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Tuesday, February 3, 2015

Snails, Disease and Shade Are Related

Q. I have been noticing tiny little snails climbing up my red brick planter during the fall. I have thousands of those shells all through my planters and yard. My roses have now developed powdery mildew disease which they never have in the past. My lawn is thinning I think because of the snails. I have shade in my yard because of some older mulberries. I sent you some pictures of my yard.

Readers yard with shade
A. After seeing the pictures and reading your description I think that the shade is contributing to a number of things going on. Increased shade causes plants and the soil to stay wet longer.

Snail shells from another readers question
Staying wet longer favors snails and slugs. Increased shade increases the probability of powdery mildew and other diseases. Increased shade causes lawns to thin and eventually fail as well.
          You will see an improvement in everything if you remove some lower limbs of the trees. Limb removal will allow more light on your property and improve the roses, reduce disease problems, thicken the lawn and reduce snail problems.

Cool season lawn grasses like fescue and ryegrass needs direct sunlight at least five hours a day or filtered sunlight so that no more than 50% of the lawn is shaded. Shading lawns and flowering plants more than this is going to hurt them.
Shady lawns are not vigorous enough to withstand any kind of traffic. The lawn will thin and bare soil will appear in the more shaded areas.
Plants that flower, like roses, have fewer blooms and the blooms will be poor quality in the shade. Powdery mildew loves the shade. Powdery mildew also likes splashing water. If there is overhead irrigation that is splashing on the leaves of roses and they are shaded, it will spread powdery mildew from rose to rose.
          Snails are difficult to control. The usual control methods are trapping and baiting. Trap snails by placing wet newspapers or cardboard between the plants. When the sun comes up, snails and slugs like to have parties under wet paper or cardboard.

Powdery mildew on rose

Pick them off of the underside of the cardboard or from the ground and put them in a plastic bag for disposal. If you do this on a regular basis, say weekly, you will start to put a dent in their population.

Snail and slug baits also works well on snails. These are typically spread around the plants periodically and according to the label. These can be purchased in most nurseries and garden centers or online.

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