The leaves on my maple tree are covered with a black, sooty material. What is it and is it harming the tree?

The black sooty material is likely sooty mold. Sooty mold is caused by several different fungi. The fungi don’t infect plants, but grow on the sugary honeydew excreted by aphids, scales, mealybugs and other insects. In Iowa, sooty mold is most common on pine, maple, linden and elm trees.

While sooty mold can reduce plant vigor by blocking sunlight and interfering with photosynthesis, the damage is mainly aesthetic. Sooty mold does not cause serious harm to healthy, well established trees. Sooty mold does not need to be controlled.

While sooty mold is not a serious problem, the scales, aphids, and mealybugs may need to be controlled. Properly identify the insect pest and follow recommended control measures if their presence threatens the health of the tree.

How do I control spider mites on houseplants?

Spider mites are a common pest of houseplants. Spider mites use piercing-sucking mouthparts to puncture the plant tissue and feed on the liquid within the cells. In light infestations, the foliage will appear to be speckled with very tiny yellowish-green spots. Heavy mite infestations can turn the foliage to greenish-yellow and eventually tan or brown. Heavily infested plants often drop their leaves. Close examination of infested plants may reveal very fine webbing produced by the mites on the leaves and stems.

When mites are present, determine the extent of the infestation and the value of the plant. It is usually easier, quicker and more convenient to discard a small plant that is heavily infested than it is to return it to good health and appearance. If possible, prune heavily infested portions of larger plants before attempting mite control. Washing or syringing infested plant foliage may reduce light mite populations. Move plants outdoors or into the bathtub or shower and then use a forceful spray of water to dislodge mites from an infested plant.

Several miticides (pesticides that control mites) are available for houseplants. Check with your local nursery or garden center. When using pesticides, carefully read and follow label instructions. Keep plants watered and fertilized to promote health and vigor and to reduce the impact of mite feeding.

When should I harvest tomatillos?

Gardeners should be able to begin harvesting tomatillos 75 to 100 days after transplanting. For best flavor, harvest tomatillos when the husk changes from green to tan while the fruit is still green. The size of the husk and fruit, as well as fruit color and flavor, varies depending on the cultivar. Fully ripe fruit turn yellow or purple and lose their tangy flavor.

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