Author
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Spurgeon, Dale |
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Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings Publication Acceptance Date: 1/16/2009 Publication Date: 5/11/2009 Citation: Spurgeon, D.W. 2009. Observations of diapause characters in the western tarnished plant bug, Lygus hesperus. Proc. Beltwide Cotton Conf., National Cotton Council, Memphis, TN. pp. 807-812. Interpretive Summary: Knowledge of overwintering strategies of the western tarnished plant bug, Lygus hesperus Knight, is essential to the development of ecologically-based management strategies. The western tarnished plant bug overwinters as an adult in a state of reduced metabolic activity called reproductive diapause. This diapause is marked by the development of a suite of internal morphological characters. Although this diapause has been studied, development of the diagnostic characters over time has not been examined. We raised plant bugs from egg to adulthood under long (14:10) and short (10:14, Light:Dark h) daylengths at 28°C and dissected the adults at various ages. While diapause characters could generally be distinguished at 3 d of age, the distinction between diapausing and reproductive bugs was not clear because the characters indicating diapause were not fully developed. Differences between diapausing and reproductive bugs became more distinct as adult age increased to 10 d. In addition to the diapause characters previously reported (enlarged fat bodies and undeveloped ovaries) the glands associated with the male reproductive tract were also informative. Although fat bodies characteristic of those previously reported were observed, appearance of the fat bodies was highly variable. Fat body condition alone was not an adequate criterion to distinguish diapausing bugs. These results provide baseline information to improve the accuracy of classification of physiological condition in future studies of western tarnished plant bug diapause. Technical Abstract: Knowledge of overwintering strategies of the western tarnished plant bug, Lygus hesperus Knight, is essential to the development of ecologically-based management strategies. The adult diapause of L. hesperus has been studied, but temporal patterns in the development and exhibition of morphological characters of diapause have not been defined. We reared L. hesperus from egg to adulthood under long (14:10) and short (10:14, L:D h) photoperiods at 28°C and dissected the resulting adults at various ages. While diapause characters could generally be distinguished at 3 d of age, the distinction between diapausing and reproductive bugs was not unambiguous because the morphological characters indicative of the respective conditions were not fully developed. Differences in the morphology of diapausing and reproductive bugs became more distinct with increasing age up to 10 d. In addition to the diapause characters previously reported (hypertrophied fat bodies and undeveloped ovaries) accessory gland condition in males was informative. Although we observed fat bodies characteristic of those previously reported (reproductive, translucent and sheet-like; diapause, white and in well-formed globules) appearance of the fat bodies was highly variable. Fat body condition alone was not an adequate criterion to distinguish diapausing bugs. These results provide baseline information to improve the accuracy of classification of physiological condition in future studies of L. hesperus diapause. |
