Elucidating the Factors Behind the Rapid Biotype Displacement of the Stone Leek Leafminer <i>Liriomyza chinensis</i>（Diptera: Agromyzidae）in Japan

The Japanese bunching onion, Allium fistulosum L., is an important vegetable in East Asia. However, the stone leek leafminer, Liriomyza chinensis (Kato), is a serious insect pest that invades the Allium species. As the feeding punctures on the leaf surface caused by the female adults as well as the larval mining inside the unifacial leaves reduce the commercial value of A. fistulosum, it is essential to control L. chinensis during its growth. The accession ‘Beicong’ has shown resistance to L. chinensis due to its egg-killing defense, but the degree of resistance varies within the ‘Beicong’ population. Therefore, in the present study, we selected highly resistant selfed lines from the ‘Beicong’ population by artificially inoculating L. chinensis eggs into the leaves to breed A. fistulosum with a resistance to L. chinensis. A highly resistant line was obtained by continuously self-pollinating the resistant ‘Beicong’ individual among the 191 individuals, which was inherited in the F1 hybrid of the resistant line and the susceptible variety. However, the F1 hybrid’s degree of resistance was an intermediate of the two parents’. It was also revealed that the resistance of ‘Beicong’ was due to both egg- and larval-killing defense mechanisms by artificially inoculating the eggs and larvae into the leaves. Hence, developing a highly resistant line could contribute to integrated pest management in A. fistulosum cultivation by decreasing the population of L. chinensis.

In recent years, widespread damage caused by biotype B of the stone leek leafminer, Liriomyza chinensis（Kato）（Diptera: Agromyzidae）, has become an issue in Welsh onion fields throughout Ibaraki Prefecture. This study aims to evaluate the efficacy of granular insecticides in controlling L. chinensis in Welsh onion fields harvested in early autumn. Specifically, we applied either cyantraniliprole-thiamethoxam granules（6 kg/10 a）or dinotefuran granules（9 kg/10 a）to the base of the plants in late August, and compared their effectiveness to a non-granule control. Although all treatments showed an increase in the number of flies from mid to late September, the percentage of damaged leaves in the groups treated with granules was lower than that in the non-granule control. Furthermore, the effectiveness of dinotefuran was equal to or greater than that of cyantraniliprole-thiamethoxam. These results suggest that dinotefuran is a lower-cost alternative with saved times of usage of insecticide components, in late August on Welsh onions harvested in autumn.

The stone leek leafminer, Liriomyza chinensis (Kato), has become a serious pest on Allium spp. However, knowledge concerning the biology of L. chinensis, which affect development of control programs, is still limited. Therefore, this experiment was conducted during 2020 at Entomology Laboratory, Faculty of Agronomy, University of Agriculture and Forestry, Hue University, Vietnam to study the effects of temperature on development, longevity, feeding and fecundity of L. chinensis under laboratory conditions. Liriomyza chinensis used for the present study were collected from green bunching onion fields at Hue City, Central Vietnam and reared on green bunching onion, Allium fistulosum L. in an environmental chamber at a constant temperature of 25 ± 0.5, 27.5 ± 0.5 and 30 ± 0.5°C, 70±10% RH and a 16L: 8D photoperiod. Developmental time, longevity, feeding and fecundity were inversely proportional to temperature. Total developmental times from egg to adult emergence decreased from 20.9 to 13.4 days for temperatures from 25 to 30°C. The longevities of L. chinensis were 9.2, 10.8 and 12.0 days at 25, 27.5 and 30°C, respectively. Females made the average of 1004.2, 1716.8 and 2549.0 punctures during her lifespan at 25, 27.5 and 30°C, respectively. The females laid means of 54.2, 115.2 and 134.8 eggs at 25, 27.5 and 30°C, respectively. These data are useful for predicting population dynamics of L. chinensis under field conditions and determining the maximum proportion of susceptible individuals for facilitating improved timing of application of control measures.

The stone leek leafminer, Liriomyza chinensis (Kato) (Diptera: Agromyzidae) , is recognized as one of the most destructive pests of the bunching onion. Varietal resistance against L. chinensis has been reported in Allium fistulosum in Japan. We report a new method for evaluating the antibiosis of bunching onions with varietal resistance to L. chinensis by artificially inoculating leaves with L. chinensis eggs. New no-choice tests were performed via the collection and artificial inoculation of L. chinensis eggs into unifacial leaves with a plunger microsyringe and the quantification of the number of individuals that reached the pupal stage in the soil after 14 days of inoculation at 24 °C; these tests were established and conducted to determine the resistance categories of several varieties of A. fistulosum. Antibiosis studies revealed a significant difference in survival to the pupal stage, forewing lengths of adults and development time from the egg to pupal stages among the resistant and susceptible varieties of A. fistulosum, indicating that antibiosis is an important factor in the varietal resistance of A. fistulosum. Furthermore, the antibiosis of the highly resistant varieties ‘Beicong’ and ‘Kokusen natsuyo’ revealed egg killing defenses against L. chinensis.

