Liriomyza huidobrensis (Blanchard) (Diptera: Agromyzidae), pea leafminer (commonly known as potato leafminer fly in Indonesia) has become a major problem in potatoes and many other vegetable and flower crops grown in highland areas in Indonesia since 1994. Liriomyza sativae (Blanchard), vegetable leafminer, is also now well established in lowland areas in Indonesia where it is a major pest of beans, tomatoes and cucumber. Liriomyza chinensis (Kato), onion leaf miner, has continued to be spread in lowland areas of West and Central Java where it is found in damaging numbers on shallots These three pests have not yet been recorded in Australia.

Comprehensive information on the distribution of leafminers and their parasitoids in vegetable crops in West Java, North Sulawesi, South Sulawesi and Bali has been obtained following a second surveying season being successfully completed at each site. The LUCID keys being constructed for leafminer parasitoids and for economically important leafminers are well advanced.

Both L. sativae and L. huidobrensis have now been recorded from Bali, Lombok and South Sulawesi. In North Sulawesi, L. sativae and L. brassicae are the most abundant species but there has still been no record of L. huidobrensis.

The braconid parasitoid, Opius sp., has increased in abundance in the highland areas of West Java and Bali, but not yet in South Sulawesi where Hemiptarsenus varicornis remains the dominant species. In Central Kalimantan, the main parasitoids of L. sativae on yard-long bean, French bean and cucumber were Asecodes deluchii, H. varicornis and Chrysocharis sp.

Studies of the population dynamics of L. huidobrensis in unsprayed commercial potato crops in West Sumatra and South Sulawesi continued in the second year of the project. The trial crops continue to be troubled with severe infections of late blight. The farmer practice fields showed more damage and lower levels of parasitism than the study plots (only sprayed with fungicides). The impact of predatory flies (Coenosia sp.) was unclear in these trials. Field studies in Australia, using L. brassicae and L. chenopodii as host leafminers, showed that the standard method of leaf sampling over-estimated abundance of ectoparasitods such as H. varicornis compared to endoparasitoids such as Opius sp. An alternative technique, involving exposing mined plants only for 24-hour periods, gave more accurate estimates of parasitoid abundance.

Postgraduate students at IPB and Universitas Udayana have completed detailed studies on the biology of H. varicornis, Opius sp. and Neochrysocharis formosa. They studied immature development, survival and fecundity, host feeding, host instar preference and influence of host plant on parasitism. Field studies with the predatory fly Coenosia sp. found that 60% of prey items caught by adults were agromyzids. Laboratory studies showed that feeding punctures and number of first-instar larvae of L. huidobrensis were significantly lower on leaves treated with kaolin and lime. Similarly, under field conditions, both treatments reduced the abundance of leafminer population on potatoes. Field studies also revealed that significantly higher numbers of leafminer flies (monitored using sticky traps) were found on potato grown with plastic mulch, but that no differences were detected on degree of plant damage. In addition, mulching significantly increased tuber yield.

At IPB, a thelytokous (female-only) strain of the eucoilid parasitoid, Gronotoma micromorpha, shows promise as a candidate for mass-production and release in the field. High temperature or antibiotic treatments yielded several males, suggesting that the strain may be infected with Wolbachia. Samples have been sent to La Trobe University for checking. Bi-parental strains were found in the field in other parts of Indonesia.

Insecticide susceptibility data for three populations of L. huidobrensis for abamectin, cyromazine and dimehypo have been completed in Indonesia. No resistance was detected to cyromazine or dimehypo, but significant levels of resistance to abamectin were recorded from one population collected from a heavily sprayed commercial glasshouse. The response of H. varicornis to cyromazine, abamectin and mancozeb has been studied in Indonesia and Australia. Dr Michelle Robinson (CESAR) spent 6 weeks at IPB working with Mr Djoko Prijono to ensure techniques used in both laboratories were comparable.

To date, fifteen species of leafminer parasitoids have been identified from samples collected in Victoria. This suggests that it is unlikely that foreign importation of parasitoids would be required for control of polyphagous Liriomyza spp. in Australia.

