Protect your Plants from Sucking Pests

Are your roses sporting new leaves that glisten in the sunlight and are slightly sticky to the touch?  See a trail of ants crawling up the trunk of your plum tree? How about powdery black stuff on your camellia bush or the garden furniture next to it? All are indicators that sucking insects may have arrived and need your attention.

There’s a group of soft-bodied insects – aphids, mealybugs, scale, and whiteflies being the most common, that feed by sucking juices from plants. They cause spotted, bleached, or curled foliage and stunted growth to the plant. These bugs can’t use all the sugar they suck from the plant, and so pump it out honeydew that looks just like drops of honey on foliage. The sticky honeydew can drip from one part of the plant to another, or to anything around it – other plants, walls, walkways and more.  And that honeydew provides the perfect growth medium for sooty mold, a black or dark gray coating on the surface of plant leaves and stems (or other non-living surfaces). This unsightly fungus doesn’t attack plants directly but can weaken them. Then there are the ants. They love honeydew and will fiercely protect those soft-bodied producers, especially aphids, from predators, in order to keep that sugary stuff coming.  

You can save yourself a whole lot of energy and protect your plants by preventing sucking pests from getting established. Some general measures include:

  • Purchase pest-free plants.
  • Inspect plants often for the presence of aphids, mealybugs, scale, and whiteflies, honeydew, sooty mold, or ants crawling up woody plants or trees.
  • Don’t overfertilize; high levels of nitrogen fertilizer can over stimulate new plant growth, attracting pests.
  • Encourage natural enemies; provide habitat conducive to their needs – a variety of nectar and pollen producing species, shelter, and some pests to feed on.

If you do see any of the honeydew producers, act quickly. Light infestations can usually be eliminated with a minimum of effort. Start by knocking pests off plants with a strong spray of water and repeating every few days as needed. Prune out any shoots, leaves, twigs, or other plant parts that are infested and discard. Where ants are visible, wrap the trunk of the plant or tree with sticky tape to catch the ants and prevent them from tending to the sucking pests.

Sucking pests are difficult to control with pesticides; developing and maintaining healthy populations of natural enemies, both predators (lady beetles, lacewings, and soldier beetles) and parasites, is a more effective long-term management strategy. 

Oh, and if you do find sooty mold (and have removed the source of honeydew), it will gradually weather away, or can be washed off with a strong stream of water or soap and water.

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