The further development of seed treatments to control cabbage stem flea beetle and other pests on winter oilseed rape

Abstract

The first year pilot study (Project Report OS43) identified three potential replacements for gamma-HCH. Imidacloprid + beta-cyfluthrin (as UK 805 from Bayer plc) provided similar or improved reductions in cabbage stem flea beetle adult damage compared with the previous industry-standard gamma-HCH. A 90% reduction in the percentage of plants infested by aphids was obtained at one site where a significant infestation developed. Indications were obtained from the manufacturer that UK 805 may also provide useful suppression of the incidence of slug damage.

In this project, the second year of the study, UK 805 was tested against other coded products, and methiocarb and carbosulfan which were available as commercial treatments in mainland Europe. Bayer UK 894, containing a lower rate of imidacloprid that available in UK 805, was also included as this product seemed the most likely candidate for approval to be obtained for use in the UK. 

Imidacloprid + beta-cyfluthrin at the rate used in the first year's trials reduced cabbage stem flea beetle larval damage by 45%, a similar mean reduction to that obtained in year 1. UK 894 provided a similar mean reduction in damage of 52%. Fipronil treatments reduced the attack by a mean of 58%, carbosulfan by 65%, bifenthrin by 81% and methiocarb by 11%. A pyrethroid spray of lambda-cyhalothrin at early larval invasion in the autumn reduced larval numbers by 78%. UK 894 followed by the spray gave a marginal improvement compared with the spray alone and reduced numbers by 86%. 

As in the first year, significant reductions in mean percentage of plants infested with aphids, predominantly peach-potato aphid, were obtained at one site. Results from UK 805 and UK 894 were similar to those from an autumn-applied pyrethroid spray. 

Imidacloprid + beta-cyfluthrin and methiocarb seed treatment provided significant reductions of 53-55% of plants damaged by slugs at site 1 where a moderate level of slug activity was recorded. 

In summer 2001, an HGCA Topic Sheet (TS48) was prepared and distributed within the industry. This provided a summary of the key action points for growers. 

The seed treatment UK894 based on imidacloprid (100 g/litre) + beta-cyfluthrin (100 g/litre) has now received approval from the Pesticides Safety Directorate for use in the UK as 'Chinook'. 

The registration for UK 894 as Chinook is for use as a seed treatment for autumn-sown crops of oilseed rape to reduce the damage to seedlings caused by early attacks of cabbage stem flea beetle with the objective of improving crop establishment. Chinook is recommended for use as a seed treatment for winter oilseed rape at 2.0 litres of product per 100 kg seed. The seed must be drilled and not broadcast to minimise wildlife risks.