Sunday, 16 December 2018

Aphid Alert

Wheat Drilled into Oat Stubbles
I think this could have possibly been one of the best autumns for establishing winter crops I can remember for quite some time. After the very dry summer months we started to get rain at just about the right time. This rain enabled weeds to germinate in the stubble's and cover crops before the main crops were planted. We had enough rain over the planting period to make sure that the seeds we planted germinated rapidly and emerged very quickly.
This year we have only used seed dressings with Zinc and Manganese on them to kick start the growth of the young plants, except on 1 block of barley we are growing for seed. Every year we have tested leaves for deficiency and these trace elements have always come up short.
One dilemma I have had is whether or not we should be spraying an autumn insecticide to control aphids. The aphids (Bird Cherry-Oat and Grain Aphids) could be carrying a virus called Barley Yellow Dwarf Virus which stunts the growth of plants and reduces yield. The only problem is you don't know if the aphids in our crops are carrying the virus and if the plants have been infected until the spring, when its too late to treat. The AHDB has developed a tool to assess when you should spray for aphids. This can play a crucial role when we are using Integrated Pest Management to responsibly use pesticides. This means that when we see a pest, we monitor its development and then spray with the correct product, with the correct amount of water and the correct dose rate to take the pest out. The tool can be found HERE 
As we are trying to reduce the levels of insecticide we apply on our fields I have decided not to spray half of the wheat area that was later planted but rely on our beneficial predators to help reduce the numbers of aphids. There are always lots of spiders webs across the fields and the aphids should provide a tasty snack! The Game and Wildlife Conservation Trust did some research which indicated that the effect on beneficial insects of that autumn spray was still apparent the following June.
Providing grassy margins around our field boundaries and beetle banks within larger fields also help create habitat for beneficial insects to live ready to strike at invading aphids. We will see in the spring whether or not this was a good decision! We need a good hard winter to help kill off as many aphids as possible.

No comments: