Helicoverpa Sea and Heliothis Phloxiphaga (Lepidoptera: Noctuidae) in the Sacramento and San Joaquin Valleys of California
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Area-Wide Pheromone Trapping of Helicoverpa sea and Heliothis phloxiphaga (Lepidoptera: Noctuidae) in the Sacramento and San Joaquin Valleys of California MICHAEL P. HOFFMANN,' LLOYD T. WILSON,2 AND FRANK G. ZALOM Department of Entomology, University of California, Davis, California 95616 J. Econ. Entomol. 84(3): 902-911 (1991) ABSTRACT In 1986 and 1987, traps baited with the pheromone of Hellcoverpa zea (Bod- die) were operated adjacent to fields of processing tomatoes (Lycopersicon escufentumMiller) in the Sacramento and San Joaquin valleys of California to determine the seasonal flight patterns of male H. zea and Hehothis phfoxtphaga Grote & Robinson. The latter species was attracted to the pheromone of H. zea and was commonly captured in traps. Results indicate there are at least two generations of H. zea per year in the Sacramento and San Joaquin valleys. In general, trap catches of H. zea increased rapidly starting in mid-August and peaked during late August or early September. The timing of trapping events, defined as first catch, first peak, initiation of late peak, and late peak, was similar among locations monitored. This indicated that regional monitoring of this pest may be feasible, although further effort is needed to define early-season events better. Males of H. phloxiphaga were captured at all locations; these were generally trapped in greatest numbers in May and usually exceeded the numbers of H. zea captured from February to June. The capture of H. phloxiphaga in traps intended for H. zea can make interpretation of trap catches difficult, especially early in the season. Moon phase did not appear to influence the timing of peaks in H. zea trap catch. KEY WORDS Insecta, Noctuidae, pheromones, tomato SEVERAL AREA-WIDE BLACKLIGHT and pheromone ever, their efforts were limited to one location in monitoring programs have been undertaken to in- the Sacramento Valley. vestigate the seasonal flight patterns of HeldothZs The density of H. zea eggs generally begins to spp. Information generated from area-wide mon- increase in early August and peaks 2-3 wk later itoring programs is useful in determining the sea- across most fields of processing tomatoes (Lyco- sonal occurrence (Goodenough et al. 1988), move- persicon esculentum Miller) in the Sacramento ment (Schneider et al. 1989), migration (see review Valley (Hoffmann et al. 1990). Roltsch & Mayse by Fitt 1989), and spatial distribution (Slosser et al. (1984) reported similar across-field trends in to- 1987) of Heliothis adults. Such information is use- matoes in Arkansas. Based on results from a single ful to regional pest management programs by help- season, it appears that oviposition by H. zea in ing to predict when and where infestations may processing tomatoes in the southern Sacramento occur or indicating when management tactics need Valley is positively correlated with pheromone trap to be implemented. Witz et al. (1985) found that catches of male H. zea during the period of late pheromone trap catches recorded early in the sea- July (initiation of late-season oviposition) through son were useful in predicting the subsequent sea- peak oviposition (unpublished data). A similar re- sonal population dynamics of Helicoverpa zea lationship between pheromone trap catches and (Boddie) and Helicoverpa virescens (F.)in cotton. oviposition by Heliothis spp. in cotton has been Little effort has been made in the San Joaquin or reported by Leonard et al. (1989). Because of sim- Sacramento valleys of California to monitor adult ilarities in across-field timing of oviposition in to- male H. zea using pheromone traps on an area- matoes and because of the apparent correlation wide basis, although such data could be useful in between trap catch and oviposition, it may not be improving regional management of this pest on necessary to operate traps in every field. A few several crops. Lange & Bronson (1981) reported traps may be adequate to monitor counties or that adult male and female H. zea catches in black- regions of the state. lights increased rapidly late in the season. How- Currently, pest control advisors begin sampling for eggs of H. zea at 722 degree-days (DD) (lower threshold of 10%) after planting (Brendler et al. ' Current address: Department of Entomology, Comstock Hall, 1985). This sampling commences even though it is Cornell University, Ithaca, N.Y. 14853. Current address: Department of Entomology, Texas A&M generally only those fields harvested after mid- University, College Station, Tex. 77843. August that are likely to incur economic levels of 0022-0493/91/0902-0911$02.00/0Q 1991 Entomological Society of America ~ June 1991 HOFFMANNET AL.: AREA-WIDEPHEROMONE TRAPPING OF Heliothis 903 phloxiphaga, and if H. phloxiphaga would be