Agromyzid Leafminers Research Articles

Seasonal Abundance of Liriomyza sativae (Diptera: Agromyzidae) and its Parasitoids on Vegetables in Southern Vietnam

Native to the North America, Liriomyza sativae (Blanchard) (Diptera: Agromyzidae) is widespread worldwide but mostly occurs in the temperature regions including South East Asian countries (Spencer, 1973; Murphy and LaSalle, 1999). Recently, L. sativae has been also recorded from China (Zhao and Kang, 2000) and Japan (Iwasaki et al., 2000). In Japan, L. sativae was found for the first time in 1999 in Kyoto and Yamaguchi Prefectures (Iwasaki et al., 2000). This species has quickly spread and become a serious pest of vegetable and ornamental crops in the fields and greenhouses. This rapid spread was mainly caused by transportation of plant materials for greenhouses and plastic tunnels. In northern areas beyond latitude 34 N in China, L. sativae can not overwinter in the outdoors (Zhao and Kang, 2000). In Vietnam, L. sativae is an economically important pest of a wide variety of vegetable and ornamental crops in the open fields (Andersen et al., 2002; Tran et al., 2005a, b). Recent outbreaks of the leafminer were treated by a wide range of conventional insecticides, but control was unsatisfactory (Johansen et al., 2003; Tran and Takagi, 2005). Frequent applications of these broad spectrum insecticides can adversely affect parasitoid abundance in the vegetable agro–ecosystems (Saito et al., 1996; Johansen et al., 2003), can promote the development of pesticide resistance within fly populations (Keil et al., 1985, Johansen et al., 2003; Hofsvang et al., 2005) and frequently lead to an increase in leafminer density (Oatman and Kennedy, 1976; Murphy and LaSalle, 1999). Agromyzid leafminers are known to have rich natural enemy communities. Eighteen species of hymenopteran parasitoids have been recovered from Liriomyza leafminers in central and southern Vietnam. Among them, Neochrysocharis beasleyi Fisher & LaSalle, Neochrysocharis okazakii Kamijo, Neochrysocharis formosa (Westwood) and Asecodes delucchii (Boucek) (Hymenoptera: Eulophidae) are numerically dominant species (Tran et al., 2006). They have played a very important role in leafminer suppression in natural ecosystems and cultivated areas with reduced insecticide use (Johnson et al., 1980; Murphy and LaSalle, 1999). The objectives of this study were to survey damage caused by L. sativae in two important vegetable–growing areas of the Ho Chi Minh City, southern Vietnam, and to monitor the seasonal abundance of the leafminer and its parasitoids. In this paper, the seasonal occurrence of L. sativae in Vietnam and Japan was also discussed. Seasonal Abundance of Liriomyza sativae (Diptera: Agromyzidae) and its Parasitoids on Vegetables in Southern Vietnam

Kapasitas Reproduksi, Lama Hidup, dan Perilaku Pencarian Inang Tiga Spesies Parasitoid Liriomyza sativae

Liriomyza sativae is a polyphagous agromyzid leafminer and it has invaded large part of world, i.e Hemiptarsenus varicornis, Gronotoma micromorpha, and Opius dissitus. This research were conducted to investigate progeny, immature development period, longevity of female parasitoids of L. sativae, and to study female parasitoid behaviour in host finding. Host finding behaviour was observed by examining their visit frequency to the leaves that mined by leafminer larvae and healthy leaves. Results showed that H. varicornis produced more progenies (10.70 ± 2.58 progenies/female), but not significantly different (P

Fecundity, Longevity, and Host Finding of Three Parasitoid Species of Liriomyza sativae

Liriomyza sativae is a polyphagous agromyzid leafminer and it has invaded large part of world, i.e Hemiptarsenus varicornis, Gronotoma micromorpha, and Opius dissitus. This research were conducted to investigate progeny, immature development period, longevity of female parasitoids of L. sativae, and to study female parasitoid behaviour in host finding. Host finding behaviour was observed by examining their visit frequency to the leaves that mined by leafminer larvae and healthy leaves. Results showed that H. varicornis produced more progenies (10.70 + 2.58 progenies/female), but not significantly different (P Key words: fecundity, longevity, behavior, Hemiptarsenus, Gronotoma, Opius, Liriomyza sativae

