DISEASE
 
   NAME
     Spotted Wilt Virus
     Various Spotted Wilt Virus

Description
Viral problem that infects the leaves and stems of many plants.

Symptoms
Spotted Wilt Virus is a systemic disease that attacks a variety of plants with variable symptoms. In tomatoes young plants are particularly venerable, as indefinite mottling or rings first form on the upper surface of young leaves, eventually covering the leaf, causing it to shrivel and die. Stems and petioles or peduncles develop brownish streaks as the virus spreads eventually killing the young plants. 

 Pawpaw

Older plants that are attacked produce new foliage that is mottled with bronze colouring which soon turns black causing the leaf to shrivel and die. Stems can also be affected with brown streaks and fruit of an infected plant, ripens unevenly and is marked with circular blotches. This may cause premature fruit fall.
Spotted wilt also causes plants to become stunted and for flowers to develop reddish or yellow rings.

 Fruit

Source and Dispersal
The virus is found on other infected plants and is spread by thrips, particularly Onion thrips (Thrips tabaci) and Western Flower Thrips (Frankliniella schultzei). The virus may also be dispersed in infected rhizomes or tubers or nursery stock.

Favoured Conditions
Hot dry weather favours thrips activity particularly during summer, spreading the virus which appears 2 to 3 weeks later.

Affected Plants
A wide range of vegetables and ornamentals are attacked include capsicums, potatoes, broad beans and 
Amaryllis, Anemone, Antirrhinum, Aster, Begonia, Calceolaria, Calendula, Chrysanthemum, Dahlia, Gerbera, Lactuca, Lathyrus, Lilium, Lycopersicon (Tomato), Nasturtium, Papaver, Pericallis, Petunia, Phlox, Schizanthus and Zinnia species.

All have simular symptoms with yellowish wavy marks that spread causing the leaf to distort turn brown and die.
Other plants such as Zephyranthes species develop yellow or parallel streaks on the leaves that spread to the stems. 

Non-chemical Control
Preventative measures are important for the uninfected plants by not planting near tomato crops and the removal of weeds. The controlling of thrip infestations greatly reduces distribution of the virus.

Chemical Control
There is no chemical control of viral problems.