Mark S. Hoddle

Nuclear-Mitochondrial Barcoding Exposes the Global Pest Western Flower Thrips (Thysanoptera: Thripidae) as Two Sympatric Cryptic Species in Its Native California

ABSTRACT Over the past three decades, Western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), has become a major worldwide pest of many agricultural and horticultural crops. In response, much time, money, and effort have been put into pure and applied research focusing on the biology and control of this pest, Western flower thrips is native to Western North America and widespread in California. High levels of variation in basic biology, pest status, and resistance to insecticides bring into question the specific status of Western flower thrips. We used nuclear-mitochondrial barcoding to compare DNA sequences of nuclear and mitochondrial genes between Western flower thrips populations across California, looking for association between these unlinked loci. Sequences of D2 domain of 28S and cytochrome c oxidase I gene revealed the existence of two distinct but sympatric genetic entities, and we describe a simple polymerase chain reactionbased method for diagnosing these entities. The complete association of these nuclear and mitochondrial loci in areas of sympatry is indicative of reproductive isolation and the existence of two cryptic species, both of which key out to Western flower thrips by using morphological characters. The finding that Western flower thrips is a complex of two species has important implications for past, current, and most importantly future research on these pests.

DISTRIBUTION AND PLANT ASSOCIATION RECORDS FOR HOMALODISCA COAGULATA (HEMIPTERA: CICADELLIDAE) IN FLORIDA

Scientific Notes DISTRIBUTION AND PLANT ASSOCIATION RECORDS FOR HOMALODISCA COAGULATA (HEMIPTERA: CICADELLIDAE) IN FLORIDA M ARK S. H ODDLE 1 , S ERGUEI V. T RIAPITSYN 1 AND D AVID J. W. M ORGAN 2 Department of Entomology, University of California, Riverside, CA 92521 California Department of Food and Agriculture, Mt. Rubidoux Field Station 4500 Glenwood Drive, Riverside, CA 92501 The glassy-winged sharpshooter, Homalodisca coagulata (Say) is the focus of a major classical bi- ological control program in California. This insect presents a serious threat to several agricultural commodities and potentially native plants as well because of its ability to vector the xylem-inhabit- ing bacterium Xylella fastidiosa, the causative or- ganism of “scorch like” diseases such as Pierce’s Disease of grapes and oleander leaf scorch, a seri- ous malady of oleanders (Purcell & Saunders 1999). Homalodisca coagulata is an invasive pest in California and its native range is the southeast- ern and northeastern regions of the USA and Mex- ico, respectively (Triapitsyn & Phillips 2000). Homalodisca coagulata probably was translocated to southern California as egg masses via the move- ment of ornamental plants in the late 1980’s (So- rensen & Gill 1996) and without an accompanying natural enemy fauna; inordinate populations of glassy-winged sharpshooters have resulted. During foreign exploration by MSH and SVT for H. coagulata and associated egg parasitoids in Florida in August 2001, the authors visited the Florida State Collection of Arthropods, Bureau of Entomology, Florida Department of Agriculture and Consumer Services in Gainesville. Following discussion with colleagues there, specimen re- ceipt vouchers for H. coagulata were provided that had been sent in for identification by lay peo- ple, ornamental, horticultural, and agricultural growers from around Florida. A total of 229 re- ceipts were catalogued for adult H. coagulata over the period 1958-2001 inclusive, and chits con- tained information on date of collection, locality, host plant, and sex of specimens. These data were used to determine possible host plant records, dis- tribution densities, and submission frequencies for H. coagulata for different areas of Florida. Homalodisca coagulata was collected from at least 72 plant species in 71 genera contained in 37 families and Citrus spp. were the most com- mon plants from which adult H. coagulata were captured (Table 1). Of these plant association records in Table 1 it is uncertain which can sup- port development of H. coagulata from egg to adulthood. Adult H. coagulata are vagile and known to be highly polyphagous while the rela- tively immobile immature stages have a nar- rower host range (Turner & Pollard 1959). Citrus may be over-represented in this dataset because of regular pest surveys in this economically im- portant crop. To determine if regional differences in numbers of H. coagulata specimens sent in for identification existed, Florida was divided into thirds: (1) top third was north of 29° Latitude; (2) middle third was 27°-29°; and (3) the bottom third was south of 29°. Specimen receipts for each county in each section of the state were assumed to have been submitted for identification accord- ing to a poisson distribution and proportions were compared using a Log-likelihood Ratio Test (i.e., G-test). Pair-wise comparisons between regions from which specimens were received were made using χ 2 as sample sizes were large (Sokal & Rohlf 1995). The G-test was also used to determine if the frequency with which samples were submitted from each region significantly differed. Significant differences in the number of specimens received by region existed ( χ 2 = 11.03; df = 2; P = 0.004). Sig- nificantly more specimens were received for iden- tification from north Florida, intermediate numbers from central Florida, and fewest speci- mens came from south Florida (Fig. 1). No signifi- Fig. 1. Proportion (±95% CI) of specimens and sub- missions of adult Homalodisca coagulata from north, central, and south Florida to the Florida State Collec- tion of Arthropods in Gainesville for identification over the period 1958-2001. Bars with the same letters (upper case [specimen comparisons] or lower case [submission comparisons]) are not significantly different from each other at the 0.05 level of significance.