Diglyphus isaea (Hymenoptera: Eulophidae): a probable complex of cryptic species that forms an important biological control agent of agromyzid leaf miners

Diglyphus isaea (Walker 1838) (Hymenoptera: Eulophidae) is a primary parasitoid of agromyzid leaf miners (Diptera: Agromyzidae) and has been commercialized as a biological control agent. Diglyphus isaea occurs throughout much of the world and different populations are morphologically identical. Using nuclear ribosomal internal transcribed spacer 1 (ITS1) sequences, we examined variation among Chinese populations of D. isaea. Phylogenetic analyses combined with an analysis of sympatry indicated that D. isaea consists of at least four species in mainland China. The results imply that ITS1 is an efficient marker for identifying congeneric species of parasitic waSPS, and that cryptic species could be common in temperate and subtropical regions. Zusammenfassung Diglyphus isaea (Walker, 1838) ist ein primarer Parasitoid von blattminierenden Agromyziden (Diptera) und wird zu ihrer biologischen Kontrolle vermarktet. Die in weiten Teilen der Welt vorkommenden verschiedenen Populationen sind morphologisch identisch. Untersucht wurden Unterschiede in den nuklearen ribosomalen ITS1-Sequenzen zwischen chinesischen Populationen. Ergebnisse der phylogenetischen Analysen, kombiniert mit einer Sympatrie-Analyse, zeigen, dass D. isaea auf dem chinesischen Kontinent aus mindestens vier Arten besteht. Aus den Ergebnissen geht hervor, dass ITS1 ein effizienter Marker zur Identifizierung congenerischer Arten parasitischer Wespen ist und dass kryptische Arten in gemasigten und subtropischen Regionen verbreitet sein konnen.

Mitochondrial phylogeography of a leafminer parasitoid, Diglyphus isaea (Hymenoptera: Eulophidae) in China

Diglyphus isaea is one of the primary parasitoids of agromyzid leafminers. Mitochondrial cytochrome oxidase subunit I sequences from 10 Chinese localities were used to investigate geographic variation within this widespread and morphologically uniform parasitoid. Phylogeographic analyses and sequence variation indicated that this species was actually a species-complex. We used an amber fossil record of the genus Entedon (Eulophidae: Entedoninae) as a reference to estimate the divergence time of major clades within D. isaea . With reference to the fossil record of its hosts, our results indicate that associations between parasitoids and leaf-miners could have been possibly established 38.2 million years ago.

Survey of leafminers and their parasitoids to find endosymbionts for improvement of biological control

Agromyzid leafminers cause serious pest problems in Japan. These leafminers are parasitized by their native parasitoids. The objective of our research is to find symbionts that may be useful in improving the biological control of Agromyzid leafminers by using their native parasitoids in Japan. Among the four species of leafminers, we detected two strains of Wolbachia from Liriomyza trifolii (Burgess) (Diptera: Agromyzidae) and Liriomyza bryoniae (Kaltenbach) (Diptera: Agromyzidae). Although Wolbachia induces strong cytoplasmic incompatibility (CI) in L. trifolii , the level of Wolbachia infection in the population was not fixed and it was maintained at frequencies that must be regarded as unstable. Among the 15 species of leafminer parasitoids, we found a Wolbachia in Hemiptarsenus varicornis (Girault) (Hymenoptera: Eulophidae) and a Rickettsia in Neochrysocharis formosa (Westwood) (Hymenoptera: Eulophidae). H. varicornis was observed to be infected with Wolbachia very similar to that of the native leafminer L. bryoniae . This Wolbachia strain did not induce CI or parthenogenesis in H. varicornis . N. formosa is thelytokous and infected with Rickettsia , in practically all populations that were studied, the Rickettsia infection has reached fixation. Many leafminer parasitoids including N. formosa , belong to the family Eulophidae. It is possible that the Rickettsia of N. formosa may be used to render other Eulophidae thelytokous as well as a method to increase the biological control efficiency.

