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Index : Pests
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- 2. Protect Plants from Mites and Other Spring Insect Pests - Top
- Spring provides the ideal environment for a number of common garden and landscape insect pests. Warm weather promotes lush, succulent plant growth that serves as food for new generations of insect pests. So, be on the look out for mites, aphids, thrips, and caterpillars doing harm to your plants. Here’s what to look for:
If some of your plants have a dusty appearance, maybe with a brown or gray cast, they may be infested with spider mites! Rosemary (rosemary), pyracantha (pyracantha), Italian cypress (Italian cypress) , juniper (juniper), arbor vitae (arbor vitae) and cedar (cedar) are a few of the favorite plants for these tiny sucking pests.
Because mites work from the ground up, the place to look for them is at the bottom or interior of the plant. The easiest way to test of spider mites is to hold a white sheet of paper under suspicious stems and tap them sharply against the paper. If small dust-like specks are seen crawling against the white background, mites are present. A simple 10 power magnifying lens also is helpful in detecting mites using the white background.
Mites are best controlled by spraying infested plants periodically with a strong jet of water from a garden hose attachment. The water literally knocks them off! They rarely crawl back, but repeated weekly spays with water are recommended to eliminate any newly emerging mites. When our monsoon rains arrive, sprays can be curtailed.
In addition to controlling mites, water sprays are great for eliminating another common garden and landscape pest - the aphid. These green soft-bodied insects once called plant lice, are similar in size to lice; small but visible. They congregate and feed on the soft new growth of most flower and vegetable plants, roses (roses), citrus (citrus), and oleander (oleander). Oleander aphids are orange! All suck fluids from leaves and in the process, secrete a sweet, sticky substance called ‘honeydew’. One of the tell-tale signs of aphids is this honeydew. It resembles shiny varnish on leaves underneath the feeding aphids. If you see these varnished leaves - look for aphids.
Aphids can do serious harm to young flower and vegetable plants. On roses and other larger woody-stemmed plants the damage is mainly cosmetic. As aphids feed they cause the leaves to cup and curl. Leaf yellowing may also develop. Water sprays do a great job of control! On young plants to tender for harsh water sprays, apply a mild soap spray made by mixing one tablespoon of liquid dish washing detergent in one gallon of water. One or two applications will be sufficient.
In addition to mites and aphids, thrips are also common spring visitors on a number of plants, most notably citrus (citrus) and roses (roses). These tiny thread-like insects cause cupping, curling and silver streaking of leaves on citrus. On roses, damage from thrips appears on the flower petals. They too appear streaked and blemished. Although thrips don’t do any real damage to plants, many rose growers often use systemic insecticides to prevent thrips from damaging rose petals. Systemic insecticides cannot be used on citrus, nor would they be warranted if they could be! No real damage to citrus will result- so not control is necessary.
Finally, caterpillars have begun to show up on Texas mountain laurel (Texas mountain laurel) and citrus (citrus) trees. Inspect these plants for signs of feeding. On citrus, hand picking and disposal of the orange dog caterpillar is all that’s needed. However, to control Texas mountain laurel caterpillars, I recommended periodic sprays of BT (Bacillus thuringiensis), a safe biological control product available wherever garden sprays are sold.
Written by John Begeman, College of Agriculture and Life Sciences, the University of Arizona,
520-626-5161.
- Updated: April 22, 2007
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