Gadenin日本語Get the appThe common problems
Most garden stands of milk vetch reach flowering with little trouble. The problems below are the ones worth recognizing, mostly in spring as growth speeds up and the weather warms.
| Problem | Signs | When |
|---|---|---|
| Aphids | Clusters of small insects on tips and buds, sticky leaves, distorted growth | Spring |
| Alfalfa weevil | Leaves chewed to a lacy skeleton, small green larvae on the tips | Spring |
| Powdery mildew | White powdery coating on leaves and stems | Dry days with cool nights, crowded stands |
| Sclerotinia (white mold) | Plants collapse in patches, white fluffy growth at the base, hard black bodies | Cool, wet weather, waterlogged soil |
Aphids
Aphids are the pest you are most likely to see. They gather on the soft growing tips and flower buds, sucking sap and leaving sticky honeydew. Light infestations are often cleaned up by ladybugs, lacewings and hoverflies, which milk vetch itself helps to attract.
For heavier outbreaks, knock them off with a strong spray of water or pinch out the worst-affected tips. If you must spray, use an insecticidal soap and avoid doing so while the plants are in flower and bees are working them.
Alfalfa weevil
Alfalfa weevil is a serious pest of milk vetch in Japan, where it was introduced and spread widely, and it is also a long-established pest of alfalfa in North America. The small green larvae feed on the growing tips and leaves in spring, and a heavy infestation can skeletonize a stand before it flowers.
In a garden, check the tips regularly as growth picks up and hand-pick or shake larvae off onto a sheet. Turning the stand in promptly after flowering removes the food source before the next generation develops. Where it has been a severe problem, consider a different cover crop for a year.
Look closely at chewed tips: the larvae are well camouflaged and easy to mistake for part of the plant.
Powdery mildew
Powdery mildew shows as a white, dusty coating on leaves and stems, typically in spring when days are dry and nights cool, and most of all in dense, poorly ventilated stands. It weakens plants but rarely kills a stand outright before flowering.
Prevention is the main approach. Avoid sowing too thickly, keep the plants evenly watered rather than drought-stressed, and do not overfeed. In a cover crop that will be turned in after flowering, light mildew can usually be tolerated.
Sclerotinia (white mold)
Sclerotinia is the most damaging disease, especially on poorly drained soil in cool, wet weather. Plants wilt and collapse in patches, a white cottony growth appears at the stem bases, and hard black resting bodies called sclerotia form on and in the dead stems. These sclerotia survive in the soil for years and can also infect other crops, including beans, lettuce and many other vegetables.
Improve drainage, avoid overly dense sowing, and remove and dispose of collapsed plants rather than composting them. Where white mold has appeared, rotate away from milk vetch and other susceptible crops in that bed for several years.