Control of Liriomyza langei on chrysanthemum by Diglyphus isaea produced with a standard or modified parasitoid rearing technique

Abstract: Overproduction of male parasitoids during mass rearing will increase costs for biological control because wasp shipments contain fewer females and only females kill hosts directly. We have developed a rearing technique capable of significantly reducing male‐biased sex ratios in Diglyphus isaea (Walker) (Hym., Eulophidae), a commercially reared parasitoid of agromyzid leafminers. In this study, we examined the effect of rearing technique on the efficacy of D. isaea for biological control of Liriomyza langei Frick (Dip., Agromyzidae) on chrysanthemum, Dendranthema grandiflora Tzvelev var. ‘Miramar’. We produced D. isaea on mixtures of small and large hosts (our modified technique) or on only large hosts (simulating commercial mass‐rearing) and compared: (1) control of L. langei with D. isaea produced by the two rearing techniques, and (2) damage and yield of unprotected and protected plants. The two rearing techniques produced similar numbers of waSPS per rearing cohort, but the ‘modified’ technique reduced the proportion of males by approximately 13%. The two techniques also produced females of similar size, but the ‘modified’ technique produced smaller males. In greenhouse trials simulating leafminer infestations of potted chrysanthemums during commercial production, we found no significant differences between the levels of control obtained by releasing identical numbers and sex ratios of adult waSPS produced by either rearing technique. Mine counts on plants protected by waSPS of either rearing history were similar and around 30–70% less than unprotected plants during most of the 11‐week crop cycle. At crop harvest, more than half of the foliage on protected plants was undamaged compared with <10% on unprotected crops. Damage to the flower stems of protected plants was relatively light in the top half of the canopy compared with the bottom half. Protected plants were around 10–15% taller and produced twice as many flower buds compared with unprotected plants. Our ‘modified’ rearing technique can reduce overproduction of males in D. isaea with no compromise in biological control efficacy. Adoption of our rearing technique by commercial insectaries could reduce implementation costs for not only D. isaea but also other parasitoids that show host‐size‐dependent sex allocation.

Pesticide applications on Java potato fields are ineffective in controlling leafminers, and have antagonistic effects on natural enemies of leafminers

In Indonesia a range of insecticides is routinely applied to control agromyzid leafminers. Insecticide applications can reduce parasitism by indigenous parasitoid wasps and also decrease numbers of the predatory muscid fly, Coenosia humilis, and these effects reduce control of leafminers. In replicated field trials, repeated applications of Profenofos were ineffective in controlling L. huidobrensis numbers on potatoes. Applications of Profenofos and Carbosulfan decreased rates of parasitism byHemiptarsenus varicornis and Opius chromatomyiae, and reduced numbers of C. humilis. These detrimental effects of the pesticides observed may have contributed to the increased damage and decreased yield in the pesticide-treated fields. An alternative control strategy involving the applications of Abamectin led to a reduction in leafminers without harmful effects on parasitoids and predators. Abamectin applications provide one potential component of an effective Liriomyza control strategy for Indonesian potato farmers.

Species composition and population dynamics of leafmining flies and their parasitoids in Victoria

Abstract Mined leaves were sampled from unsprayed sites in Victoria to record the range of leafminers and their parasitoids. Three agromyzid leafminers, Liriomyza brassicae (Riley), Liriomyza chenopodii (Watt) and Chromatomyia syngenesiae Hardy, and one drosophilid leafminer, Scaptomyza flava (Fallén), were collected, along with 15 parasitoids, mainly Eulophidae. The most common parasitoids were Hemiptarsenus varicornis (Girault) (42.5%), Diglyphus isaea (Walker), 14.6%, Closterocerus mirabilis Edwards & La Salle (10.5%), and Opius cinerariae Fisher (8.5%). Most parasitoids were collected from two or more leafminer hosts. Weekly collections from Chinese cabbage (Brassica rapa var. pekinensis) infested with L. brassicae and S. flava, and beetroot (Beta vulgaris var. crassa) infested with L. chenopodii were made over two seasons at Knoxfield, Victoria to assess the relative impact of these parasitoids on agromyzid fly populations in crops. A further two parasitoid species were identified at low densities. Hemiptarsenus varicornis and D. isaea were the most numerous parasitoids collected in both crops. A different sampling method in the second year showed that O. cinerariae made up 25% of the sample from Chinese cabbage and was probably more common than estimated in the first season. Control exerted by local parasitoids was high, with 100% control of L. chenopodii reached in beets within 1–3 weeks of mines appearing and 100% control of L. brassicae within 6 weeks.

