Barley Yellow Dwarf Virus in Cereal Crops

Early sowing and high aphid populations in the autumn of 2014, have resulted in many grazing cereal crops suffering from Barley Yellow Dwarf Virus (BYDV).

BYDV is an aphid borne virus that affects wheat, barley, triticale and oats, plus over 150 species of grasses. It is generally spread by aphids from infected grasses to crops.

Crops most at risk are those sown early when conditions are mild and aphids are active. In the last 3 to 5 years, oats have been particularly affected, but in 2014 widespread impact has been observed on early sown Wylah and Wedgetail crops.

Symptoms appear as yellow, red or purple colouring on the leaves, plus stunted plant growth. Traditionally these symptoms have occurred in patches or hotspots coinciding with aphid infestation, generally appearing after the end of tillering. Yield loss in these situations is minimal.

However in 2014, infection has occurred across whole paddocks and become evident much earlier in the season, often prior to or soon after the end of tillering.   Plant pathologists are suggesting that yield loss estimates are based on the number of infected plants in the paddock. Given that in many cases it appears infection levels are 100%, it is possible that yield loss may be significant.

Observations this year suggest that the use of an insecticide seed treatment has deterred early aphids, with these crops currently free of BYDV symptoms. This approach should be taken for crops sown early in 2015 where aphid infestation may occur.

Control of the green bridge (or host plants) is useful in reducing aphid numbers, however due to the wide range of hosts and the mobility of the aphids, removal of the green bridge alone is unlikely to eliminate BYDV.