maleic hydrazide (Royal MH-30)
Rate 2 lb ai/a (1.33 gal/a)
Time Apply when bulbs are fully mature, with soft necks and five to eight green leaves, or when about 50% of the tops have fallen but are still green.
Remarks Apply at temperatures below 80 to 85°F to avoid crystallization on leaf surfaces. Using a spray adjuvant is suggested in arid regions west of the Rocky Mountains. Avoid early sprays, before maturity, to reduce spongy onions. Apply in a minimum of 30 gal of water per acre.
Caution Do not treat seed onions.
Site of action Not well understood
Chemical family None generally accepted