Species and Cultivar Influences on Infestation by and Parasitism of a Columbine Leafminer (Phytomyza aquilegivora Spencer)

Abstract Columbine, Aquilegia spp., are regularly attacked by agromyzid leafminers, Phytomyza spp. Effects of columbine species and cultivars on infestation by the leafminer Phytomyza aquilegivora Spencer, and subsequent parasitism by hymenopterous parasitoids was evaluated in two-year field trials at four locations in central and north Georgia. Among 20 columbine taxa planted in non-irrigated, wooded sites in central and north Georgia, two selections (A. flabellata and A. caerulea ‘Dwarf Fantasy Mix’) were comparable to the moderately resistant native species A. canadensis. In irrigated sites in central and north Georgia, all cultivars were equally infested by the leaf miner. The most heavily attacked selections among all sites were A. alpina, A. chrysantha ‘Yellow Star’, A. caerulea, A. caerulea ‘McKana mix’, A. caerulea ‘Music hybrid’, A. skinneri, and A. x hybrida ‘Ruby Port’. The variegated selection, A. vervaeneana ‘Woodside’, sustained intermediate infestation levels as did A. vulgaris ‘Winkie Blue & White’. Cultivar influences on parasitism of leafminers was quantified at two sites. Eleven species of hymenopteran parasitoids representing three families were recovered. Leafminers infesting A. chrysantha ‘Yellow Star’ were most heavily parasitized at both locations. Chrysocharis pentheus Walker was the most abundant parasitoid, representing 41% of all parasitoids collected and 48.4% of the species reared from leafminers in central Georgia. Seladerma sp. was the only parasitoid reared from leafminers collected in north Georgia and represented 22.1% of all parasitoids obtained.

Looks are important: parasitic assemblages of agromyzid leafminers (Diptera) in relation to mine shape and contrast

Summary We test the hypothesis that leaf mine appearance can affect the risk of leafminers being discovered by parasitoids, and therefore influence parasitic assemblages, using a comparative study of parasitic complexes associated with 28 agromyzid species in Central Argentina. Analyses were based on size, structure (defined as the number of species in host‐range categories) and impact (percentage parasitism) of parasitic complexes on leafminers. Mine appearance was defined in terms of shape (linear, linear‐blotch, blotch) and colour (high or low contrast with the leaf lamina). Irrespective of the agromyzid species involved, significant differences were found in the structure of the parasitoid complexes: specialists were more abundant and generalists rarer than expected in blotch and cryptically coloured mines. There were no differences in average parasitoid species richness and parasitism rates among differently coloured or shaped galleries. However, mine appearance significantly affected parasitic assemblage structure, with shape driving generalist species richness and contrast influencing that of specialists. Mine shape also affected parasitism rates, which were highest for generalists in linear mines, and for specialists in blotch mines. The existence of a gradient of discovery from the cryptically coloured blotch mines to the most apparent highly contrasting linear ones was supported by significant correlations of this gradient with richness and parasitism rates of generalist and specialist parasitoids. Taxonomic composition of parasitic complexes (analysed through parasitoid species abundance) was separated significantly according to host mine shape. An even more significant classification of assemblages was achieved when the combination of mine shape and colour was considered in the discoverability gradient. Our results suggest that despite leaf mines being an ecologically homogeneous resource, their morphology might offer varying degrees of refuge against different parasitoids.

History of an invader, Scaptomyza flava (Fallen, 1823) (Diptera: Drosophilidae)

In New Zealand, the European leaf mining fly, Scaptomyza (Scaptomyza) flava (Fallen, 1823) (Diptera: Drosophilidae), is a pest of gypsophila and brassicas. Scaptomyza flava was first found in Levin (March 1964) and in 1965 was found in Hastings (March), Lincoln (July), and Nelson (December). By January 1968 it was found in Auckland and Gisborne. Voucher specimens in New Zealand show the species was correctly identified by the Commonwealth Institute of Entomology in 1965. However, this information was lost, and parasitoids of Agromyzidae were released (1969–71) to control what was initially assumed to be an agromyzid leaf miner of brassicas. The identity of the fly as S. flava was confirmed by Bock in 1988. In this study, six New Zealand insect collections were examined and field collections were made to confirm host associations, parasitism, and colonisation. Two parasitoids have been reared from S. flava in New Zealand, and overseas at least two other parasitoid species are known from this species. This investigation emphasises the need for good communication about new pests and proper care for voucher specimens.

