Dear Growers,

TomatoesNZ has continued to work with MPI to keep the embargo in place for imported Australian tomatoes. The window for imported tomatoes is now over until next winter so MPI will work with their Australian colleagues to find out more information about the source and spread of the ToBRFV to work out if to reopen the market in time for next winter. The most up to date information on what is going on in Australia is available here on the PIRSA website.

The best activity that growers in NZ can do is still to review and put in place hygiene measures. I have prepared a question and answer guide for you. If you still have questions at the end of it, please get in touch.

What are the biggest virus threats to my tomato greenhouses at the moment?

There are 2 threats – one that is in New Zealand now which we are finding new cases of, Pepino Mosaic Virus (PepMV). And one not currently in New Zealand but present in many other countries around the world including Australia – Tomato Brown Rugose Fruit Virus (ToBRFV).

Tell me more about PepMV, why should I worry about it?

PepMV is an unwanted organism (a plant virus that can cause a lot of harm) in New Zealand and can have a big impact on your tomato plants, causing symptoms on the tomatoes as well as the plant and a reduction in yield. These symptoms can appear soon after the fruit has set, prior to your first harvest.

The symptoms can mean that you will have tomatoes that you can’t sell to market and fewer tomatoes being produced. Both of which would reduce your income. There have been growers who, after several years, have learnt to grow with PepMV in NZ but it has been a steep learning curve for them; understanding which tomato varieties cope better*, what conditions lead to less stress in the plants (low GH temperatures, the presence of other diseases common in NZ etc can lead to increased PepMV symptoms). Some growers have managed to get rid of PepMV but it isn’t easy and usually involves switching to another crop for a season as well as replacing the substrate and deep cleaning.

Tell me more about ToBRFV and why should I worry about it?

ToBRFV will infect 100% of your plants and you can potentially lose 30-75% of your crops. Can you afford to lose even 30% of your income, never mind 75%? It is much harder to get rid of ToBRFV from your greenhouse than PepMV, as it is a very stable virus. You will probably need to grow cucumbers or courgettes for several seasons before thinking about returning to tomatoes.

All viruses infect greenhouses no matter how big or small they are, so you need to take this seriously

But haven’t these viruses been around in other countries for a long time and they still grow tomatoes?

Yes, both PepMV and ToBRFV have been present in other countries for some time. The difference is that other countries have better access to safeguards than we do in New Zealand. Many countries have access to a PepMV vaccine which means that the infected plants don’t show the same symptoms and loss of yield. Registering the vaccine in New Zealand would take many years, with no guarantee of success.

ToBRFV resistant strains of seeds have been trialled in other countries for longer because they have had this disease. There is huge demand for resistant varieties around the world and it will take some time for this seed stock to increase. Until then we have no defence against ToBRFV if it comes to NZ. Don’t forget that resistant varieties might cost more, with potentially yield and consumer preferences for taste and colour not being matched to the seed varieties you normally use.

 So is it possible to get both PepMV AND ToBRFV in the same crop?

Yes it is. Reports from other countries suggest that even resistant varieties don’t cope well if both viruses are present in the same plants. You would need to pull out your tomato plants, throw away your substrate, clean thoroughly and change to a different, crop such as courgettes if you get both viruses at the same time.

So what can I do to prepare for these viruses?

Even small growers can take affordable hygiene steps that should become part of your everyday growing. These are minimum steps to safeguard your greenhouse from all viruses.

• Don’t let suppliers, reps workers from other greenhouses into your greenhouse
• Set up a handwashing and sanitising station near the entrance to your greenhouse
• Buy a supply of disposable gloves
• Buy a footbath and chemical like Virkon and set this up at the entrance to your greenhouse

The main way that viruses are spread are through touch. Wash your hands, sanitise your hands, put on disposable gloves, walk through the footbath and go into the greenhouse to start work. You should change your gloves or re-sanitise them after every row. You don’t want to spread a virus from one row of plants to the next row.

• Have work clothes and shoes that are just for your greenhouse
• Put these on and take them off near the greenhouse
• Don’t wear these clothes or shoes if you help friends in their greenhouses

Unfortunately regular washing cycles don’t kill many viruses – you would need to wash at 90 degrees to kill PepMV and use an agricultural strength washing powder to kill ToBRFV.

• Sanitise your tools after every row
• Don’t take your tools to another greenhouse if you’re helping someone
• Don’t take crates into your greenhouse, have your own containers that you wash regularly with a chemical like Virkon

After hands and clothes, tools and crates are the biggest threat to your plants for spreading disease. You don’t know if crates have been on an infected property and how well they have been sanitised. Keep retail crates for packing only, away from the inside of your greenhouse.

• Cigarette smoking is another issue. Tobacco is grown in countries where hygiene measures are low and viruses are present. Tobacco could be a host for PepMV and ToBRFV so could be spread from cigarettes directly onto the plants if you or your employees smoke during breaks
• Only buy seed and plants from reputable seed companies and nurseries
• Don’t bring tomatoes from anywhere outside of your greenhouse onto your property for example an employee bringing a packed lunch to work

For more information about what cleaning products to use for different viruses, talk to your horticulture supplier. It could be that your usual product is sufficient.

*It is thought that smaller tomatoes don’t show the same symptoms of PepMV as larger varieties but talk to your seed supplier about this.

If you would like to take part in TomatoesNZ surveillance by having your drainage water tested for these 2 viruses, please get in touch.

If you have any questions, please let me know.

Kind regards,

Dinah dinah.cohen@tomatoesnz.co.nz