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Western flower thrips (WFT), Frankliniella occidentalis(Thysanoptera: Thripidae), is the most important insect pest for greenhouse flower crops, but chemical control is often difficult because of the thrips' location in flowers and buds. Thripinema nicklewoodi(Tylenchida: Allantonematidae) is an entomoparasitic nematode that attacks and sterilizes WFT, but its biology and impact on WFT are poorly understood. Methods to propagate and study T. nicklewoodiwith a microscope slide arena for observation and a rolled bean leaf arena for rearing were developed. On average, 21.4 nematodes were excreted per day by a parasitized female WFT. The sex ratio of the excreted nematodes was 6.0/1.0 (female/male). After dissection of adult WFT, a maximum of 11 ovoid-shaped first-generation nematodes in a female thrips and 6 in a male thrips were found. There were more second-generation nematodes in the adult female WFT (192.6) than in the adult male WFT (93.7). When 50 healthy first instar WFT were exposed to 4 parasitized female WFT in a rolled bean leaf, a 75.3% mean parasitization rate in the adult stage of the thrips was obtained. In contrast to previous reports, male WFT can be parasitized as readily as females. Parasitism reduced the longevity of both adult female and adult male WFT, and the degree of reduction was higher in adult male WFT. T. nicklewoodi,when presented with various WFT life stages (first instar, second instar, prepupa, pupa, adult female, and adult male), achieved the highest attack rate in first and second instars and prepupa. The free-living nematodes excreted by the hosts actively migrated to a trichome on leaf disks in the observation arena and moved up this structure. Then, the nematode actively waved the anterior part of its body while attaching itself to the trichome with the posterior part of its body. After a nematode contacted the leg of a thrips, the nematode immediately moved up along the leg toward the abdomen of the host. Increased understanding of the biology of T. nicklewoodiis important to better assess its potential for biological control of WFT.

We evaluated several factors to identify features or practices that might increase the probability of establishment following the release of two root-feeding insects (the cochylid moth Agapeta zoeganaL. and the weevil Cyphocleonus achatesFahraeus) that attack the invasive plant, spotted knapweed (Centaurea maculosaLamarck). At each of 99 sites where releases had been made in previous years, we assessed (1) the number of insects of each species released, (2) the number of years in which releases were made, (3) the number of years since the first release, (4) the size of the knapweed infestation, (5) its shape (linear, large single patch, many small patches), (6) the knapweed plant density, and (7–18) 12 physical site characteristics: habitat type, elevation, percentage slope, aspect, topographic type, forest structure at or by the site, disturbance factors, land use category, percentage forest canopy at or near site, percentage bare soil, annual precipitation, and soil type. We found that continuous, nonlinear patches of spotted knapweed on loamy soil that were surrounded by even-age forest stands had the highest rates of establishment for A. zoegana, but likelihood of establishment was not greater for larger releases (>200 adults). This suggests that roadside strips of knapweed should not be selected as release sites and that many, smaller releases (100–200 adults) are better than fewer, larger releases (300–500 adults or greater). For the weevil C. achates, we found that the probability of establishment was also greatest in continuous knapweed patches, rather than in strips, and that larger infestations (>2 ha) were better than smaller infestations. Establishment was also highest at mid-elevations (750–1500 m), compared to higher or lower locations.