Plant-Related Intraspecific Size Variation in Parasitoids (Hymenoptera: Parasitica) of a Polyphagous Leafminer (Diptera: Agromyzidae)

Body size of polyphagous parasitoids of agromyzid leafminers directly depends on that of their hosts. The possible influence of plant host on parasitoid body size was studied for the pea leafminer, Liriomyza huidobrensis Blanchard, and three of its most abundant solitary parasitoids: Phaedrotoma scabriventris (Nixon) (Braconidae), Halticoptera helioponi De Santis (Pteromalidae), and Chrysocharis flacilla (Walker) (Eulophidae) on 12 plant species. The relationship between host and parasitoid sizes was also examined to determine whether parasitoids use a consistent proportion of the host or whether different host plants allow varying degrees of resource exploitation. Significant differences were found in L. huidobrensis wing length, as well as in body and wing length of all parasitoid species studied, depending on the plant where the leafmining larvae had fed. Female parasitoid and host sizes were highly correlated. Despite leafminers attaining large body size, the host exploitation rate was consistently lower on Beta vulgaris cycla L., suggesting that plant aspects other than those determining leafminer size could be impairing host suitability on this plant. Within the range of plant hosts considered, Vicia faba L. would be the most adequate for rearing L. huidobrensis and the three parasitoid species studied, providing large individuals and an efficient biomass exploitation.

Host-size-dependent sex ratio theory and improving mass-reared parasitoid sex ratios

Although an effective parasitoid of agromyzid leafminers, Diglyphus isaea (Walker) (Hymenoptera: Eulophidae) is an expensive biological control agent in terms of production costs. In part, these costs arise from the production of male-biased offspring sex ratios. Here, we present a mass-rearing technique that will increase the proportion of females produced and reduce the need for frequent releases in biocontrol programs. By presenting female D. isaea groups of sequentially larger leafminer hosts to attack, we are able to generate progressively more female-biased sex ratios. After three days of providing increasingly larger hosts, we were able to reduce the sex ratios produced by individual females from 57% male to 36% male; sex ratios produced by groups of females dropped from 64% male to 45% male. Several attributes of D. isaea sex allocation allow us to manipulate sex allocation behavior. First, D. isaea is a solitary idiobiont; resources available to each offspring are present at the time of attack allowing the ovipositing female to accurately assess host quality. Host size positively affects both male and female wasps. Females laid more daughters in larger hosts and more sons in smaller hosts. We show that the observed relationship between host size and offspring sex ratio is due to maternal sex allocation decisions rather than differential mortality. Furthermore, assessment of the size threshold was relative to prior host encounters rather than an absolute assessment. Our simple memory model suggests that while females are influenced most strongly by recent encounters, females also base their assessment of the host-size threshold on prior host encounters.

Effects of cyromazine and abamectin on the leafminer, Liriomyza huidobrensis and its parasitoid, Diglyphus isaea in celery

SUMMARYField trials were conducted for 2 yr on celery (Apium graveolens L.) to determine the effects of two translaminar insecticides (abamectin and cyromazine) on the agromyzid leafminer, Liriomyza huidobrensis (Blanchard), and the eulophid parasitoid, Diglyphus isaea Walker. Abamectin and cyromazine were applied once early in the growing season by spray or drip application. Yellow sticky traps and leaf samples were used to monitor population levels; a gas chromatograph‐mass spectrometer was used to monitor cyromazine residues within the celery plants during 1 yr. Spray applications of abamectin and cyromazine significantly reduced larval leafminers and D. isaea. Contrary to grower practices, application of cyromazine by drip irrigation systems had minor effects on larval leafminer and D. isaea as compared to spray application. Cyromazine residues in the plants treated by spray application declined sharply after 1 wk, and no residues were detected 2 wk after application; less than 0.05 ppm cyromazine residues were detected in plants treated by drip application. Implications of these results on management practices are discussed.

