Harvested crops – August 2020

Ensuring stores are clean and free of pests is essential to prevent any problems after all the hard work of growing and harvesting the crop

Bear in mind that no pests of grain come in from the field – they are all loitering in the store or on associated machinery, trailers, pits, ducts just waiting for grain to arrive. They keep themselves ticking over on spilled grain, which can be found in crevices, on ledges, in pits and ducts. Consequently, giving the store a thorough cleaning can reduce the risk of pests such as weevils, saw-tooth grain beetle, mites and psocids (book lice) in particular being a problem. Don’t forget to treat associated machinery as well as the walls of stores. The use of bait bags to see what may be present in the store now is highly recommended, and if any pests are present insecticide treatments can be applied to the store to get rid of them. Any suspicious insects or bait bags can be sent to the Crop Clinic for a rapid identification of any insects present.

Note that the use of pirimiphos-methyl as a treatment to the store structure is no longer available – it can still, however, be applied directly to the grain.  With the withdrawal of chlorpyrifos-methyl products, alternatives for store structure treatment are now restricted to deltamethrin and cypermethrin.

Ideally, once the grain has been harvested, the moisture content should be reduced to 14% or lower, which might be a challenge this season unless we get a hot spell of weather. Getting the moisture down in store is the key to stop grain pests such as mites, beetles and weevils from breeding and surviving.

The presence of blue-black beetles in harvested oilseed rape seed or seen on the trailers is an advance warning that there could be a problem in the next winter oilseed rape crop from cabbage stem flea beetle. The beetles won’t harm the seed in the store and will be desperate to get out of the store and find an oilseed rape crop to feed on. We would welcome any reports of cabbage stem flea beetle at harvest as this provides information that impacts the management of this pest on the next crop of winter oilseed rape.