cap- tured in sufficient numbers to interfere with the interpretation of H. zea catches. Red Bluf? Materials and Methods chlco 4 1 Princeton Traps and Locations. Scentry Heliothis traps I Arbuckle * Woodland (Scentry Inc., Buckeye, Ariz.) (after Hartstack et Davis al. 1979) were used at all locations and were at- tached to metal stakes or fence posts, with the trap entrance about 1 m above soil level. Moths were removed from traps at least once per week. Traps were operated by U.C. farm advisors, commercial pest control advisors, or by personnel from the De- partment of Entomology, U.C. Davis. Cooperators placed captured moths in small jars containing 75% ethyl alcohol and sent them to U.C. Davis where male moths were identified to species and numbers of individuals were recorded. H. zea were distin- guished from H. phloxiphaga using characteristics described by Lange & Michelbacher (1937). Pheromone lures for H. zea consisted of rubber septa impregnated with a 3.0:0.09-mg dichloro- methane solution of Z11-16:Al and Z9-16:Al (Halfhill & McDonough 1985). Lures were pre- pared at Yakima, Wash. (USDA-ARS), and shipped Fig. 1. Map of California indicating locations at to us where they were stored at -9°C until needed. which Scentry Hellothis traps \%'ere operated in 1986 Septa were placed in the center of the large open- and 1987. In some cases, more than one trap was operated ing at the bottom of the traps and were shaded in the vicinity of the location indicated on the map. See from direct sunlight by placing them in an open- text for a complete listing of trap locations. ended section of white polyvinyl chloride (PVC) pipe (2.54 cm long, 1.91 cm diameter). In 1986 and 1987, traps were generally installed damage from N. zea (Lange & Bronson 1981). in April or May and operated until September or iiowever, if N.zea pheromone traps could be used October. Sites extended from near the southern end 10 predict or indicate the timing of activity on a of the San Joaquin Valley to near the northern end regional basis, then initiation of sampling for H. of the Sacramento Valley and encompassed a direct :pa eggs in processing tomatoes could be better north-to-south distance of about 544 kin (a range limed. from about 35" to 40" N latitude) (Fig. 1). This A potential problem in using pheromone traps investigation was originally intended to be limited for H. zcw is the unwanted capture of males of to areas where processing tomatoes were grown; Ildiothis phloxiphaga Grote & Robinson, a widely however, cooperators were available at the two (hibuted species in California (Lange & Mich- northernmost locations which were outside of the qlbacher 1937). Kaae et al. (1973) reported capture typical processing tomato production area. Traps this nonpest species in traps baited with virgin operated in 1986 or 1987 or both were located in f"de H. zea. Raina et al. (1986) determined the the following locations (km north of Arvin): Red thical constituents of the p~ieromone of H. Bluff (5.14). Chico (197), Princeton (473), College I'hlo*iphaga and further examined cross-attractan- City (426), Arbuckle (131),N.E. Yolo County (410), between these two species. Although the adult Woodland (399), E. Yolo County (396), East Davis of H. zea and H.phloxiphaga are morpho- (379), U.C. Davis (378), King Island (325), Fire- '%ically distinct (Lange 6: h4ichelbacher 1937), baugh (182), Mendota (16.i), U.C. Westsicle Field between these species becomes dif- Station at Five Points (134), Huron (114), and Arvin. ficult after moths have been in a pheromone trap The traps located at King Island and south were lor a few days. After a few days, most scales are in the San Joaquin Valley; all others to the north abraded away and identification can be accom- were in the Sacramento Valley. Traps located at p lished only by examination of male genitalia. Arbuckle and north were designated to be in the The objectives of this research were to determine northern region, and those at Firebaugh and south Ihe Seasonal flight activity of male H.zea in the were designated to be in the southern region. The Sacramentoand San Joaquin valleys of California, remaining traps were in the central region. hilar the H. zea activity was over the area Although the number and specific sites of traps the seasonal flight activity of male H. varied between years, traps were always located 904 JOURNAL OF ECONOMIC ENTOMOLOGY Vola 84, no. 3 near the locations described above. The U.C. Davis 1986 and May and June 1987, four locations during location had two traps spaced about 300 m apart; July 198i, and three locations during other months In the second analysis, the frequency of t all other locations had a single trap. Traps were rap placed within commercial agricultural areas, but catch peaks occurring during each moon phase to prevent damage from agricultural equipment, (full, last quarter, new, first quarter) were corn. they were not placed directly in crops.