Break-out exercise 2
Pest Data Sheet – Gooklia inventus (vegetarian moth)
International Plant Health Risk Analysis Workshop
PLEASE NOTE: All aspects of this case example, including the pest and pest biology, taxonomy, ecology and information about Australia and New Zealand have been generated explicitly for use in the International Plant Health Risk Analysis workshop. While aspects of the information is based on existing conditions, much of the information has be fabricated and as such should not be consider valid for use in actual analyses.
1. Background to Risk Assessment
The following official request has been received by the New Zealand National Plant Protection Organisation (NPPO) from a New Zealand-based company. The request, to import goods considered by the New Zealand NPPO to represent a potential phytosanitary risk to New Zealand, has now been allocated resources to allow a risk analysis and import requirements to be developed.
Agricultural Opportunities Ltd
New Lyn, New Zealand
29 February 2005
New Zealand NPPO
Would you please consider the following request to import nursery stock of Tilia nonulus (pink lime) from Australia. My company, Agricultural Opportunities Ltd, has a long history of importing live plants from Australia with few problems.
Under an arrangement recently agreed with our sister company in Australia, Agricultural Opportunities Ltd can move 1 metre potted plants from the nursery in Australia to our holding facilities at ports in New Zealand within 6 days, including the 3 day voyage time from Australia. All plants exported to New Zealand are also guaranteed to be free of surface pesticide residue, as no spraying will be undertaken within 60 days of shipping.
Our sister company in Australia will inspect all plants being exported to New Zealand under the supervision of the Australian National Plant Protection Agency. Further we will ensure that the plants selected for export to New Zealand will be in the same new pots they were originally planted. We therefore guarantee that the plants will be pest free on arrival in New Zealand.
I would be happy to provide any further information
2. Summary of the New Zealand Environment and Economy
New Zealand lies the South Pacific, around 500 km east of Australia. Made up of two main islands, the North and South Islands, New Zealand is surrounded by a number of smaller offshore islands. Overall New Zealand is a similar size to that of the United Kingdom, and like the United Kingdom has a relatively mild temperate climate, although New Zealand has a more sub-tropical climate in the north of the North Island. Around one third of New Zealand is held in natural reserves, leaving the remaining 2 thirds to agriculture and forestry, and urban areas. New Zealand’s population of 4 million can be mainly found in the upper half of the North Island, where around 75% of the population resides.
As a nation New Zealand is critically dependent on “safe trade”. From an economic standpoint, tourism is now New Zealand’s single biggest earner at around 6% of the gross domestic product (GDP). New Zealand’s large and varied areas of natural reserves, which include untouched sub-tropical rain forests, high mountains, glaciers, rivers, and unspoilt coast line, together with adventure activities such as skiing, mountain walks, golden beaches, and fresh and salt water fishing, are all considered important to the economy and the national culture.
A combination of all types of agriculture accounted for just under 50% of New Zealand’s annual export receipts, or 17% of New Zealand’s GDP. New Zealand is unique as a developed country in its dependence on agricultural and environmental trade. Compliance with the Sanitary and Phytosanitary (SPS) Agreement of the World Trade Organisation is critically important for New Zealand’s continued access to world markets; but as a direct result New Zealand stands to loose more than most other countries from phytosanitary risks, particularly to our economy.
The main threats to New Zealand’s natural environment from a phytosanitary perspective are believed to come from areas that contain a similar flora. Tilia, a tree genus native to both Australia and New Zealand, plays an important role in both natural environments. In New Zealand, Tilia tigrum (flowering lime) is a dominant forest tree growing the length of New Zealand and paying a central role in sustaining New Zealand’s abundant bird life. Tilia topseya (fruiting lime) is a major New Zealand tree crop providing almost $1 billion in annual revenue and employing over 30,000 people in fruit harvest, logging and timber production.
New Zealand is has also more recently developed some of the world’s greatest wine growing regions. Found in areas of low rainfall and long hot summers, the wine industry is now estimated to contribute as much as $2 billion to the New Zealand economy annually.
3. Pest information
The following text provides information related to the phytosanitary risk of a fictitious pest of plants. The information is provided in a format similar to that of the CABI Crop Protection Compendium from which aspects of the fictitious pest information was extracted.
3.1 Pest Name
Gooklia inventus (vegetarian moth)
3.2 Notes on Taxonomy and Nomenclature
Gooklia inventus is a member of the Gookliidae family of Lepidoptera. Approximately 35 genera and 250 species of Gookliidae have been described from the world fauna. Since early attempts to revise the Gookliidae group no satisfactory classification has been proposed on a world basis. A few regional revisions have been written and some synonymic lists. This species has been placed in various genera before being assigned to the genus Gooklia and there are several species and subspecies that have been synonymized with Gooklia inventus. A worldwide revision of the Gookliidae is currently underway.
