Avoid Prolonged Leaf Wetness and Soil Saturation.
The less time plant foliage is wet, or the root system is saturated, the better chance you have of managing Phytophthora disease.
Nursery crops generally are irrigated using overhead sprinklers, line source drip systems, or a micro-spray system. While these are adaptable to diverse nursery crops, they have built-in characteristics that can encourage disease if improperly managed. For example:
Drip or micro-irrigation systems can water-log soil if operated for extended periods.
Overhead sprinklers should be turned off so that foliage dries quickly.
While cyclic or frequent irrigation works well with micro-irrigation, it can promote Phytophthora disease when used with overhead sprinklers.
Remember that Phytophthora needs excessive water to cause disease in nursery crops. Anything you can do to reduce the amount of irrigation water will help manage this disease.
Water application efficiency is the amount of water applied during irrigation compared to the amount of water that ends up in the root zone. Two ways to improve water application efficiency are:
Apply water uniformly
Schedule irrigations based on crop needs