FALL ARMYWORM! OVIPOSITION AND EGG DISTRIBUTION ON RICE

FALL ARMYWORM! OVIPOSITION AND EGG DISTRIBUTION ON RICE Alberto Pantoja,' C. M. Smith,3 and J. F. Robinson 4 Abstract: Oviposition by the fall armywonn, Spodoptera {rugiperda (J. E. Smith), was studied on selected United States rice cultivars. "Chinese" and "Saturn" rice were highly preferred, while oviposition was Iowan "Bellemont" and "Lacrosse." Foliage was preferred over stems, and the top leaf surface was preferred over the bottom. Most eggs were laid on leaves two, three, fouf, as compared to leaves one, five, six, seven, eight, and nine. Key Words: Fall armyworm, Spodoplera {rugiperda, rice, Oryza sativa, oviposition, preference. J. Agric. Entomol. 3(2): 114-119 (April 1986) In the United States, fau armyworm, Spodoptera {rugiperda (J. E. Smith), damage to rice, Oryza satiua L., was reported 8S early as 1845 (Luginbill 1928). Currently, S. frugiperda is 8 major pest of rice in Central America (Navas 1966). Puerto Rico (Chandler et al. 1977) and an occasional pest of rice in the United States (Bowling 1978)_ Studies by Combs and Valerio (1980) and Pitre et al. (1983) have investigated S. frugiperda oviposition on other crops. but no information on S. {rugiperda oviposition on rice exists. Our objectives were to determine the preferred oviposition site of S. {rugiperda on the rice plant and oviposition preference among selected rice cultiv8fs. MATERIALS AND METHODS Insects Adults used in the experiment were obtained from a Puerto Rican strain of S. {rugiperda (Pantoja et al. 1985) in culture at the Louisiana State University Department of Entomology. LaIVae were reared on pinto bean diet (Bowling 1967) following the procedure described by Perkins (1979). Larvae and adults were maintained at 26 ± O.SoC, LD 14:10 photoperiod, and SO ± 10% RH. Sexed pupae (n = 75 of each sex) were placed in moist vermiculite in one liter cardboard containers. Adult emergence was monitored daily and containers were transported to the greenhouse (2S ± SoC, 70 ± 10% RH) after approximately ls% of the adults emerged. Containers with pupae and adults were suspended from the top of 8 2 X 2 X 1.5m (height X width X length) cage inside the greenhouse. The cage bottom was lined with four mil clear plastic sheeting to hold water (2 ern deep). Light (LD 14:10 photoperiod) was supplied with eight Sylvania(!) plant growth bulbs on top of the cage. A container of 50% beer. 25% water. and 25% honey solution w/l g ascorbic acid/goo ml solution was suspended from the top of the cage in a plastic 30 ml 1 LEPIDOPTERA: Noctuidae. Accepted {or publication 28 April 1986. 2 Curront address: Crop Protection Department, Puerto Rico Ai,'licultural EJ:pcriment Station, P. O. Box 21360, Rio Piedras, Puerto Rico 00928. 3 DCI)artment of Entomology, Louisiana Agricultural EJ:perimellt Station, Louisiana State University Agricultural Center, BatoD Rouge, LA 70803. 4 USDA.ARS Rice Entomologist, Louisiana State University Research Station, Crowley, LA 70526. 114

