Host Location and Ovipositional Behavior of Platygaster demades Walker (Hymenoptera: Platygastridae), an Egg Parasitoid of Apple and Pear Leaf Curling Midges

The foraging responses of 1–2-day-old naïve female Platygaster demades to odors of apple and pear foliage and host insect eggs were measured. The host origin of P. demades had no effect on the parasitoids’ longevity, host preference, or foraging behavior. Four distinct behaviors related to oviposition were identified. In choice experiments, more female parasitoids responded to apple foliage with no midge eggs than to midge eggs alone. In a Y-tube olfactometer, parasitoids preferred the plant cues to clean air, and responded equally to both apple and pear odors. The results indicate that P. demades utilizes plant cues to locate the habitat of its host and then searches for host eggs to parasitize.     

Oviposition preferences of the Hessian fly and their consequences for the survival and reproductive potential of offspring

1. The relationship between oviposition preference and offspring performance was investigated experimentally for the Hessian fly Mayetiola destructor (Say) using 10 grass genotypes that represented five different genera and six different species. Oviposition preferences were quantified in a choice test using arrays of 200–400 plants. Offspring performance was estimated by recording survival during three phases of the insect–plant association and by measuring wing length, a correlate of adult reproductive potential. Density effects were examined for all offspring variables, and were taken into account when offspring performance was compared across the 10 grasses. 2. Egg counts from the oviposition choice test revealed a consistent ranking of plants: 18ITSN triticale > Otane bread wheat = Caldwell bread wheat = Stacy bread wheat > 3424 bread wheat = PND durum wheat = Fleet barley = Valetta barley = Matua brome grass > Awapuni oat. 3. Survival and adult wing length varied significantly on the 10 plant types. Survival was ranked: Otane bread wheat > 3424 bread wheat = Fleet barley = Matua brome grass > Caldwell bread wheat = Valetta barley > 18ITSN triticale = PND durum wheat = Stacy bread wheat > Awapuni oat. Adult male and female wing lengths were greatest on Otane, the bread wheat that also provided the best survival. 4. For Hessian flies on each of the 10 plant types, data on survival, wing length, and wing length–fecundity relationships were combined into a single fitness measure. When these fitness measures were compared with egg counts, no overall pattern emerged. On seven of the 10 plant types, there was a positive linear relationship between egg counts and offspring fitness. On the other three plant types, egg counts were high while fitness was low. Possible reasons why Hessian fly females lay eggs on plants that are poor hosts for their offspring are discussed.     

Characterisation of microRNAs from apple (<Emphasis Type="Italic">Malus domestica</Emphasis>'Royal Gala') vascular tissue and phloem sap

Background  

Plant microRNAs (miRNAs) are a class of small, non-coding RNAs that play an important role in development and environmental responses. Hundreds of plant miRNAs have been identified to date, mainly from the model species for which there are available genome sequences. The current challenge is to characterise miRNAs from plant species with agricultural and horticultural importance, to aid our understanding of important regulatory mechanisms in crop species and enable improvement of crops and rootstocks.     

Studies on the partial characterization of extracted glycosaminoglycans from fish waste and its potentiality in modulating obesity through in-vitro and in-vivo

Glycoconjugate Journal - Glycosaminoglycans (GAGs) are bioactive polysaccharides or glycoconjugates found in the fish waste having significant health impacts. In the present study it has been...     

Yield and quality of forage maize (<i>Zea mays</i> L.) with different levels of subsurface drip irrigation and plant density

The scarcity of water in arid and semiarid regions of the world is a problem that every day increases by climate change. The subsurface drip irrigation (SDI) and changes in population density of plants are alternatives that can be used to make a sustainable use of water. Therefore, the objectives of this study were to determine the combination that allows for an increased corn performance and efficient use of water without losing the quality of forage. Three different irrigation levels were applied through a system of a SDI at three different densities of forage maize plants in an arid region. The results demonstrated that by applying different levels of water, either enough or lack of soil moisture is created, which is directly reflected in crop yield, and its determining variables such as green forage and dry matter yield, and nutritional quality. The irrigation level to a 100% of potential evapotranspiration (PET), at a density of 80000 plants/ha, increased yield of green forage to 57664 kg/ha; crude protein was 8.59%, while the rest of the quality parameters decreased. This study allowed to conclude that the irrigation level was the major factor in the response of the crop.     

Trapping Dasinuera mali (Diptera: Cecidomyiidae) in apples

The midge Dasineura mali (Kieffer) (Diptera: Cecidomyiidae) is a significant pest of apples (Malus spp.), and the recent identification of the female sex pheromone is enabling new direct control tactics to be considered. Direct control using male suppression will require knowledge of the frequency of multiple mating, dispersal and colonization rates, and the efficiency of male removal. Males were able to mate up to five times, with a mean of 2.7 times when presented in a 10 female-to-1 male group, designed to simulate male suppression. Male catch in response to the pheromone loading was curvilinear over 4 orders of magnitude from 3 microg to 30 mg on rubber septa. Trapping using a high-dose pheromone lure was combined with oil-based traps similar to the inexpensive New Zealand "Lynfield trap" used for tephritid surveillance, to test male suppression in young orchard blocks at 500 traps per ha. Monitoring traps indicated 96% lower catch in the treated plots compared with control plots, over 137 d. However, a lack of shoot tip infestation in both treated and untreated plots indicated limited colonization and prevented an assessment of potential population suppression. Furthermore, a contribution to these results from communication disruption cannot be ruled out. Replicated transects of frequency of infested shoots from a mature orchard across the adjacent young block confirmed that colonization by ovipositing females was essentially limited to the first 30 m.     

Quantitative comparison of stylet penetration behaviors of glassy-winged sharpshooter on selected hosts

New Zealand is threatened by invasion of the glassy-winged sharpshooter, Homalodisca vitripennis (Germar) (Hemiptera: Cicadellidae), an important vector of Xylella fastidiosa, a gram-negative bacterium that causes Pierce's disease in grape (Vitis spp.) and scorch diseases in many other horticultural crops. Therefore, an understanding of the host acceptability, feeding behavior, and potential vector efficiency of glassy-winged sharpshooter on New Zealand crops is important. We tested host plant acceptance and feeding behaviors of glassy-winged sharpshooter on three common horticultural crops grown in New Zealand (apple [Malus spp.], grape, and citrus [Citrus spp.]), and a native plant (Metrosideros excelsa [=tomentosa] Richard, pohutukawa), using the electrical penetration graph (EPG) technique. Probing (stylet penetration) behaviors varied among the host plants, primarily due to differences in waveform event durations. Apple and grape were the most accepted host plants, on which glassy-winged sharpshooter spent the majority of its time on the plant probing and readily located and accepted a xylem cell for ingestion. This resulted in long durations of sustained xylem fluid ingestion. In contrast, pohutukawa was the least accepted host. On this plant, glassy-winged sharpshooter spent less time probing and engaged in longer and more frequent testing/searching and xylem-testing activities, rejected xylem cells frequently, and spent less time with stylets resting, before accepting a xylem cell and ultimately performing the same amount of sustained ingestion. Citrus plants contaminated with sublethal insecticide residues were intermediate between these extremes, with some acceptance of xylem, but less ingestion, probably due to presumed partial paralysis of the cibarial muscles. Implications of the results in terms of host plant acceptance and the development of a stylet penetration index are discussed.     

Laboratory and field studies supporting the development of Heringia calcarata as a candidate biological control agent for Eriosoma lanigerum in New Zealand

Studies supporting a project seeking to introduce Heringia calcarata (Loew) (Diptera: Syrphidae) to New Zealand (NZ) to supplement biological control of woolly apple aphid (WAA), Eriosoma lanigerum (Hausmann) (Hemiptera: Aphididae) are reported. Annual surveys of H. calcarata presence and abundance in a Virginia, USA apple orchard revealed a bimodal distribution, with peaks in mid-June and mid-September. In the field, female H. calcarata oviposited on sentinel apple shoots infested with WAA, providing an efficient method for egg collection and larval production. Similarly, most field-collected females readily deposited viable eggs on WAA colonies in laboratory cages, demonstrating that mated females will oviposit in captivity. Survivorship of eggs and larvae transported to NZ was good, yielding adult flies in containment in Auckland. Adult, virgin female H. calcarata reared from eggs in captivity developed mature oocytes, providing an important step toward future mating studies in containment. Oviposition and larval feeding studies examined aspects of the intraguild interactions between H. calcarata and Aphelinus mali (Haldeman) (Hymenoptera: Aphelinidae), the sole biological control agent of WAA in NZ. Field tests using paired sentinel apple shoots with a non-parasitized or parasitized WAA colony revealed that although H. calcarata deposited eggs on both parasitized and non-parasitized colonies, fewest eggs were deposited on heavily parasitized colonies. Feeding studies showed that larval H. calcarata consumed fewer mummified aphids or aphids in an earlier stage of parasitization than non-parasitized aphids.