Effect of humidity and a superabsorbent polymer formulation on the efficacy of Heterorhabditis zealandica (Rhabditida: Heterorhabditidae) to control codling moth,Cydia pomonella (L.) (Lepidoptera: Tortricidae)

Adequate moisture levels are required for nematode survival and subsequent efficacy as entomopathogens. Formulation of nematodes aimed at aboveground applications may assist in maintaining such moisture levels. In this study, we report the effects of a superabsorbent polymer formulation, Zeba® on the performance of an entomopathogenic nematode, Heterorhabditis zealandica Poinar, for controlling diapausing codling moth, Cydia pomonella (L.) larvae in cryptic habitats on trees. Water activity (a_w-value) on bark was considered to be an indication of moisture levels on trees in cryptic habitats where codling moth larvae are known to occur, thereby influencing nematode efficacy. H. zealandica was only able to infect codling moth larvae at a_w≥0.92, with a_w50=0.94 and a_w90=0.96. Laboratory experiments in which nematode concentration was investigated indicated a positive linear relationship between the concentration of nematodes applied and the level of control obtained, with the highest level of mortality recorded at 80 IJs/larva, requiring at least 4 h of conditions conducive to nematode activity to ensure infectivity and subsequent efficacy. Further experimentation showed that the use of the Zeba formulation, together with the nematodes, improved the level of control obtained at 60% and 80% RH in the laboratory and that it also enhanced the survival and infection-ability of the nematodes in the field. The study conclusively illustrates that the tested formulation assisted in maintaining adequate moisture levels on the application substratum, as required for nematode survival and subsequent efficacy.     

Pheromone receptors in Bombyx mori and Antheraea pernyi

Summary The cellular organization of freeze-substituted antennal sensilla trichodea, which contain the sex pheromone receptors, was studied in male silkmoths of two species (Bombyx mori, Bombycidae; Antheraea pernyi, Saturniidae). The cellular architecture of these sensilla is complex, but very similar in both species. A three-dimensional reconstruction of a sensillum trichodeum of B. mori is presented. Two receptor cells (in A. pernyi 1–3) and three auxiliary cells are present. Of the latter, only the thecogen cell forms a true sheath around the receptor cells. A unique thecogen-receptor cell junction extends over the entire area of contact. Septate junctions occur between all sensillar cells apically, and in the region of the axonal origin basally. Gap junctions are also found between all cells except the receptor cells. The trichogen and tormogen cells show many structural indications of secretory activity and are thought to secrete the receptor lymph. Their apical membrane bordering the receptor-lymph space is enlarged by microvilli and microlamellae, but only those of the trichogen cell show regularly arranged membrane particles (portasomes), indicating secretory specialization among the auxiliary cells. Epidermal cells are found as slender pillars between sensilla, but extend apically along the non-sensillar cuticle and basally along the basal lamina.     

Wingtip folds and ripples on saturniid moths create decoy echoes against bat biosonar

Media player

Topical application of a plant extract to different life stages of Trichoplusia ni fails to influence feeding or oviposition behaviour

We have previously determined that larval feeding experience with a feeding/oviposition deterrent modified the feeding responses of larvae and oviposition responses of subsequent moths. These behavioural changes were attributed to learning, but the possibility of chemical legacy could not be ruled out. In the present study, we have topically applied a feeding/oviposition deterrent plant extract from Hoodia gordonii (Masson) Sweet ex Decne (Asclepiadaceae) to larvae, pupae, and adults of Trichoplusia ni (Hübner) (Lepidoptera: Noctuidae) to determine whether the feeding response of larvae and oviposition response of subsequent female moths is similarly modified by chemicals applied to the external surface of the insect. Our results indicate that traces of the extract that may be present internally or externally on the larvae do not reduce the feeding deterrent response of larvae. Furthermore, traces of the extract in or on larvae, pupae, or adult moths did not alter oviposition choice of female moths, leading us to discount the role of experience through topical application in this study. The fact that feeding/oviposition choice was only influenced by prior feeding experience of the larvae and not by topical administration suggests that habituation via sensory stimulation through mouthpart chemosensilla is likely a central phenomenon. Continuous exposure of adult moths to the extract over a period of 7 days did not affect the oviposition response of the female moths, ruling out the role of adult experience on host-plant selection in T. ni . To the best of our knowledge, this is the first study to examine the role of experience via topical application of chemicals onto all life stages of the insect except the egg. Chemical legacy may not be playing a role in influencing the oviposition choices of female T. ni moths.     