PANTOJA et at.: Fall Armyworm Oviposition on Rice 115 diet cup containing a ceuucotton wick, to supply food to adults. Fresh solution was supplied daily until the experiment was tenninated. Egg Mass Distribution Test Seeds of "Mars," a commonly-planted medium-grain United States rice cultivar, were genninated in 100 X 10mm plastic petri dishes on moistened Whatman #3 mter paper and transplanted (n-= 40 pots; 2 plants per pot) into soil in 15 cm diameter X 25 cm tall plastic pots. Plants at the 9.0 stage of growth (ninth leaf of main stem fully elongated, ca. 160 cm high) (Yoshida 1981) were placed inside each of two oviposition cages (n = 20 pots per cage) and adult S. frugiperda were released following the procedure described above. The number of egg masses per plant, position of each egg mass on the upper or lower side of each leaf and the position of each mass on the plant (leaf number) were recorded. Leaf numbers were assigned following the method of Yoshida (1981) where lear one is the first leaf to emerge, and leaf two the second leaf to emerge, etc. Cultiuar Preference Test Twenty-five United States rice cultivars were obtained from the Louisiana State University Rice Research Station, Crowley, Louisiana. Seeds were germinated and transplanted as described above into 5 em X 5 cm diameter plastic pots (n 5 pots per cultivar, 2 plants/pot). When plants reached the 5.0 (Yoshida 1981) stage of growth, all 125 pots were placed inside a single oviposition cage in a completely randomized design with five replications and moths were released. Plants were inspected daily for egg masses, and each experiment was tenninated three days after the first day on which oviposition occurred. In the cultivar preference test, counts of the number of egg masses were subjected to the SAS General Linear Models (GLM) procedure (Freund and Littell 1981). Means were separated by Duncan's multiple range test at the 0.05 level of probability (Duncan 1955). RESULTS Egg Mass Di!;lribution 7'est A total of 163 egg masses was deposited on test plants. Leaves two, three. and four were preferred over leaves one, five, six, seven, eight, and nine (Fig. 1). Sixty-eight percent of the egg masses on foliage were located on the underside of the leaf and 32% on the upperside. Eighty-six percent of the egg masses were deposited on foliage, while only 14% were laid on the stem. Most egg masses on the stems were located in the lower third of the plant fobage, ca. 25 cm from ground level. Cultivar Preference Test Egg masses were placed by moths on plants of all cultivars provided, but significant (P < 0.05) differences occurred in the number of egg masses per plant among cultivars (Table 1). Since plants were only in the five leaf stage, differences between cultivars in plant height were minor. Tillering had just begun; therefore, there were no differences in canopy density between seedlings. Differences in leaf blade width were not recorded. Oviposition ranged from 0.2 to 3.4 egg masses per plant. The mean numbers of egg masses on "Bellemont" and "Lacrosse" were significantly (P 0.05) lower than those on "Saturn" and "Chinese."

t :z: 5 ca.. " en en SI 41 ; 31 21, = :z: 1:0< 1' - :bl 1 2 3 of 4 5 LEAF... 6 7 8 9 NUMBER - '" -,.. > ':l o - '" - " o,... 0- S '" Z? - '0 -::: '".e '" Fig. 1. Distribution of Spodoptera (rugiperda egg masses among leaves of "Mars" rice plants. Boton Rouge, LA - 1984.

PANTOJA ct al.: Fall Armyworm Oviposition on Rice 117 Table 1. Oviposition by Spodoptera {rugiperda adults on selected United States rice cultivars. Baton Rouge, LA - 1985. Cultivar name Bellemont Lacrosse Pecos Rexark Lemont Arkrose Colusa Rexoro Labelle Calrose 76 Lebonnet Calrose Bluebelle Toro Fortuna Caloro LA 110 Newrex Magnolia Della Gutfrose B1uerose Honduras Saturn Chinese Mean- no. egg masses per plantt 0.2a 0.3a O.4ab 0.6ab 0.8ab 0.8abe 1.0abe 1.2abe 1.2abe 1.2abe l.4abe l.4abe l.5abe l.6abe l.6abe 2.0abc 2.5abc 2.8abe 2.8abe 3.0be 3.4c n - 5 replicates; 2 plunts per replicate. t Menna with a letter in common are not significantly (P = 0.05) different According to DUllcun's multiple range test (DuncAn 1955). DISCUSSION Egg mass distribution of S. frugiperda on rice (leaf top> leaf bottom> stem) was similar to that reported by Pitre et ai. (1983) on com, cotton, sorghum, and soybean. Reduced levels of oviposition by S. {rugiperda on leaf one was probably related to plant age. When moths were released in the cage, most plants were in the 9.0 stage of growth and leaf one was partially dry and chlorotic. The senescing condition of leaf one in our test apparently did not provide an attractive site for oviposition. Pitre et al. (1983) demonstrated that S. {rugiperda adults prefer dark green plant coloration for oviposition. Our observation of high numbers of egg masses in the middle section of the rice plant was consistent with the results of Pitre et a1. (1983), who recorded a large number of egg masses on leaves between nodes 3 to 9 of corn, cotton, sorghum, and soybean plants. The cultivars "Chinese" and "Saturn" were highly preferred for oviposition by S. {rugiperda adults, while oviposition was low on "Bellemont" and "Lacrosse."

