Withdrawal of agrochemicals used widely to control common pests of new grass reseeds should not hamper livestock farmers’ ability to renew swards, as the threat can be minimised through effective cultivations and/or the strategic use of break crops.
That’s according to David Little of forage specialist Germinal in response to the ban from April 1, 2016 of the use of all chlorpyrifos–ethyl products (e.g. Dursban).
“These agrochemicals have been used effectively for many years to control pests of new grassland such as leatherjackets and frit fly, but they are being withdrawn,” he explained.
According to Little, these pests can devastate new leys if not controlled, but the risks can be avoided through effective cultivations and the use of brassica break crops.
“The use of fast–establishing hybrid brassicas (such as Swift or Redstart) or Maris Kestrel kale have the added benefits of providing an additional source of high quality grazing, reducing the effect of any forage shortfalls between leys. This can be timed to provide late summer, autumn or even winter grazing for cattle or sheep.”
Leatherjackets
Leatherjackets result from the crane fly laying its eggs in late summer, with these then developing into larvae over the winter months.
These larvae (leatherjackets) feed on the roots and stems of plants just below the surface and cause crop damage (loss of yield and large bare patches) from early spring until mid–summer when they pupate.
Frit fly
The frit fly frequently produces three generations a year, with the larvae of the third generation emerging in late summer. These larvae can cause a great deal of damage to grass leys and cereals when they tunnel into the centre of the plant causing dead–hearts before then moving to another tiller or plant.
Solution
According to Little, ploughing and cultivating in summer, and sowing a break crop, will disrupt the life cycle of the crane fly and is known to reduce leatherjacket populations by 50%, adds David Little.
“In a similar way, the risk of frit fly damage can be minimised with the use of break crops, particularly when the period between planting and utilisation is at least two months.”
