Viral diseases of cotton are of economic significance in many parts of the world. Only two virus diseases have been reported from Australian cotton crops, Cotton bunchy top (CBT) and Tobacco streak virus (TSV). However, many of the most economically damaging virus diseases of cotton remain serious biosecurity threats. These include Cotton leaf curl disease (CLCuD), Cotton leaf roll dwarf virus (CLRDV; causing Cotton blue disease) and Cotton leaf crumple virus (CLCrV).

Insect vectors for Cotton leaf curl disease, Cotton leaf crumple and Cotton blue disease are common and widespread in many cotton growing regions of Australia. Surveillance in Australia for viral diseases of cotton will be important to help protect the cotton industry from these serious biosecurity threats. Unusual virus-like symptoms in NSW cotton crops such as tall sterile plants have also been observed by CSIRO staff in several locations. If found, transmissibility studies may be able to determine if the cause is pathogenic.

While significant progress has been made by previous researchers into several aspects of the biology of Cotton bunchy top disease, it is still unclear what natural alternative hosts this pathogen has in and around cotton crops. This information will be important to effectively minimise the risk of this disease entering crops. Results from current CRDC project (DAQ0002) indicate that while TSV appears to be currently restricted to Central Queensland, some of the alternative hosts such as Fleabane and Crownbeard are commonly found in many other cotton growing regions.

Cotton blue disease has caused economic losses in cotton from Brazil and Argentina but little is known about the diversity of the Asian or African strains. There is also currently no expertise in Australia for diagnostics of Cotton blue disease. It is important to identify the diversity of the viruses that cause Cotton blue disease to determine the likely effectiveness of resistance currently available.

Transgenic resistance to viruses has been successfully used in a range of plant species. It is possible that this may be a useful strategy to utilise in cotton as preparedness for an incursion of Cotton leaf curl disease.