118 J. Agric. Entomol. VoL 3. No.2 (1986) However, choice tests with Larvae have shown "Bellemont," "Lacrosse," and "Saturn" to be heavily defoliated by S. {rugiperda while defoliation on "Chinese" was low (pantoja et al. 1986). Although these defoliation experiments were separate from oviposition preference tests, plants were approximately the same age. Thus, adult ovipositional preferences do not necessarily correlate with larval food preferences. Luginbill (1928) reported indiscriminate oviposition by S. frugiperda adults among corn, wheat, sugarcane, alfalfa, cowpcas, tobacco, crabgrass, and Bennudagrass. Pitre et ai. (1983) reported differences in oviposition by S. frugiperda among five crops, but no larval preference studies are available with these crops to correlate oviposition preference with larval preferences. Results of this study indicate that some rice cultivars which suffer low S. {rugiperda larval defoliation are preferred by S. {rugiperda moths for oviposition, and this oviposition may contribute to S. frugiperda population outbreaks on plantings of these cultiv8fs. Additional studies are needed to examine S. frugiperda larval development on these cultivars preferred for oviposition. Information provided here will also benefit field survey personnel, since precise sites for sampling S. {rugiperda egg masses on rice plants have now been determined. ACKNOWLEDGMENTS The authors are grateful to Dr. K S. McKenzie, Louisiana State University Rice Research Station at Crowley, LA, for providing seed for the test and to R. A. Goyer, E. A. Heinrichs, and T. J. Riley for critical review of the manuscript This research was supported by the Louisiana Agricultural Experiment Station and USDA Special Grant 85-CRSR-2-262L REFERENCES CITED Bowling, C. C. 1967. Rearing two lepidopterolls pests of nee on a common artificial diet. Ann. Entomol. Soc. Am. 60: 1215-1216. Bowling, C. C. 1978. Simulated insect damage to rice: Effects of leaf removal. J. Econ. Entomol. 71: 377-378. Chandler, J. V., F. Abruna, J. Lozano, S. Silva, A. Rodriguez, and C. T. Ramirez. 1977. Cultivo intensivo y perspectivas del arroz en Puerto Rico, Univ. de Puerto Rico, Estacion Ex:perimental Agricola, Boletin 25. Combs, R. L. t and J. R. Valerio. 1980. Oviposition by the fall armyworm on four varieties of bermudagrass. J. Ga. Entomol. Soc. 15: 164-167. Duncan, D. B. 1955. Multiple range and multiple F tests. Biometrics 11: 1-41. Freund, R. J. t and R. C. Littell. 1981. SAS for Linear Models. SAS Institute, North Curolina. Luginbill, P. 1928. The fall armyworm USDA Tech. Bull. 34. Navas, D. 1966. Evaluacion del dano que ocasionan algunas plagas del arroz en Panama. In Programa cooperativo centroamericano para el mejoramiento de cultivos alimenticios, Xll: 77-78. Pantoja, A., C. M. Smith, and J. F. Robinson. 1985. Natural control agents affecting Spodoptera {rugiperda (Lepidoptera: Noctuidae) infesting rice in Puerto Rico. Fla. Entomol. 68: 488-490. Pantoja, A., C. M. Smith, and J. F. Robinson. 1986. Evaluation of rice germ plasm for resistance to the fall armyworm (Lepidoptera: Noctuidae). J. Econ. Entomol. 79 (In press). Perkins, W. D. 1979. Laboratory rearing of the fall armyworm. Fla. Entomol. 62: 87-91.

PANTOJA et a1.: Fall Annyworm Oviposition on Rice 119 Pitre, H. N" J. E. Murooney, and D. B. Hogg. 1983. Fall armyworm (Lepidoptera: Noctuidae) oviposition: Crop preferences and egg distribution on plants. J. Econ. Entomol. 76: 463-466. Yoshida, S. 1981. Fundamentals of rice crop science. lot. Rice Res. lnst.. Los Banos, Philippines. p. 12.