INTEGRATED MANAGEMENT OF COTTON PESTS: PLANT GENETICS, BIOLOGICAL CONTROL, AND NOVEL METHODS OF PEST ESTIMATION
Title: Temperature-dependent reproductive development of Lygus hesperus (Hemiptera: Miridae)
Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: May 30, 2012
Publication Date: August 9, 2012
Citation: Spurgeon, D.W., Cooper, W.R. 2012. Temperature-dependent reproductive development of Lygus hesperus (Hemiptera: Miridae). Environmental Entomology. 41(4):941-949.
Interpretive Summary: Recent studies to better understand how the western tarnished plant bug (Lygus) injures cotton have identified important differences in Lygus feeding depending on gender and the extent of reproductive maturity. These findings indicate a need to better understand the relationship between Lygus reproductive development and temperature. We measured the rates of Lygus reproductive development at temperatures from 55 to 95 degrees F. In addition, we evaluated whether Lygus reproductive maturity could be predicted based on insect color. The rate of insect development normally increases in a predictable pattern with increased temperature. When the rate of development is less than expected at very low or very high temperatures, this is called inhibition. For most stages of the reproductive organs of male and female Lygus, development was mildly inhibited by temperatures above 85-90 degrees F. For complete development of the seminal vesicles, which store sperm in the males, development was mildly inhibited at temperatures around 55 degrees F., and strongly inhibited at temperatures above 90 degrees F. Development of the reproductive organs of both sexes was highly variable among individual bugs, especially at low temperatures. A dark aqua coloration of the underside of the Lygus abdomen was associated with reproductive maturity, especially in females. However, predictions of reproductive maturity based on bug color were often inaccurate for bugs that developed under temperatures much above or below 80 degrees F. Therefore, the use of Lygus color as an indicator of reproductive maturity seems inappropriate. The results provide information that will facilitate improved planning and interpretation of studies in which the extent of adult reproductive maturity is important.
Recent studies to elucidate relationships between the western tarnished plant bug, L. hesperus Knight, and injury to cotton (Gossypium spp.) have identified important differences in feeding behaviors among adults of different gender and reproductive states. These findings suggest a need for improved knowledge of L. hesperus temperature-dependent reproductive development. We used non-linear biophysical development rate models to describe the reproductive development of adult L. hesperus held under constant temperatures from 12.8 to 35.0 degrees C. In addition, abdominal coloration was evaluated as a non-destructive indicator of reproductive maturity. The non-linear models indicated most stages of ovary, seminal vesicle, and medial accessory gland development were subject to mild high-temperature inhibition, except for the stage of filled seminal vesicles. Development of filled seminal vesicles was subject to minor low-temperature inhibition and severe high-temperature inhibition. Estimated development times reflected extensive inter-individual variation, especially at low temperatures. This variation suggests the opportunity to select for more rapid or more consistent reproductive development under the conditions of laboratory culture. Although presence of a dark aqua coloration of the ventral abdominal cuticle was statistically associated with reproductive maturity, especially in female L. hesperus, color-based predictions of reproductive maturity were often inaccurate for bugs reared at temperatures above or below 26.7 degrees C. Therefore, use of abdominal coloration as an indicator of reproductive development in ecological studies seems inappropriate. The results provide mathematical descriptions of L. hesperus temperature-dependent reproductive development which should facilitate improved planning and interpretation of studies involving manipulation of adult reproductive status.