Surinam Cockroaches
The Surinam cockroach is not a new cockroach to Texas, but it is often first encountered in the winter months when plants are moved indoors. This cockroach is about ¾ inch in length, has a shiny brown to black pronotum with a white band in the front, and has olive-green wings. The Surinam cockroach nymphs look similar to the nymphs of Oriental cockroaches, but they can be distinguished by the rough appearance on the end abdominal segments (compared to the smooth abdomen of the Oriental cockroach). This cockroach likes to burrow and is often brought into homes, greenhouses, shopping malls, and restaurants through potted plants.
The cockroach hides during the day under the soil in containers, on the sides of benches, under boards, in barrels, in holes and crevices in the walls of buildings, and in other dark areas where they can conceal themselves. At night, they come out in great numbers and gnaw on the stems of plants. No males are found in the United States, so this cockroach reproduces through parthenogensis. The egg capsule is retained within the abdomen, so the female gives birth to live young.
Control Options
Removing leaf piles, woodpiles and other potential harborages will reduce the cockroaches’ habitat. It is also important to seal exterior cracks and to ensure that all foundation and attic vents have tight-fitting screens.
Application of bait to infested potted plants will often control indoor infestations. Outdoors, granular cockroach baits can be applied to active harborages, and insecticidal sprays can be applied to foundation plantings, wood piles, mulch, and other infested locations.
Use of Oils to Manage Insects
The use of oils as part of a general control program is becoming favored over the use of synthetic pesticides. Oils can be distilled from petroleum — horticultural oils, Volck oils, summer oils, dormant oils or mineral oils — or oils can be extracted from plants and animals — neem oil or fish oils. Oils are generally effective against aphids, scale crawlers, mealybugs, spider mites, whiteflies and small caterpillars.
When oils are applied, a thin layer covers the insect or mite. The oil clogs the spiracles or pores through which the insect breathes, causing death by suffocation. Oils can also disrupt membrane function or structure or disrupt feeding. Multiple applications may be needed for control.
Sometimes oils can injure a plant, causing leaf scorching, defoliation, reduced flowering and stunted growth. There are details on the label to be aware of, such as unsulfonated residues, viscosity, and distillation. Usually the higher the unsulfonated residue (UR), the less likely the plant injury. Likewise, the lower the viscosity, the less likelihood there is of plant injury. In addition, the distillation range is a measure of the purity of the oil fraction, so distillation ranges of 80 F or less are considered appropriate.
Apply oils when temperatures are lower than 85 F. Ninety percent humidity is recommended, since the longer the wet oil remains on the foliage, the greater the chance of phytotoxicity. It is not advisable to treat stressed plants with oils. Some plants are sensitive to oil – for example, azalea, hibiscus, impatiens, photinia, and spruce should not be treated with oil.
About the author: Kimberly Schofield is a program specialist in the field of urban integrated pest management at the Texas A&M Research Center in Dallas.
Mention of commercial products is for educational purposes only and does not represent endorsement by Texas AgriLife Extension or The Texas A&M University System. Insecticide label registrations are subject to change, and changes may have occurred since this article was written. The pesticide user is always responsible for applying products in accordance with label directions. Always read and carefully follow the instructions on the container label.
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