Strolling through the garden one morning I was awed by all the beauty that surrounds us. The pallet of reds, blues, greens, yellows and purples blooming there was truly a beautiful sight to see. As I continued my stroll I noticed something odd about some of the leaves and buds on the roses and mums. I wondered, what is that little brown hole in the rose bud, why are those leaves so speckled, and what in the world are those little black things leaving that sticky goo on the mums? Upon closer inspection I realized it was the work of the Troublesome Trio-Aphids, Spider Mites, and Thrips.
Aphids are a variety of common pests that attack plants and feed on the juices. They can be black, red, yellow, gray, or white in color. They have needle-like “piercing sucking” mouthparts that allow them to puncture plant tissue and remove the sap or cell contents. They are very small, usually less than 1/8 inch in size and reproduce very rapidly. Aphids seldom kill the plant but when in abundance they will reduce the vigor and stunt its growth. They take in more sap than they can absorb or use so they excrete the excess on the leaves of the plants. It appears as a clear, sweet sticky substance, known as “honeydew”. Ants love this honeydew.
Spider Mites are an almost microscopic relative of spiders and ticks, which tend to feed on the under- side of rose leaves, especially older leaves. They have rasping mouthparts, which pierce the skin of the leaves and inject some of their saliva in the process. This causes minute chlorotic spots to appear as the leaf tissue collapses. The rose foliage will take on a bronzed color and look speckled. The leaves will look yellow and dusty from a distance. Heavily infested leaves will turn brown, curl and fall off. Spider mites are common in dry low rainfall areas so keep plants watered and apply mulch during high drought conditions.
Thrips are small cigar shaped insects approximately a millimeter in length whose mouthpart rasps leaf and flower tissue and feed on the plant juices. In roses the female thrip makes a small slit in the side of the bud and lays her eggs inside. Evidence of this happening is the small brown hole the slit leaves on the bud. In a few days the eggs hatch and the Larvae, which resemble the adults in general body form, begin sucking the plant fluids until they are fat enough to pupate. If you break the bud open and pull back the petals and see small slivers of crčam, yellow, brown or black scurrying about this is the thrip larvae. If you have thrip damage the bud may not open at all and if it does the petal edges look brown or discolored.
If these three pests are identified in the early stages of infestation, a frequent high pressure water blast will dislodge them from the plant. Be sure to blast both upper and lower leaves for aphids and spider mites. Beneficial insects such as ladybugs and green lacewings are also a good defense. If stronger measures are needed, consult a reputable Garden Center for products that are safe for humans, pets, and the environment, but won’t destroy the beneficial insect population as well.
Information for this article was obtained from gardening books in the Somervell County Master Gardener Library located at the Texas AgriLIFE Extension Office 1405 Texas Avenue and gardenguides.com