Reducing damage to oilseed rape by woodpigeon trials with I. Cinnamamide; II. Breeding high glucosinolate varieties.

Abstract

The aim of the project was to evaluate two methods of reducing woodpigeon damage to oilseed rape by reducing the palatability of the crop: through the application of an avian repellent, cinnamamide, and modification of rape leaf glucosinolates.

Cinnamamide:

In a pilot field trial carried out prior to the current project, cinnamamide was shown to reduce pigeon damage to rape, however, the persistence of cinnamamide on the leaves was poor. A more weather-resistant suspension concentrate (SC) formulation of the avian repellent cinnamamide, has been developed. Studies of this improved formulation, which uses a 10 % Acronal / 2 % Emoleo L1 mix in the ratio 3:1 v/v as the sticker, suggested that leaching would be less than half that of the original formulation (the inclusion of Emoleo L1 was also beneficial as it reduces leaching associated with freezing and thawing cycles). A bioassay using captive pigeons showed that the modified stickers do not mask the repellent properties of cinnamamide; hence the improved formulation was suitable for use in subsequent field trials. Trials carried out over three years showed that the persistence of the new cinnamamide formulation has been greatly improved compared to that used in the pilot trial.

In the final field trial there was sufficient woodpigeon damage to the field site to assess the effectiveness of the improved cinnamamide formulation and compare it with the high glucosinolate JIC line of rape. Cinnamamide was shown to reduce the level of pigeon damage to rape, and towards the end of January treated plots had only 73 % of the damage found on control plots. Although the cinnamamide did not keep the pigeons off the plots altogether, there was a significant reduction in the number of plants which were severely damaged. It is these severely damaged plants which are least likely to recover, and so have the greatest effect on yield. The JIC rape was also shown to be less palatable to pigeons. Plots with the 'double protection' of the cinnamamide spray and the high glucosinolate rape were the least damaged. By the end of January, plots of the JIC rape which were also sprayed with cinnamamide, had only 70 % the damage of untreated Apex plots.

The project has demonstrated that when cinnamamide is present on leaf surfaces, the amount of severe pigeon damage is reduced. As such it would provide an effective and environmentally benign means of reducing woodpigeon damage to oilseed rape. Although cinnamamide is not yet registered for use as a repellent on oilseed rape, industrial sponsorship is currently being pursued to take it through to the registration procedure.

Glucosinolates:

Winter oilseed rape double haploid lines have been developed which have enhanced levels of 2-propenyl glucosinolates and 3-butenyl glucosinolates in their leaves, but which retain low seed glucosinolates (GLS's). From small plot trials, lines with good GLS profiles, which showed a reduction in pigeon grazing and which yielded within the normal range of advanced breeding lines, were selected for larger scale field trials. In 1999/2000, a number of fields at farms across Britain were sown with either pure modified GLS line (JIC1) or as a mixture with other double low cultivars. At the majority of sites, a reduction in pigeon grazing was observed in these fields compared to surrounding fields, where pigeon damage was significant. It is concluded that the development of OSR with enhanced glucosinolates has the potential to reduce pigeon damage, and that it is most likely to be viable in practice if used as a mixture with the latest high yielding lines.