Project details
Status: Current
At a glance
- Codling moth is one of the most economically damaging pests of apples.
- Sterile insect technique is an environmentally friendly method of controlling insect pests.
- This pilot program is assessing sterile moth viability and competitiveness.
Pilot program
A pilot sterile insect release program for controlling codling moth is being evaluated in three Tasmanian apple orchards.
Codling moth a major pest
Codling moth (Cydia pomonella) is a major pest of apples in all growing regions of Australia except Western Australia. It is one of the most economically damaging pests of apples causing direct damage to fruit as it feeds. If left unchecked codling moth can damage 50-90% of fruit, decimating the crop. Codling moth also infest quince, pear, nashi, summer fruit, walnut and chestnut which if left unmanaged, can reinfest nearby apple orchards.
Sterile insect technique
The use of sterile insect technique (SIT) is an environmentally friendly method of controlling insect pests that can work well in conjunction with other methods of integrated pest management.
The pilot program is assessing sterile moth viability and competitiveness, determining the logistics of importation and release, developing recommendations for adoption and integration of sterile releases into an integrated pest management program, and undertaking an economic assessment of the release program.
The use of sterile insect technology (SIT) is a relatively new strategy being developed for a range of pests, with fruit fly being a prime example of SIT technology in Australia. The method is an environmentally friendly way of controlling insect pests that can work well in conjunction with other IPM methods.
SIT programs work by flooding the wild population with large numbers of sterile males to substantially reduce the number of fertile eggs produced. When this is repeated over a number of seasons, the population crashes and infestations drop below damage threshold levels.
- Environmentally friendly
The sterile codling moth release program has reduced codling moth pesticide use by over 90% in both Canada and New Zealand where the program has been running for many years. - Effective management of codling moth
Wild codling moth levels have been reduced by over 90% in Canada and New Zealand orchards using the sterile codling moth program. Treated regions of Hawkes Bay in New Zealand have recorded an impressive 98% reduction in the catch of wild moths after only a few years of the program.
Import
The project has established a secure import pathway for sterile codling moths from the production facility Okanagen-Kootenay Sterile Insect Release (OKSIR) facility in Canada. The sterile moths are chilled and packaged then air freighted to Tasmania, the whole process currently takes 48 hrs from packing to release in Tasmania.
Release
The sterile moths are imported and released every week from November through February. Around 6,000 moths are released per hectare over three trial sites in the Huon Valley in Southern Tasmania. The release sites have been chosen due to their isolation from export apple blocks, large buffers of non-host vegetation and minimal pesticide use.
Monitoring
Sterile and wild codling moth numbers are monitored with traps located in both the treated trial orchards and nearby control orchards. Each week the number of moths are counted and verified as either sterile or wild.
Testing
The program is laboratory testing the vigour, health and mating ability of imported sterile codling moths. Samples from three shipments will undergo laboratory tests including: Counting males and females; Longevity - how long do moths live after arrival under different; conditions? Mating ability - how many female moths successfully mate with male moths; Flight ability - how well do sterile moths fly?
Economic evaluation
The program will evaluate the cost-benefit of a sterile codling moth release program. This will explore the options of both importing live moths from OKSIR and the establishment of a production facility in Australia.
Frequently Asked Questions (FAQ)
There is a lot to know about sterile insect technology so we have put together some answers to some more common questions.
How are codling moths sterilised?
The moths are treated with controlled low dose gamma irradiation to sterilise the adult moths. The irradiation prevents viable offspring being produced. If a wild male moth mates with a sterile female moth or a sterile male moth mates with a wild female moth, no viable offspring are produced. The wild-sterile matings produce either unfertilised eggs that fail to hatch or sterile offspring. Similar technology is used to produce sterile fruit fly which are currently produced and released in Australia to combat this pest.
Where are the sterile moths produced?
The sterile moths are produced by the Okanagan-Kootenay Sterile Insect Release (OKSIR) program in British Columbia, Canada. Each year, OKSIR produces around 220 million sterile codling moths, which are released into commercial orchards in Canada every week during the growing season.
New Zealand have been importing sterile codling moths from OKSIR since 2014 for release into commercial orchards. In both Canada and New Zealand, codling moth numbers have been reduced by over 90% in regions where sterile moths have been released.
Are the sterile moths radioactive?
No. Just as a person is not radioactive after receiving a medical x-ray, codling moths receiving a sterilizing dose of radiation are not radioactive and safe to release into the environment. Gamma rays are similar to X-Rays but have a different energy level and wavelength. The source of the gamma radiation used in the OKSIR facility is Cobalt-60. Gamma radiation is used widely in industry and medicine, including sterilisation of equipment and radiation therapy for cancer.
Are the sterile moths a GMO?
No. The process of sterilisation causes DNA damage to the moth chromosome, but the moth itself is not a genetically modified organism. Sterile insects, including sterile codling moths, are released as part of area-wide pest control programs in certified organic orchards in many countries.
How long do the sterile moths live for?
Codling moths in the orchard live for up to three weeks depending on temperature and other environmental conditions.
