Urban Pests and Plant Interactions

When the frost of winter recedes, we look ahead to the world coming to life once again. As plants emerge from their hibernation, so too do the creatures that call their leaves and stalks home. And PMPs can use these plants as an important harbinger for pest comings and goings.

Pest professionals would be wise to take time this upcoming spring to examine these leafy areas for the creatures that use them.

Indeed, just as a janitor can glean clues as to the previous day’s activities from the rubbish and stains he cleans up, you too may be able to source a pest issue from the clues its friends or foes leave behind.

MORE HONEYDEW, MORE PROBLEMS. One mutualistic relationship to look for is the one between the insects that produce honeydew and the insects that feed on it. Honeydew (often known as “aphid poop”) is a tasty, sugary liquid that some insects excrete after feeding on plant sap.

Not just aphids produce honeydew, though; scale insects have similar production methods.

Scale insects are a strange group of true bugs that grow under a waxy cover. Eggs are laid by the females under this cover. At hatching, immature crawlers have legs and select a spot on a plant to grow their own scales.

These honeydew-producing insects are of particular interest to sugar-loving ants, who guard them with all the jealousy of a farmer protecting his or her golden-egg-laying goose. Ants, such as the odorous house ant or Argentine ant, will spend their time protecting and cultivating these honeydew-producing insects so that they can get their sugar fix, while predators of these insects, such as lady beetles, are often attacked by ants in order to protect their crop.

Some plants are more prone to scale and aphid infestations, including bamboo, cherry laurel, fig, pine and roses. Knowing how to read the signs of plant infestation or even cohabitation can be essential to proper pest identification in any setting — even the home of a pest professional.

POTTED PLANT INVADERS. I myself had odorous house ants sneaking into my house last spring. Having followed their trail to one of my potted plants, I discovered that they had made a satellite nest inside the ceramic container. Daily trips to water, prune and fertilize did not encourage any concern over the sticky substance on the window next to the pot.

Upon closer inspection, it was obvious that the ants were nesting under a major food source: the honeydew produced by brown scales. I had totally missed the major sign — the honeydew had been collecting on my window for weeks. The ants were removed, the scale insect problem was resolved, and I turned my attention to the other odorous house ant-conducive conditions around my house.

FINAL THOUGHTS. It’s important to look at surrounding vegetation to determine if there is a honeydew-producing insect problem. The best time to control these insects is in the spring before their numbers get too large. You may see the pests directly or just signs of their presence, such as sticky leaves. Let your customers know if they have a scale or aphid issue that could lead to ants or is causing their ant issue.