Controlling root flies with exclusion fences?

Protecting crops with insect fences is currently being considered as an alternative to row cover netting and synthetic insecticides. Previous studies reported efficacies of such fences with 50-90 % reduction in crop damage by root flies. We conducted trials with a 1.70 m fence over two years to monitor carrot rust fly (Psila rosae) in carrots and cabbage root fly (Delia radicum) in radish. There was a significant reduction in cabbage root fly damage in fenced plots whereas no such effect could be found with carrot rust fly. The structure of the overhang at the top of the fence and the mobility of this particular species may be important elements to consider in fence design. The length of the overhang also seemed to be important for cabbage root fly (Delia radicum) control, as a statistically significant treatment effect was observed only when the overhang was 35 cm long. Using radish as a test crop, the fences reduced damage by 55 % in the second year of the trial. The population size of overwintering cabbage root flies was also an important factor, as the number of flies in the year that the fence was effective was lower than in the previous year

Strohmulch gegen Blattläuse im Gemüsebau

One way to prevent the colonisation of crops by insect pests is to disrupt their host finding behaviour. As immigrating aphids alight on potential host plants using optical stimuli, this process can be manipulated by altering the contrast between plant and background. This study aims to test the aphid repelling properties of straw mulch in vegetables. We applied straw to broccoli, head lettuce, bush bean, vegetable broad bean and carrot. The trials were conducted in 2002 and 2003 at several locations in the area of Brunswick, North Germany. Numbers of aphids were insignificant in carrots but noticeably reduced in mulched broccoli, bush bean and broad bean (Brevicoryne brassicae and Aphis fabae respectively). However, this result was significant only in one of two growing locations. We could not observe any reduction of aphid numbers in mulched lettuce. This finding might relate to lettuce leaf colour. Natural antagonists of aphids as well as other vegetable pests such as lepidoptera and root flies were not affected by straw mulch. The influence of soil type, number of immigrating aphids and cropping environment on the effectiveness of straw mulch warrants further research

Reduzierung des Blattlausbefalls an ausgewählten Gemüsekulturen durch Mulchen mit verschiedenen Materialien und Farben

Ziel des Projekts war die Prüfung von Mulchmaterialien im ökologischen Pflanzenschutz zur Reduzierung des Blattlausbefalls in Freilandgemüse. Weizenstroh und farbige Polypropylenvliese wurden in diversen Gemüsekulturen auf mehreren Standorten in Norddeutschland eingesetzt. Versuchsdurchführung und Datenerhebung wurden durch extreme Niederschläge und durch Trockenheit und Hitze erheblich beeinflusst. Bei dem Einsatz von Strohmulch in Brokkoli, Buschbohne und Dicker Bohne war der Blattlausbefall auf einem von zwei Versuchsstandorten bis zu 50 % vermindert. Die Wirkung war auf einen verringerten Einflug von Blattläusen in strohgemulchte Parzellen zurückzuführen. Strohmulch zeigte in Kopfsalat keine Wirkung auf den Blattlausbefall. In Möhren war die Anzahl Blattläuse zu gering, um zur Auswertung beizutragen. Die Ergebnisse deuten darauf hin, dass die Wirkung von Strohmulch von der Stärke des Blattlauseinflugs, der Blattfarbe der Pflanzenart sowie dem Bodentyp und der Witterung abhängig ist. Das Auftreten weiterer tierischer Schädlinge wie Raupen oder Gemüsefliegen als auch Krankheiten oder Nützlinge wurde durch Strohmulch nicht beeinflusst. Auch die Erträge von strohgemulchtem Gemüse unterschieden sich nicht oder nur geringfügig von ungemulchtem Gemüse. Der Einsatz von farbigen Mulchvliesen (Schwarz, Weiß, Grün, Rot, Blau, Dunkelblau, Silber) wurde in den Kulturen Brokkoli, Kopfsalat und Buschbohne getestet. Der Befall mit Blattläusen war in den Mulchfarben Silber, Rot und Weiß bis zur Hälfte reduziert. Dagegen schienen diese Farben attraktiv auf Schmetterlinge zu wirken. Jedoch waren die Unterschiede zur Ernte nicht mehr statistisch abzusichern. Die Anbauvarianten Kontrolle, Grün und Schwarz waren zeitweise am stärksten mit Blattläusen befallen. Ein Einfluss auf nützliche Antagonisten wie Parasitoide und Schwebfliegen wurde nicht festgestellt. Pflanzenbaulich befriedigten die Materialien Rot und Weiß mangels Unkrautunterdrückung nicht und verhinderten eindeutige Aussagen zum Ertragsvergleich. Das aluminiumbedampfte Silbervlies zeigte neben einem geringen Blattlausbefall auch die höchste Ertragssteigerung

Food foraging in adult parasitoid Cotesia rubecula : how sugar sources contribute to survival and reproduction / by Gitta Siekmann.

Bibliography: leaves 133-148.xii, 148 leaves : ill. ; 30 cm.Examines sugar foraging in the field by adult female parasitoid wasp, Cotesia rubecula (Hymenoptera, Braconidae), to determine its effect on fecundity and lifespan. In the field, the area in which wasps search for sugar is likely to depend on the degree of association of hosts with nectar or honeydew, supporting the hypothesis that sugar encounters in the field happen opportunistically during host foraging activities. The survival gained by sugar feeding my often be severely limited by quality and quantity of sugary food and extrinsic mortality factors such as adverse weather conditions and predation, so the need for food must be studied in relation to a species' adaptation to its environment. Concentrations of sugar sources may distract wasps from host-foraging when the density of hosts is low. This has implications for flower propagation in agro-ecosystems with a view to supporting natural enemies of insect pests.Thesis (Ph.D.)--University of Adelaide, Dept. of Applied & Molecular Ecology, 200

What is STEM? The need for unpacking its definitions and applications

The generality of the umbrella term \u27STEM\u27 as a synonym for a diverse group of skills and academic fields poses various problems in terms of workforce planning and targeted interventions. This summary brings together findings from NCVER research investigating educational and occupational concepts and their associated definitions raised in the literature review. As there is no universally shared definitions of STEM skills there cannot be comparable \u27STEM\u27 statistics on any number of people, subjects, courses or occupations in the science and technology domain; these should be reported per defined field or grouping e.g. natural sciences, engineering, finance and health

What is STEM? The need for unpacking its definitions and applications

The generality of the umbrella term \u27STEM\u27 as a synonym for a diverse group of skills and academic fields poses various problems in terms of workforce planning and targeted interventions. This summary brings together findings from NCVER research investigating educational and occupational concepts and their associated definitions raised in the literature review. As there is no universally shared definitions of STEM skills there cannot be comparable \u27STEM\u27 statistics on any number of people, subjects, courses or occupations in the science and technology domain; these should be reported per defined field or grouping e.g. natural sciences, engineering, finance and health

The Sweet Tooth of Adult Parasitoid \u3ci\u3eCotesia rubecula\u3c/i\u3e: Ignoring Hosts for Nectar?

Investing time and energy into survival and reproduction often presents a trade-off to many species of animals. In parasitic wasps, both hosts and sugar sources contribute to the forager’s fitness but are often found in different locations. The decision to search for hosts or for food can have a strong impact on fitness when the forager’s lifetime is short and resources are not abundant. We investigated the tendency of flowers and hosts to attract 1-day-old female Cotesia rubecula Marshall (Hymenoptera: Braconidae) with different feeding histories in a wind tunnel. Only well-fed wasps exhibited a preference for hosts. In comparison, unfed wasps visited hosts and flowers in equal proportions. Feeding experience had a strong impact on the searching behavior and the number of landings on both resources. Host and food stimuli seem to be equally attractive to hungry parasitic wasps such as C. rubecula. We expect that under field conditions the time available for active food searching in female C. rubecula is short and influenced by the presence of hosts

Controlling root flies with exclusion fences?

Abstract: Protecting crops with insect fences is currently being considered as an alternative to row cover netting and synthetic insecticides. Previous studies reported efficacies of such fences with 50-90 % reduction in crop damage by root flies. We conducted trials with a 1.70 m fence over two years to monitor carrot rust fly (Psila rosae) in carrots and cabbage root fly (Delia radicum) in radish. There was a significant reduction in cabbage root fly damage in fenced plots whereas no such effect could be found with carrot rust fly. The structure of the overhang at the top of the fence and the mobility of this particular species may be important elements to consider in fence design. The length of the overhang also seemed to be important for cabbage root fly (Delia radicum) control, as a statistically significant treatment effect was observed only when the overhang was 35 cm long. Using radish as a test crop, the fences reduced damage by 55 % in the second year of the trial. The population size of overwintering cabbage root flies was also an important factor, as the number of flies in the year that the fence was effective was lower than in the previous year

Feeding and survival in parasitic wasps: Sugar concentration and timing matter

Sugar consumption can increase the longevity and lifetime fecundity of many species of parasitic wasps. Consequently, for these insects the availability of sugar sources in the field is important for their reproductive success. As sugar sources can be highly variable in quantity, space and time, the chances of finding a sufficient amount of sugar to increase longevity might be very low. Therefore, the reward from a single feeding event can be critical for the forager’s fitness. We measured the longevity of the parasitoid Cotesia rubecula after a single honey meal differing in sugar concentration (25, 47, 86% w/w) and timing (day of emergence and 24 h later). Survival was analyzed with Cox’s Proportional Hazards Model. The risk of starving to death in sugar-fed wasps was reduced by 0–73% in comparison to unfed wasps, depending on sugar concentration and timing. Longevity was significantly increased by sugar concentration and by feeding later in life. Our results suggest that in the field, adult C. rubecula has to locate food at least once per day to avoid starvation

Einsatz der Pheromonverwirrungstechnik zur Regulierung der Rosskastanien-Miniermotte - Cameraria ohridella Deschka u. Dimic (Lep.: Gracillariidae)

The horse chestnut leafminer is an introduced invasive pest that every year causes extensive damage to the leaves of the white flowering horse chestnut tree. An environmentally friendly method to control insect pests involves the use of sex pheromones for mating disruption. A large quantity of artificial pheromone is released into the insect plant system confusing males to the extend that they are unable to locate receptive females. In order to test the potential efficacy of the mating disruption technique on the horse chestnut leafminer we set up semi-field trials with closed experimental units and varying leafminer densities.We counted the number of leaf mines on pheromone treated horse chestnut trees and compared them with an untreated control. Mating disruption lead to a significant reduction in damage by more than 90% in the first and second generation of the leafminer, irrespective of the initial leafminer density. Although these results are very encouraging, high population densities of the horse chestnut leafminer in nature and the patchy distribution of horse chestnut trees in the cities will challenge the efficacy of mating disruption in the field. Further experiments are plannedwith open experimental units and typical horse chestnut trees in various parks and gardens.Gitta Siekmann, Rainer Meyhöfer and Martin Homme