Rev. Soco Entomol. Argent. 56 (1-4): 151-1-53,1997

Population parameters of Epinotia aporema (: ) on soybean

SÁNCHEZ, NORMA E., PATRICIA C. PEREYRA, AND MARtA V. GENTILE Centro de Estudios Parasitológicos y de Vectores (CEPAVE), calle 2 no. 584, 1900 La Plata, Argentina.

o ABSTRACT. Epinotia aporema (Walsingham) is a majar soybean pest in Argentina and Brazil. Larvae feed mainly on buds causing serious damage. An age-stage specific life table including both sexes and variable develop­ ment rates of individuals was constructed based on laboratory data. High mortality (82 %) was observed during the egg and larval stages. Mean fecun­ dity was 119 eggs/female and the fecundity rate was maximal from days 42 to 44. The reproductive value reached a peak of 90 at the 38th day. The values of r, Ro, and T were 0.057, 9.52, and 43.74, respectively.

RESUMEN. Parámetros poblacionales de Epinotia aporema (Lepidoptera: Tortrici.dae) en soja. Epinotia aporema (Walsingham) es una importante plaga de la soja en la Argentina y Brasil. Las larvas se alimentan principalmente de brotes causando serios daños. Se construyó una tabla de vida en laboratorio incluyendo ambos sexos y tasas de desarrollo variables de los individuos. Se observó una alta mortalidad (82 %) en los estados de huevo y larva. La fecun­ didad promedio fue del19 huevos/hembra y la tasa de fecundidad fue máxima entre los días 42 y 44. El valor reproductivo a lcanzó un valor de 90 el día 38. Los valores de r, Ro y T fueron de: 0,057, 9,.52 Y43,74, respectivamente. O

INTRODUCTION MATERIAL AND METHODS

The budborer Epinotia aporema (Walsingham) Larvae were collected on soybean, Glvcine max occurs from the southern United States to Argen­ (Merrill), in lhe Experimental Field Station "lng. Julio tina (Correa Ferreira,1980; Ripa, 1983) and is a Hirschhorn" (Faculty of Agronomical and Forestry major soybean pest in Argentina (Rizzo, 1972; Sciences, Nalional University of La Plata) in Los lannone & Parissi, 1979) and Brazil (Correa Ferreira Hornos (Buenos Aires province, Argentina). They & Smith, 1976; Panizzi et el., 1977). The larvae were maintained in the laboratory until they reached feed primarily on vegetative buds and can also bore the adult stage and eggs were laid. An initial cohort into stems and floral buds. There are four or five of 50 eggs was placed individually in Pelri dishes generations per year and at least two of them occur (10 cm diamcrer), with rnoistened filterpaper. Newly on soybean, the others on different legume host hatched larvae were fed daily with soybean buds plants (Olalquiaga Fauré, 19.53; Caballero,1972; and feces removed. Pupae were sexed according Pereyra & Sánchez, unpublished data). The boring to Morey (1972) and paired. Each pair was placed behavior and the existence of a Iternative host plants in a plastic cylinder (9..5 cm diameter, 23 cm height). make control measures very difficult. Despite of the As adults emerged, fresh fully expanded soybean economic importance of this , very little is leaves placed in water were provided for oviposi­ known about its biology (Morey,1972; Correa tion. Adults were fed with a sucrose solution (15 Ferreira, 1980) and population ecology (Pereyra el %). Survivorship and fecundity were registered ev­ el., 1991; Sánchez el el., 1991). ery 24 h. The experiment lasted from February 13 In order to construct a model that contributes lo April 4 and was heId under natural light condi­ to the management of Epinotia aporema, a series of tions of 13: 11 (L:D). Average lemperature was 2.5 studies were initiated about plant-herbivore inter­ ::t 3 "C and relalive humidity was not controlled. An action (Pereyra el al., 1991; Sánchez et el., 1991), age-slage life table was constructed including both nutritional ecology (Pereyra & Sánchez, unpub­ sexes and variable developmenl rates among indi­ lished data), and population dynamics. In this pa­ viduals as proposed by Chi & Liu (198.5) and Chi per we report population parameters of this spe­ (1988). This method describes the population struc­ cies on soybean under laboralory conditions. ture based on age-c1asses and stages by construct- Rev. Soco Entomol. Argent. 56 (1-4), 1997 ing three matrices: a growth rate matrix, a develop­ ment rate rnatrix, and a fecundity matrix. Survival E rates are considered to be a function of growth and development rates and both males and females are included. Egg survival was not daily monitored, and was estimated from the number of newborn larvae. Egg mortality was assumed to occur on the last day of the stage. Mean developmental time of stages, maximal adult longevity, mean length of life of the cohort, fecundity (nurnber of eggs per fe­ male), and preoviposition and oviposition periods, were estimated under similar conditions. The fol­ lowing population parameters were computed: 1', the intrinsic rate of increase (instantaneous rate of Fig. 2. Age-stage specific survivorship of E. aporema. E: eggs, L: larvae, P: pupae, F: adult female, and M: change of population size per individual); Ro, the adult maleo net reproductive rate (mean number of offspring per individual during its life): T, the mean genera­ and female are economically important. For these tion time (average time between two successive reasons, Chi and Liu's method seems to be more generations), and the age-stage reproductive val­ realistic and more appropriate for practical appli­ ues (contribution to the future population that one cation in pest management, because it takes vari­ individual will make) (Pianka, 1983). A Jacknife ability in development rates among individuals into method (Caswell, 1989) was used to estimate varia­ account, and deals with the total population. Age­ tion in 1', Ro, and T. stage specific reproductive values increased from the egg to the adult, reaching a peak at 3 8 days (Fig. 3). These curves present low values at the egg and RESUI.TS AND DISCUSSION larval stages, increasing abruptly in the pupal and

