Wheat curl mite and the wheat streak mosaic virus

Recent research by the Centre for Environmental Stress and Adaptation Research (CESAR) has led to the discovery of two species of wheat curl mite within Australia. This finding could complicate further studies into the wheat curl mite (Aceria tosichella), the organism primarily responsible for transmitting the wheat streak mosaic virus.  

Findings that were released last week indicate that not only are there two species of wheat curl mite present in Australia, but both are widespread across the wheat belt (although only one species has been collected in Queensland). CESAR director, Ary Hoffmann, said that only one of these species is likely to carry the name Aceria tosichella – the other may yet prove to be a new, undescribed species.

The wheat curl mite acquires the virus when it feeds on infected plants. The mite directly damages young growth through feeding, and is also responsible for the transmission of another important disease of wheat, the high plains virus. A new diagnostic test has been developed by CESAR to distinguish the species of wheat curl mite. It is still unclear as to whether one or both species are vectors of the wheat streak mosaic virus.

Monitoring of wheat crops by the NSW Department of Primary Industries continues to occur throughout this season. Earlier this year, the wheat streak mosaic virus was detected in NSW (see PestFacts Issue No. 2) and plant pathologist, Dr Gordon Murray (NSW DPI), says two more suspected cases have recently been detected. If confirmed, the outbreak at Eugowra is as far west as wheat streak mosaic virus has been found in the Central West Slopes and Plains district of NSW. The other incident was reported from Cowra, also in the Central West Slopes and Plains district. Plant material from the affected paddocks is currently being analysed for the presence of the virus.

Plants infected with wheat streak mosaic virus initially have light green streaks on the leaves which later develop into yellow stripes running parallel to the leaf veins. These symptoms can sometimes be confused with nutritional, environmental and chemical damage. Affected plants can die prematurely, become stunted or fail to grow. Heads on infected plants can be sterile and contain no seed, or can contain small shrivelled grain.

Although unconfirmed, Gordon says that the recent detection of wheat streak mosaic virus symptoms in wheat crops serves as a timely reminder to be on the lookout for the virus. Last season, the symptoms were apparent from late August onwards, although the weather conditions were a little warmer than those experienced this year. If you observe any symptoms that resemble wheat streak mosaic virus, contact your local agronomist or Gordon Murray on 02 6938 1879 or by email: gordon.murray@dpi.nsw.gov.au.

For further information on the recent discovery of two species of wheat curl mite click here.