Brazilian Peppertree Seed Chalcid: Wasp Wages War on Widespread Weed
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Brazilian Peppertree Seed Chalcid: Wasp Wages War on Widespread Weed J. P. Cuda1, G.S. Wheeler2, and D. H. Habeck1 In 1988, an insect previously unknown Introduction to Florida was reared from the drupes of Brazilian peppertree, Schi- Brazilian peppertree collected in Palm nus terebinthifolius Raddi (Anacardia- Beach County (Habeck et al. 1989). The ceae), is an evergreen shrub or small insect was subsequently identified as tree native to Argentina, Paraguay and Megastigmus transvaalensis (Hussey) Brazil (Ewel et al. 1982). Introduced into (Hymenoptera: Torymidae), a phytopha- Florida as a landscape ornamental in gous seed chalcid wasp (see cover). The the late 19th century, the popularity of Brazilian peppertree seed chalcid M. Figure 1. Distribution of Brazilian peppertree as an ornamental transvaalensis, also known as the Brazilian Brazilian peppertree, plant was attributed to the numerous peppertree drupe feeding wasp, is an Schinus terebinthifolius, bright red drupes produced during the adventive species that probably arrived and drupe feeding wasp holiday season in Florida. Brazilian in Florida as a contaminant of the fruits Megastigmus transvaalensis peppertree is now recognized as a sold as pink peppercorns in gourmet in Florida. Red circles indicate highly invasive species that quickly food stores (Habeck et al. 1989). Other counties where the wasp has dominates disturbed sites as well as possible modes of arrival in Florida been collected. Map created natural communities where it forms include wasp-infested drupes of Brazil- from information obtained from dense thickets that completely shade out ian peppertrees imported as ornamental the following sources: Wunderlin and displace native vegetation. Brazilian plants (Grissell and Hobbs 2000), or and Hansen (2000), Wheeler et peppertree is the most widespread of infested drupes sold at craft stores for al. (2001) and D. H. Habeck, unpublished data. Florida’s invasive weed species (Schmitz holiday decorations (Wheeler et al. 1994), and is considered one of the 2001). most important threats to biodiversity against this highly invasive weed (Cas- because it disrupts native plant and sani 1986, Cassani et al. 1989). One Distribution animal communities. Birds occasionally of the reasons for conducting these Worldwide, the Brazilian peppertree become intoxicated following ingestion domestic surveys was to conserve seed chalcid has been reared from drupes of the drupes (or fruits) that remain on limited resources and valuable time of Schinus spp. collected in Argentina the trees for several months (Campello that would otherwise be wasted survey- (Wheeler et al. 2001), Brazil (Grissell and Marsaioli 1974). Furthermore, vola- ing for natural enemies in Brazil that and Hobbs 2000), the Canary Islands tiles produced by the flowers can cause might already be established in Florida. (Grissell 1979), Réunion, Mauritius sinus and nasal congestion in sensitive Although an extensive list of insects (Habeck et al. 1989) and South Africa, humans, and direct contact with the associated with Brazilian peppertree was where it is considered a native species plant’s sap can irritate the skin and cause compiled during these surveys, none of (Grissell 1979). In the United States, the allergic reactions similar to poison ivy. the insects identified severely damaged wasp has been reported from California The distribution of Brazilian peppertree the drupes of the plant. Because Brazil- (Harper and Lockwood 1961), Hawaii extends from the Keys to Duval County ian peppertree reproduces and spreads (Beardsley 1971), and Florida (Habeck et on the east coast and to Levy County mostly by seeds (Langeland and Burks al. 1989). In Florida, the insect has been on the west coast of Florida (Fig. 1) 1998, Tobe et al. 1998), the introduction recovered from Brazilian peppertree (Wunderlin and Hansen 2000). of a natural enemy that preferentially drupes collected in the following coun- In the 1980s, surveys of the arthropods attacks the drupes would contribute to ties: Brevard, Broward, Charlotte, Col- associated with Brazilian peppertree the biological control of this invasive lier, Dade, DeSoto, Glades, Hardee, were conducted in Florida as a first weed by limiting the production and Hendry, Hernando, Highlands, Hills- step towards developing a classical (or dispersal of the seeds. The importance borough, Lake, Lee, Martin, Orange, importation) biological control program of seed predation was recognized in Palm Beach, Pasco, Pinellas, Polk, Sara- an earlier biological control program sota, Seminole, St. Lucie, and Volusia 1Assistant Professor and Professor Emeritus, against Brazilian peppertree in Hawaii, (Fig. 1) (Wheeler et al. 2001, D. H. respectively, Entomology and Nematology Depart- and eventually led to the introduction Habeck, unpublished data). ment, University of Florida, PO Box 110620, Gaines- ville, FL 32611-0620 jcuda@ mail.ifas.ufl.edu. of the seed-feeding beetle Lithraeus atronotatus (Pic) (Coleoptera: Bruchidae) Description 2Research Entomologist, USDA, ARS Invasive Plant