Flowering clematis vines (Clematis spp.) produce an abundance of brightly colored blooms in U.S. Department of Agriculture plant hardiness zones 3 through 11. Clematises are generally low-maintenance plants but can come under attack from various garden pests. They're susceptible to aphids, soft-bodied insects that consume the sap coursing through the plant. Aphids can be easily controlled.
1. Aphids Identification and Damage
Aphids are all-too-common garden pests that pierce the tender portions of plants to consume the phloem sap. Aphids are tiny and may have a waxy or woolly coating covering their pear-shaped bodies. Even though most adult aphids are wingless, a few species have a winged form. As the aphids feed on the clematis, the leaves begin to yellow, wilt, distort and fall from the plant. Aphids also secrete honeydew, which encourages the growth of sooty mold. Sooty mold is a fungus that rarely causes serious damage to the clematis but can negatively affect the look of the plant and -- in extreme cases -- interfere with photosynthesis.
2. Predatory Insects
Predatory insects that feed on aphids will naturally keep their numbers in check. An aphid outbreak typically occurs when something -- such as pesticides -- disrupts the life cycle of these natural enemies. Growing certain plants in your garden will attract these predatory insects back to the area. Fragrant annual herbs -- such as dill (Anethum graveolens) -- and flowering perennials -- such as yarrow (Achillea filipendulina), which grows in U.S. Department of Agriculture plant hardiness zones 2 through 9 -- attract various species of beneficial insects that prey on aphids.
3. Cultural Control
Good care goes a long way in keeping a clematis free of aphids and other pests. Avoid over-fertilizing clematis, water it correctly and keep the ground near and around the plant free of debris. Removing all weeds growing near the clematis will also help prevent aphids because the pests hide in weeds.
In most cases, insecticides are not necessary unless the aphids severely damage the clematis. Plant-based neem oil works on aphids and is an organic pesticide. Most neem oil insecticides require diluting with water at a rate of 1 ounce per 1 gallon of water. Follow the directions on the bottle for rates and application methods. Once you have diluted the insecticide, put it in a spray bottle or garden sprayer and thoroughly cover the foliage of the clematis with the solution, making sure not to forget about the undersides of the leaves. Wear gloves, long sleeves and long pants when using neem oil. Treat again after seven to 14 days if you still see aphids.
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