In March 2006, tomato leaf curl disease was found in cherry tomato crops in the south and west periphery of Brisbane. The disease has been found in many crops, with infection levels ranging from 5 to 100 per cent of plants.
Losses in severely affected crops have been very high and the disease is a major threat to tomato production. In April 2006, infected plants were also found around Bundaberg. By June 2007, the virus was present in the Lockyer Valley, Fassifern Valley, Esk, Caboolture and Redlands areas. Since 2009 it has become a serious production constraint around Bundaberg. In February 2011, it was found in backyard tomato plants in Mareeba on the Atherton Tablelands.
Tomato leaf curl disease is caused by viruses in the Geminivirus family of plant viruses, and is spread by whiteflies.
The virus causing this disease is tomato yellow leaf curl virus (TYLCV). This virus is distinct from tomato leaf curl Australia virus (TLCV), which occurs in the Northern Territory and at several locations on Cape York Peninsula.
|Symptoms and damage compared with other diseases and disorders|
TYLCV can be confused with several other tomato conditions such as tomato big bud, tomato yellow top, physiological leaf roll and phosphate and magnesium deficiency.
Tomato yellow leaf curl virus (TYLCV)
Tomato big bud
Tomato yellow top virus
Physiological leaf roll
|Spread of TYLCV|
Tomato leaf curl disease is not transmitted in seed, soil or from plant to plant by handling. It is harboured in infected host plants, some of which may be hosts that do not show symptoms. The virus causing tomato leaf curl disease is spread from plant to plant by silverleaf whitefly (SLW) (the biotype B of Bemisia tabaci). SLW is a serious pest in tomatoes and other vegetable crops in the coastal and some inland areas of Queensland and New South Wales. It is an established pest in Western Australia and cotton production systems in Queensland.
Although the nymphal stages of SLW can acquire virus from infected plants, it is the active adult insects that are responsible for almost all virus spread into and within crops.
SLW adults acquire the virus while feeding, using their piercing-sucking mouthpart to pierce plant cells and suck sap through a stylet. The virus persists in the insect which can then transmit the virus throughout its life. SLW need to feed on infected plants for at least 15 minutes to acquire the virus and then feed on another host plant for 15 to 30 minutes to transmit the virus. Transmission efficiency increases as the duration of the feeding times increases.
Although the transmission efficiency of individual insects may be low, the enormous populations of SLW moving within and between crops can result in rapid spread and high disease levels. Research results are inconclusive, but TYLCV is probably not carried from generation to generation through the SLW egg. This virus is not spread by other sap-sucking insects such as aphids or leafhoppers nor by leaf-eating pests such as grasshoppers, heliothis larvae or beetles.
|TYLCV host plants|
Tomato is the major host of TYLCV, however, many other species are also TYLCV hosts. Some other host plants are:
There are two key points to managing the spread of TYLCV:
If moving plants and fruit that host TYLCV to markets:
Good farm management and farm hygiene practices will help manage the spread of TYLCV:
Some tomato cultivars with resistance to TYLCV are commercially available, but these must be used with good farm managment and hygiene practices to keep the resistance.
See the guide below for chemical control options for SLW: