Potato spindle tuber viroid has been found for the first time in New Zealand.
A ministry of Agriculture survey confirmed its presence on tomato crops at three sites around Auckland and one at Nelson. It has not yet been found in potatoes.
The virus is thought to have entered the country through imported seed.
The viroid is more a threat to potatoes than tomatoes. It causes stunted growth estimated to reduce production of an infected tomato plant between 10-20 percent. In potatoes the loss of production can be as high as 60 percent.
Control is by propagation of PSTV-free seed, avoidance of contact of healthy and diseased plants, and the transfer by implements or tools.
Propagation by true seed is ineffective as a means of control, as is roguing of diseased plants because of the frequently indistinct symptoms.