The project team met in Bogor between 4 and 7 June 2002 to review progress in research to date and to revise work plans for the remainder of the project. At the meeting, Dr John LaSalle, CSIRO Entomology, and Dr Mali Malipatil, DPI, Victoria, assisted team members with identification of parasitoids and leafminers. Ms Bron. McDonald (DPI, Victoria) made a presentation on evaluation needs and issues to project members and assisted in the preparation of the initial draft of the project evaluation plan. Dr Michelle Robinson and Prof. Ary Hoffmann (CESAR) provided training to the team on field assessment of parasitoid impact.

Liriomyza huidobrensis (Blanchard) (Diptera: Agromyzidae), pea leafminer (commonly known as potato leafminer fly in Indonesia) has become a major problem in potatoes and many other vegetable and flower crops grown in highland areas in Indonesia since 1994. Liriomyza sativae (Blanchard), vegetable leafminer, is also now well established in lowland areas in Indonesia where it is a major pest of beans, tomatoes and cucumber. Liriomyza chinensis (Kato), onion leaf miner, has continued to be spread in lowland areas of West and Central Java where it is found in damaging numbers on shallots These three pests have not yet been recorded in Australia.

Comprehensive information on the distribution of leafminers and their parasitoids in vegetable crops in West Java, North Sulawesi, South Sulawesi and Bali has been obtained following a second surveying season being successfully completed at each site. The LUCID keys being constructed for leafminer parasitoids and for economically important leafminers are well advanced.

Both L. sativae and L. huidobrensis have now been recorded from Bali, Lombok and South Sulawesi. In North Sulawesi, L. sativae and L. brassicae are the most abundant species but there has still been no record of L. huidobrensis.

The braconid parasitoid, Opius sp., has increased in abundance in the highland areas of West Java and Bali, but not yet in South Sulawesi where Hemiptarsenus varicornis remains the dominant species. In Central Kalimantan, the main parasitoids of L. sativae on yard-long bean, French bean and cucumber were Asecodes deluchii, H. varicornis and Chrysocharis sp.

Studies of the population dynamics of L. huidobrensis in unsprayed commercial potato crops in West Sumatra and South Sulawesi continued in the second year of the project. The trial crops continue to be troubled with severe infections of late blight. The farmer practice fields showed more damage and lower levels of parasitism than the study plots (only sprayed with fungicides). The impact of predatory flies (Coenosia sp.) was unclear in these trials. Field studies in Australia, using L. brassicae and L. chenopodii as host leafminers, showed that the standard method of leaf sampling over-estimated abundance of ectoparasitods such as H. varicornis compared to endoparasitoids such as Opius sp. An alternative technique, involving exposing mined plants only for 24-hour periods, gave more accurate estimates of parasitoid abundance.

Postgraduate students at IPB and Universitas Udayana have completed detailed studies on the biology of H. varicornis, Opius sp. and Neochrysocharis formosa. They studied immature development, survival and fecundity, host feeding, host instar preference and influence of host plant on parasitism. Field studies with the predatory fly Coenosia sp. found that 60% of prey items caught by adults were agromyzids. Laboratory studies showed that feeding punctures and number of first-instar larvae of L. huidobrensis were significantly lower on leaves treated with kaolin and lime. Similarly, under field conditions, both treatments reduced the abundance of leafminer population on potatoes. Field studies also revealed that significantly higher numbers of leafminer flies (monitored using sticky traps) were found on potato grown with plastic mulch, but that no differences were detected on degree of plant damage. In addition, mulching significantly increased tuber yield.

At IPB, a thelytokous (female-only) strain of the eucoilid parasitoid, Gronotoma micromorpha, shows promise as a candidate for mass-production and release in the field. High temperature or antibiotic treatments yielded several males, suggesting that the strain may be infected with Wolbachia. Samples have been sent to La Trobe University for checking. Bi-parental strains were found in the field in other parts of Indonesia.

