Disease-causing fungi are incredibly diverse and can infect nearly every part of a plant including the leaves, the roots, and the vascular system. For this reason, there are many types of fungicides and many different ways to apply them. It is important to pair the proper application method with the proper treatment at the proper time of the season.

Symptoms of a foliar fungus, such as apple scab, will show up in the late summer/early fall; however, the infection took place back in the spring. Spray treatments are timed for the release of spores. Foliar diseases are not typically as life-threatening to a tree as vascular diseases but can still present serious health risks. In cases where protecting the smallest twigs high up in the canopy is crucial, such as with Dutch elm disease, only high volume macro-infusion has been proven effective. For other vascular wilts where protecting the trunk and root system is more critical, such as oak wilt and laurel wilt, low volume macro-infusion is shown to provide predictable results.