3.3 Host List
3.3.1 Major hosts
Abies alba (silver fir), Abies fabri (Faber fir), Abies nephrolepis (Khingan fir), Carpinus betulus (hornbeam), Carpinus cordata, Tilia cordata (small-leaf lime),Tilia nonulus (pink lime), Tilia platyphyllos (large-leaved lime), Tilia topseya (fruiting lime), Tilia tuan.
3.3.2 Minor hosts
Ailanthus altissima (tree-of-heaven), Pinus densiflora (Japanese umbrella pine), Ulmus americana (American elm), Vitis vinifera (grapevine)
3.3.3 Wild hosts
Taxodium distichum (bald cypress), Tilia tigrum (flowering lime).
3.4 Host Range
Gooklia inventus attacks a narrow range of forest and fruit trees. The recorded host range is wider in areas where the pest has been introduced than in its Tasmanian home, but this may be in part an observational artefact.
The two species that Gooklia inventus prefers and most often damages in Australia are Tilia nonulus (pink lime) and Tilia topseya (fruiting lime).
Laboratory investigations of Gooklia inventus preferences and utilization of Australian host plants provide limited and contradictory information. For example, laboratory studies rank the preferred species, pink and fruiting lime, as intermediate to low in food value.
Affected Plant Stages: Vegetative growing stage.
Affected Plant Parts: Leaves and whole plant.
The eggs of Gooklia inventus are spherical, approximately 0.5 mm in diameter, slightly depressed in the middle of the upper surface, and often flattened on the lower surface. The eggs are pink (blue-green if reared on an artificial diet) at first, and later white with an opalescent shine. The eggs are deposited in small clumps that are glued together without a covering of hair. The female does not deposit all of her 70 to 300 eggs in one place and generally hides them in folds in the leaves.
Newly hatched larvae are approximately 4 mm long.
The second-instars appear pink with a few lighter spots and have two white patches that almost encircle each dorsal verrucae on the third thoracic segment, but do not meet along the mid-dorsal line. There is also a light patch that fills the mid-dorsal space between the verrucae from the middle of the fourth to the middle of the sixth abdominal segments. The larvae have small, paired glands on the first and fifth abdominal segments and large, single orange eversible glands on the sixth and seventh, which are clearly visible.
From the third-instar on, the head of the larva is orange-brown with numerous brown and black freckles. The mid-dorsal stripe is a mottled brown to black. The dorsal verrucae of the larva are all bluish. The dorsal spot or patch patterns present in the second-instar persist through the later instars. The mature larvae appear tanish, greenish or dark-greyish, with extensive brown or black mottling and are 30 to 40 mm long. The colour of the larvae conceals them when they rest on the branch of a lime tree.
Bluish-grey, attains 60 mm when fully developed, and has 40 small warts surmounted by characteristic tufts of hair.
The pupa has 100 characteristic appendages at the posterior end.
Moth with a wingspan of 25-40 mm; forewings are bluish and have black spots arranged in a number of rows; hind-wings are bluish-grey with a small pink spot on the leading part.
3.5.1 Similarities to other species/conditions
Gooklia inventus is the only member of its genus, and is distinguished within its family (Gookliidae) by the colonial, nest-building habits of its larvae. It is not likely to be confused with other Lepidoptera.
3.6 Distribution List
Gooklia inventus is native to Tasmania (Australia), where it is widespread. It was introduced into mainland Australia immediately after the First World War and has since spread considerably within Australia.
Figure 1: Distribution of Gooklia inventus in Australia, including the pheromone trap survey sites. Location records collated from the Australian National Insect Collection (unpublished data) and the Tasmanian Department of Primary Industries Water and Environment, (unpublished data).
3.7 Biology and Ecology
In Tasmania, emergence from over-wintered pupae begins in late April or early May, and is completed in 4-6 weeks. Mass flight lasts for 7-10 days at average temperatures above 18°C, and activity is greatest at 20-28°C. Flight ceases at temperatures of 15°C and below. The most favourable conditions are 70-80% RH and temperatures not exceeding 22-25°C.
Figure 2: The potential distribution of Gooklia inventus in Australia modelled using CLIMEX with a 0.025 degree climate surface grid derived from Esoclim.
