Importance of Collection Overhangs on the Efficacy of Exclusion Fences for Managing Cabbage Flies (Diptera: Anthomyiidae)

Abstract

Fine nylon mesh fences (135 cm high) with varying lengths of downward-sloping collection overhangs were evaluated for efÞcacy in excluding the female cabbage ßies Delia radicum (L.) from plots of radish, Raphanus sativus (L.). During three trials conducted in 1994 and 1995, fences without overhangs, fences with 12.5-cm overhangs, or fences with 50-cm overhangs were tested against fences with standard 25-cm overhangs and unfenced control plots. In fenced plots with standard 25-cm overhangs, the mean number of D. radicum females caught on yellow sticky traps placed within plots was 85% less than those caught in corresponding control plots. The mean numbers of D. radicum females caught in fenced enclosures with no overhangs, 12.5-cm overhangs, or 50-cm overhangs, were 61, 67, and 94% less than those caught in corresponding control plots, respectively. The mean proportion of radishes damaged by D. radicum larvae inside enclosures with 25-cm overhangs was 62% less than in corresponding control plots. The mean proportions of radishes damaged inside fences with no overhangs, 12.5-cm overhangs, or 50-cm overhangs were 33, 59, and 81% less than those caught in corresponding control plots, respectively. Results are discussed in terms of deÞning an appropriate fence design for commercial use.

Using physical barriers to prevent carrot fly (Psila rosae (Fabricius)) damage in domestic production

“…Moreover, the patterns of yield and the numbers of harvested carrots follow roughly the same pattern as damage levels. Finally, the yield from plots protected by a 60 cm barrier with an overhang was greater than that from those plots with a 60 cm barrier alone and the overhang is unlikely to have caused much of an increase in shelter but is known to provide addition protection against the fly (Bomford et al, ); it therefore seems likely that early season carrot fly attack may have been the main contributing factor. Regardless of the reason, however, improved yield would be of interest to carrot growers, and so this information could be used to make more informed decisions regarding barrier choice and whether to completely cover the plots.…”

Physical Control: An Important Tool in Pest Management Programs

“…Vernon and Mackenzie (1998) showed that there was an inverse linear relationship between the number of cabbage flies (Delia radicum (L.)) entering a rutabaga plot and fence height. Bomford et al 2000 demonstrated that proper construction of the fence is an important factor in achieving maximum catch and retention of flies; an overhang at a 45° angle at the top of the screening significantly improved fly catches. Blua et al (2005) studied the effect of a 5 m high barrier screen used to prevent the movement of the sharpshooter Homalodisca coagulate (Say), which is a vector of the plant pathogen Xylella fastidiosa, into high value vineyards and nursery stock.…”

A review of research to address carrot fly (Psila rosae) control in the UK1

“…Researchers in North America and Norway have investigated the use of vertical fences to prevent colonization by pest insects, particularly cabbage root fly (Päts & Vernon, 1999; Bomford et al. , 2000; Meadow & Johansen, 2005), and the technique has also been evaluated in Canada (Vernon & McGregor, 1999), Switzerland (Wyss et al.…”