Should arthropod parasitoids and predators be subject to host range testing when used as biological control agents

Testing of candidate biological control agents to estimate their likely field host ranges in the area of release has been part of weed biological control for several decades, with evolving techniques and goals. Similar efforts have been made less often for parasitoids and predators being introduced for arthropod biological control. Here, we review both techniques of host range testing and social objectives of such screening. We ask whether agents introduced for arthropod biological control should be subjected to host range testing before release, and if so, are methods used for estimating host ranges of herbivorous arthropods appropriate, or are different approaches needed. Current examples in which host range testing has been employed for arthropod biological control are reviewed. We conclude with recommendations concerning guiding principles about use of host range testing. We recommend modest expansion of host range testing for arthropod biological control for projects on continents. We recommend more extensive testing for projects of introduction onto islands. We note that introductions to islands could provide opportunities to gain experience in use of host range estimation for this class of organisms and to conduct post release evaluations of host ranges. We urge caution in efforts to mandate host range testing but simultaneously recommend consultation between biological control workers and insect conservationists.

Molecular Identification Key for Pest Species of Scirtothrips (Thysanoptera: Thripidae)

Abstract Effective plant quarantine and biological control initiatives require rapid and accurate identification of exotic and potentially invasive taxa that may cause high economic losses or environmental damage. The genus Scirtothrips Shull includes several species that are serious agricultural pests, and, because of their minute size and cryptic behavior, prone to undetected transport through international trade of plant material. Although assigning specimens to the genus Scirtothrips is straightforward using traditional taxonomic methods, identification of species is much more difficult and requires expert knowledge of the genus. Furthermore, the validity of some Scirtothrips species is questionable. Therefore, an easy, accurate, and highly reliable technique is desirable for Scirtothrips identification. Here, we provide a simple molecular key based on the internal transcribed spacer regions 1 and 2 (ITS1 and ITS2) of nuclear ribosomal DNA. Individual specimens can be identified by amplification of their ITS1 and ITS2 regions with general primers and determining the size of the products by using standard agarose gel electrophoresis, followed in some instances by DNA digestion with the restriction enzymes SacII or PspOM I. The advantage of this identification system is that nonspecialists are able to quickly and cheaply identify individual specimens. Material analyzed for this work was collected in the United States (California), India, South Africa, Kenya, Mexico, Guatemala, Honduras, Nicaragua, Costa Rica, Panama, Australia, New Zealand and Raiatea (Society Islands French Polynesia). We have identified seven pest species with the molecular-based methods described here. It is hoped that this system can be extended to other members of the genus as their ITS1 and ITS2 sequences become available. We also provide molecular confirmation for two new Scirtothrips species, one species from Honduras and one species from New Zealand.

The effect of prey species and environmental complexity on the functional response of Franklinothrips orizabensis: a test of the fractal foraging model

Abstract. 1. The hypothesis proposed by the fractal foraging model, that prey procurement by predators declines as habitat complexity increases, was tested. To evaluate this hypothesis, the effect of two prey species, second‐instar larvae of Scirtothrips perseae Nakahara and Heliothrips haemorrhoidalis (Bouché) (both Thysanoptera: Thripidae), and environmental complexity on the functional response of the predatory thrips Franklinothrips orizabensis Johansen (Thysanoptera: Aeolothripidae) was examined.

The economic impact of Scirtothrips perseae Nakahara (Thysanoptera: Thripidae) on California avocado production

In 1996, Scirtothrips perseae Nakahara (Thysanoptera: Thripidae) invaded California avocado orchards and moved pest management practices that relied almost exclusively on biological control to strategies dependent on insecticides to maintain thrips densities below economically damaging levels. By 1998, average losses due to thrips feeding damage in untreated infested groves reduced industry revenues by 12%. Producer costs increased by about 4.5% when S. perseae populations required management. In the short run (i.e., the time period during which the industry adapts to managing a new pest), producers cannot fully adapt to increases in production costs and the annualcost of S. perseae to producers with a thrips infestation is estimated to be

Attraction of thrips (Thysanoptera: Thripidae and Aeolothripidae) to colored sticky cards in a California avocado orchard

8.65 million (US). In the long run (i.e., the time period after which the industry has fully adapted to the effects of a new pest), producers are able to fully reallocate resources to their most efficient use and the annual cost of S. perseae is calculated to be

The Lesser of Two Weevils: Molecular-Genetics of Pest Palm Weevil Populations Confirm Rhynchophorus vulneratus (Panzer 1798) as a Valid Species Distinct from R. ferrugineus (Olivier 1790), and Reveal the Global Extent of Both

5.22 million (US) per year. For the entire USA avocado industry, the annual short-run loss attributable to S. perseae in California is calculated to be

Engineering an invasion: classical biological control of the glassy-winged sharpshooter, Homalodisca vitripennis, by the egg parasitoid Gonatocerus ashmeadi in Tahiti and Moorea, French Polynesia

8.51 million (US) and

Foreign exploration for Scirtothrips perseae Nakahara (Thysanoptera: Thripidae) and associated natural enemies on avocado (Persea americana Miller)

4.45 million (US) in the long run. r 2003 Elsevier Science Ltd. All rights reserved.