Australian native flowering plants enhance the longevity of three parasitoids of brassica pests

Floral resources from native plants that are adapted to the local environment could be more advantageous than the use of nonnative plants. In Australia, there is a dearth of information on the benefits of native plants to natural enemies and their selectivity against pests. Accordingly, we examined the longevity of the parasitoids Diaeretiella rapae (McIntosh) and Cotesia glomerata (L.) (both Hymenoptera: Braconidae), and Diadegma semiclausum (Hellen) (Hymenoptera: Ichneumonidae) exposed to flowering shoots from Australian native plants which was compared with the nonnative buckwheat (Fagopyrum esculentum), often used in conservation biological control. Longevity of parasitoids was significantly enhanced by the Australian natives Westringia fruticosa, Mentha satureioides, Callistemon citrinus, Leptospermum cv. ‘Rudolph’, Grevillea cv. ‘Bronze Rambler’, Myoporum parvifolium, Lotus australis, and nonnative F. esculentum. The highest mean survival by native plant species was 3.4× higher for D. rapae with Leptospermum sp. and 4.3× higher for D. semiclausum with M. parvifolium. For C. glomerata, Grevillea sp. increased longevity by 6.9× compared with water only. Longevity of Plutella xylostella (L.) (Lepidoptera: Plutellidae), a major crop pest, was enhanced by all plants against which it was screened except Acacia baileyana, a species that had no effect on parasitoid longevity. Several Australian native plant species that benefit parasitoids were identified. None of the plant species provided a selective benefit to the parasitoid D. semiclausum compared with its host P. xylostella; however, the benefit of M. parvifolium and Grevillea sp. on the longevity of D. semiclausum was relatively higher compared with the pest. These results suggest the need for field studies to determine whether native Australian plants increase P. xylostella impact in nearby brassica crops.     

Wind‐modulated landscape effects on colonization of Brussels sprouts by insect pests and their syrphid antagonists

相似文献   

Effects of grapevine bunch exposure to sunlight on berry surface temperature and Lobesia botrana (Lepidoptera: Tortricidae) egg laying,hatching and larval settlement

相似文献   

Resistance to the pink potato aphid, Macrosiphum euphorbiae, in two accessions of Lycopersicon hirsutum f. glabratum

An integrated programme of pheromone-mediated mating disruption using Isomate-C®, post-harvest removal of fruit, and trapping overwintering larvae with cardboard tree bands, was used to control codling moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae), in four commercial organic apple orchards in Cawston, British Columbia during 1989–1992. One application of 1000 dispensers ^{– 1} on May 1 delivered estimated seasonal totals of 16.6, 16.5 and 19.9 g of E,E-8,10-dodecadien-1-ol [=codlemone] ^{– 1}in 1990, 1991 and 1992, respectively, at median rates of 8.4, 8.3, and 13.3 mg · < ha^–1 · ha^–1 during dusk flight periods of first brood and 5.3, 4.7 and 4.6 mg · ^{– 1}· ha^–1 in second brood, respectively. Over this 3-year period damage from codling moth at harvest ranged from 0.08 to 2.4%, and averaged 60.7% in these four organic orchards, while damage in five conventional orchards receiving sprays of azinphosmethyl ranged from 0.02 to 1.85%, and averaged 0.5%. Damage in an experimental orchard that was banded only, ranged from 43.5 to 56.7%, and averaged 48.9%. Between 1990 and 1992 cumulative male catches in Pherocon 1-CP wing traps baited with 10 mg of codlemone declined by 52% and densities of overwintering codling moth larvae declined an average of 49.5% in all organic orchards. Overwintering populations in the banded experimental orchard showed an increase of 57.7% during this study period. We conclude that an integrated programme of pheromone-mediated mating disruption, post-harvest fruit removal and tree banding, controls codling moth effectively enough to make organic apple production viable in British Columbia.     

Selective choice of sucrose solution concentration by the hovering hawk mothMacroglossum stellatarum

To determine the preference of the hovering hawk mothMacroglossum stellatarum for different sugar concentrations, the foraging behavior of adults were analyzed under laboratory conditions. Six sucrose concentrations (range, 10–60%, w/w) were simultaneously offered in six artificial ab libitum feeders. The number of feeding bouts and the duration of each visit were automatically recorded and stored in a computer. Results showed that the frequency of visits to the feeders did not vary among the different solutions offered, but the gathered volume by the group attained a maximum at between 20 and 50% (w/w). Moths invested more time in front of the feeder with the more concentrated sugar solutions. It was assumed that factors different from maximizing energy intake, such as water balance and viscosity of concentrated nectars, have to be considered in order to understand the observed patterns of nectar choice.