Cuticular lipids were extracted and chemically characterized from the pupal exuviae and associated dorsal extrusions and palisade wall of the exuviae that are secondary structures of the greenhouse whitefly, Trialeurodes vaporariorum (Westwood), and from pupal exuviae of the sweetpotato whitefly, Bemisia tabaci (Gennadius), type B reared on tomato, poinsettia, broccoli, tobacco, or lettuce. The pupal exuviae of T. vaporariorum separates completely at adult eclosion from its palisade wall (not present in B. tabaci), allowing removal of the exuviae for analysis of its cuticular lipids. Four classes of lipids were detected from all hosts in the exuviae of T. vaporariorum: paraffins, alcohols, aldehydes, and acetates, whereas variable combinations of paraffins, alcohols, and aldehydes were detected in B. tabaci. T. vaporariorum exuviae on all hosts had significantly more total lipids than did B. tabaci. Both lipid class and constituent abundance were influenced significantly by different interactions of the whitefly and host plant. In the greenhouse whitefly, the four lipid classes were insect controlled and variability within class was influenced by the host plant, whereas in the sweetpotato whitefly type B, lipid class variability was random and directly related to host. Alcohols were the most abundant lipid found in T. vaporariorum, whereas no particular lipid class was consistently predominant in B. tabaci. Alcohols were not detected from exuviae of B. tabaci reared on the solanaceous tomato or tobacco plants but were detected on B. tabaci reared on poinsettia and broccoli. The cuticular lipids of B. tabaci type A and B on sweetpotato and cotton were compared and no major differences were found. Therefore, measurable differences in the cuticular lipids of T. vaporariorum and B. tabaci can be used to distinguish between these two whiteflies but cannot be used to distinguish the two types of B. tabaci when reared on the same host plant. The composition of lipid classes and individual chemical constituents in the secondary structures of T. vaporariorum differed significantly.

A new dispenser for (+)-disparlure was designed for use in gypsy moth, Lymantria dispar (L.), detection traps; this new dispenser is an alternative to the currently used plastic laminate. The dispenser consists of twisted nylon twine coated with polyvinyl chloride containing 500 mug of the pheromone. Comparison tests showed that this twine dispenser prolonged the release of (+)-disparlure at a rate greater-than-or-equal-to 30 ng/h for longer (240 versus 80 h) than did the 1989 batch of the standard laminate dispensers in an accelerated oven aging test at 59-degrees-C. Field tests showed that male moth captures with twine dispensers, pre-aged 16 wk in a greenhouse, were as high as or higher than those with unaged, laminate dispensers (from either 1988 or 1989 batches). Pheromone contents and release rates as a function of duration of aging showed extended and more effective delivery of the active ingredient by the twine dispenser in comparison with the laminate dispenser. The twine dispenser is simple and inexpensive to make and is at least as effective as the presently used laminate dispenser.

Seven controlled-release dispenser formulations containing 500 μg of gypsy moth pheromone (+)-disparlure, were compared in laboratory and field tests. Pheromone release rates, residual pheromone contents, and male moth captures in traps baited with the dispensers were compared following pre-aging of the dispensers in a greenhouse at 35 °C for 0, 4, 12, and 16 wk. The laminate dispenser, now used in USDA detection traps, became less attractive over time as its pheromone release rate and content dropped below the threshold values previously reported as necessary for effective attraction. A polyvinyl chloride coated twine dispenser produced high male moth captures and gave release rates and residual contents above these thresholds (30 ng/h release rate and 100 μg content) at all aging periods. The tube-A dispenser was the most effective of the new commercially prepared formulations, followed by the membrane and tube-B whose male moth captures and release rates tended to increase with aging time. The capsule and film dispensers were the least effective of the formulations tested.

Emission rates from cotton wicks baited with 1-400 μg of (+)-disparlure ranged from 7 to 2,000 ng/h at 35°C in a laboratory oven. A 100-μgdose, which is a reference in field tests, produced a rate of 470 ng/h. Release rates, residual lure contents, and captures of male gypsy moths, Lymantria dispar (L.), were correlated with duration of greenhouse aging. High male captures were obtained in tests with controlled-release, plastic laminate dispensers when the pheromone release rate was at least 30 ng/h and the residual content was at least 100 μg. These thresholds were provided by laminates aged in a greenhouse (mean low, 24.4-27.5°C; mean high, 36.7-39.1°C) for as long as 8-11 wk. Release rates from the laminates increased 3.5-fold for each 10°C increase in temperature. Several commercial dispensers with (+)-disparlure were evaluated, but the laminate design generally performed better than other designs with respect to the number of males captured.

Comparison of laboratory-measured release rates with boll weevil captures showed that dispensers containing 10 mg of grandlure with a release rate of 10 μg/hr or higher generally produced weevil captures which were at least 50% as high as those with the reference, fresh cigarette filter. Emission rates of ca. 3 μg/hr or lower and amounts of residual grandlure of ≤ 2 mg generally resulted in weevil captures below the 50% threshold. Comparisons of commercial dispenser formulations containing 10 mg of grandlure showed that a Hereon orange plastic laminate (H-OL-T) was most effective in prolonging the release of grandlure in both field and laboratory evaluations. Its emission rate was least affected by temperature changes. Scentry PVC dispensers (S-T-T, S-C-T, S-S-T, and S-YS-T) and the Consep membrane (C-M-T) lost grandlure more rapidly than did the laminate; however, differences in weevil captures were often not significant. Fermone black PVC squares (F-S-T and F-OS-T), AgriSense polymeric rods, (A-50R-T and A-35R-T) and the cigarette filter (CF-T) were less effective in extending the release of grandlure. Dispensers mounted in the capture cylinder lost grandlure more rapidly than did similar dispensers mounted in the cooler trap base. A layer of stickum on one side of flat dispensers to facilitate attachment to the trap resulted in a somewhat lower release rate of grandlure.

Dispensers containing the aggregation pheromone grand lure are extensively used in traps for detecting, monitoring, and suppressing the boll weevil, Anthonomus grandis Boheman, in areawide management programs and for monitoring on a field-by-field basis. The effective period of pheromone release from these dispensers is substantially influenced by the nature of the dispenser formulation and by temperature and other variables. A laboratory procedure was developed to measure the relative release rates of grand lure from candidate dispensing systems under conditions of constant temperature and air flow. Release rates were found to increase by as much as 13 times as the temperature was raised from 28 to 62. Field studies were conducted on 12 dispenser formulations to measure insect capture as a function of dispenser aging time over 3-wk periods; emission rates and residual grand lure contents were measured on similarly aged dispensers. A laminate with 400-μm outer layers and the cigarette filter gave the best overall performance. Laboratory-measured release rates correlated with boll weevil captures (Test 1; linear regression analysis with r2 = 0.83). Accelerated aging of dispensers in an oven set at 54 gave similar profiles of release rate versus time as did the field-aged dispensers; relative performance of dispenser formulations can be determined in the laboratory as a preliminary evaluation before costly and lengthy field tests are undertaken.