The Agromyzidae are a diverse family of small flies whose larvae mine plant tissues, often with a high degree of host specificity. However, several species of Liriomyza-including the vegetable leafminer (Liriomyza sativae Blanchard), pea leafminer (Liriomyza huidobrensis [Blanchard]), American serpentine leafminer (Liriomyza trifolii [Burgess]) and tomato leafminer (Liriomyza bryoniae [Kaltenbach]) - are highly polyphagous and pose significant biosecurity risks to Australian agriculture. The stone leek leafminer (Liriomyza chinensis [Kato]), though host-specific to Allium spp., is also a concern. Effective surveillance and diagnosis are challenging due to the flies' small size, rapid life cycles, and morphological similarities. While previous quantitative PCR (qPCR) assays have enabled detection of L. sativae, L. trifolii, and L. huidobrensis, and the non-pest species Liriomyza brassicae (Riley) (cabbage leafminer), we extend this capability by developing species-specific assays for L. bryoniae and L. chinensis. The new assays were highly specific across 16 agromyzid species collected globally and demonstrated strong sensitivity. A revised assay for L. huidobrensis, targeting the mitochondrial ND5 region, eliminated cross-reactivity observed with the original qPCR assay. We also validated a simplified DNA extraction method suitable for field use and demonstrated successful in-field diagnosis using the portable FranklinTMthree9 real-time PCR themocycler. These assays have already proven valuable during post-incursion surveys and general surveillance efforts. Together, they provide a flexible and rapid diagnostic toolkit to support the early detection and management of Liriomyza pests in Australia and elsewhere.

The stone leek leafminer, Liriomyza chinensis (Kato), has become a serious pest on onioncrops in the whole Vietnam, and it is treated by a wide range of conventional insecticides. Growers apply insecticides early after a few mines on several leaves have been seen, and repeated applications are usually made. Field trial was conducted to evaluate the effects of a single application of four currently and potentially used insecticides on L. chinensis. These insecticides were applied at recommended field rates. Leaf samples were used to monitor larval population, and yellow sticky traps were used to monitor adult population. Cyromazine was effective on the larvae, but no effective on the adults. Cartap, permethrin and phenthoate were not or less effective on neither larvae nor adults of the leafminer. These results suggest that cyromazine application provide one potential component of an effective L. chinensis control strategy for Vietnamese onion farmers.

Investigation of seasonal prevalence of the stone leek leafminer, <i>Liriomyza chinensis</i> (Kato), by yellow sticky-trap method

The effect of nine constant temperatures (15, 17.5, 20, 22.5, 25, 27.5 30, 32.5, and 35 degrees C) on the development of the stone leek leafminer, Liriomyza chinensis (Kato), on Japanese bunching onion, Allium fistulosum L., was studied in the laboratory. Developmental times for immature stages were inversely proportional to temperature between 15 and 30 degrees C but increased at 32.5 degrees C. Total developmental times from egg to adult emergence decreased from 69.6 to 17.1 d for temperatures from 15 to 30 degrees C, with pupae requiring more time for development than the combined egg and larva stages. Both linear and nonlinear (Logan equation VI) models provided a reliable fit of development rates versus temperature for all immature stages. The lower developmental thresholds that were estimated from linear regression equations for the egg, first, second, and third instars, total larva, egg-larval, pupa, and total combined immature stages were 12.1, 10.6, 13.6, 8, 9.6, 11.3, 11.2, and 11.4 degrees C, respectively. The degree-day accumulation was calculated as 312.5 DD for development from egg to adult emergence. By fitting the nonlinear models to the data, the upper and optimal temperatures for egg, larva, pupa, and total immature stages were calculated as 37.8 and 31.7, 34.9 and 30.1, 35.8 and 30.6, and 35.0 and 30.9 degrees C, respectively. These data are useful for predicting population dynamics of L. chinensis under field conditions and determining the maximum proportion of susceptible individuals for facilitating improved timing of application of control measures.

We established a method for mass-rearing the stone leek leafminer, Liriomyza chinensis (Kato) (Diptera: Agromyzidae), one of the most destructive pests of Welsh onion, Allium fistulosum L. We examined three methods that allow L. chinensis to produce eggs year-round. By recording the number of emerged adults for 4 years, we determined the optimal mass-rearing method as follows. Allium fistulosum plants used for oviposition are grown in pots and maintained in a growth chamber with temperature and photoperiod set to 22 ℃ and 14 L:10 D, respectively. Allium fistulosum plants are exchanged for a new set of plants three times in a 7-day period. On the first day, 300 adults are placed in the rearing cage. On the fifth day, another 100 emerged adults are placed in the rearing cage. Using this rearing method, it becomes possible to obtain more than 1,000 L. chinensis eggs in a day. Our goal is to select and breed a highly resistant line of A. fistulosum using a novel method for evaluating egg killing defenses via artificial inoculation of plants with L. chinensis eggs. Here we present our mass-rearing method to obtain large quantities of L. chinensis eggs.

Development of a novel nuclear DNA marker to identify biotypes A and B of the stone leek leafminer, Liriomyza chinensis (Diptera: Agromyzidae)

The larva of stone leek leafminer, Liriomyza chinensis (Kato), is known to infest alternately just below the epidermis and inner surface of hollow cylindrical leaves of allium crops, resulting in the formation of discontinuous linear mines (mine form: discontinuous). However, after the fall of 2016, a novel mine form of the same species (mine form: continuous) was detected in Welsh onion fields of Kyoto Prefecture, Japan. We hypothesized that these mine forms were associated with flies having different genetic backgrounds; hence, we compared the mine forms and the partial mtCOI gene of flies collected from Welsh onion fields from 2018 to 2019. The results demonstrated that the flies that emerged from different mine forms could be classified into two haplogroups, i.e., flies displaying a discontinuous mine form were of haplogroup A, whereas those that displayed continuous mines were of haplotype B. Additionally, using populations of these flies reared in the laboratory, we confirmed that the mine form of the larvae of haplotype A on Welsh onions was discontinuous, whereas that of haplotype B was continuous. We named the population that exhibited a discontinuous mine form as biotype A and the population displaying a continuous mine form as biotype B.

Stone leek leafminer Liriomyza Chinensis is an exotic pest that currently has become a major pest in onion plantings in the island of Bali. This study was conducted to determine the behavior of flight, population development and to analyze the level of attack of stone leek leafminer against five varieties of onion (Bima Brebes, Bauji, Tajuk, Probo and Bali Karet). The results showed that adult L. Chinensis has begun to invade the plant since the appearance of leaves of onion plants to the soil surface. The peak of the invasion occurs when the plant is 3 weeks after planting (WAP). While the most adult flight activity occurs at 08.00-11.00. The development of the adult population has begun to appear since 1 week and peaked at 3 WAP, then decreased to 5 WAP and rose again at 6 WAP then decreased to 8 weeks while the larval population began to monitor 3 WAP and peaked at 5 WAP and then decreased steadily to 8 WAP. The average percentage of stone leek leafminer attack against Bima Brebes varieties (12.91%), Bauji (9.68%), Tajuk (10.09%), Probo (9.96%) and Bali Karet (13.56%). Likewise, the average intensity of stone leek leafminer attack against Bima Brebes varieties (19.79%), Bauji (15.55%), Tajuk (16.80%), Probo (17.10%) and Bali Karet (20.20%). This shows that the five varieties of onion tested were susceptible to stone leek leafminer, but Bauji varieties tended to be more resistant to it.

I investigated the stone leek leafminer, Liriomyza chinensis Kato (Diptera: Agromyzidae), and its hymenopterous parasitoids emerging from the leaves of Welsh onion collected in Kyoto Prefecture, Japan, from July to August 2002, from June to August 2003, and from May to June 2005. The parasitoids that emerged from L. chinensis larvae or pupae were Halticoptera circulus (Walker) (Pteromalidae), Pnigalio katonis (Ishii) (Eulophidae), Diglyphus isaea (Walker) (Eulophidae), Chrysocharis pentheus (Walker) (Eulophidae), Neochrysocharis formosa (Westwood) (Eulophidae), and Closterocerus trifasciatus Westwood (Eulophidae). The dominant parasitoid species in 2002 was D. isaea, and that in 2003 and 2005 was P. katonis.

Intra- and inter-specific competition between two stone leek leafminer Liriomyza chinensis (Diptera: Agromyzidae) biotypes in Japan

The insecticide susceptibility of the stone leek leafminer, Liriomyza chinensis Kato, on Welsh onion was evaluated at 25°C under a 15L-9D photoperiod. Among 21 insecticides tested on second instar larvae using the leaf dipping method, CVP (mortality: 98.0%), thiocyclam (98.0%), cyromazine (80.9%) and nitenpyram (81.8%) produced high mortality. Adults of L. chinensis were highly susceptible to CVP (mortality: 85.4%), ethofenprox (100.0%), and spinosad (85.7%). Cartap, thiocyclam, ethofenprox, cypermethrin and emamectin benzoate reduced the number of feeding and oviposition punctures made by adult L. chinensis females.