Phthorimaea absoluta is the original name for what is commonly known amongst growers as Tuta absoluta. It is a major insect pest in tomato production areas in parts of the world, widespread in Europe, South America, Africa, the Middle East, and western regions of Asia. In some of these production areas, crop losses of 50-100% and extensive economic damage have been reported.
Tuta absoluta is also commonly called tomato leaf miner because the larvae cause leaf mines in the leaves of tomatoes and other host plants. They also burrow into the fruit. Impacts overseas have seen an increase in tomatoes being sent for processing, a reduction in value, closure of trade routes, increased insecticide application, and increased production costs.
"An incursion of Tuta absoluta would threaten New Zealand tomato exports as most of our key export markets are free from Tuta absoluta. Domestically, there could be a reduction in the availability of fresh tomatoes, leading to potential price increases," said the TomatoesNZ team. So, what needs to be done?
How do we keep Tuta absoluta out of New Zealand?
The first line of defense to keeping Tuta absoluta out of New Zealand is at the border, where consignments of imported tomatoes and other host crops are inspected for unwanted organisms (pests that are currently not in New Zealand). Countries that export tomatoes to New Zealand are required to meet conditions set out in Import Health Standards, which specify any treatments or measures that may be required to manage the risks associated with imported fresh produce. However, despite best efforts, an unwanted organism could still unknowingly enter the country and lead to an incursion.
What has TomatoesNZ been doing to prepare for an incursion?
"TomatoesNZ has been working with MPI to produce guidelines that will be used by Response teams if there is a Tuta absoluta incursion in New Zealand," the team said. These guidelines, called 'Operational Specifications,' are science-based and will inform the operations of a biosecurity response. By working together MPI and TomatoesNZ can ensure the best outcomes for the tomato industry.
"Operational Specifications outline the processes to be used by the Response team with vital information to ensure control and eradication plans can be developed and implemented quickly. The quicker an incursion can be determined, the response can move quickly, and the outcome will be less damage to crops and less effect on livelihoods. The situation can quickly worsen if it takes longer to respond, making it more difficult to eradicate the organism.," they point out. Acting quickly is key to a successful outcome. It will be easier to control the incursion and eradicate the organism because it has not spread too far, and the response will take less time. A shorter response will also be less expensive because industry and MPI have already agreed on how the response should be run. If the response is over sooner, there will also be less disruption to production. "Previous responses have taught us that the sooner a response can begin, a positive result is more likely in terms of the overall impact on the whole industry. "
What do growers need to know?
What happens if Phthorimaea absoluta/ Tuta absoluta is suspected? According to TomatoesNZ, if Phthorimaea absoluta is suspected in an area, MPI will investigate to confirm the suspected detection and determine the extent of the spread of the insect. Response zones will be set up with an inner zone of approximately 1-kilometre radius close to the suspected detection and a wider zone of approximately 10-kilometre radius. Response activities will focus on the inner zone where all insects and host material will be removed and destroyed. The wider zone will be subject to surveillance, random testing of host plants, and movement control of host plant material. The response zones can change depending on the surveillance results.
What happens if Tuta absoluta is detected and confirmed?
1. Response begins & response governance group is established
When detection of Tuta absoluta is confirmed, a response will begin, and a governance group will be established to provide oversight for the response. The group includes MPI Response team members, technical experts, and industry representatives to ensure that the interests of growers are taken into consideration in any decisions, such as the ability to continue to operate during a response. Response Governance is also responsible for setting the objectives of the response, such as achieving eradication.
2. Movement control of infested plant material and risk goods
Movement controls are a large part of managing a response to help reduce the spread of unwanted organisms from infested areas. Growers will be asked to do their part by limiting the movement of items that pose a significant risk of spreading the organism, including host plant material, fruit for sale or export, machinery, vehicles, and other equipment that has been in contact with infested plant material. Export tomatoes will also be subject to controls if they have been grown within or are moved through response zones. Any restrictions will need to satisfy the requirements of trading partners.
To further reduce the risk of spread, MPI will place signs around the perimeter of the response zone at major exit and entry points to indicate quarantine areas and restricted movement. There will be controlled entry to affected areas and properties, and property owners and residents will be notified there is a response in the area, as well as their obligations to avoid unintentionally transporting insects out of the response zone.
Permits granted by MPI may be needed to move host plant material and sell produce (fruit and vegetables) from the 'Controlled Area' designated by MPI. The produce may be subject to temporary restrictions, which can include (i) applying post-harvest treatment and carrying out post-harvest inspection, (ii) using packaging and transport systems that prevent insect entry, and (iii) extensive labeling on bins, cartons, and containers. These temporary conditions allow for containment and control during the response.
3. Removal, destruction, transport of infested plant material and fruit
In an outdoor or indoor setting, a similar approach can be used to remove host plant material from the risk zone and should take place immediately after official identification. In a greenhouse, the entire plant needs to be removed from the growing system and destroyed in a secure manner. Precautions need to be taken to avoid spreading insects, which may include applying insecticide to all plants, including those not infested. Infested greenhouses need to be cleaned and sanitized before planting for the next production cycle. Other host plants in the zone around the greenhouse may also need to be treated and removed. It is important to follow the instructions of MPI to ensure that the most appropriate methods are used for plant removal, transport and disposal or destruction.
What information will growers receive if their property is in the response zone?
MPI will place a 'Restricted Place' notice on the infested property, and this will specify the restrictions placed on the movement of risk goods to and from the property. Information on the 'Controlled Area' and a 'Notice of Direction' will describe the movement controls and the inner and wider response zones. Property owners in the response zone will also be notified of their obligations. Public events, such as farmers' markets, may also be affected, with plant material and fruit prevented from leaving the response zone.
Under the Biosecurity Act 1993, an appointed person will be available to answer questions and provide information. For example, questions could include: what help and support is available? Where and how can I get help? What are my obligations as a grower in the response zone? Is there compensation for loss of income? Asking questions will help to understand what will be a stressful situation.
How does growing tomatoes in greenhouses affect a response?
Greenhouses are treated as being part of the outdoor environment as they have vents and are, therefore, open to the outdoors. The setting of the inner and wider response zones may take the size of the greenhouse into consideration. Because greenhouse-grown crops are intensively worked during production, greenhouse workers can be trained to visually identify the early symptoms of Phthorimaea absoluta infestation. Visual checking would, therefore, be carried out on a regular basis.
When does a response end?
A response will end when the response objectives have been met or when a suitable plan is established for controlling the pest. This decision will be based on a scientific assessment of surveillance information and trade requirements. If eradication has been possible, in general, surveillance will continue for a period of time to provide confidence that Tuta absoluta is no longer present in the response area. Some actions, such as trapping, will be scaled down or stopped, and movement controls adjusted to minimize inconvenience.
What can growers do to help to reduce this risk of an incursion?
Maintaining good on-farm biosecurity and hygiene practices will go a long way in reducing the threat of Tuta absoluta. Installing and regularly monitoring insect traps, keeping staff up to date in pest identification and biosecurity practices are all a good way to approach all biosecurity threats.
In an incursion, good record keeping helps MPI trace the movement of potential risk goods, so keep records of visitors, contractors, and farm inputs such as plants, fertilizer, and growing media. These steps will not only reduce the threat of an incursion but will also help keep the threat contained if Tuta absoluta is found. Continue to maintain best-practice hygiene procedures to reduce the spread of insects (adults, larvae, pupa, eggs) from the risk zone and when moving between the greenhouse, fields, and adjacent properties.
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