The sex ratio is usually 1:1, females living for 4-8 days and males for 1-2 days less. Adults emerge in the evening and rest initially on branches, twigs and leaves before flying to preferred food plants. They are able to fly several kilometres. Females each lay 70-300 eggs, mostly during 1-2 days, on the lower surface of the leaves on the upper and outer parts of trees; even heavy rain does not dislodge the eggs. There are two generations annually and occasionally a partial third. Lime is the most favourable host for female fecundity and larval development; however, most larval nests of the first generation are found on Abies alba (silver fir), and those of the second generation on fruit trees. In Queensland Australia, it was demonstrated that, although Gooklia inventus is polyphagous, normal development occurs only on the preferred food plants, i.e. Tilia or Abies.
In Queensland, there are two generations per year and the larvae pass through seven instars. Optimum sunshine hours are 1950-2050 annually, with an average temperature of 17°C during the vegetative period and RH 65-70%, with 300-350 mm precipitation; 9°C is considered the threshold for development. Once accumulated temperatures above this level exceed 280 degree days, larvae hatch (and accurate forecasts can be made to within 1-2 days). Hatching of eggs occurs mainly during the morning (between the hours 07:00-11:00) and evening (17:00-01:00). Pupae are cold resistant if well hidden in bark, where 82-84% of them hibernate. Others over-winter in the soil to a depth of 10 cm. Copulation occurs only once a day, for a few minutes, before sunrise. Eggs are laid in groups of about ten. Larvae can withstand up to 5 days starvation, although the resultant reproductive capacity of the adult will be adversely affected.
In Western Australia females lay about 20 eggs, all in one mass, on leaves and small branches. Larvae construct a colonial web and feed together within it. Diapause is facultative and depends on climate. On average, males live for about 8 days. There are two generations per year, one generation in spring and one in the late summer, and the species passes through 11 larval instars.
Figure 3: Larval mortality for Gooklia inventus as a function of temperature.
Figure 4: Daily pupal mortality as a function of temperature under constant temperature laboratory conditions.
Figure 5: Daily egg mortality for Gooklia inventus expressed as a fraction of the surviving cohort.
Figure 6: DYMEX model results run with Owairaka temperatures, and initialised with four consecutive egg batches each week from 7 March 1990. Mortality values taken from temperature-based survival functions derived under laboratory conditions.
No more egg batches were observed when monthly average minimum temperatures fell below 10.7°C and monthly average temperatures were 14.2°C in Adelaide, Australia. This may indicate that females stoped laying eggs when average temperatures were closer to 17°C, or that egg batches were dying at the lower temperatures. Another interpretation is that egg batches may have been present, but were at numbers that were too low to detect. In either case, it is likely that young larvae are less able to deal with very low temperatures experienced during mid winter, and this could be a source of mortality that stops the successful recruitment of larvae from eggs laid in late April and early May that would otherwise give rise to pupae in December, extending the flight period dramatically beyond what has been observed.
3.8 Symptoms Text
Woven silk nests enclosing a number of leaves are conspicuous. Rapid defoliation of forest and fruit trees occurs.
Symptoms by affected plant part
Leaves: external feeding; webbing.
Whole plant: external feeding.
3.9 Notes on Natural Enemies
Gooklia inventus was first recorded in Tasmania in 1840 and in mainland Australia in 1919, and was widespread in mainland Australia by the time a biological control programme was initiated in 1975. Introductions of a number of the more important parasitoids from Tasmania were attempted and continued into the 1990s. However, none of them are known to have become established, and subsequent biological control attempts have focused on the use of Bacillus thuringiensis sprays.
Both mechanical (destroying nests) and chemical means are used for control. In Queensland, Australia, diflubenzuron gave adequate control of Gooklia inventus as well as fenvalerate, cypermethrin and permethrin which induced 100% larval mortality in laboratory experiments. However, chemical control with insecticides is not without problems.
There has been much research on biological control. The most used and researched antagonistic organisms are subspecies of Bacillus thuringiensis. Preparations of B. thuringiensis kurstaki were reported to be most effective in Queensland, Australia. Other pathogenic organisms are the fungi Beauveria bassiana and B. globulifera and the egg parasite Trichogramma dendrolimi.
Entomophagous nematodes (Steinernema feltiae) can be also used to reduce Gooklia inventus populations.
3.11 Means of Movement/Dispersal
Gooklia inventus can spread by natural adult flight and this has certainly been the main mode of spread within Australia where the pest was introduced. Gooklia inventus is liable to be carried on vegetative host-plant material and vehicles. The facility of the larvae to withstand starvation for up to 5 days means that they can be transported on vehicles to different areas and survive to initiate new infestations. Mass migrations due to exhausted food plants or the search for new sites often end in urban areas where the pest invades wood piles, houses, roads and vehicles (which can transport it to new and uninfested areas). Transportation of Gooklia inventus also occurs relatively often in wood logs where it inhabits cracks or holes in the bark. There is a certain risk of entry as eggs and larvae imported by amateur entomologists, and eggs are difficult to see on visual inspection of similar coloured foliage.
