INDUSTRY NEWS
Karissa and Talia Eichenberger Caputo deflowering the ABA budwood trees to prevent pollen-borne viruses.
evidence of spread by vectors including mites. Apple Mosaic Virus Ilarvirus( ApMV) has a broad host range of 65 herbaceous and woody plants including almonds, apples, pears, stone fruit and strawberries. It causes a severe yield reduction between 30 – 50 % and poor tree vigour with reduced lifeexpectancy.
• Symptoms include leaf chlorosis in the form of blotching, mottling, mosaic, line patterns, yellow vein clearing, deformed leaves and stunted tree growth. In sensitive hosts ApMV can have a significant impact on fruit quality, particularly associated with fruit size and shape, and on yield. In almond ApMV is associated with flower and leaf bud failure. The presence of other viruses, such as PNRSV can exacerbate disease symptoms.
• Transmission occurs on infected propagation material and plants. Transmitted by grafting. The virus is not thought to be transmitted through seed or pollen and no insect vectors have been identified.
Apple Chlorotic Leaf Spot Virus( ACLSV) occurs worldwide and can affect plum, peach, sweet and sour cherry, and apricot. While it may be of significance in apricot and plum it may not be important in almond as a single infection.
• Symptoms may be associated with chlorotic leafroll of almond in
combination with PDV.
• Transmission is through infected propagation material and plants. Transmitted by grafting, including root grafting.
Plum Bark Necrosis Stem Pitting
Associated ampelovirus( PBNSPaV) is associated with plum bark necrosis and stem pitting disease in susceptible almond, plum, prune, peach, cherry and apricot varieties. It has limited distribution to Australia, North America, Europe, Jordan, Morocco and Egypt. It can have significant impacts on almonds yields in the case of mixed infections with other viruses and / or abiotic stress such as nutrient deficiencies.
• Symptoms include bark gummosis( gum-balls) and bark necrosis( die-off), pitting of the vascular tissue along branches and trunks, flattening of the scaffold branches. Graft union incompatibilities leading to decline. Chlorotic mottle ringspots or line patterns on leaves. Yield loss. However symptomless infections can occur.
• Transmission is on infected propagation material and plants. Transmitted by grafting, including root grafting. Natural spread occurs although no vector is reported. Other virus species in the genus are transmitted by mealybug and scale insects.
Ilarvirus is a genus of virus that includes PNRSV, PDV and ApMV.
Because of the genetic diversity amongst these viruses a generic test is used to help detect their presence if missed through the specific testing.
What growers can do Keep a look-out for virus symptoms. Virus symptoms may often be confused with other diseases or abiotic stress. If something unusual is sighted, be proactive and collect samples for laboratory testing. This is best done during October- December as results may take six weeks, and it allows time for retesting if required. Samples should be collected on Monday to Wednesday to make sure they reach the laboratory by the weekend. Make sure hands and equipment are clean and sterilised between each sample. Collecting five growing tips from the symptomatic tree, including five mature( whole) leaves from the tip. Place tips into a plastic zip-lock bag. Each bag should be clearly labelled and kept in an esky with ice. Contact the laboratory and complete a specimen submission form before sending samples to the diagnostic facility as soon as possible. The ABA has developed a new factsheet about Recognising and managing almond viruses and it can be found in the Grower Resources section of the website.
industry. australianalmonds. com. au
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