Allium Leaf Miner
A sample of unsprayed/unprotected volunteer garlic near Asbury on the Hunterdon/Warren County border today showed 68% of plants infested with allium leaf miner (ALM). These maggots were all later stage, and found in the necks, about 1″ above the bulb (see photo at upper left). We should expect that all untreated/unprotected allium crops are similarly affected at this time. Interestingly, 100% of infested plants had visible feeding/egg laying scars (see photo at center above), while 100% of uninfested plants showed no visible signs. None of the plants had mines visible on the surface, but cross sections of the neck revealed clean tunnels the maggots had created on their way down (see photo at right, above).
Our colleagues at Cornell, operating in the Hudson Valley had notified us that they had had no success catching ALM adults on sticky cards, and we have had the same difficulty in NJ this Fall. This is unlike our experience in the Spring, when we were able to catch numerous individuals at nearly every trap site. Additionally, the generation of adults emerging in the Spring here in NJ heavily infested chives; the earliest possible host. This Fall, chives appear to be largely uninfested, while onions, scallions, and leeks are showing the most feeding/egg laying scars.
Be aware that if no program of protection was enacted roughly 3 weeks ago, Fall allium crops may be heavily infested at this time.
