become active and emerge in the spring when temperatures reach 9.5°C, and mate shortly thereafter. Eggs are laid singly on lower leaf surfaces whenever night temperatures are above 10 -12°C. Females lay up to 100 eggs over a 3-4 week period. When eggs hatch, larvae enter leaves to mine tissues (leafminer stage). After several days, larvae move towards the centre (heart) of the plant where young leaves are formed. After several weeks of active feeding, larvae climb out onto foliage and spin their cocoons. Pupation lasts about 12 days, depending on weather conditions. Leek moth numbers and associated damage typically increase as the season progresses.
Period of Activity
There are three flight periods of leek moth per season in Ontario. The first flight (overwintering population) appears to begin late April ending mid-May. The second flight period (first generation) can begin as early as mid-June but may not begin until the end of June and extends respectively into early to mid-July. If the second flight period started early July, then the last flight (second generation) usually begins late July ending mid-August. If, however, the second flight period starts in mid-July, the last flight period will begin mid-August ending in late-August.
Scouting Notes
Leek moth presence and activity can be monitored using commercially available pheromone trapping systems. In Ontario, research has consistently found that pheromone traps alone can be used to properly time insecticide applications. When insecticides are applied 7-10 days following a peak flight of leek moth adults (as determined through the use of the pheromone trap system previously described), the leek moth population and amount of damage is greatly reduced.
Thresholds
None established in Ontario. In Quebec, a threshold of 5% is recommended.
Management Notes
- Research in Ontario has found that insecticides, including organic formulations, can control leek moth populations and reduce overall damage when insecticides applications are properly timed.
- Cultural controls including crop rotation, delayed planting, removal of old and infested leaves, destroying pupae or larvae, early harvesting (to avoid damage by last generation larvae and population build-up), positioning susceptible crops away from infested areas and destruction of plant debris following harvest may be effective in reducing populations below damaging levels.
- Tillage / burial of debris can also help to eliminate larvae and pupae that remain in the field following harvest.
- Ontario research has consistently shown that the use of lightweight floating row covers can protect developing plants from leek moth damage. Row covers can be easily removed during the day for weeding or scaping and as long as they are reassembled prior to dusk there is little risk of leek moth entering the enclosures.
- Currently, Agriculture and Agri Food Canada researchers are evaluating native North American species that may offer control as well as European biological control candidates for release in Canada.