Insecticide susceptibility data for three populations of L. huidobrensis for abamectin, cyromazine and dimehypo have been completed in Indonesia. No resistance was detected to cyromazine or dimehypo, but significant levels of resistance to abamectin were recorded from one population collected from a heavily sprayed commercial glasshouse. The response of H. varicornis to cyromazine, abamectin and mancozeb has been studied in Indonesia and Australia. Dr Michelle Robinson (CESAR) spent 6 weeks at IPB working with Mr Djoko Prijono to ensure techniques used in both laboratories were comparable.

To date, fifteen species of leafminer parasitoids have been identified from samples collected in Victoria. This suggests that it is unlikely that foreign importation of parasitoids would be required for control of polyphagous Liriomyza spp. in Australia.

The project team met in Bogor between 4 and 7 June 2002 to review progress in research to date and to revise work plans for the remainder of the project. At the meeting, Dr John LaSalle, CSIRO Entomology, and Dr Mali Malipatil, DPI, Victoria, assisted team members with identification of parasitoids and leafminers. Ms Bron. McDonald (DPI, Victoria) made a presentation on evaluation needs and issues to project members and assisted in the preparation of the initial draft of the project evaluation plan. Dr Michelle Robinson and Prof. Ary Hoffmann (CESAR) provided training to the team on field assessment of parasitoid impact.

Year 3 (01/01/2003--31/12/2003)

Liriomyza huidobrensis, commonly known as potato leafminer fly in Indonesia, has become a major problem in potatoes and many other vegetable and flower crops grown in many highland areas in Indonesia since 1994. Liriomyza sativae, vegetable leafminer, is also now well established in lowland areas in Indonesia where it is a major pest of beans, tomatoes and cucumber. Liriomyza chinensis, onion leaf miner, has continued to spread in lowland areas of West and Central Java where it is found in damaging numbers on shallots. In 2003, it was found in some highland areas in West Java. Another two leafminer species were identified for the first time in Indonesia. These species, L. katoi and L. yasumatsui probably originate from Japan. They appear restricted to chrysanthemum, wild chrysanthemums and other Compositae. The females of these two species are very similar to another important polyphagous pest, L. trifolii, and their discovery has highlighted the need for rapid molecular diagnostic tests. So far, these two species have only been found in North Sulawesi. None of these important Liriomyza species have yet been recorded in Australia.

A measure of control can be obtained through wasp parasites. Analysis of the survey data on the distribution of leafminers and their parasitoids in vegetable crops in West Java, North Sulawesi, South Sulawesi and Bali has shown that L. huidobrensis is mainly found above 1000 m above sea level (asl), whereas L. sativae is generally restricted below 700 m. asl. However, there is very little overlap between the two species. Specific experiments are being undertaken to resolve the confounding effects of elevation and host plant on the distribution of both leafminer species and their most abundant parasitoids.

The LUCID keys being constructed for leafminer parasitoids and for economically important leafminers are continuing to be refined. In addition, two taxonomic papers describing new species of leafminer parasitoids from Indonesia and Australia have been written. The braconid parasitoid, Opius sp., has increased in abundance in the highland areas of West Java and Bali, but not yet in South Sulawesi where Hemiptarsenus varicornis remains the dominant species. In Central Kalimantan, the main parasitoids of L. sativae on yard-long bean, French bean and cucumber were Asecodes deluchii, H. varicornis and Chrysocharis sp.

Insecticide susceptibility data for three populations of L. huidobrensis for abamectin, cyromazine and dimehypo have been analysed and accepted for publication. The response of H. varicornis to cyromazine, abamectin and mancozeb has been studied in Indonesia and Australia. It was clear from these trials that there were no sub-lethal effects of the commonly used fungicide, mancozeb, on H.varicornis.

Studies of the population dynamics of L. huidobrensis in unsprayed commercial potato crops in West Sumatra and South Sulawesi concluded in the third year of the project. The trial crops continue to be troubled with severe infections of late blight. Detailed analysis of these data is being undertaken. The impact of predatory flies (Coenosia sp.) was unclear in these trials. Postgraduate students at Bogor Agricultural University are completing detailed studies on the biology of Gronotoma micromorpha and Asecodes deluchii.