Insect–Plant Food Webs Could Provide New Clues for Pest Management

Food webs describe feeding interactions in a community. Parasitoid food webs concentrate on such interactions among plants, phytophagous insects, and their parasitoids. Studies of them have not been applied to agricultural systems, despite the widespread use of parasitoids in insect pest management programs. This article compares parasitoid food webs from a native and a cultivated habitat in the same region, focusing on aspects relevant to pest management and seeking to elicit further interest in this type of study. The study system involves Agromyzid leaf miners, their plant hosts and parasitoids, from Cordoba (central Argentina). Inspection of the webs suggests interesting possibilities for detecting useful parasitoids and plant-alternative host-parasitoid interactions.

Parasitoid assemblage size and host ranges in a parasitoid (Hymenoptera)–agromyzid (Diptera) system from central Argentina

AbstractA parasitoid community on agromyzid leafminers from Cordoba, Argentina was analysed in terms of parasitoid assemblage size and host ranges of parasitoid species. Samples were taken during 1991–1995 at natural, urban and agricultural habitats. The system consisted of 69 parasitoid species and 51 leafminer species on 109 plant species. On average, 12 species parasitized each host, when only numerically well represented leafminer species were considered for analysis. Each parasitoid species exploited on average seven species and three genera of agromyzid leafminers. Both parasitoid assemblage size and parasitoid host range were notably high when compared with similar systems from other regions.

マメハモグリバエに対するｍｉｌｂｅｍｅｃｔｉｎ乳剤の殺虫効果と幼虫寄生蜂イサエアヒメコバチ幼虫の生存に及ぼす影響

The acaricide milbemectin causes high mortality of newly hatched larvae of the agromyzid leafminer, Liriomyza trifolii (Burgess) on kidney bean plants. A similar effect is observed with use of emamectin, which, like milbemectin, is derived from chemicals produced by soil bacteria. Most of the 1- and 2-day-old leafminer larvae died after application of milbemectin at 20ppm. Even at 7.5ppm, significantly fewer larvae grew to pupa compared to controls. Use of milbemectin did not have any adverse effect on development of the parasitoid Diglyphus isaea (Walker) during the larval and pupal stages nor on the survival rate of the emerged adult wasps. These results indicate that milbemectin can be integrated into IPM programs to control both L. trifolii and mites.

Taxonomic Composition of Hymenopteran Parasitoid Assemblages from Agromyzid Leaf-miners Sampled in Central Argentina

This paper deals with the taxonomic composition of parasitoid assemblages reared from agromyzid leaf-miners of 28 species collected in Cordoba, Central Argentina. The relative representation of each parasitic family was estimated, taking into consideration their species richness and abundance. Sample size affected the total species richness in each complex, and also that of Eulophidae and Pteromalidae, indicating that not only size but also taxonomic structure of parasitic assemblages are influenced by sampling effort. 3 superfamilies and 5 families of Hymenoptera Parasitica were represented, with Eulophidae (Chalcidoidea) specifically and numerically dominant both in the total community of parasitoids and in the parasitic assemblages of individual hosts. Chrysonotomyia, Chrysocharis (Eulophidae), Halticoptera (Pteromalidae) and Phaedrotoma (Braconidae) were the most relevant genera in terms of number of species and number of specimens reared. The parasitoids obtained from samples taken in agroecosystems differed from the global spectrum of taxa mainly by showing a numerical dominance of Braconidae, despite a noticeable specific impoverishment of this family.

Vibration–mediated interactions in a host–parasitoid system

The aim of this paper was to obtain behavioral evidence of vibration mediated interactions between the apple tentiform leafminer Phyllonorycter malella (Ger.) (Lepidoptera, Gracillariidae) and its parasitoid Sympiesis sericeicornis Nees (Hymenoptera, Eulophidae). The experimental set–up allowed the simultaneous recording on video film of both the parasitoids and the hosts behavior, thus enabling us to contrast their respective responses to the leaf vibrations produced by the other party. We analysed the one step transition probabilties from one behavioral state to the following. Active larval movements had a marked influence on the parasitoid's behavior, while feeding and still had no detectable effect. We found no evidence for vibrotaxis on the part of the parasitoid. While parasitoid searching behavior on the leaf surface did not seem to alter the leafminers behavior, ovipositor insertions triggered a characteristic avoidance response. The described interactions are discussed in the context of the ‘princess and monster’ model developed in search and game theory.