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M K Harris

Publications and source records attributed to M K Harris.

3 recordsLinked to original sources
PubMed2001

Density-yield relationships and economic injury levels for Bemisia argentifolii (Homoptera: Aleyrodidae) in cantaloupe in Texas.

A range of infestation levels of the whitefly Bemisia argentifolii Bellows & Perring were established across experimental field plots of cantaloupe by varying insecticide treatments to evaluate the relationships between whitefly density and crop yield and quality. High levels of whitefly adults and immatures were associated with significant reductions in fruit yield, a decrease in fruit size, and an increase in the percentage of fruits with sooty mold. Yield loss rates (kg/ha/adult or nymph) decreased in a nonlinear fashion with increasing whitefly numbers. Estimated economic injury levels varied as a function of whitefly density, whitefly stage, control cost, crop cultivar, and crop season. Estimates of economic injury levels for one ($31.2/ha), five ($156/ha), and 10 ($312/ha) insecticide treatments ranged from 0.02 to 0.39, from 0.12 to 1.96, and from 0.24 to 3.92 adults/leaf, and from 0.20 to 5.43, from 0.98 to 27.17, and from 1.97 to 54.35 nymphs/6.45 cm2, respectively.

Animals↗
PubMed2000

The quality and comparability of child care data in U.S. surveys.

This paper examines the quality and comparability of child care data obtained from eight waves of data from four nationally representative data sources: the National Longitudinal Survey of Youth (1986 and 1988), the Survey of Income and Program Participation (1986, 1987, 1988, and 1990), the National Child Care Survey, and the National Survey of Families and Households. We examine whether different study designs and survey techniques for asking questions about child care produce similar results on both the levels and determinants of child care. We identified four main sources of difference in the data sets that could impact the quality and comparability of child care research: when the interview is conducted; screening questions used to determine who is asked about child care; the population of parents and children represented in the survey; and the way child care questions are asked. Our findings indicate that summer interviews and screening on mother's work status produce the largest differences in the levels and effects of child care across these studies. Even after removing the effects of summer interviews and screening questions, however, substantial differences exist across the studies.

Child↗