YIELD AND GROWTH-RESPONSE OF ONION TO SIMULATED STORM DAMAGE

Severe storms with high winds, hail, rain, and blowing soil particles can injure onion (Allium cepa L.) leaf and neck tissues. Our study was conducted to determine the growth response of onions to simulated storm damage during bulb development. The effect of removing 33% and 67% of the onion foliage at 14, 28, 42, and 56 days before maturity was examined. In 2 years, 67% defoliation reduced yields more than 33% defoliation. At both levels, defoliation had a greater impact on total marketable yield and yeild of individual market classes when it occurred near the onset of bulbing. Of the different market classes of onions, the jumbo (> 8.25 cm in diameter) was most consistently affected by defoliation. A moderate (33%) and a severe (66%) foliage loss delayed crop maturity, decreased total marketable yeild and potential market value, and changed the market class distribution of a sweet Spanish-type onion.