Hot Peppers As a Host for the Mexican Fruit Fly Anastrepha Ludens (Diptera: Tephritidae)
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Scientific Notes 603 HOT PEPPERS AS A HOST FOR THE MEXICAN FRUIT FLY ANASTREPHA LUDENS (DIPTERA: TEPHRITIDAE) DONALD B. THOMAS United States Department of Agriculture, Agricultural Research Service Kika de la Garza Subtropical Agricultural Research Center, 2413 E. Hwy 83, Weslaco, TX 78596 On the 28th of April, 2003, a shipment of man- will breed in rotting vegetable matter including zano chile peppers (Capsicum pubescens Ruis & chile peppers, but these are non-pest species, and Pavon cv Rocoto) entering the United States at this incident involved sound fruit (Fig. 1). No Pharr, Texas, was found to be infested with insect dipterans are listed as economic pests of chile pep- larvae. USDA inspectors first noted maggots pers by English & Lewis (2004). Baker et al. crawling in the bed of the truck underneath the 16 (1944) cited incidents of A. ludens in “bell peppers cardboard boxes (240 Kg) containing the chile pep- and chili peppers” and there are equally ambigu- pers. Further inspection confirmed that the larvae ous reports of another tephritid, Zonosemata vitti- were in, and emerging from, the fleshy pods. Two gera (Coquillet), taken in “peppers” (Cole 1969). of the larvae were immediately preserved in alco- Zonosemata electa (Say) is known as the “pepper hol while 50 more larvae were kept alive. All spec- maggot” (Peterson 1960) and has been reared imens were hand carried to the nearby USDA- from “Capsicum annuum L.” (Smith & Bush ARS laboratory in Weslaco, Texas for identifica- 1999). The latter solanaceous plant species in- tion. Microscopic examination established that cludes both hot and sweet peppers. The usual host the larvae had the morphological characteristics plants for Zonosemata spp. are members of the ge- of the Mexican fruit fly, Anastrepha ludens (Loew), nus Solanum (Norrbom 2002). To confirm the spe- as described by Steck et al. (1990). However, this cific identity of the larvae infesting the manzano identification was tentative because there are ap- peppers, the available live larvae were placed in proximately 200 described species in this genus culture and maintained in the laboratory to obtain (Norrbom et al. 1999) and the larval stages are adults. Larval specimens that died before pupari- known for only thirteen. Several kinds of maggots ation were preserved in alcohol and sent to Bruce Fig. 1. Larvae of Anastrepha ludens infesting a manzano pepper intercepted at the U.S.-Mexico border. Note the black seeds characteristic of Capsicum pubescens. 604 Florida Entomologist 87(4) December 2004 A. McPheron of Pennsylvania State University for Nonetheless, the more intense inspections failed to genetic fingerprinting. Based on sequencing of a result in further interceptions of infested chile pep- fragment of the mitochondrial 16S ribosomal RNA pers of any species. gene, the specimens were indistinguishable from In order to further our understanding of hot sampled populations of A. ludens (Silva et al. peppers as potential hosts of A. ludens, a series of 2001). This gene has been studied and is diagnos- experiments were conducted. To provide material tic for 40 of the most important species of Anas- for these tests, arrangements were made with the trepha (McPheron et al. 1999). International Services branch of USDA-APHIS to A total of 42 larvae pupariated and of these provide fresh manzano peppers from Mexico, inas- eleven eclosed as adults. All were A. ludens, a de- much as these peppers are not commercially culti- termination confirmed by Allen L. Norrbom of the vated in the United States. One box (15 kilos) of USDA-ARS Systematic Entomology Laboratory manzano peppers was acquired at a market in in Washington D.C. At Weslaco, all non-eclosed Mexico City and shipped by air to our satellite lab- puparia were examined and the number of tu- oratory in General Teran, Nuevo Leon, Mexico. On bules on the anterior spiracles did not differ from arrival, technicians discovered that these peppers those in puparia of A. ludens. On the 2nd of May, also were heavily infested with A. ludens larvae. the 16 boxes of embargoed manzano peppers were Questions raised by these incidents include taken to a disposal site for burial. At that time ad- whether other species of hot peppers are suscep- ditional larvae were seen egressing the fruit and tible hosts for oviposition by A. ludens; whether some of these were collected as voucher speci- the host status of chile peppers is determined pri- mens by USDA-APHIS personnel. marily by physiological or ecological factors; Because records indicated that shipments of whether the flies infesting the manzano peppers manzano peppers had cleared customs in the days were adaptively different from other populations immediately previous to the discovered infesta- of A. ludens (host-races); and are flies reared on tion, an