Common Disease Problems
Bacterial Soft Rot: This is mostly an issue with on mature bulbs. Affected bulbs first appear water-soaked and pale yellow to light brown or bleached gray to white. As the disease progresses, infected tissue becomes soft and sticky with the interior of the bulb breaking-down. A watery, foul-smelling thick liquid can be squeezed from the neck of diseased bulbs. It is spread by water and some insects through wounds on the plant. Burpee Recommends: Avoid overhead watering where possible, and control insect pests such as onion maggot, that can spread it.
Downy Mildew: This fungus causes whitish grey patches on the undersides and eventually both sides of the leaves. Burpee Recommends: Rotate crops with plants in a different family. Avoid overhead watering. Provide adequate air circulation, do not overcrowd plants. Do not work around plants when they are wet.
Onion White Rot: This soil-borne fungus causes yellowing and wilting of foliage above ground. Below ground, the roots rot and the fungus also infects the bulb. At the base of the bulb, a white fluffy fungus will appear with black fungal bodies. Burpee Recommends: Remove infected bulbs. Practice crop rotation with members of the onion family.
Common Pest and Cultural Problems
Leafminers: These insects bore just under the leaf surface causing irregular serpentine lines. The larvae are yellow cylindrical maggots and the adults are small black and yellow flies. They do not usually kill plants, but disfigure the foliage. Burpee Recommends: Remove affected foliage.
Onion Maggot: This insect causes damaged roots and bulbs. The adult is a greyish colored fly which lays its eggs around the base of the plant. The maggots bore into the roots. Burpee Recommends: Remove all bulbs at the end of the season and remove all volunteer wild onion plants. Floating row covers can prevent the females from laying eggs. Check with your Cooperative Extension Service for pest controls.
Slugs: These pests leave large holes in the foliage or eat leaves entirely. They leave a slime trail, feed at night and are mostly a problem in damp weather. Burpee Recommends: Hand pick, at night if possible. You can try attracting the slugs to traps either using cornmeal or beer. For a beer trap, dig a hole in the ground and place a large cup or bowl into the hole; use something that has steep sides so that the slugs can’t crawl back out when they’re finished. Fill the bowl about ¾ of the way full with beer, and let it sit overnight. In the morning, the bowl should be full of drowned slugs that can be dumped out for the birds to eat. For a cornmeal trap, put a tablespoon or two of cornmeal in a jar and put it on its side near the plants. Slugs are attracted to the scent but they cannot digest it and it will kill them. You can also try placing a barrier around your plants of diatomaceous earth or even coffee grounds. They cannot crawl over these.
Do alliums make good cut flowers? Yes, they make long lasting cut flowers. The onion smell will go away once the flowers are placed in water.
Can you dry allium flowers? Yes, leave the flowers in the garden and allow to dry on the stalks, then cut the flowers for indoor arrangements.
Are alliums deer resistant? Yes, deer do not generally eat alliums, however if deer are very hungry they may eat them.
How late can I plant the allium bubs in the fall? Ideally the bulbs should be planted at least 6 weeks before the ground freezes.