TomatoesNZ has continued to collaborate with MPI to maintain the embargo on imported Australian tomatoes. The period for importing tomatoes has now concluded until the next winter, so MPI will collaborate with their Australian counterparts to gather more information about the origin and spread of the ToBRFV to determine whether to reopen the market in time for the next winter season. The most current information regarding the situation in Australia can be accessed on the PIRSA website.
The most beneficial action that growers in NZ can undertake is to review and implement hygiene measures. A question and answer guide has been prepared for them. Should there be any remaining questions after reviewing it, they are encouraged to make contact.
The question arises: What are the biggest virus threats to tomato greenhouses at the moment?
There are two primary threats – one that is currently in New Zealand, which is seeing new cases, the Pepino Mosaic Virus (PepMV), and another that is not currently in New Zealand but is present in many other countries around the world, including Australia – the Tomato Brown Rugose Fruit Virus (ToBRFV).
One might seek further details regarding PepMV and its potential impact.
PepMV is considered an undesirable organism in New Zealand, posing significant risks to tomato cultivation. It can inflict considerable damage on both the tomato fruits and the plants, leading to symptoms that manifest soon after the fruit sets, even before the first harvest. The manifestation of these symptoms can result in unmarketable tomatoes and a diminished yield, adversely affecting income. While some growers have adapted to the presence of PepMV over the years, learning which tomato varieties are more resilient and the conditions that mitigate plant stress, such as lower greenhouse temperatures and the management of other common diseases, it has been a challenging journey. Although a few have successfully eradicated PepMV, it often requires drastic measures like crop rotation and extensive cleaning procedures, including substrate replacement.
Inquiry into ToBRFV reveals more concerning aspects.
This virus is capable of infecting 100% of tomato plants within a greenhouse, with potential crop losses ranging from 30-75%. Such a significant loss can drastically affect one's financial stability. Eradicating ToBRFV from a greenhouse is notably more challenging than dealing with PepMV due to its stability. It may necessitate several seasons of alternative cropping, such as cultivating cucumbers or courgettes before it becomes feasible to consider replanting tomatoes.
Indeed, both PepMV and ToBRFV have been present in various countries for an extended period, and those countries continue to cultivate tomatoes. The key distinction lies in the enhanced protective measures available in these nations compared to New Zealand. For instance, many countries have access to a PepMV vaccine, which helps prevent the visible symptoms and yield loss typically associated with the virus. However, the process of registering such a vaccine in New Zealand could span several years without any assurance of approval.
Furthermore, seeds resistant to ToBRFV have undergone trials in nations that have been dealing with the virus for a longer duration. Given the global demand for these resistant varieties, it is anticipated that it will take a considerable amount of time for the supply of such seed stock to meet the demand. In the interim, New Zealand lacks any form of defense against ToBRFV should it enter the country. It's also important to note that these resistant varieties might come at a higher cost and may not align with the yield, taste, and color preferences that consumers and growers are accustomed to with the seed varieties traditionally used.
It is indeed possible for a single crop to be infected with both PepMV and ToBRFV simultaneously. Experiences from other countries indicate that even varieties resistant to these viruses struggle when both are present in the same plants. In such cases, the recommended course of action involves removing the infected tomato plants, disposing of the substrate, conducting a thorough cleaning, and switching to an alternate crop, such as courgettes, to manage the situation effectively.
Even small growers can implement cost-effective hygiene practices that should become a routine part of their everyday operations. These practices are essential minimum steps to protect their greenhouses from all types of viruses.
They should restrict access to their greenhouses, preventing suppliers, representatives, and workers from other greenhouses from entering. Establishing a handwashing and sanitizing station near the entrance of the greenhouse is recommended. Additionally, purchasing a supply of disposable gloves and setting up a footbath with an effective disinfectant like Virkon at the entrance can further enhance biosecurity measures.
The primary mode of virus transmission is through touch. Therefore, it's advised to wash and sanitize hands, wear disposable gloves, utilize the footbath, and then proceed to work within the greenhouse. It's important to change gloves or re-sanitize them after working on each row to avoid transmitting a virus from one row of plants to another.
Growers are encouraged to have specific work clothes and shoes designated for greenhouse use only. These should be put on and taken off near the greenhouse, and not worn when visiting other greenhouses to prevent cross-contamination. Regular washing cycles may not eliminate many viruses; washing at high temperatures, such as 90 degrees Celsius, and using agricultural-strength washing powder are necessary to kill viruses like PepMV and ToBRFV.
Sanitizing tools after each row and avoiding taking tools to another greenhouse are crucial steps. Similarly, not bringing crates into the greenhouse and instead using personal containers that are regularly washed with a disinfectant like Virkon can help prevent disease spread. Tools and crates are significant risks for spreading disease after hands and clothes, especially if crates have been on an infected property.
Cigarette smoking poses an additional risk since tobacco is grown in countries with low hygiene standards and prevalent viruses. Tobacco could harbor PepMV and ToBRFV, potentially spreading these viruses to plants if employees smoke during breaks.
It is also vital to source seeds and plants only from reputable companies and nurseries, and to avoid bringing tomatoes from outside into the greenhouse environment, for instance, through an employee's packed lunch.
For detailed information on appropriate cleaning products for different viruses, growers should consult with their horticulture suppliers. The efficacy of usual cleaning products against specific viruses should be verified.
It is believed that smaller tomato varieties may not exhibit the same symptoms of PepMV as larger varieties, but growers should discuss this with their seed suppliers for more tailored advice.
Source: TomatoesNZ.