Survivorship (Ix)and age specific fecundity (rnx) 100 curves are illustrated in figure 1. High mortality was fIl observed in the egg and larval stages (22 % and 60 (1) 80 ;:l % respectively). Similar results were obtained by Ripa iil :> (1983) and by Pereyra & Sánchez (unpublished data) Q) 60 :> for larvae reared on artifítial diets and on different '+l fresh legumes, respectively. Maximal fecundity rate ~ '"O 40 (mean number of eggs per individual) was observed o 1-0e, during the period of 42nd to 44th day (Fig. 1). ~ 20 Age-stage survivorship curves are shown in fig­ E ure 2. Due to the variation in individual develop­ O ment rates, stage overlapping was observed, par­ 10 20 30 40 50 60 age (days) ticularly between larvae and pupae. Our field ex­ perience indicates that overlapping of stages in Fig. 3. Age-stage specific reproductive values of E. natural populations is common, and thatboth male aporema. E: eggs, L: larvae, P: pupae, F: adult female.

adult stages. These results suggest that an optimal --_.•_---_. - 14 timing of control of f. aporema should be the larval 1.0 12 stage, because not only present damage could be e:::-x 10 x avoid, but also would prevent the population to e, 0.8 3 reach its highest reproductive values. :.E 8 fIl Mean development time is presented in Table 1-0 0.6 .e- o :> 6 :B L Larvae were all born at the same time, so the '1:'" § 0.4 u development time is constant. Results on adult lon­ § 4 ...... (1) fIl gevity, mean length of the cohort Iife,fecundity and 0.2 2 length of the preoviposition and oviposition peri­ O O ods are summarized in Table 11. Table 111 shows 10 20 30 40 50 60 mean population parameters (1', Ro, and T) and the age (days) standard errors generated through Jacknife method. Fig. 1. Survivorship (Ix) and age specific fecundity Because of the lack of studies, it is difficult to (mx) curves of E. aporema. compare the biotic potential of f. aporema under