Research Laboratory, 3205 College Avenue, Ft. into the islands in the 1950s (Julien and Adult. Adults of the Brazilian pepper- Lauderdale, FL 33314 wheelerg@ eemail.com. Griffiths 1998). tree seed chalcid are pale yellow-brown 18 WINTER 2002 WILDLAND WEEDS 19 Figure 3. Line drawing in color (see cover photo). Males range of egg stage of in size from 2.3 to 2.9 mm whereas Megastigmus wasp. females tend to be larger. Body length Source: H. E. Milliron for female wasps ranges from 3.1 to 3.4 (1949). mm; the length of the abdomen and Figure 4. Line drawing ovipositor range in size from 1.2 to 1.4 of mature larva of and 1.5 to 1.9 mm, respectively. Almost Megastigmus wasp. half of the overall body length in females Source: H. E. Milliron is attributed to the ovipositor (Hussey (1949). 1956). Gravid females of M. nigrovar- iegatus, another Megastigmus wasp for inside the developing drupe where all Figure 5. Female which there is more published descrip- life stages of the wasp are passed. The pupa of tive information, normally contain 10 egg incubation period is short, and Megastigmus to 25 eggs (Milliron 1949). Presumably, larvae probably hatch in 4 to 5 days. wasp prior to females of M. transvaalensis are capable After several months, a single adult adult emergence. of producing the same number of eggs. emerges from the drupe. However, Note ovipositor Egg. The egg stage of M. nigrovarie- this period may be shorter in M. trans- curved over the gatus is composed of three parts: a long vaalensis as adults emerged a few back of the narrow anterior stalk, an elongate-oval weeks after flower initiation (G. S. abdomen. body, and a short spur-like posterior Wheeler, unpublished data). Prior to Source: H. E. stalk (Fig. 3) (Milliron 1949). Individual emergence of the adult wasp, it is dif- Milliron (1949). eggs range in size from 0.99 to 1.5 mm ficult to distinguish between attacked in length, are grayish white in color, and unattacked drupes because there seed production and may reduce the and the entire surface is glossy and apparently is no external evidence of spread of Brazilian peppertree into smooth, lacking ornamentation. The the insect developing inside until the natural areas where this invasive weed eggs of M. transvaalensis probably are adult chews a circular emergence hole is displacing native species. In a two- similar in shape, size and texture. in the wall of the drupe. year study, up to 31% and 76% of the Larva. The Brazilian peppertree seed The Brazilian peppertree seed chalcid Brazilian peppertree drupes were dam- chalcid presumably has five instars, apparently has two generations per year aged by the wasp during the winter the same number of instars reported that are synchronized with the winter and and spring fruit production periods, for M. nigrovariegatus (Milliron 1949). spring drupe production periods of its respectively (Wheeler et al. 2001). The Although more than one egg may be host plant. The sex ratio of wasps emerg- single seed developing inside the drupe deposited inside a drupe, the larvae ing from drupes of Brazilian peppertree also fails to germinate when damaged are cannibalistic and usually only one averaged over a two-year period was 2:1 by the wasp. larva (Fig. 4) is capable of completing (females: males) (Wheeler et al. 2001). An augmentation program is cur- its development. Occasionally, a single rently underway in the Everglades drupe will support complete develop- Host Plants National Park (G. S. Wheeler, personal ment of two larvae. The Brazilian peppertree seed chalcid communication). Wasps are being reared Pupa. After the larvae of the Brazil- is capable of developing and reproducing and released in remote areas infested ian peppertree seed chalcid attain their on plants in the genera Rhus and Schinus. with Brazilian peppertree where the maximum size, they transform into the The host range of the insect includes insect is not established. Further research pupal stage (Fig. 5) and remain in a at least three Rhus spp. native to South is needed to determine why a higher prolonged diapause (or resting) period Africa, including Rhus laevigata L. and incidence of wasp-damaged drupes was for several months. Adult emergence R. angustifolia L. (Hussey 1956, Grissell observed in Brazilian peppertree plants seems to be photoperiod-induced and 1979, Yoshioka and Markin 1991). Schinus occurring north of Lake Okeechobee occurs when the drupes containing molle L. and S. terebinthifolius, both native and in more inland rather than coastal viable pupae are exposed to short to South America, are considered novel sites (Wheeler et al. 2001). daylength (12- hr photoperiod), which host plants (Hussey 1956, Habeck et coincides with the flowering phase of al. 1989). No native members of the Acknowledgements Brazilian peppertree during the fall of Anacardiaceae, or cashew family, found We thank Howard Frank and Mar- the year (Wheeler et al. 2001). within the Florida distribution of Brazil- jorie Hoy for reviewing the manuscript ian peppertree are attacked by the wasp and Mike Sanford, Department of Ento- Life Cycle despite numerous attempts to rear the mology and Nematology, University The complete life history of M.