It’s a numbers game. Releasing a large number of sterile moths into an orchard reduces the chance of wild moths mating with each other. Instead, it increases the likelihood that wild moths will mate with sterile moths. With less mating between wild moths, fewer viable offspring are produced. Over several seasons, the population should significantly decline.
Where are the sterile codling moths being released?
The sterile codling moths are being released in selected blocks in three orchards in the Huon Valley. The study is a pilot study to assess the economic, environmental and social benefits of a sterile codling moth release program. If successful, it will be expanded to include other apple growing regions of Australia.
Will the sterile moths spread to my orchard nearby?
The release sites in Tasmania have been chosen so that there is a large buffer between them and other commercial orchards. Pheromone traps in both the release orchards and adjacent orchards are monitored weekly for codling moths, both wild and sterile.
How many sterile codling moths are being released?
Sterile codling moths imported from OKSIR are being released at three trial sites. The release rate in treatment blocks is up to 6,000 moths per hectare per week (up to 3,000 male moths per hectare per week), from late October through to mid-February each year.
Are both male and female sterile moths imported and released?
Yes, both sterile male and sterile female moths are released. There is no cost-effective way to separate male and female moths on a commercial scale.
What are the benefits of a Sterile Insect Release program
The program can reduce both codling moth damage and codling moth pesticide use in apple production. The Canadian program has been running since 1991, and they have achieved a 96% reduction in the amount of pesticide used.
Do sterile moths need to be released every year?
Yes, annual releases will aid in preventing any wild moths from building their population back up to damaging numbers.
How long does it take to get area wide control of codling moth using sterile moths?
In New Zealand, wild codling moth populations in release orchards were reduced by over 90% within a few years of using sterile codling moths. The population reduced progressively until a very low level was achieved. This level is lower than the threshold level set for pesticide application meaning growers no longer need to apply pesticides to control codling moth, even for export markets that require pest free shipments. The program works best if the initial levels of codling moth are not high.
Can sterile codling moths reproduce?
The dose of irradiation (200 Gy) applied completely sterilises the female moths and produces a high level of sterility in the male moths so that very few viable offspring are produced from wild-sterile matings.
How can I tell the difference between a wild and sterile codling moth?In the rearing facility, codling moth larvae (caterpillar) are fed a diet containing red food dye. This red dye remains in their bodies as adults. Squashing a sterile moth releases the bright red body contents so that they are easily distinguished from wild moths.
Do wild females still lay eggs after mating with a sterile male?
Yes, the female can still lay eggs but these either don’t hatch or produce sterile offspring.
Does a female codling moth mate multiple-times or just once?
In an orchard situation, female moths commonly mate 2- 3 times.
How many eggs does a codling moth lay?
The adult female codling moth typically oviposit 50-100 eggs, about the size of a pinhead, on the surface of the leaves, fruit or spurs when the average temperature is over 15 degrees in spring and early summer.
Codling moth eggs hatch after 10 days and the small caterpillars (larvae) emerge to feed on the leaf surface and make their way to the fruit. They burrow into the fruit and head for the core. They will spend about three to five weeks inside the fruit feeding and putting on body mass until they are ready to emerge and find a place to pupate. By this time they are about 20mm long and cream to pink in colour.
Can I still export my apples to protocol markets if I am using SIT to manage codling moth?
Detecting sterile codling moths in a registered export block poses no risk to importing countries. The Australian Government Department of Agriculture, Fisheries and Forestry has confirmed that any sterile codling moths caught on an export block monitoring trap do not count towards suspension thresholds.
What damage does a codling moth do to apples?
Codling moth larvae cause two types of damage. The first larvae to reach fruit often feed on the surface of the fruit before finding a site into which to tunnel. This initial feeding results in shallow excavated areas, which can become scarred or deformed. The second type of damage is when the larvae tunnel and excavate as they feed their way towards the core of the apple. Once they reach the core they feed on the seeds. Often the fruit flesh around these tunnels is broken down by bacteria and the tunnels are plugged by the insects using excreta (frass), which can be seen exuding from the entry hole. As the larvae leave the fruit they again tunnel through the flesh to reach the exterior. This internal injury can lead to premature ripening and fruit drop. (Adapted from APAL Integrated Pest Management for Australian Apples & Pears 02/10)
Do codling moth attack fruit other than apples?
Yes. Codling moth infest pears, crab apples, quinces, summer fruit, walnuts and chestnuts
What other methods are available for managing codling moths in orchards?
Cultural, chemical and biological methods can be used to control codling moth. Strategically applied insecticides are used at the time when larvae are present.
There are chemical and biological control options. The biological options include Bacillus thuringiensis (BT), a naturally occurring bacterium found in soil and plants (sold as Dipel) and the highly specific Grandex insecticide which contains a granulovirus of codling moth. Mating disruption using pheromone ties in trees may be suitable for large, sheltered orchards.
Natural enemies of codling moth can be encouraged by planting a diversity of flowering species or introducing commercially reared insect species such as Trichogramma wasp and Mastrus wasp. Sterile insect technology complements biological management of codling moth.
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Acknowledgements:
This project has been funded by Hort Innovation using the apple and pear research and development levy and funds from the Australian Government.