Note the presence of black plastic mulch. Cropping history and length of rotation period do not appear to be reliable predictors of MWVD incidence or severity. In some cases, watermelon vines begin to wilt as early as mid-June just as fruit begin to gain size. In other cases, decline and collapse occur later, shortly before harvest. Wilting vines are often observed first in low, poorly drained areas of the field and the incidence of symptomatic plants increases over time to include plants on higher ground.
Affected plants have few secondary roots.
The primary roots of affected plants exhibit a variety of symptoms including a wet rot or crater-like dry rot. Symptom development does not generally include stem cankers or vascular discoloration. Preliminary greenhouse seedling inoculations using isolated fungi or dried, ground roots from symptomatic plants have failed to reproduce MWVD symptoms. Each plot measured 15.24 m in length and was planted with the watermelon hybrid 'Desert Storm' at 1.52 m intervals on May 16. Experimental plots treated with Mefenoxam-PCNB, BioYield 213 or untreated were completely randomized and each treatment was replicated 16 times.