Phloem amino acids in Cucumis melo L. were measured to determine whether changes in nitrogen availability might affect life-history traits and flight activity of Bemisia tabaci Gennadius (Homoptera: Aleyrodidae). During plant development, nineteen of the twenty common amino acids, plus hydroxyproline, citrulline, ornithine and γ -aminobutyric acid (GABA) were identified. For most essential amino acids, there were two peaks observed: an initial large peak associated with young plants, and a later small peak associated with senescing plants. For histidine, ornithine and citrulline, medium to large peaks in relative abundance were observed in mature plants. Arginine peaked during the first few weeks of development and was no longer detectable after wk 7. Serine and glutamine/glutamic acid were the only amino acids that peaked during plant senescence. Factor analysis was used to create a reduced number of orthogonal factors, which corresponded well with the trends that were observed for the various groups of amino acids. No single or combination of factors explained a significant amount of the variability in oviposition. For both males and females, factor 1 (predominantly essential amino acids) was the single most important predictor of adult weight. As the relative concentrations of essential amino acids decreased, whitefly weights decreased. Factors 1 and 3 (predominantly histidine and ornithine) were the most important predictors of developmental time. As these amino acids decreased in relative concentration, developmental time increased. Percent emergence was positively associated with factor 1 and negatively associated with factor 6 (predominantly aspartic acid). The distributions of flight duration for whiteflies emerging from young, mature and senescing melon plants were compared and they were always skewed towards short flights; however, the frequency of long-duration flights increased when melon plants began to senesce. Whiteflies from all plant-age categories were capable of flying for more than 2 h with fully developed eggs, but the presence of more than four mature eggs was associated with flights of reduced duration.

Bemisia tabaci exhibited their longest flights between 3 and 5 days following adult eclosion. They rarely engaged in flight when they were < 4 hr old and were only capable of short-duration flights after day 7. This difference in flight capacity appears to be associated with changes in the flight musculature and mitochondria. Myofibrils and mitochondria accounted for approximately 50% and 33% of the area within the flight muscles, respectively. These two elements, however, varied with the age and sex of the whitefly. The percentage of the total area occupied by myofibrils was lower in 9-day-old males relative to females and all other age categories. Sarcomere length decreased in older whiteflies, regardless of the sex. Myofibril diameter did not vary with the age of the whitefly, but the diameter of female whitefly myofibrils was greater than the diameter of male whitefly myofibrils. The number of myosin filaments within a myofibril unit increased with age, peaking at 5 days of age for females and 7 days of age for males. In all age groups, females had more myosin filaments than were found in males. Changes in mitochondria and levels of glycogen were related to the observed differences in flight activity. The area occupied by mitochondria was small in < 4-h-old and 9-day-old whiteflies, and mitochondrial cristae were undeveloped in newly emerged whiteflies. In 7- and 9-day-old whiteflies the cristae began to separate, leaving visible spaces within the mitochondria. Glycogen granules were abundant in the flight musculature of newly emerged (< 4-hr-old), 1-day-old and 3-day-old whiteflies, but by 5 days of age only 25% of whiteflies contained glycogen granules. Seven- and 9-day-old whiteflies contained no visible glycogen. An examination of the flight muscle of whiteflies after flights of varying duration (up to 60 min) revealed no relationships between flight duration and the number of mitochondria or the percentage of the total area occupied by mitochondria. There was, however, a positive relationship between flight duration and the percentage of total area occupied by myofibrils. © 1995 Wiley-Liss, Inc.

‘Russet Burbank’ potatoes were planted 21 Apr. at Parma, Idaho in Greenleaf-Owyhee silt loam soil. Each plot consisted of a single row 15 ft long, and treatments were replicated four times in a randomized block design. Sprays were applied on 30 Jun. with a CO2 pressurized hand sprayer at 50 lb/in2 that applied 40 gal spray per acre. Pre- and posttreatment counts were made by walking along the row and recording adults and larvae that could be seen without moving foliage.

Plots were located in a commercial hop yard near Greenleaf, Idaho. Each plot consisted of eight hills. Treatments were arranged in a randomized block with four replicates. Aphid treatments were applied 11 July with a truck mounted sprayer with hose and handgun that applied 75 gal/acre at 100 lb/in2 . Miticide treatments were applied 30 Aug. with a Solo Air Blast Mist Blower at 50 gal/acre. Mite numbers were estimated by taking 10 leaves from the top of plants in each plot. Leaves were processed through a brushing machine and mites were counted under a compound microscope. Aphids were counted on 25 leaves from each plot.