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Kiwifruit's most unwanted

Kiwifruit's most unwanted

There are eight organisms identified as the biggest biosecurity threat to New Zealand's kiwifruit industry.

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 Kiwifruit's most unwanted

Kiwifruit's most unwanted

Invasive Phytophthora

Phytophthora is present around the world, including New Zealand, in a wide range of hosts. There are over 100 known species of Phytophthora, with thoughts there could be up to 500 more yet to be identified.

There are many reports of different Phytophthora damaging kiwifruit vines in different regions globally, such as P.drechsleri, which has caused significant impacts to the kiwifruit industry in Korea.

It is considered highly likely that under certain conditions (i.e. wet soils) kiwifruit would be susceptible to several Phytophthora species. Predicting which species will impact which cultivars, and under what conditions, is difficult if not impossible to predict. Because of this, KVH is undertaking readiness planning and research for invasive Phytophthora species as a whole, as opposed to focusing on one specific species.

Threat Levels
Likelihood of entry
Medium
Likelihood of establishment
Medium
Production impacts
High
Market access impacts
Very Low

Pest ranking based on the KVH risk matrix

View risk matrix

The biosecurity threat of Phytophthora to the New Zealand kiwifruit industry is largely unknown. It could come from the introduction of a new Phytophthora species, or from a species already here that may not yet have been exposed to kiwifruit.

Management practices, cultivar susceptibility and the environment may also play key roles in any future outbreaks. Phytophthora are Oomycetes (or water moulds), so wet, soggy soils are an ideal environment for them to thrive. As such, low-lying land, poorly drained orchards and additional irrigation are more susceptible to infection.

Symptoms

One of the difficulties with detecting Phytophthora disease symptoms is that they are variable and often are not distinct from those resulting from other plant pathogens (such as Armillaria root rot which can sometimes be misdiagnosed as Phytophthora root rot).

The other difficulty with Phytophthora symptom detection arises from asymptomatic plants, where the pathogen can lay dormant for long periods until conditions change and symptoms are expressed. There are many types of symptoms associated with Phytophthora species that may occur singly or in combination.

Phytophthora usually infects kiwifruit vines from root wounds or the root tips early in spring. During the warmer summer months, vines may rapidly decline or alternatively show gradual decline in productivity over several seasons. Symptoms include reduced shoot growth; small, chlorotic leaves; and an open canopy. Vines with the graft union below ground level or mechanically wounded trees are easily infected. Infected root and root crowns commonly show a red brown rot that is easily observed when cutting into the outer layer of tissue. Generally, there is observable margin where healthy, white tissue meets infected, discoloured tissue. Infected roots become dark and feeder roots are often black, decayed and few in number (see image below).


phytophthora photos and videos

Infected roots become dark and feeder roots are often black, decayed and few in number.

phytophthora reference material

  • Kiwifruit Phytophthora survey on New Zealand orchards - KVH, Zespri and Plant & Food Research are working together on a survey of Phytophthora pathogens in kiwifruit orchards throughout New Zealand. This project will support New Zealand’s biosecurity by better understanding our current baseline of Phytophthora species associated with kiwifruit.
  • Potential impacts on kiwifruit and kiwiberry - a literature review presenting detailed information on the potential threat posed by Phytophthora, and three case studies highlighting principles of spread, management and control.

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LATEST NEWS

13 Dec 2024

Our Biosecurity Act submission is available now

KVH’s submission on proposed amendments to the Biosecurity Act (as completed and submitted on Friday 13 December) can be read here. The Ministry for Primary Industries (MPI) is leading the review consultation process and our comprehensive submission on behalf of the kiwifruit industry addresses most of the proposed changes, as these have a bearing on how the biosecurity system will operate in the future. Significant areas for our sector that we have commented on relate to funding and compensation, readiness and response, and long-term management. MPI will now analyse submissions, publish a summary, and make recommendations to the Minister for Biosecurity. It is anticipated Cabinet will consider final policy proposals in 2025. Thank you to those who have discussed the submission with us. We welcome any further questions or feedback about the process at info@kvh.org.nz. Visit the MPI Biosecurity Act review webpage for detailed proposed amendments information Read more about how we developed our submission

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02 Dec 2024

KVH Biosecurity Act draft submission

In the last Bulletin we mentioned the consultation underway on several proposed amendments to the Biosecurity Act 1993. Our draft submission is now available to view here. We welcome the opportunity for further discussion so please do get in touch at info@kvh.org.nz by 13 December when the submission is due if you have questions. The consultation and our submission have been part of our presentation at the recent Grower Roadshows too, and we thank those of you who have already spoken with us about it. The Ministry for Primary Industries (MPI) is leading this process and our comprehensive submission on behalf of the kiwifruit industry will address most of the proposed changes, as these have a bearing on how the biosecurity system will operate in the future. Some of the proposals are significant to our sector, particularly those in the sections about funding and compensation, readiness and response, and long-term management.

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02 Dec 2024

Fun Fact

The holidays are almost here and with them come extra biosecurity risks posed by unpacking Christmas goodies and luggage. Remember, and be sure to remind family and friends, to be on the lookout for unwanted guests of the “bug” kind and carefully unpack and check any packages or bags from overseas for hitchhiking pests. Open parcels in a closed room and if you find anything unusual, catch it, photograph it, and report it. Looking across previous years it is estimated that around 3,400 items of undeclared fresh produce will be seized from passengers over the Christmas period alone! Kiwifruit growers and other passengers associated with primary sectors travelling over the Christmas and New Year period may find they experience more interventions when returning to New Zealand. This is because they potentially pose a greater biosecurity risk based on the likelihood they may have visited offshore orchards and farms during their travels. KVH has produced a useful one-page poster outlining everything growers can do to help reduce biosecurity risk and what you can expect through border control when returning home.

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