effort was made to track these shipments chile peppers reproductively competent. to their destinations. Manzano peppers infested The flies used in these experiments were from with larvae were recovered from Chicago, IL; De- two sources. One line was established from adults troit, MI; Atlanta, GA; Richmond, VA; and at two reared from the initial interception of manzano retail outlets in Pinellas County, FL. Two weeks peppers at Pharr, Texas in April 2003. The second later, on 16 May 2003, an adult A. ludens was source was the research colony of A. ludens main- found in a fruit fly trap in Orlando, FL. Because tained at the USDA-ARS laboratory in Weslaco, the previous detection of this species in Florida Texas. This laboratory colony originated with was in Sarasota in 1972 (Steck 1998) the new de- specimens collected from yellow chapote, Ca- tection was presumed to have originated with the simiroa greggii (S. Wats.) Chiang, in Nuevo Leon, infested manzano pepper shipments. Mexico in 1994. Yellow chapote is a wild Rutaceae Anastrepha ludens is a major pest of citrus and and the primary native host of A. ludens in Mex- mangoes with a wide host range known to include ico (Plummer et al. 1941). at least 60 varieties of fruit (Norrbom & Kim 1988). Two sets of experiments were conducted. In Sweet peppers, cultivars of Capsicum annuum the first set of tests the flies were offered fresh that lack the alkaloid capcaicin, are occasionally fruits in both choice and non-choice configura- infested by A. ludens, but confirmed records of hot tions under laboratory conditions. In the second peppers (cultivars containing capcaicin) as larval set of experiments the flies were released into a hosts have not been reported. According to the in- green house within the Weslaco quarantine facil- spectors who first discovered the infested ship- ity with potted pepper plants to determine the ac- ment, just standing next to the open truck with the ceptability of the living, undehisced pods as manzano peppers caused their eyes to water. On oviposition sites. the Scoville scale manzano peppers (also marketed The Weslaco colony flies were reared on an ar- as “rocoto” or “perón” peppers) are rated at 12-30K tificial larval media described by Spishakoff & (by comparison, jalapeños are rated 2.5-8K Scoville Hernandez-Davila (1968). Because wild flies are Units) (DeWitt & Gerlach 1990). Although man- reticent to lay eggs in the artificial substrate used zano peppers are a low volume specialty item, ac- in mass-rearing colonization, the flies bred from counting for much less than 1% of all peppers the manzano peppers were offered fresh fruit for exported by Mexico (McClure 2003), chile pepper oviposition. Placed in the cage with these adults species in aggregate are a major commodity im- were manzano peppers, bell peppers, grapefruit ported to the United States. Because of its non-host and mangoes. Although the flies were observed status, chile pepper importations had not required “stinging” all of these fruits with the aculeus, only a disinfestation treatment or more than cursory in- the mangoes became infested. spection. In response to this incident, higher than Flies and fruit were distributed among sepa- normal inspection rates were implemented on all rate fine mesh screen cages, 30 × 30 × 30 cm in di- peppers, and a stricter protocol established for mension. The cages were maintained in an shipments destined to citrus producing states. environmental chamber at 24°C, 12:12 DL. Each Scientific Notes 605 cage contained a glass vial filled with distilled wa- alone or in combination with the mango. This test ter plugged by a cotton wick and an open petri was also conducted with the Nuevo Leon strain dish with granulated sugar and torula yeast. All with the same numbers and conditions as the pre- flies were females of 15 d age that had been caged vious test. with males up until the time of the experiment. This test was conducted with progeny of the Females are capable of laying eggs at age 11 d larvae found in the intercepted manzano chile when maintained at 24°C (Liedo et al. 1993). The peppers at Pharr in April 2003. These were test fruits were set in the cage on short wooden reared in mangoes maintained under a constant pegs so that flies could access the bottom side of temperature and light regime. Both sexes of adult the fruit. Aluja et al. (1999) cite field observations flies were maintained together until the flies were that A. ludens always “sting” oranges on the bot- 11 d old. The test was conducted in the ARS quar- tom side. antine security green house with naturally cy- Test 1: This test used the Nuevo Leon strain cling temperatures and light regime. Ten females from the USDA colony. Ten female flies were re- were released into a large screened cage (78 × 48 leased into each cage. In order to approximately × 32 cm) containing three potted chile pepper equalize surface area of fruit, one sour orange plants with mature fruit.