152 SÁNCHEZ, N. E. et al., Epinotia aporema

Table I. Mean developmental time (days) of stages los semilleros de alfalfa y trébol rosado en Chi­ of E. aporema. le. Rev. Perno Entomo/. 15: 201-214. CA5WELL, H.1989. Matrix popu/ation mode/s. Sinauer Egg Larva Pupa Adult Assoc., Massachusetts. X 7.00 18.00 11.00 19.50 eHI, H. 1988. Life-table analysis incorporating both S. E. 0.00 0.81 1.09 1.28 sexes and variable development rates among n 39 9 6 6 individuals. Environ. Entomo/. 17: 26-34. ------_._----- CHI, H. & H. Liu. 1985. Two new methods for the study of population ecology. Acad. Sin. Table 11. Life cyele data for E. aporema under labora­ Bul/. Inst. Zoo/. 24: 225-240. tory conditions. ------_._._------CORREA FERREIRA, B. S.1980. Sampling Epinotia apore­ Maximal adult longevity 23 (male), 21 (female) ma on soybean. In: Kogan, M. (ed.), Sampling (days) Methods in soybean entomology, Springer Ver­ lag, pp. 374-38l. Mean length of the cohort life 20.20 ± 2.12 CORREA FERREIRA, B. S. &J. G. SMllH.1976. Ocorrencia (days) (X ± S.E.) e danos de Epinotia aporema {Walsingham, 1914} {Lepidoptera, Tortricidae} em soja. An. Fecundity (No. eggs / female) 119.00 ± 47.30 Soco Entomo/. Bras. 5: 74-78. (X ± S.E.) (n = 4 females) IANNONE, N. & R. PARISSI. 1979. Importancia del daño Preoviposition period (days) 3.25 ± 0.62 del barrenador del brote Epinotia aporema (X ± S.E.) (n = 4 females) (Wals.) (Lepidoptera: Grapholithidae) en rela­ ción a la cosecha mecánica de la soja. Carpe­ Oviposition period (days) 12.25 ± 1.18 ta Produc. Veg. 18, INTA Pergamino, 3 pp. (X ± S.E.) (n = 4 females) ._------MOREY, es. 1972. Biología y morfología larval de Epinotia aporema {Wals.} {Lepidoptera, Oleth­ reutidae}. Univ. Rep. Fae. Agron. Montevideo Table 111. Mean population parameters of E. aporema and standard errors estimated by Jacknife method. Bo/. 123: 14pp. OLALQUIAGA FAURE, G.1953. Plagas de las leguminosas Parameier Mean s. E. en Chile. Bot. Fitosanit. FAO 1:174-176. PANIZZI, A. R., B. S. CORREA FERREIRA, D. L. GAllONI, E. B. r (day') 0.0570 0.0175 OllVEIRA, G. e NEWMAN & S. G. TURNIP5EED.1977. Ro (offspring/individual) 9.5200 5.6800 Insetos da soja no Brasil. EMBRAPA/CNOSoja T (days) 43.74 1.24 Bo/. Tec. 1: 4-20. PEREYRA, P.e, N. E. SÁNCHEZ & M. V. GENTlLE.1991. laboratory conditions with that of other related bor­ Distribución de los huevos de Epinotia aporema ing species. Although its potential for increase does {Lepidoptera, Tortricidae} en la planta de soja. not seem to be as high as in other soybean pest Eco/. Austra/ 1: 1-S. species, like Rachip/usia nu {Noctuidae} {Sánchez PIANKA, E. E. 1983. Evo/utionary ec%gy. Harper & & Pereyra, 1995}, it is important to note that pest Row Publ., Nueva York. status is not only defined by population parameters RIPA, R.1983. Desarrollo de una dieta artificial y but also by otherbiological and ecologicaIattributes. método de crianza para Epinotia aporema The particularfeeding behavior, the parts ofthe plant {Wals.} (Lepidoptera: Olethreutidae). Rev. Peru. damaged, the phenological stage on which the at­ Entomo/. 26: 59-61. tack occurs, and the number of generations on the Rzzo, H. F. 1972. Enemigos animales del cultivo de crop, makes the injury caused by this species of soja. Rev. Inst. Bo/sa Cerea/es 28S1: 1-6. very high economic importance. SÁNCHEZ, N. E., P. e PEREYRA & M. V. GENTILE.1991. Relación entre las preferencias de oviposición de las hembras y los sitios de alimentación de ACKNOWLEDCMENTS las larvas del barrenador del brote de la soja, Epinotia aporema {Lepidoptera: Tortricidae}. We are grateful to Dr. H. Chi for providing tech­ Eco/. Austra/l : 6-10. nical support and helpful comments and suggestions. SÁNCHEZ, N. E. & P.e PEREYRA. 1995. Life tables of the soybean looper Rachip/usia nu (Lepidop­ tera: Noctuidae) in the laboratory. Rev. Soe. En­ L1TERATURE CITED toraol. Argent. 54{1-4}: 89-96.

CABALLERO, e v. 1972. Reconocimiento, biología y Recibido: 19-VII -1995 control de las principales plagas que afectan Aceptado: 19-VI-1996

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