Pest Insects in the Landscape

Only two percent of insects are actually pests. We’ll introduce you to a few that have a negative impact on your landscape.

Scientists state that 98 percent of known species of insects are considered beneficial in the landscape as pollinators, decomposers of organic material and predators that feed on other insects.

The remaining identified insect species are known to damage plants, trees, buildings, bite humans and animals, and spread diseases or pathogens. This article focuses on a few that have a negative impact on your landscape.

All insects have to eat and when they feed, they either damage plants and trees directly or by spreading plant diseases. The major pest insects in the landscape include: aphids, scales, mealybugs, red imported fire ants (aka fire ants) and caterpillars.

Aphids, Scales and Mealybugs

More often than not, the average homeowner finds sap-sucking insects damaging their plants. These include aphids, scales and mealybugs. All three can multiply quickly in the absence of predators like ladybugs. They feed on the sap of plants and excrete sugar water, or honeydew, as waste. In turn, this honeydew supports the growth of powdery mildew and mold on plant leaves. Another insect in this group (the sharpshooter leafhopper) spreads bacterial and viral diseases in oleanders, maples, sycamores and citrus.

Fire Ants

Fire ants are welcomed by few and hated by most. These South American natives prefer moist soil in sunny areas and are both pest and predator in the landscape. They feed on a wide variety of insects and small animals, but their stings, large mounds and affinity for electricity present a real problem for homeowners. In addition, fire ants actually protect and encourage the growth of aphids and other sap-sucking insects in order to collect the sweet honeydew to feed their colonies during times of drought.


Lastly, caterpillars are mentioned here simply because they eat leaves and cause direct, visible damage to trees, gardens and landscapes. That said, many caterpillars in gardens and landscapes develop into butterflies. For herb enthusiasts, swallowtail butterfly caterpillars love to eat dill, parsley and rue. For gardeners, the cabbage white butterfly may be a pretty thing to watch, but their caterpillars love to feast on cabbage!

Other caterpillars such as the yellow genista caterpillar that feeds on Texas mountain laurel leaves or the webworm that defoliates pecan, mulberry and walnut trees are examples where a large amount of damage occurs over short period time as the numbers of caterpillars increase.

Remember, only two percent of insects are actually pests. The silver lining: 98 percent of insects are benign or beneficial to us!

Picture of Nathan Riggs
Nathan Riggs
Nathan Riggs is a SAWS project coordinator and licensed irrigator who also happens to have a degree in entomology from Texas A&M University. Yes, Nathan’s a bug expert, and not just on water bugs! When he’s not hard at work on SAWS conservation projects, he enjoys a wide variety of interests including: landscaping, hiking, photography of flowers, insects and other critters, and planning his next adventure with his wife Ella and family.
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