Monday, July 15, 2019

Early drilled rape minimises damage from flea beetle

April 1, 2019 by  
Filed under Crops

Growers are drilling oilseed rape increasingly early in a bid to avoid damage from cabbage stem flea beetle, confirms a study.

Crops sown in the first week of August 2018 had little or no pest damage, according to Simon Kightley of independent agronomists NIABTAG, who analysed over a thousand responses submitted by rape growers from all over the UK.

But later crops suffered, with damage increasing weekly in crops drilled throughout August and into September, when the combined effects of flea beetle and drought produced severe damage or crop write-off in 71% of reported fields.

Most of the rape for harvest 2019 was drilled around the fourth week of August – a bit later than ideal, with many growers waiting for rain. At this time, 53% of crop had zero to mild pest damage whilst 23% was severe or a write off, according to this survey.

Peak migration

“This coincided with the peak migration of flea beetle into the crop.” says Mr Kightley. The findings suggest that very early sown rape crop can limit damage by flea beetle by avoiding peak pest invasion times, he adds.

“This pest is one of national significance and we no longer have the neonicotinoids or reliable help from pyrethroid insecticides to fall back on,” Mr Kightley explains. “Any cultural control method is worth considering.”

Research conducted by NIABTAG over four years shows that drilling rape before 10 August will avoid the worst of the flea beetle invasion. “This is providing that other stresses such as the heat or soil moisture do not slow down crop establishment.”

Nearly four times as much winter oilseed rape was lost in autumn 2018 compared to autumn 2017, according to the Kleffmann Group, which surveyed 403 UK rape growers. It estimated an original planted area in autumn 2018 of 581,030ha of winter rape.

Failed crops

Some 68 farmers reported failed crops amounting to 6.28% of the total original planted area. This represents 36,000ha lost. In the 2017/18 season, the percentage loss was just 1.62% so autumn 2018 was almost four times more hostile to rape survival.

The survey also revealed a clear difference in failed crops by breeding method. In conventional varieties the area lost was 7.52% (21,000ha) of the area planted. Of the restored hybrid varieties, some 5.16% of the crop planted (15,000ha) were lost.

The south-east region had the highest area of failed crop at 12.60%, followed by Yorkshire and the Humber Region at 9.75%. Between these extremes were the East Midlands (3.5% loss), south-west (4.34%), West Midlands (5.34%) and East Anglia (7.29%).

Reasons for crop losses were varied and included cabbage stem flea beetle damage, poor establishment and a lack of moisture which hindered germination in some areas.

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