Controlled laboratory experiments were conducted to study the influence of temperature on production of eggs by a sunflower stem weevil Cylindrocopturus adspersus. Maximum egg production occurred when the temperature was 30± 1°C. At 27C the rate of egg production was lower than at 30°C but significant only at the P \u3c 0.1 level. At 20, 23. and 35C egg production was significantly lower than at 30°C (P \u3c 0.05) indicating that temperature can be an important factor in regulating the fecundity of this species

Barker, John F

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Influence of Temperature on Egg Production in Sunflower Stem Weevil \u3ci\u3eCylindrocopturus Adspersus (Coleoptera: Cucurlionidae)

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The Great Lakes Entomologist Volume 20 Number 4 - Winter 1987 Number 4 - Winter 1987 Article 2 December 1987 Influence of Temperature on Egg Production in Sunflower Stem Weevil Cylindrocopturus Adspersus (Coleoptera: Cucurlionidae) John F. Barker Metabolism and Radiation Research Laboratory Follow this and additional works at: https://scholar.valpo.edu/tgle  Part of the Entomology Commons Recommended Citation Barker, John F. 1987. "Influence of Temperature on Egg Production in Sunflower Stem Weevil Cylindrocopturus Adspersus (Coleoptera: Cucurlionidae)," The Great Lakes Entomologist, vol 20 (4) Available at: https://scholar.valpo.edu/tgle/vol20/iss4/2 This Peer-Review Article is brought to you for free and open access by the Department of Biology at ValpoScholar. It has been accepted for inclusion in The Great Lakes Entomologist by an authorized administrator of ValpoScholar. For more information, please contact a ValpoScholar staff member at scholar@valpo.edu. 1987 THE GREAT LAKES ENTOMOLOGIST 177 ~TLUENCE OF TEMPERATURE ON EGG PRODUCTION IN Sl..~rLOWER STEM WEEVIL CYLINDROCOPTURUS ADSPERSUS (COLEOPTERA: CUCURLIONIDAE) John F. Barker l ABSTRACT Controlled laboratory experiments were conducted to study the influence of tempera­ture on production f eggs by a sunflower stem weevil Cylindrocopturus adspersus. ~Iatimum egg production occurred when the temperature was 30± 1°C. At noc the rate of egg production was lower than at 30°C but significant only at the P < 0.1 level. At 20, 23. and 3YC egg production was significantly lower than at 30°C (P < 0.05) indicating rhat temperature can be an important factor in regulating the fecundity of this species. lbe known range of Cylindrocopturus adspersus (LeConte), a sunflower stem weevil, :;. from southern Canada throughout the Great Plains (Oseto 1977, Rogers and Jones !'F9J into the Texas high plains (Rogers and Serda 1982). In the northern Great Plains, C. adspersus is reproductively active during late June, July, and August. Populations of this species are sporadic and cyclic which strongly suggests that various environmental fa..."tCOfS influence their abundance. The influence of temperature on egg production was IDyestigared to determine the influence o  temperature on fecundity of this species. MATERIALS AND METHODS Llnae of C. adspersus were field collected from sunflower stalks and stored at 4°C. _-\iter chilling for at least five weeks the larvae were brought out to 27°C to pupate. Pupae ';I.ere sexed as described by Reinecke (1981) and separated shortly after eclosion. Five to - da~s after emergence as adults, the males were marked with a small spot of quick drying enamel paint and six males and six females were added to each of five hat boxes measuring 17 x 26 x 34 mm (n = 30 females for each temperature tested). The box .:Dyers had yentilation holes cut into them, and the holes were covered with a screen to keep the w evils confined. Each cage contained a short section of sunflower stalk and a cut surulower leaf. To maintain freshness the leaf and stem were inserted into a small boule of water. The leaf and stem were changed every 48 h. All experiments were cooducted in a controlled environment chamber. Temperature was held constant ± 1°C ';I.