Nocturnal Pollinators Significantly Contribute to Apple Production.

Agricultural dependency on insect-mediated pollination is increasing at the same time that pollinator populations are experiencing declines in diversity and abundance. Current pollinator research in agriculture focuses largely on diurnal pollinators, yet the evidence for pollination by moths and other nocturnal pollinators is growing. Apples are one of the most valuable and important fruits produced globally, and apple production is dependent on insect-mediated cross-pollination to generate a profitable crop. We examined contributions to apple production provided by nocturnal insects via an exclusion experiment. We compared the relative contributions to apple production provided by nocturnal and diurnal pollinators using fruit set, the likelihood of cluster pollination, and seed set. We found nocturnal pollinators capable of facilitating the production of as many apples at similar levels of pollination as diurnal pollinators. We further found evidence that nocturnal and diurnal pollinators pollinate synergistically, with pollination contributions being additive in one year of our study. Our research identifies significant contributions to apple production provided by nocturnal pollinators, which may interact with diurnal pollinators in ways that are currently unrecognized. Expansions of this research into additional pollinator-dependent crops and focused investigations on specific nocturnal insects will provide more accurate assessments of nocturnal-pollinator roles in agriculture and improve our overall understanding of pollination in agriculture.

Influence of oviposition experience on multiparasitism by Pimpla disparis Vierick and Itoplectis conquisitor Say (Hymenoptera: Ichneumonidae).

We evaluated the potential for competition between the exotic ichneumonid parasitoid Pimpla disparis Vierick and the native ichneumonid Itoplectis conquisitor Say, in the form of multiparasitism and destructive host feeding, by examining how previous oviposition experience influenced host selection. Both species commonly attack the host species, bagworm, Thyridopteryx ephemeraeformis (Haworth) (Lepidoptera: Psychidae), in central Illinois. We used in our study adult female parasitoids that were naïve, had previously oviposited into hosts that contained heterospecifics, or had oviposited into hosts that initially were unparasitized. Naïve parasitoids of both species were disinclined to oviposit into hosts that already were parasitized by heterospecific larvae, suggesting that female parasitoids could detect the larvae. However, parasitoids with prior oviposition experience were less selective and oviposited into hosts that already were parasitized and unparasitized hosts. Female P. disparis and I. conquisitor probed parasitized hosts more frequently than unparasitized hosts. Adult female parasitoids of both species rarely directly fed on hosts, but those that did preferred to feed on hosts that already were parasitized. For both parasitoid species, the first larva to colonize a multiparasitized host was the most likely to survive to adulthood.

Nutritional suitability of corn pollen for the predator Coleomegilla maculata (Coleoptera: Coccinellidae).

The nutritional suitability of corn pollen for the facultatively phytophagous predator Coleomegilla maculata was studied in the laboratory. Dry matter, organic matter, ash, crude protein, amino acid, and quercetin contents of pollen from 10 hybrids of field corn were determined. C. maculata were reared on pollen or aphids + artificial diet for their entire lives; larval duration, post-mortem adult dry weights, fecundity within 7 days of mating, and mortality rates were compared among the treatments. In another experiment, C. maculata larvae were reared on pollen; weight gained, pollen ingested, and frass produced were compared among instars. Also, consumption relative to increases in larval biomass and the efficiency with which larvae converted corn pollen into biomass were compared among instars. Beetles reared on aphids had greater weights and fecundity and a shorter larval duration relative to the pollen-fed beetles. The percentages of organic matter and ash in corn pollen were significantly correlated with C. maculata mortality, and we hypothesize that some micronutrient or phytochemical is at sub-optimal levels for C. maculata development in some of the pollens. We observed an increase in the conversion efficiency of pollen and a decrease in the consumption relative to biomass of C. maculata as the larvae aged, which suggests a physiological or behavioral alteration in the feeding behavior of C. maculata during the larval stage.

Effects of insect growth regulators on citrus mealybug parasitoid Leptomastix dactylopii (Hymenoptera: Encyrtidae).

In this study, we measured the effects of three commonly used insecticides classified as insect growth regulators, on the encyrtid parasitoid Leptomastix dactylopii (Howard) when parasitizing citrus mealybug, Planococcus citri (Risso). Kinoprene, pyriproxyfen, and azadirachtin were evaluated in both petri dish and a cage experiment at label-recommended rates to measure their effects on the mortality, parasitization rate, and sex ratio of L. dactylopii. Insecticides were applied to petri dishes and plants either immediately before, 24 h before, or 48 h before release of the parasitoid. Kinoprene applied 24 h before parasitoid release caused 100% mortality of L. dactylopii in petri dishes within 48 h. Mortality rates for L. dactylopii exposed to azadirachtin and pyriproxyfen did not exceed 5% regardless of release time. There were no release time x insecticide interactions on L. dactylopii parasitization rate. The insecticide alone, however, did significantly affect parasitization rates of L. dactylopii on P. citri; the kinoprene treatment significantly reduced L. dactylopii parasitization rates compared with azadirachtin and pyriproxyfen. In a cage experiment with coleus, Solenostemon scutellaroides (L.) Codd, applications of both pyriproxyfen and kinoprene resulted in fewer P. citri parasitized by L. dactylopii than azadirachtin or the control. The sex ratio was equivalent in the petri dish experiment, whereas in the cage experiment the sex ratio was biased toward males, particularly for the kinoprene treatment. Based on the results from this study, we suggest that kinoprene is not compatible with releases of L. dactylopii to control citrus mealybugs.

Dimethylfuran-lactone pheromone from males of Galerucella calmariensis and Galerucella pusilla.

Male Galerucella calmariensis and Galerucella pusilla (Coleoptera: Chrysomelidae) emit an aggregation pheromone while feeding on host foliage. Isolation of the compound from collected volatiles was guided by comparisons of gas chromatograms of extracts from males and females and by gas chromatography-electroantennographic detection. The compound was identified by a combination of spectrometric methods and microchemical tests as the novel dimethylfuran lactone, 12,13-dimethyl-5,14-dioxabicyclo[9.2.1]tetradeca-1(13),11-dien-4-one. The structure was confirmed by synthesis, and the synthetic compound attracted males and females of both species in field bioassays. These beetles were previously introduced into North America as biological control agents for the invasive wetland weed, purple loosestrife Lythrum salicaria, and the pheromone could become a tool for monitoring populations. A new method is described for distinguishing the two species based on the tibial spurs of the males.

Quantification and development of teratocytes in novel-association host-parasitoid combinations.

We studied the development of teratocytes derived from two congeneric gregarious endoparasitic species, Cotesia chilonis and C. flavipes, parasitizing two congeneric novel hosts, Diatraea saccharalis and D. grandiosella. The host-parasitoid combinations studied allowed us to investigate relationships between host suitability and teratocyte development. D. saccharalis was a suitable host for both parasitoids, whereas D. grandiosella was suitable for C. chilonis development but often encapsulated C. flavipes progeny. Encapsulation of C. flavipes by D. grandiosella commenced around the time of parasitoid egg hatch, when teratocytes were released into the host's hemolymph. The gregarious parasitoids studied here released about 200 teratocytes per egg. Both absolute and normalized (teratocytes/parasitoid) numbers decreased over time. D. saccharalis supported more C. flavipes-derived teratocytes than D. grandiosella, possibly because of the unsuitability of the latter host. On intermediate assay days the number of C. flavipes-derived teratocytes was greater than for C. chilonis. However, C. chilonis-derived teratocytes grew larger than C. flavipes. Teratocytes in all host-parasitoid combinations doubled in size during parasitoid development. Teratocytes generally grew larger in D. grandiosella, which was a less suitable host.