Expect and Prepare for Downy Mildew in Basil

Downy mildew of basil is a new, destructive disease that appears to be here to stay. It was first reported in south FL in October 2007. In 2008 downy mildew was confirmed in both fieldand greenhouse-grown basil crops, as well as home gardens, in many states: NC, PA, NJ, NY, MA, NC, KS, and MO. Likely it occurred elsewhere but was not recognized. Growers generally did not realize their basil had a disease because the most noticeable symptom on affected plants was yellowing resembling a nutritional deficiency. The downy-appearing sporulation of the pathogen only develops on lower leaf surfaces. And, since downy mildew of basil is so new in the USA, few knew about it. Complete crop loss occurred for some growers because leaves with any injury are unmarketable. This disease was also reported in Canada in 2008 and in greenhouse-grown basil in Argentina in February 2008. In 2009 basil downy mildew was found in the western USA, and early in 2011 it was reported in Hawaii for the first time as well as in FL as usual.