Everything you want to know about stink bugs
A behemoth covering all aspects of the biology of stink bugs, Invasive Stink Bugs and Related Species has 260 pages devoted to six prominent invasive pentatomids, a short chapter on three potentially invasive species, and a 45-page chapter on management of insects in general with some sections particularly relevant to stink bugs. This is to say that, despite the title, the book is not primarily about invasions, but it is so massive that, with editing, the sections on invasions could have constituted a book in their own right. The emphasis throughout is on agricultural damage and management in agricultural settings, but in several instances authors have noted where a species has constituted a nuisance or caused ecological damage.
The Big Six are the painted bug (Bagrada hilaris), brown marmorated stink bug (Halyomorpha halys), kudzu bug (Megacopta cribraria), harlequin bug (Murgantia histrionica), southern green stink bug (Nezara viridula), and redbanded stink bug (Piezodorus guildinii). For invasion scientists only the brown marmorated stink bug, the kudzu bug, and to a lesser extent the southern green stink bug have attracted substantial attention. Each of these six species is treated in exhaustive detail (e.g., ca. 300 references for the brown marmorated stink bug alone), including the biology and biogeography of the species (and in several cases environmental niche models of potential future spread), history and mechanisms of the invasion, impacts in native and introduced ranges, management methods and their effectiveness to date, suggestions for expanded or novel management approaches, and a brief discussion of future prospects for spread, impacts, and management.
The brown marmorated stink bug, from Asia, has become legendary in North America (it has also invaded Europe and Chile), where it was first detected in Allentown, Pennsylvania in 1996 after almost certainly arriving in a Mid-Atlantic port. Genetic analysis pinpointed a single introduction from a source region near Beijing, but more recent specimens collected on the West Coast suggest subsequent introductions from other areas. From Allentown it spread rapidly to most states and became notorious for massing in people’s homes during late fall and winter; the record is apparently 26,205 individuals in a 6-month period. This habit garnered enormous media attention, some with copious interesting detail (e.g., Schulz 2018). Less well-known to the public is serious agricultural damage. As with almost all the Big Six, the species has an enormous list of host plant species (over 175 in the United States alone), although many species may represent collateral damage on plants on which the stink bug could not complete its life cycle. Its main hosts appear to be trees, including citrus, apple, pear, and peach trees. In its native range it also causes substantial damage to soy and grains. In the United States, in addition to trees, it damages mainly soy and corn. As with other stink bugs, management is almost wholly by broad-spectrum insecticides, although research has been initiated on biological control. Perhaps the initially most promising agent, the samurai wasp (Trissolcus japonicus), proved to attack many other stink bugs, including natives. However, during the testing, populations of this wasp, genetically different from the quarantined test populations, were found to be already present at several sites on the East and West Coasts. In any event, polyphagy or not, there is now hope but also skepticism that T. japonicus can be part of an effective biocontrol program (Schulz 2018). In Asia the brown marmorated stink bug vectors a plant pathogen that greatly damages the princess tree (Paulownia tomentosa), a major invasive problem in the United States, but to date no such transmission has been detected in North American areas where the tree and the stink bug coexist.
The Asian kudzu bug first surfaced in Georgia (US) in 2009 and has now spread to at least 14 states. Genetic analysis shows the origin to be the Kyūshū region of Japan, and the first location, far from seaports but relatively near to the Atlanta airport, suggests the most likely scenario is accidental transport in cargo or luggage unloaded at Atlanta. During the initial search, spurred by reports of the species as a nuisance in homes, it was discovered only on kudzu, and several reports in the popular media initially heralded it as a potential adventitious control of kudzu, but it was quickly found attacking soy to an economically substantial degree. It has been found eating ca. 100 plant species, although many may be incidental hosts on which it cannot complete its life cycle. Soy is the only economically significant host to date, and it is a potential impediment to trade, as soy from the United States with live kudzu bugs has been intercepted in Honduras. Its impact on kudzu appears to be minimal in early research. The main management approach to date is broad-spectrum insecticides.
The other members of the Big Six, as agricultural pests, have not attracted nearly as much attention from the public or invasion scientists, although occasionally some striking finding (e.g., over 5100 nymphs of the harlequin bug on one corn plant) receives some notice. For all, the main management tool is broad-spectrum insecticides, and biological control is not yet an option for any of them. Pentatomids have particularly been pests of soybean, and as soybean production has greatly expanded in many parts of the world, including the United States and Brazil, their pentatomid pests have been the subject of much more research, including alternatives to the broad-spectrum insecticides with their substantial non-target impacts. The sheer amount of broad-spectrum insecticide that must be released to the environment in managing these species can only stagger a conservation-minded reader and render one much less enthusiastic about eating, e.g., conventional broccoli or anything made with soy. For the painted bug and brown marmorated stink bug, authors detail the particular burden on organic growers, with no effective alternatives to insecticides. Cultural control methods, such as intercropping, are mentioned but appear not to be very effective. The enormous host plant lists of these species include many ecologically important species, but reports of ecological damage are barely on the radar of conservation biologists.
The many other sections of the book detail all aspects of pentatomid biology, for invasive as well as other species. Separate chapters exhaustively treat systematics, diapause, seasonal cycles, vectoring of plant pathogens, symbiotic microorganisms, and semiochemistry. Occasionally some interesting detail in one of these chapters relates to one of the Big Six invaders and has not been mentioned in the relevant species chapter. Examples concern, i.e., voltinism, seasonal cycles, and vectored pathogens. The chapter on general insect management covers all the methods but is thus very brief on each (e.g., two pages each on chemical control and biological control). It includes some recent literature on new genetically based techniques, including gene-silencing but not the very recent EPA approval of corn engineered with a gene that manufactures a lethal dsRNA when a western corn rootworm (Diabrotica virgifera virgifera) eats it (Zhang 2017).
This book is copiously illustrated, including with beautiful color plates of key species and those that resemble them. For the invasive species there are maps of the dynamics of the invasion as well as of predicted ranges generated by the environmental niche models. A problem is that, for the dynamics maps, the spread by year is indicated by different colors rather than isopleths, making it difficult to capture the general nature of the spread at a glance or even after longer study. Many of the maps are printed in gray scale within the chapters, where they are especially difficult to read, but repeated more clearly in the color plate sections.
- Schulz K (2018) Home invasion. New Yorker 94(4):32–40Google Scholar
- Zhang S (2017) The EPA quietly approved Monsanto’s new genetic engineering technology. https://www.theatlantic.com/science/archive/2017/06/monsanto-rna-interference/531288