·itb relariH~ humidity maintained at 55%. Temperature effects were tested at 20,23,27, 30. and 35T. Each test was made with five replicates. The photophase was held at 15:9 lighr:dark cycle. Fluorescent light intensity at the level of the holding shelf was 350 lux. 1be eggs oyiposited during each 48-h period were used to quantify the rate and total egg production. C. adspersus females oviposited on the cut stalk and leaf stem of the [~ktabolism and Radiation Research Laboratory, USDA, ARS, Fargo, NO 58105. 1Barker: Influence of Temperature on Egg Production in Sunflower Stem WeevPublished by ValpoScholar, 1987178 THE GREAT LAKES ENTOMOLOGIST Vol. 20, No.4 Table 1. Effect of temperature on egg production in C. adspersus. Temperature Eggs/female/day Total egg production' 35±I°C 30±I°C 27±I°C 23±I°C 20±I°C 3.2±0.3b A 4.7±OA B 3.6±0.3 AB 1.4±0.1 C 0.4±0.0 D 1483 5842 4826 1945 711 aup to 75 days. bDifferent letters indicate the means are significantly different at the P < 0.05 level. sunflower plant placed in the hat box. Eggs were removed from the section of stalk and cut leaf and counted. The mean numbers of eggs in different temperature groups were compared by a one-way analysis of variance and an F test (Guenther 1964). RESULTS The effect of temperature on total egg production and the number of eggs per female per day are summarized in Table L The total number of eggs oviposited and the number of eggs per female per day increased up to 30°C, while longevity decreased with increasing temperature. Each experiment at each temperature began with 30 females. The majority of females (22 of 30) held at 27 and 30nC lived at least 45 days while the majority (19 and 23 respectively of 30) held at 23 and 20°C were still alive at 75 days. In contrast, those held at 35°C were all dead by 30 days. The greatest number of eggs were produced when the temperature was 30 ± l°C. Oviposition at 35, 23, and 20°C w s significantly lower than at 30°C. At 27°C egg production was lower than at 30°C but significant only at the P < 0.1 level. DISCUSSION The above results suggest temperature is important in the regulation of egg production in C. adspersus. Reproduction is inhibited at fairly warm temperatures of 20-23°C and is lower even at 27°C than at 30°C. It is probable that extended summertime temperatures below 2rC can contribute to down-cycles of wild populations of this species in the northern Great Plains. At 35°C the mortality was high with a subsequent reduction in total egg production. Temperatures above 30°C could reduce fecundity through increased stress and mortality. At temperatures of 20-23°C, the insects produce about 12-33% as many eggs, respectively, as at 30°C. Longevity increased almost two fold at these temperatures but the insects would have to live three times as long or longer to produce the equivalent number of eggs as at 30°e. It is unlikely that under natural conditions in the northern Great Plains, egg production at 20 or 23°C could catch up to production at 30°C due to the onset of fall conditions and the maturation and drying of the host plant occurring at the end of August. ACKNOWLEDGMENTS I thank Sharon Grugel and Kelly Jones for providing the insects for this study. 2The Great Lakes Entomologist, Vol. 20, No. 4 [1987], Art. 2https://scholar.valpo.edu/tgle/vol20/iss4/21987 THE GREAT LAKES ENTOMOLOGIST 179 LITERATURE CITED Guenther. W. C. 1964. Analysis of variance. Prentice-Hall Inc., Englewood Cliffs, N. J. Osew. C. Y. 1977. Biology and control of stem weevils, Cylindrocopturus adspersus and Baris stremua. Sunflower Forum 2:4. Sunflower Assoc. Am. Reinecke. J. P. 1981. Sexing living pupae and teneral adults of a sunflower stem weevil Cylindrocopmrus adspersus. Southwestern EntomoL 6:201-204. Rogers. C. E., and O. R. Jones. 1979. Effects of planting date and soil water on infestation of sunflower by larvae of Cylindrocopturus adspersus. J. Econ. EntomoL 72:529-531. Rogers. C. E., and J. G. Serda. 1982. Cylindrocopturus adspersus in sunflower: Overwintering and emergence patterns on the Texas high plains. Environ. EntomoL 11:154-156. 3Barker: Influence of Temperature on Egg Production in Sunflower Stem WeevPublished by ValpoScholar, 1987

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Influence of Temperature on Egg Production in Sunflower Stem Weevil \u3ci\u3eCylindrocopturus Adspersus (Coleoptera: Cucurlionidae)

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