The biology of the bean thrips

Abstract

The Biology of the Bean Thrips 469 Hilgardia [Vol. 7, No. 12 wing, 0.784 mm; average length of hind wing, 0.740 mm; fore wing with one branched vein in the center of wing dividing at inner edge of dark band. Anterior branch becomes contiguous with costal vein and posterior branch continues distinct to center of white area near tip. Costal spines usually 20; number of spines on posterior fork of midvein variable, 5 to 7 ; number of hairs in fringe on hind margin of wing variable, usually 30. Fore wing grayish brown, darkest along veins; dark area in center of wing equal to about one-half of wing's length, basal fourth white, and distal fourth equally divided into light and dark areas, tip dark. Hind wing uniformly grayish brown, basal fourth light ; one longitudinal vein in center of wing becoming indistinct near base and not reaching t i p ; spines on costal margin about 32 in number ; number of hairs in fringe variable, usually 42 ; entire surface of wings covered with very fine hairs. Femora dark brown except at tips; tibiae with central portion dark brown, ex tremities yellow; fore tibiae somewhat lighter brown; setae distributed irregularly on tibiae and tarsi ; hind femora only with setae ; spines present also on lateral mar gins of head, prothorax, and abdomen ; ninth and tenth segments of abdomen with a row of long spines on posterior margins. Short, strong spines are present on pos terior-lateral margins of abdominal segments. Abdomen slightly broader than thorax, ovate, tapering sharply to last segment. Ovipositor visible under magnifica tion, extending up into eighth segment. Approximate length of ovipositor, 0.167 mm. Adult Male.-The male differs but slightly from the female; it is somewhat smaller in size, the abdomen tapers more gradually, and the terminal abdominal segment is more blunt (fig. 2, A). The coloration, markings, and setae are practi cally identical. Under magnification the reddish-orange testes may be seen suspended in the seventh and eighth abdominal segments. The external portions of the genetalia may be seen to extend slightly beyond the end of the abdomen.

Populations of North American bean thrips, Caliothrips fasciatus (Pergande) (Thysanoptera: Thripidae: Panchaetothripinae) not detected in Australia

“…Overwintering C. fasciatus are quiescent and will break dormancy to feed when winter temperatures reach approximately 24-27°C for short periods (Bailey 1933). Concealed C. fasciatus provide a major quarantine issue for countries, including Australia, that import fresh navels from California, although this is not a new problem.…”

“…No claim to original US government works A current problem with C. fasciatus concerns the contamination of Californian grown navel oranges by adult thrips that overwinter inside the navel from early November to late March (Bailey 1933). Overwintering C. fasciatus are quiescent and will break dormancy to feed when winter temperatures reach approximately 24-27°C for short periods (Bailey 1933).…”

“…Repeated initial introductions can enhance the gene pool of founding populations, and temporally stratified introductions are more likely to coincide with benign environmental conditions that ease barriers to establishment (Kowarik 2003 Given the long history of navel imports into Australia from California, the regular contamination of fresh fruit with overwintering C. fasciatus, and the high probability that the receiving environment at some stage would be favourable for the incursion of the thrips, it seemed curious that this insect had not been recorded as established in Australia (Mound 1996). Areas in Australia with suitable year-round climate for bean thrips survival were chosen for surveying based on the results from CLIMEX models (Sutherst et al 2004) that were parameterised from regression analyses of Bailey's (1933) temperature studies on bean thrips development and survival rates. Consequently, surveys for bean thrips were conducted during summer 2005 around pre-selected major Australian cities and agricultural areas, to determine whether C. fasciatus had established in Australia despite being unrecorded.…”

“…Reports of C. fasciatus populations elsewhere are considered dubious, a fact that has not changed since 1933 (Bailey 1933). In California, C. fasciatus was once considered to be a serious pest of a variety of agricultural crops, including alfalfa, beans, cantaloupes, cotton, lettuce, pears, peas and walnuts.…”

“…Bean thrips can breed on various weed species including thistles, cheeseweed and fennel (Bailey 1938). The significance of this insect as an agricultural pest in California has waned substantially since Bailey's (1933Bailey's ( , 1937Bailey's ( , 1938 treatises were published. The reasons for this decline are unclear, but could be due to the development of integrated pest management programs, more effective insecticides used on crops that are most vulnerable to C. fasciatus outbreaks, and development of resistant cultivars.…”