What is Avocado Phytophthora Blight?
A specific species of fungus causes blight in avocado seedlings: Phytophthora palmivora. It favors humid and moist, warm conditions, especially after big rains. This infection is most common in subtropical areas, like southern Florida. In fact, the first infection discovered in the U.S. was in Florida in the 1940’s. Signs you may have this kind of blight in your avocado seedlings are reddish or brownish patches on the mature leaves that are irregular in shape. You may also see that the terminal bud on the seedling has been killed. The younger leaves may curl or exhibit darker spots. There will also be lesions on the stems, but these are less obvious.
Phytophthora Blight Control in Avocado Seedlings
The best way to deal with this blight is to prevent it in the first place. When growing an avocado tree from seed, give it plenty of room to let air flow through, especially if your climate is humid and rainy. It also helps to raise them up off the ground for planting so that they do not get contaminated soil splashed on the leaves during a rain. This also allows for more air flow. If you do get avocado seedlings with blight symptoms, you can try a fungicide recommended at your local nursery or extension office. Depending on the extent of the infection, though, it may be too late to manage it. The good news is that if you live in a dry climate, like many parts of California, you can grow avocado seedlings without worrying about blight.
