PHYSIOLOGICAL ECOLOGY Life Table Studies of Elasmopalpus lignosellus (Lepidoptera: Pyralidae) on Sugarcane HARDEV S. SANDHU,1,2 GREGG S. NUESSLY,1 SUSAN E. WEBB,3 1 1 RONALD H. CHERRY, AND ROBERT A. GILBERT Environ. Entomol. 39(6): 2025Ð2032 (2010); DOI: 10.1603/EN10038 ABSTRACT The lesser cornstalk borer, Elasmopalpus lignosellus (Zeller) (Lepidoptera: Pyralidae) is an important pest of sugarcane (a complex hybrid of Saccharum spp.) in southern Florida. Repro- ductive and life table parameters for E. lignosellus were examined at nine constant temperatures from 13 to 36ЊC with sugarcane as the larval food source. The pre- and postoviposition periods decreased Downloaded from https://academic.oup.com/ee/article/39/6/2025/359113 by guest on 05 October 2021 with increasing temperatures and reached their minimums at 33 and 36ЊC, respectively. The ovipo- sition period was longest at 27ЊC. The mean fecundity, stage-speciÞc survival, stage-speciÞc fecundity, intrinsic rate of increase, and Þnite rate of increase were greatest at 30ЊC and decreased with increasing or decreasing temperature. The net reproductive rate was greatest at 27ЊC. The Logan-6 model best described the relationship between temperature and intrinsic rate of increase. The generation and population doubling times were longest at 13 and shortest at 33 and 30ЊC, respectively. The most favorable temperatures for E. lignosellus population growth were between 27 and 33ЊC. Life table parameters for E. lignosellus reared on sugarcane were greater than for the Mexican rice borer [Eoreuma loftini (Dyar) (Lepidoptera: Crambidae)] reared on an artiÞcial diet at 30ЊC. The intrinsic rates of increase for the sugarcane borer [Diatraea saccharalis (F.) (Lepidoptera: Crambidae)] reared on sugarcane or corn were the same as for E. lignosellus reared on sugarcane at 27ЊC, but the net reproductive rate was four times higher for the former than the latter borer species. KEY WORDS oviposition, fecundity, intrinsic rate of increase, net reproductive rate, Logan-6 Sugarcane (a complex hybrid of Saccharum spp.) is an tively (Sandhu et al. 2010). Dead heart symptoms are important crop grown in many southern temperate produced when larvae reach the center of the shoot and through tropical regions of the world (United States damage or sever the youngest leaves or apical meristem. Department of Agriculture [USDA] 2008). Florida, Nonlethal damage is caused when larvae only chew a few Louisiana, Texas, and Hawaii are the main sugarcane millimeters into the shoot evidenced by several symmet- producing states in the United States. Florida was the rical rows of holes revealed as the leaves emerge from the leading sugarcane producing state in the United States whorl. Larval feeding damage reduces plant stand and in 2008 with 401,000 acres of sugarcane valued at vigor, sugarcane photosynthesis, number of millable $398.9M (USDA 2008). The lesser cornstalk borer, Elas- stalks and sugar yield (Carbonell 1977). mopalpus lignosellus (Zeller) (Lepidoptera: Pyralidae), Reproductive studies of the lesser cornstalk borer is a polyphagous, semisubterranean pest that is widely have been conducted on cowpeas or southern peas distributed in United States and Central and South (Luginbill and Ainslei 1917, Dupree 1965), peanuts America (Heinrich 1956, Genung and Green 1965, (King et al. 1961), soybean (Leuck 1967), and sugar- Chang and Ota 1987). Eggs are deposited mostly on the cane (Carbonell 1978). In all these studies, tempera- soil surrounding plants. Larvae bore into sugarcane ture and relative humidity were allowed to vary with stems below the soil surface and produce a silken tunnel the climatic conditions. Stone (1968) and Mack and at the entrance hole outward into the soil from which Backman (1984) reported the longevity and oviposi- they attack the plants, as well as rest, molt and pupate tion rates of E. lignosellus on an artiÞcial diet under (Schaaf 1974). E. lignosellus requires 548DD to complete controlled environmental conditions. However, quan- development on sugarcane with lower and upper devel- titative information on life table parameters, such as opmental thresholds estimated at 9.3 and 37.9ЊC, respec- intrinsic rate of increase (r), net reproductive rate ␭ (R0), Þnite rate of increase ( ), mean generation time 1 Everglades Research & Education Center, University of Florida, (T), and population doubling time (DT) was not pub- Institute of Food and Agricultural Services, 3200 E. Palm Beach Road, lished in their studies. Belle Glade, FL 33430. Life tables are powerful tools for analyzing and 2 Corresponding author, e-mail: hardy@uß.edu. understanding the impact of external factors such as 3 Entomology and Nematology Department, University of Florida, Institute of Food and Agricultural Services, P.O. Box 110620, Gaines- temperature on the growth, survival, reproduction, ville, FL 32611. and rate of increase of insect populations (Sankepe- 0046-225X/10/2025Ð2032$04.00/0 ᭧ 2010 Entomological Society of America 