Cold spring encourages tree fungus
My maple tree has suddenly developed white spots all over the leaves. Some of them are curling up and drying out at the edges. This is a big tree that shades our house in the summer so I don’t want to lose it. Help.
Karen Burgard, Spokane Valley
It’s a bad case of maple powdery mildew. According to the Master Gardener Plant Clinic volunteers, you are not alone with this problem this year. They have seen a number of cases since early May.
Maple powdery mildew affects many hardwoods besides maple including hazelnuts, birch and alder. It appears as white spots on both sides of the leaves and can cover a good bit of the leaf surface. Shoots that develop late in the season can be distorted by it. As you have seen, some leaves will begin drying on the edges.
The most likely cause is the colder than usual spring we had followed by a few intermittent warm days that allowed the fungus to gain a toehold.
Unfortunately, preventative treatments are the best way to control this and we are past that point now. Control measures applied now will slow the mildew down but won’t make the white spots disappear. Small trees are fairly easy to spray with a fungicide registered for maple powdery mildew now. A large tree like yours is going to need professional help as they have the equipment and knowledge to reach high into the tree. The good news is that powdery mildew rarely kills plants. It will just look really bad this year.
To reduce the impact of the problem this and next year, make sure the tree gets a deep soaking every couple of weeks, especially when it gets hot. Lay a soaker hose over the root area and let it run overnight. Pick up any fallen leaves through the summer and put them in the trash. This fall, collect all the leaves after they fall and take them to the transfer station. The fungus can overwinter in the leaf debris. Consult with an arborist about treating the tree before next spring to reduce the potential of another attack next year.
Not much of a mulch
Just wondered if you had tried the red plastic for tomatoes? It sure works great for me down here in Odessa.
Laura Estes, Odessa, Wash.
A lot of people swear by the red plastic mulch here, too. The idea behind it is that the red color from the plastic is reflected from the ground back up into the tomato plant hastening ripening and increasing plant vigor. Research tests in Texas however found that yields and vigor were much higher for plants supported in cages and wrapped with a porous fabric than those that were planted in silver, black or red plastic mulches. When I tried it several years ago, a lot of my tomatoes rotted when they sat in the water that collected on top of the impervious mulch. What are other people’s experiences with this mulch?