On a recent trip to a home improvement store, I discovered a forlorn collection of Rose of Sharon shrubs desperately hoping someone would buy them before they were relegated to the dumpster to make room for a sprouting forest of plastic Christmas trees. One look at blossoms that had since gone to seed revealed hordes of magnificent, scentless plant bugs decked out in harlequin costumes of orange, black, and white. With all the recent fuss about invasive species like the brown marmorated stink bug, my angst twisted on the possibility that this was yet another case of a noxious invader arriving on our shores with a shipment of exotic plants. A quick look at the labels on the Rose of Sharons revealed that these plants were homegrown. A little poking around on the internet confirmed this to be a native bug with some redeeming qualities rather than a nocent pest. Whew, what a relief!
Although this bugger was new to my eyes, Niesthrea lousianica, was long known to occur from New York to Florida and west to California in North America. This curious sucker is a gourmand for plants in the mallow family including cotton, Chinese lantern, okra, and Rose of Sharon. Like its cousins, the boxelder bug and red-shouldered bug that we met in previous episodes, Niesthrea, has sucking mouthparts used to probe vegetation and seeds and extract liquefied nutrients. Unlike stink bugs and boxelder bugs that flock to houses, Niesthrea finds a protected refuge outdoors beneath leaves and duff near its host plants.
In spring, adults return to plants, begin feeding on foliage, and, after mating, lay eggs in clusters of one to three dozen on the foliage or developing fruit of their host. After about a week, eggs hatch and tiny nymphs begin to feed. The plant bug requires little more than a month to complete a generation in summertime and in southern states, several generations occur each year. Bug of the Week has visited several exotic insects that attack our native plants after arriving in the US.
However, beautiful Niesthrea lousianica, turns the table and demonstrates how plant-feeding bugs sometimes become our allies when plants they attack are weeds. Throughout the corn and soybean growing regions of the US, an aggressive exotic weed called velvetleaf competes with our crops for nutrients and water. Velvetleaf is a member of the mallow family and thereby qualifies as a menu item for hungry Niesthrea. By attacking the pods of velvetleaf and killing developing seeds inside, this small bug plays an important role in reducing the numbers of noxious velvetleaf in many parts of the country. In one study more than 80,000 Niesthrea lousianica were raised and released in several Midwestern states. Near the points of release, Niesthrea made a serious dent in the viability of velvetleaf seeds. Score one for the hometown bug.
Bug of the Week thanks Dr. Shrewsbury for inspiring this week’s episode. Two fascinating references “Life History of Niesthrea louisianica (Hemiptera: Rhopalidae) on Rose of Sharon in North Carolina” by Al Wheeler and “Inundative biological control of velvetleaf, Abutilon theophrasti [Malvaceae] with Niesthrea louisianica (Hem.: Rhopalidae) by N. R. Spencer were used as references for this episode.