Wild Garlic and Onion in Wheat
Source: Bill Johnson and Glenn Nice, Purdue University
The perennial weeds wild garlic (Allium vineale) and wild onion (Allium canadense) can often be found in wheat fields and occasionally in corn and soybean fields that have been in a no-till system for several years. The reproductive structures, the aerial bulblets, are approximately the same size as wheat grain making them difficult contaminants to remove from harvested wheat. Wheat that is contaminated with these aerial bulblets will be docked for contamination. Although wild onion is a native to North America, wild garlic is a transplant from Europe. It is often wild garlic that is found most often in wheat grain settings, although we occasionally find wild onion as well.
Although wild garlic and wild onion are two different species they look very similar. Both weeds originate from underground bulbs. Their leaves are very similar being basal, long and narrow. However, the two weeds can be differentiated by the fact that wild garlic leaves are nearly round and hollow. Wild onion's leaves are flat and not hollow (solid). Also the underground bulbs differ; wild garlic's bulbs have a thin membranous outer coating while wild onion's bulbs have a fibrous, net-veined coating.
The reason it is important to be able to differentiate will garlic frm wild onion is that control measures for wild onion and wild garlic will differ slightly. Harmony Extra (thifensulfuron + tribenuron) is the most commonly used herbicide to control wild garlic in wheat. Harmony Extra can be applied before planting or after the wheat has reached the 2-leaf stage, but before flag leaf is visible. Apply 0.75 to 0.9 oz/A before the garlic is 12 inches tall and if possible when temperatures are 60 degrees or higher. Dupont recommends for optimum control to apply sequential (or two separate) applications of 0.75 oz/A. The first, early postemergence treatment should be made after the wheat is at the 2-leaf stage. The second treatment is made before the wheat reaches the flag leaf stage. Apply with NIS at 0.25% v/v or COC at 1% v/v. Harmony SG (thifensulfuron) also has activity on wild garlic. Peak (prosulfuron) can provide good control of wild garlic at 0.5 oz/A and be applied before the second node is detectable in stem elongation. However, Peak’s rotation restrictions to soybean are between 10 and 18 months depending where you are in Indiana, ruling out double crop soybeans.
Control measures for wild onion are more limited. Wild onion can be controlled with 2,4-D. Applications of 2,4-D should be after tillering and before jointing and the use rate should be 1 lb ai/A for effective results.
|Treatment||Rates||Application Timing||Active Ingredients||Other Weeds Controlled|
|BEST CHOICE: Harmony Extra + surfactant Sequential||0.75 oz/A followed by 0.75 oz/A||early post followed by late post between 2-leaf to before flag leaf||thifensulfuron + tribenuron||chickweed, deadnettle, henbit, mustards, wild buckwheat, lambsquarter, pigweed, and groundsel|
|Harmony Extra + surfactant||0.75 to 0.9 oz/A||between 2-leaf to before flag leaf when wild garlic is less than 12 inches||thifensulfuron + tribenuron|
|Harmony GT + surfactant||0.75 to 0.9 oz/A||betweem 2-leaf to before flag leaf when wild garlic is less than 12 inches||thifensulfuron||chickweed, mustards, and groundsel|