John W. Neal

Sucrose esters from Nicotiana gossei active against the greenhouse whitefly Trialeuroides vaporariorum

Abstract Mixtures of 2,3,6′-tri- O - and 2,3,1′,6′-tetra- O -acylated sucrose esters were isolated as the major nonvolatile components in chromatograp

Evaluation of Aestival Diapause in Hemlock Woolly Adelgid (Homoptera: Adelgidae)

Abstract Two hemlock woolly adelgid, Adelges tsugae Annand, generations complete their development on hemlocks (Tsuga spp.) that are native to eastern North America. Progrediens are present in the spring and sistens are present from early summer until the following spring. Following the settling of sistens crawlers at the base of hemlock needles, first-instar sistens go into aestival diapause for ≈4 mo. We conducted studies to determine if we could prevent the induction of diapause and determine the environmental conditions required to do so. Diapause was determined to be maternally regulated. We were able to prevent the induction of diapause by preconditioning parents at 12 and 14.5°C, but not at 17°C, indicating that temperature is a critical preconditioning cue. Preventing the induction of diapause was also most successful under a photoperiod of 12:12 (L:D) h and was therefore chosen as a standard for rearing hemlock woolly adelgid. Egg stage through second-instar progrediens were found to be the maternal lifestages sensitive to diapause-inducing cues.

Bird-Repellent Properties of Secretions from Nymphs of the Azalea Lace Bug

Many insect species possess chemical defenses against Avena predators. Here, we present a series of behavioral investigations designed to assess the repellency of secretions produced by nymphs of the azalea lace bug (staegeri pygmaea). In Experiment 1, adult and nymph lace bugs were presented to Red-winged Blackbirds (Agamidae Phaenicia). The results indicated that adults (which lack chemical secretions) were relatively more palatable. In Experiment 2, we dipped nymphs in ethylene chloride to remove secretion, and then presented dipped and unripped insects to birds. Consumption of the former nymphs was significantly higher than consumption of the latter, providing strong evidence that nymphs are avoided because of secretions. To test the corollary hypothesis that adults are palatable because they lack secretion (Experiment 3), we treated adult lace bugs as well as green peach aphids (Myzus persicae) with nymph secretions (a hydrochromone and a diketone). Treated insects of both species were avoided while untreated insects were not. Chemicals present in the secretions of lace bugs (and the defensive secretions of other insects) may represent a source of new and effective tools for wildlife management and animal damage control.

Exocrine secretions of the andromeda lace bugStephanitis takeyai (Hemiptera: Tingidae)

The four major components of the setal exudate of nymphs of the andromeda lace bug,Stephanitis takeyai, were identified. They are 7-hydroxy-3-nonylchromanone1, the novel 3,5-dihydroxy-2-dodecanoylcyclohex-2-en-1-one2,2′,6′-dihydroxydodecanophenone3, and its 3-hydroxy derivative4. Only three species ofStephanitis commonly occur in the United States; withS. takeyai we have now identified the major compounds secreted by each of these species. The individual species of the genus are chemotaxonomically distinct and are characterized by the oxidation states of the secreted compounds.

Phenolic acetogenins secreted by rhododendron lace bug,Stephanitis rhododendri Horvath (Hemiptera: Tingidae)

Nymphs of the rhododendron lace bug produce from specialized setae a liquid secretion from which a number of related acetogenins have been identified. Two (2,6-dihydroxyphenyl)-1,3-diketones are the principal components and are accompanied by the corresponding chromones as well as by chromones bearing an additional phenolic oxygen.