Physiological macules

On some varieties of zucchini and squash, we can very often see the presence of angular silver spots on the leaves (figure 1). They are caused by a local detachment of the epidermis without consequences for the plants; the presence of a layer of air between the epidermis and the parenchyma is at the origin of this silvery aspect of the macules.

The frequency of these macules varies greatly depending on the variety (in zucchini and squash) and climatic conditions.

Be careful not to confuse physiological macules with silvering, another physiological disease associated with the parasitism of the whitefly Bemisia tabaci .