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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
Likelihood of establishment
Production impacts
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.


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.


KVH investigates reports of unusual symptoms to identify and manage any biosecurity risks.

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18 Jul 2024

Are you a quizmaster like our young growers?

Annual Young Grower competitions have been taking place throughout the regions over the last few weeks and we’ve had biosecurity rounds included in many of them. Congratulations to everyone who took part – it’s great to see such knowledge and enthusiasm for the importance of biosecurity. Just yesterday at the Bay of Plenty Young Grower event we provided an interactive quiz to each of the competitors, who impressed us with their on-orchard biosecurity expertise. Congratulations to Jack Canham from Apata for winning the biosecurity section on the day. How do you compare to this year’s young growers? Think you’d outdo them? Test yourself on the Connections game here (where you will need to group words that have a common thread, into four groups of four) before seeing the set of quiz questions we asked competitors here. Answers for the quiz questions can be found here. Good luck!

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16 Jul 2024

Mature plant movements

Winter is the time when growers look to replace plants on their orchards or plant new blocks. This article is a reminder that if these plants are being moved between properties there are biosecurity requirements that must be met to reduce the likelihood of spreading pests and diseases, including Psa. These requirements also provide the best chance of a successful response if a new organism was detected in our industry. While most kiwifruit plant movements come from nurseries, growers may occasionally move mature plants between orchards. The movement of any plants are a risk pathway, and it is important for growers to understand what’s required under the Pathway Plan, as outlined below. What does this mean for you? If you are taking mature plants from your own orchard for use on that same orchard there are no requirements under the Pathway Plan. If you are moving orchard plants from your orchard to another orchard, or source orchard plants from someone else, you need to ensure that you are meeting the requirements of the Pathway Plan – by being Kiwifruit Plant Certification Scheme (KPCS) certified for example. If you are a Psa non-detected supplier, you will need to complete a Psa test. It isn’t onerous to become certified as an orchard plant supplier and there are no costs (unless diagnostic testing is required). The new Pathway Plan requirements are very similar to existing protocols. They do require planning in advance to ensure monitoring can occur while vines have leaves and are in active growth. More information about orchard plant movement information, including the KPCS manual and supporting documents, is available here.

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15 Jul 2024

Upcoming AGM and voting packs

A reminder that our Annual General Meeting (AGM) is coming up and growers will receive their AGM packs by email at the end of this month. This is a public meeting and anyone who is interested is welcome to attend. Special guest Dr Jacqueline Rowarth will be joining us to speak about precision breeding, followed by the NZKGI and then Zespri annual meetings. Where: Mercury Baypark, Truman Lane, Mount MaunganuiWhen: Wednesday 21 August

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