sprout inhibitor injury
Maleic hydrazide, a sprout inhibitor, is applied to onion crops heading to storage. If it's applied to immature crops it can result in spongy bulbs. The proper use of maleic hydrazide inhibits sprouting and lengthens the storage life of many onion cultivars. The optimum time for spraying is when 50% of the tops have fallen, but tops are still green. This usually occurs 8–14 days before harvest. Plants with less than three green leaves and/or severely diseased foliage will not absorb maleic hydrazide