The efficacy and cost of reduced release rates of the parasitoid Eretmocerus eremicusRose and Zolnerowich (Hymenoptera: Aphelinidae) when combined with application of the insect growth regulator buprofezin were compared to those of a higher parasitoid release rate used alone for whitefly control (Homoptera: Aleyrodidae) on poinsettia (Euphorbia pulcherrimaWilld. ex Koltz.). The trial was conducted in seven greenhouses in Methuen, Massachusetts from August through December 1997 and employed commercial poinsettia production practices. Two whiteflies species, Trialeurodes vaporariorum(Westwood) and Bemisia argentifoliiBellows and Perring (= Bemisia tabaci[Gennadius] strain B), were present. Three treatments were examined: (1) E. eremicusused alone at a release rate of three females per plant per week (two greenhouses); (2) E. eremicusat an intermediate release rate of two females per plant per week, combined with mid-season use of buprofezin (two applications, spaced 1 week apart, applied in weeks 9 and 10) (two greenhouses); and (3) E. eremicusat a low release rate of one female per plant per week, combined with mid-season use of buprofezin, applied as in treatment 2 (two greenhouses). In addition, observations were made in one additional greenhouse at the site, in which the grower used pesticides for whitefly control. Prior to the start of the trial, cuttings used for all treatments experienced some pesticide use, first abamectinduring rooting and later buprofezin at potting to reduce whitefly numbers, which were initially very high. At harvest, densities of live whitefly nymphs were not statistically different among the biological control treatments, indicating that a low parasitoid release rate combined with buprofezin was as effective as a higher release rate of the parasitoid used alone. Nymphal densities in separate market samples (based on smaller sample sizes) showed differences among treatments, but all treatments, including the low parasitoid release rate + buprofezin maintained densities of live nymphs + pupae at or below approximately two per leaf, a level commercially acceptable in local markets. Control costs per single-stemmed poinsettia plant were $1.18 for the high parasitoid release treatment, $0.75 for the treatment of weekly releases of two female parasitoids per plant per week + buprofezin, $0.38 for the treatment of releases of one female parasitoid per plant per week + buprofezin, and $0.14 for the chemical control greenhouse.

The compatibility of five insect growth regulators (IGRs), buprofezin, pyriproxyfen, fenoxycarb, pymetrozine, and kinoprene, were tested in the laboratory for compatibility with the whitefly parasitoid Eretmocerus eremicusRose and Zolnerowich (Hymenoptera: Aphelinidae). The survivorship of adult parasitoids foraging on poinsettia leaves with residues 6, 24, and 96 h of age was determined. The toxicity of Bemisia argentifoliiBellows and Perring (Homoptera: Aleyrodidae) patches treated with IGRs presented to female parasitoids 24 and 96 h posttreatment was quantified. Survivorship of immature E. eremicusdeveloping within B. argentifoliinymphs was determined by treating whitefly nymphs with IGRs 5 and 13 days postoviposition by female parasitoids. Finally, behavioral observations of female parasitoids foraging on IGR-treated and untreated B. argentifoliipatches presented simultaneously were quantified to determine whether IGR residues had a repellant effect toward E. eremicus.Averaging ranks for IGRs based on their compatibility with E. eremicusand their ability to kill B. argentifoliinymphs produced the following parasitoid compatibility order: buprofezin > fenoxycarb > pymetrozine = pyriproxyfen > kinoprene. Further work in greenhouses assessing the efficacy of buprofezin with E. eremicusfor B. argentifoliicontrol on poinsettias is recommended.

AbstractLathrolestes nigricollis(Thompson) (Hymenoptera: Ichneumonidae) was released in New England against Fenusa pusilla(Lepeletier) in 1979?1980 and again in 1989?1990. By 1991, the parasitoid was widely established in southern New England. From 1979 to 1990 the commonness of leafminers at the original release site in the first generation declined from 50?54% of leaves mined to under 3%. Over 4 years at five sites, parasitism of larval birch leafminers increased between leafminer generations from 10.3% (G1) to 27.6% (G2) to 39.2% (G3). In Massachusetts, parasitism decreased (from 28 to 14%) with increasing distance from the original release site, while corresponding damage increased (from 6% of leaves mined to 33%). In areas local to the original release site (<4 km) parasitism has reduced damage from birch leafminer to inconsequential levels. Some sites in other parts of southern New England, particularly roadside sites, still have high levels of mined leaves in spite of the parasitoid?s presence in the general area.

AbstractStage survival is typically calculated from estimates of numbers entering two successive life stages. We present a method that estimates stage survival by reference to the difference between directly measured recruitment to the stage and the estimate of recruitment obtained from Southwood and Jepson’s graphical technique. The method assumes mortality is constant within the stage. The method is applied to two generations (at two sites) of the egg stage of the Colorado potato beetle, Leptinotarsa decemlineata(Say) (Coleoptera: Chrysomelidae), and the predicted stage survivals are compared, for two generations, with direct field measurements of egg mortality.