Following last year’s widespread downgrading of field beans due to bruchid beetle damage the authorisation of insecticide Biscaya (thiacloprid) for its control is timely.
Frontier Agriculture’s UK pulse manager Andy Bury has observed an increase in bruchid beetle problems over the last five years and says that 2017 was particularly challenging. The UK crop of spring and winter beans ranges from 550 to 650,000 tonnes and he says that typically there is an export market for good human consumption beans of around 280,000 tonnes.
“Last year UK exports would not have reached 100,000 tonnes with bruchid beetle responsible for 80% of downgrading. Frontier can manage up to 10% total damage but beyond that the human consumption premium – typically £20/tonne – is outweighed by allowances.”
Control is all about timing he stresses. “Based upon the simple criteria of pods being present on the lowest node and the temperature having reached 20°C on two consecutive days, beans are at risk from bruchid beetle attack, so you have to move fast. Once you see yellow eggs on the bottom pods it’s too late.”
PGRO principal technical officer Becky Howard concurs and explains that reduction of damage must be achieved by reducing egg-laying at early pod set. “It was the above average temperatures in late May and June that exacerbated bruchid beetle damage last year. The heat made bruchids very active while reducing the persistence of pyrethroid sprays.”
Biscaya ought to be more persistent she says and is a welcome introduction with on-label approval for control of bruchid beetle and pea aphids in field beans.
For the reduction of bruchid beetle damage applications must be made between 1st May and 31st July. The label advises that most reliable results will be obtained from application of 0.4 L/ha when temperatures reach 20°C or more on two consecutive days at early pod set. Water volume should be 200 to 400 L/ha and the second of the two applications permitted per crop should go on a minimum of 10 days later.