What: We lose many plants to root rot during extremely wet seasons. The plant roots are damaged by staying wet over long periods. They sometimes don't show the damage until hot weather causes stress, and the roots can no longer support the plant.

Threat Level: Serious after it gets started. When it is wet outside, an ounce of prevention is worth much more than a pound of cure.

What: A fungal plant disease that causes rapid death of otherwise healthy plants during hot summer months. It is found in the soil and destroys root systems on susceptible plants. Look for a white, cotton-like substance on roots of plants that have died very quickly.

Threat Level: High for single plant. Once you figure out this might be a problem in one spot of your yard, the plant in question is dead. It is not likely to kill more plants over a wide area.

What: Leaves have irregular black spots and turn yellow as they drop from the plant.

Threat Level: Low with just a few spots. It can be a sign of needing to change garden practices.