This project addressed a serious new problem for vegetable growers in Indonesia caused by the invasion of several exotic species of Liriomyza leafminer pests. The Liriomyza problem also exists in most other countries in the region. Given the rapid spread of these pests, it is likely that vegetable and cut-flower producers in Australia will have to contend with at least some these pests in the near future.
Liriomyza huidobrensis (Blanchard) (Diptera: Agromyzidae), pea leafminer (commonly known as potato leafminer fly in Indonesia) had become a major problem in potatoes and many other vegetable and flower crops grown in many highland areas in Indonesia since 1994. This project has shown that Liriomyza sativae (Blanchard), vegetable leafminer, was also now well established in lowland areas in Indonesia where it is a major pest of beans, tomatoes and cucumber. Both flies are continuing to spread eastward through Indonesia. Since its discovery in 2000, Liriomyza chinensis (Kato), onion leafminer, has continued to be spread in lowland areas of West and Central Java where it is very damaging numbers to shallots. In 2003, the project found that it had spread to some highland areas in West Java. Another two leafminer species were identified for the first time in Indonesia. The project used PCR-RFLP to develop species-specific profiles to identify Liriomyza species of high quarantine significance to Australia - L. huidobrensis, L. sativae and L. trifolii - from a range of less important species that share one or more hosts: L. brassicae, L. chinensis, L. yasumatsui, L. katoi and L. chenopodii. None of these important Liriomyza species have yet been recorded in Australia.
Analysis of the comprehensive survey data on the distribution of leafminers and their parasitoids in vegetable crops in West Java, North Sulawesi, South Sulawesi and Bali has shown that L. huidobrensis is mainly found above 1000 m above sea level (asl), whereas L. sativae is generally restricted below 700 m asl. We found very little overlap between the two species. To date, 19 species of leafminer parasitoids have been identified from our surveys in Indonesia. Fifteen species of leafminer parasitoids have been identified from samples collected in Victoria. We conclude that it is unlikely that foreign importation of parasitoids would be required for Indonesia or Australia (in the case of an incursion of polyphagous Liriomyza spp.).
A series of Lucid matrix keys have been produced for parasitoids of agromyzid leafminers in South East Asia. Lucid keys to identify agromyzid leafminers were also developed. Detailed biological and ecological studies on the parasitoids, Hemiptarsenus varicornis, Opius chromatomyiae, Neochrysocharis okazakii, Asecodes deluchii and Gronotoma micromorpha, and the predatory muscid fly, Coenosia humilis, were carried out by postgraduate students at IPB and Universitas Udayana.
Detailed studies of the population dynamics of L. huidobrensis were undertaken on unsprayed and sprayed commercial potato crops in West Sumatra (4 cropping seasons) and South Sulawesi (4 cropping seasons). In each location, the use of insecticides generally had little impact on suppressing the leafminer population and also often reduced the level of parasitism. Bioassay data for abamectin, cyromazine and dimehypo, a nereistoxin analogue insecticide used widely in Indonesia, showed all three chemicals were effective against larvae of three Indonesian populations of L. huidobrensis with different histories of chemical exposure, but dimehypo and to a lesser extent abamectin were harmful to parasitoids. These results suggest that, in Indonesia, cyromazine can be incorporated into Liriomyza control programs that conserve parasitoids, whereas dimehypo and abamectin need to be used cautiously. Repeated applications of profenofos were ineffective in controlling L. huidobrensis numbers on potatoes in the field but reduced parasitism and predation. These detrimental effects might be responsible for the increased damage and decreased yield in the pesticide-treated fields. In contrast there were no detrimental effects associated with repeated applications of abamectin.
The project highlights the importance of local parasitoids and other beneficial insects in controlling pest leafminers, and provides the tools for identifying the parasitoids, as well as the leafminer pests. The project highlights the dangers associated with uncontrolled and indiscriminate use of hard chemicals for controlling leafminers, and the benefits of correct species identification in devising control strategies. The project also provides essential information for responding to leafminer incursions into Australia, and information for effective control strategies that can be implemented against leafminer in Indonesia. The project has successfully contributed to the training of graduate students in Indonesia and the development of strong links between scientists in Indonesia and Australia.