Powdery Mildew can cause headaches for melon growers. They know all too well the damage caused by the fungi Erysiphe cichoracearum and Sphaerotheca fuliginea.

Although there are powdery mildew fungi on many plants, these two fungi infect only muskmelon, cucumber, squash, pumpkin, gourd, and watermelon.

When it hits, Powdery Mildew can cause fruit to be smaller in size, fewer in number, less able to be successfully stored, sunscalded, incompletely ripe, and have a poor flavor.

Symptoms of Powdery Mildew:

This fungus occurs mainly on the leaves, which are the most susceptible 2 to 3 weeks after unfolding;

A whitish powdery fungal growth is present on the leaves;

Fungal growth often starts on the shaded undersurface of the crown leaves;

Severely affected leaves can become dry and brittle, or can wither and die;

Exposed vines and fruit are more prone to sunscald and the vines may shrivel.

Horticultural methods can help prevent powdery mildew. For example, choose a site with good air circulation and low humidity. Also separate new plantings from old plantings. Use a crop rotation of at least one year. Control cucurbit weeds and other weeds.

Another important tool in battling Powdery mildew is planting disease tolerant varieties such as those offered by Harris Moran Seed Company.

The scale was 1 to 10, where 1 was absence of disease symptoms and 10 was complete dieback of foliage.

Three Harris Moran varieties stood out. 

Morning Ice  and HMX 7580 scored a 1. 

Moombeam garnered a 3 on the Powdery Mildew scale.