Barley Yellow Dwarf Virus of Wheat
Uniform yellow tips of leaves often with stripes running down the leaf blade. The leaf margins may become reddened or purple with age. The leaves are not killed by the infection but the whole plant may be dwarfed especially with early infection. Heads may be sterile. Roots may be stunted.
There are often patches of infection within the crop.
Infection may occur without visible symptoms.
Species Affected:Barley, Wheat, Oats, cereals and many grasses.
Biology:Caused by a group of closely related viruses.
The virus reduces nitrogen and moisture supply from the roots to the leaves causing stunted plants and/or reduced grain size.
Transmitted by aphids and most commonly by Cereal Aphids (Wheat or Oat Aphid (Rhopalosiphum padi) & Corn Aphid (Rhopalosiphum maidis)) or Rose-Grain Aphid (Metopolophium dirhodum) that feed exclusively on green plants. The Rice Root Aphid (Rhopalosiphum rufiabdominalis) and Sitobion miscanthi are minor vectors and generally not considered important in the spread of BYDV.
It is not transmitted on seed or crop residues.
The aphids pick up the virus from infected plants and spread it to uninfected plants. The virus lives in the salivary glands of the aphids until it dies. Infected patches of crop often occur in patches or along the edges of crops following the aphid feeding pattern. Crop plants infected before the end of tillering are often stunted. Symptoms usually take more than 3 weeks to appear and are often confused with nutrient deficiency symptoms.
Cool summers, early rains and the presence of early season cereal volunteers or perennial grasses lead to greater disease incidence.
Long season crops in high rainfall areas and early sown crops in low rainfall areas that are exposed to periods of high aphid numbers are most susceptible.
Life Cycle:Transmitted by Cereal Aphids usually early in the season around April/May or in spring around August.
Origin and History:Distribution:
Significance:Cereal yield losses of 10% may occur even without visible symptoms of infection.
Heavy yield losses are usually associated with early infections on early sown crops.
Management and Control:Sow resistant varieties. See Disease Susceptibility of Wheat Varieties.
Adjust planting date so young crops aren't exposed to periods of high aphid numbers.
Apply seed dressings containing imidacloprid.
Apply aphicides or anti-feeding insecticides early in the season before aphid numbers build up.
for current risk forecasts for BYDV in WA.
Related and Similar Species:Nitrogen deficiency and waterlogging have similar symptoms. In nitrogen deficiency the older leaves have far more yellowing than young leaves.
BYDV of Barley.
BYDV of Oats.
Collated by HerbiGuide. Phone 08 98444064 or www.HerbiGuide.com.au for more information.