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

Plant Protection in organic production of Brassica vegetables and oilseed rape

Growers of organic Brassica vegetables and oilseed rape face the same potentially severe plant protection problems as their colleagues in conventional or integrated pest management systems.Management strategies in organic systems rely on preventive measures (crop rotation, crop isolation,soil management, host plant resistance, farm/field location; manipulate timing of planting or harvest; intercropping, mulching), use of functional agro-biodiversity (reduction of pest by enhancing natural enemies), release of biocontrol agents and a few approved pesticides of biological and mineral origin, as well as mating disruption or the use of anti-insect nets (Zehnder et al., 2007). The methods used in organic might also be applicable in IPM systems. However, several factors hamper wide implementation of these methods in IPM. Among the main reasons are (1) a lower efficacy compared to standard pesticide treatments, (2) higher costs, (3) lack of knowledge / information / advice on alternative methods, (4) inconvenience, and (5) the need for close collaboration between neighbouring famers to achieve good control. In the following paper, we describe the methods used in organic Brassica vegetable and oilseed rape production, and discuss their limitations

Pflanzenschutzmittel im Garten

Beitrag zum Themenschwerpunkt II Pflanzen stärken – Pflanzen schütze

Effects of landscape and region on pests and pathogens in Brassica vegetables and oilseed rape.

Abstract: Pests and pathogens of Brassica vegetables and oilseed rape are mainly managed at a field level. Management of pest insects at a farm level is only suitable for farmers owning compact areas of land, which is not the case in many central European areas. This paper discusses the effects of landscape and region on pests and pathogens in Brassica crops. Topics covered include pest and disease dispersal and persistence, regional races or biotypes, new pests and pathogens, insecticide resistance, conservation biocontrol and monitoring and forecasting

Ecological selectivity of pesticides and application methods

According to David Pimentel, 20 years ago, less than 0.1% of the pesticides applied reached their target pests (Pimentel, 1995). This was partly due to ‘poor’ application methods and partly because of the minuscule amount of pesticide either picked up or consumed by the pest. At the time, Pimentel was describing the application of pesticides mainly by sprays, including aerial spraying, and both pesticide chemistry and application technology have improved since then. However, a considerable proportion of pesticides are still applied as sprays, either to crop foliage or to the soil, and this continues to be a relatively untargeted method of application

Schlagseparierung als Ansatz zur Prävention von Möhrenfliegenschäden

Die Möhrenfliege (Psila rosae) gehört zu den wichtigsten tierischen Schaderregern im Ökologischen Möhrenanbau. In dreijährigen Erhebungen auf Praxisbetrieben wurden verschiedene beteiligte Risikofakoren für den Befall mit geo-referenzierten Daten erfasst und im Hinblick auf Verbesserungsmöglichkeiten zur Schadensprävention analysiert. Erste Ergebnisse zu räumlichen Beziehungen von Schlaggrößen und der jew. Entfernung zu Vorjahresflächen auf das Befallsergebnis ergaben, dass die Einhaltung von Distanzen um 1 km einen nutzbaren, anbauplanerischen Regulierungsbaustein darstellen kann. Dieser empirische Befund sollte aber nicht als starre Ausbreitungsstrecke aufgefasst werden, weil zusätzlich gezeigt werden konnte, dass dem Vorjahr nächstgelegene Möhrenfelder offenbar das Befallsrisiko für weitere, entfernter liegende Möhrenschläge senkend beeinflussten. Fehlen andererseits engbenachbarte Schläge, ist im Umkehrschluß damit zu rechnen, dass entsprechend einer grob geschätzten täglichen Ausbreitungskapazität auch Distanzen > 1 km überwunden werden können