2026 ENVIRONMENTAL ENTOMOLOGY Vol. 39, no. 6 rumal et al. 1989). The intrinsic rate of increase can and were counted using a hand lens. Fecundity was vary with the larval host or diet (Carey 2003). For reported as the number of eggs deposited by an indi- example, female Helicoverpa assulta Guenee (Lepi- vidual female during her entire life period. Age-spe- doptera: Noctuidae) reared as larvae on artiÞcial diet ciÞc female survival (lx, percentage of females alive at had signiÞcantly greater r values than females reared speciÞc age x) and age-speciÞc fecundity (mx, number as larvae on pepper (Capsicum frutescens L.) (Wang et of female offspring produced by a female in a unit of al. 2008). To predict the lesser cornstalk borer popu- time) were recorded for each day (x) they were alive. lation parameters on sugarcane, it is important to study The lx and mx values were calculated using results from its life history on the same host. Development and the lesser cornstalk borer immature development, sur- survivorship rates for E. lignosellus reared on sugar- vivorship, and sex ratio studies conducted concur- cane at constant temperatures were determined in a rently under the same environmental conditions recent study (Sandhu et al. 2010). The purpose of this (Sandhu et al. 2010). Age speciÞc fecundity was cal- experiment was to measure the effect of a range of culated as (f/(m ϩ f)) ϫ n, where f ϭ number of constant temperatures on reproductive (preoviposi- females, m ϭ number of males, and n ϭ number of Downloaded from https://academic.oup.com/ee/article/39/6/2025/359113 by guest on 05 October 2021 tion, oviposition, postoviposition periods, and fecun- offspring. The lx and mx were calculated for each ␭ dity) and life table parameters (r, R0, ,T,and DT)of cohort of 10 females. Data from pairs of adults in which the lesser cornstalk borer reared on sugarcane. either of the sexes died before the start of egg depo- sition were excluded from data analysis. Age-speciÞc survivorship curves were constructed using l and m Materials and Methods x x values for cohorts at each temperature treatment. Reproductive Parameters. Preoviposition, oviposi- Life Table Parameters. The age-speciÞc life table tion, postoviposition periods, and fecundity for the method was used to calculate the life table parameters lesser cornstalk borer were determined at nine con- for the lesser cornstalk borer at each of tested tem- stant temperatures [13, 15, 18, 21, 24, 27, 30, 33, and peratures (Birch 1948). The intrinsic rate of increase 36ЊC(Ϯ0.05ЊC)] at 14:10 (L:D) and 65Ð70% RH in (r) was calculated through iteration of the Euler- Α -rx ϭ temperature controlled chambers to construct time- Lotka equation ( e lxmx 1). The lx and mx values ϭ speciÞc life tables. The range of tested temperatures were used to calculate the net reproductive rate (R0 Α was selected based on those experienced by lesser lxmx, mean number of female offspring/female) and ϭ Α Α cornstalk borer in sugarcane in southern Florida. the mean generation time (T (xlxmx)/ (lxmx), Adults were obtained from immatures reared on sug- mean age of the mothers in a cohort at the birth of arcane used for companion developmental studies female offspring). The values for r at each tempera- conducted at the same temperatures and relative hu- ture were used to calculate the Þnite rate of increase midity as indicated above (Sandhu et al. 2010). Larvae (␭ ϭ er, the number of times the population multiplies were reared on sugarcane shoots (variety CP 78Ð1628, in a unit of time) and population doubling time (DT ϭ 4Ð5 leaf stage) placed horizontally in plastic contain- ln (2)/r, the time required for the population to dou- ϫ ϫ ers (30 15 10 cm) with a thin layer of vermiculite ble). To compare the thermal sensitivities of r and R0, covering the base of each shoot with Þve shoots per we plotted the relative values of these alternative container. Pupae were collected from each plastic Þtness measures against the tested temperatures. The container and placed on moistened paper towels in relative values were calculated by dividing the calcu- petri dishes. Ten male:female pairs of newly emerged lated values of each parameter at each temperature by adults (Ͻ12 h old) were Þrst released into each of their respective maximum values. three oviposition cages (17 ϫ 17 ϫ 17 cm) for mating. Model Evaluation. A nonlinear distribution was ob- Adults were provided with a 10% honey solution for served when r was plotted against the temperature feeding, because sugarcane does not produce a food treatments. To Þnd an equation that best Þt the ob- source for adults. After 24-h, pairs were moved to served relationship between r and temperature, six transparent plastic cylinders (one pair per cylinder) nonlinear models [Brie`re-1, Brie`re-2, Logan-6, Lactin, (11 cm length and 5 cm diameter; Thornton Plastic Taylor, and polynomial (fourth order) models] pre- Co., Salt Lake City, UT) lined with tubular synthetic viously used by us (Sandhu et al.