Newly hatched Gooklia inventus larvae often climb to the top of trees and can become wind blown, aided by the silk threads they produce and the specialised hairs they possess (see Morphology section for description). The larvae may also crawl to new hosts when their immediate food supply has been exhausted. Both the male and female moths fly, although females usually fly less until they have laid most of their eggs, thus contributing to the expansion of outbreaks over sequential years.
Movement in Trade
The adults are readily attracted to lights and have been observed in the vicinity of ports where they could lay eggs on plants waiting to be transported.
Plant parts liable to carry the pest in trade/transport
- Bark: Larvae; borne internally; borne externally; visible to naked eye.
- Flowers/Inflorescences/Cones/Calyx: Larvae; borne externally; visible to naked eye.
- Leaves: Eggs, larvae; borne externally; visible to naked eye.
- Stems (above Ground)/Shoots/Trunks/Branches: Eggs, Larvae, Pupae, Adults; borne externally; visible to naked eye.
The first recorded outbreak of Gooklia inventus (1953-1963) occurred in South Australia and resulted in the damage or destruction of approximately 403,000 km² of plantation forest. Since then there have been periodic outbreaks across Australia. During the longest outbreak (1978-1984), over 2 million ha of Tilia forests (one-quarter of Australia’s forests) were infested and partly defoliated. In addition, Gooklia inventus defoliation has been shown to reduce annual tree growth in Tilia in Queensland, Australia and Abies in the Perth, Australia.
Gooklia inventus damage and resulting tree loss has the potential to alter the species composition of forests where outbreaks occur. The loss of Tilia species would be more severe than that of deciduous species because they tolerate less defoliation. Any associated wildlife that depends on the affected tree species for food or nesting would be adversely affected. Nutrient and water cycling in the ecosystem may also be affected. During a Gooklia inventus outbreak in Australia, the massive quantities of frass and needle fall increased the nitrogen and phosphorus in the Tilia litter two to three times the normal level and also increased the potassium and manganese significantly.
Tilia trees killed by Gooklia inventus defoliation or subsequent attack by other organisms may not be useable for lumber because of deterioration of the wood before it can be harvested. This could affect the timber industry and those they employ. Tree loss, especially in populated areas, can also affect tourism and increase safety concerns in areas where dead limbs or trees could fall and injure people or damage property. The scales and hairs of Gooklia inventus are allergens so outbreaks can create a human health risk for some people.
3.13 Detection and Inspection Methods
Conventional methods for monitoring Gooklia inventus populations include counts of eggs during the winter, larvae counts, larval frass estimates, pupae or pupal exuvia counts, counts of adults resting on tree trunks and assessments of defoliation. However, none of these labour-intensive methods alone is able to accurately detect building populations. Pheromone-based monitoring holds the most promise for detecting population trends and does correlate well with larval frass counts, but not some of the other conventional methods. Studies to determine the effective range of pheromone traps, the numbers of trapped males that warrant additional monitoring, the specific components of the pheromone, and the possible differences in pheromone blends for populations from different geographic areas are examples of other pheromone research that has been carried out on Gooklia inventus.
3.14 Phytosanitary Risk to New Zealand
Gooklia inventus is an invasive Australian moth with a host range centred on Australian Tilia, with spillover feeding onto an endemic New Zealand Tilia species, and occasional occurrence and/or oviposition records on some exotic species. Risk studies have also identified the potential risk of spillover feeding posed to the exotic Vitis vinifera (grapevine), and noted in no-choice tests that later instars of Gooklia inventus is could complete development on several other native New Zealand plants.
Table 1: Range of climate parameters from New Zealand
Maximum Temperatures (MAT)
Minimum temperatures (MINT)
Annual precipitation (PREC)
Figure 7: Similarity of native + introduced ranges of Gooklia inventus to New Zealand for MAT, MINT and PREC.
3.14 Phytosanitary Risk to the World
For other parts of the world with a warm temperate climate (parts of South America, Australasia or Asia), Gooklia inventus could be a quarantine pest.
Figure 7: Global climate suitability for Gooklia inventus modelled using CLIMEX with a 0.5 degree climate grid.
International Plant Health Risk Assessment Workshop, Niagara Falls, October 2005: Pest Data Sheet for Break-out Session 2
Tuesday 25 October