Genome-wide SNPs of vegetable leafminer, Liriomyza sativae: insights into the recent Australian invasion

Liriomyza sativae, the vegetable leafminer, is a serious agricultural pest originally from the Americas which has now colonized all continents except Antarctica. In 2015, L. sativae arrived on the Australian mainland and established on the Cape York Peninsula in the northeast of the country. Here, we assessed genetic variation in L. sativae based on genome-wide single nucleotide polymorphisms (SNPs) generated by double-digest restriction-site associated DNA sequencing (ddRAD-seq) to uncover the potential origin(s) of this pest in Australia and contribute to reconstructing its global invasion history. Our principal component analyses (PCA) results suggested that Australian mainland populations were genetically close to populations from the Torres Strait and had connections to Bali and Papua New Guinea (PNG), whereas populations from Asia and Africa were more distantly related. Hawaii was genetically distinct from populations from Asia, Africa and Australia. Co-ancestry analyses pointed to signals of gene flow from the Torres Strait into the Australian mainland, while Indonesia/PNG were the likely sources of the initial invasion into the Torres Strait. Admixture analyses further revealed that L. sativae from the Torres Strait had genetic diversity originating from multiple sources, which has now spread to the Australian mainland. The L. sativae lineages from Asia/Africa appear closely related and may share co-ancestry. Isolation by distance (IBD) was found at a broad global scale, but not within small regions, suggesting human-mediated factors contribute to the local spread of this pest. Overall, our findings highlight the challenges in quarantine measures aimed at restricting the distribution of this global pest.

Differential Response of Leafminer Flies Liriomyza trifolii (Burgess) and Liriomyza sativae (Blanchard) to Rapid Cold Hardening

Rapid cold hardening (RCH) is a rapid and critical adaption of insects to sudden temperature changes but is often overlooked or underestimated as a component of survival. Thus, interspecific comparisons of RCH are needed to predict how phenotypes will adapt to temperature variability. RCH not only enhances cold survival but also protects against non-lethal cold injury by preserving essential functions such as locomotion, reproduction, and energy balance. This study investigated the difference in basal cold tolerance and RCH capacity of L. trifolii and L. sativae. In both species, the cold tolerance of pupae was significantly enhanced after short-term exposure to moderately cold temperatures. The effect of RCH last for 4 h in L. sativae but only 2 h in L. trifolii. Interestingly, L. trifolii adults had a RCH response but L. sativae adults failed to acclimate. Short-term acclimation also lowered the supercooling point significantly in the pupae of both species. Based on these results, we propose a hypothesis that these differences will eventually affect their competition in the context of climate change. This study also provides the basis for future metabolomic and transcriptomic studies that may ultimately uncover the underlying mechanisms of RCH and interspecific competition between L. trifolii and L. sativae.

Developing a Phototactic Electrostatic Insect Trap Targeting Whiteflies, Leafminers, and Thrips in Greenhouses

Our aim was to develop an electrostatic apparatus to lure and capture silverleaf whiteflies (Bemisia tabaci), vegetable leafminers (Liriomyza sativae), and western flower thrips (Frankliniella occidentalis) that invade tomato greenhouses. A double-charged dipolar electric field producer (DD-EFP) was constructed by filling water in two identical transparent soft polyvinyl chloride tubes arrayed in parallel with fixed separation, and then, inserting the probes of grounded negative and positive voltage generators into the water of the two tubes to generate negatively and positively charged waters, respectively. These charged waters electrified the outer surfaces of the opposite tubes via dielectric polarization. An electric field formed between the oppositely charged tubes. To lure these phototactic insects, the water was colored yellow using watercolor paste, then introduced into the transparent insulator tubes to construct the yellow-colored DD-EFP. This apparatus lured insects in a manner similar to commercially available yellow sticky traps. The yellow-colored DD-EFP was easily placed as a movable upright screen along the plants, such that invading pests were preferentially attracted to the trap before reaching the plants. Furthermore, pests settling on the plants were attracted to the apparatus, which used a plant-tapping method to drive them off the plants. Our study provided an experimental basis for developing an electrostatic device to attract and capture insects that enter greenhouses.

Overwintering, Cold Tolerance and Supercooling Capacity Comparison Between Liriomyza Sativae and L. Trifolii, Two Successively Invaded Leafminers in China

Liriomyza sativae Blanchard and Liriomyza trifolii (Burgess) are two highly polyphagous pests that successively invaded China in the 1990s and 2000s, respectively, threatening vegetable and horticultural plants. Competitive displacement of L. sativae by L. trifolii occurred during the expansion process of the latter in southern China. However, whether L. trifolii can expand their range to northern China and, if so, how they compete with L. sativae in northern China remains unclear. Overwintering and cold tolerance capacity largely determine the species distribution range and can affect species displacement through overwintering and phenology. In this study, we compared the overwintering potential, cold tolerance and supercooling point (SCP) between these two leafminer species. Our results showed that L. trifolii can overwinter at higher altitudes than L. sativae. In addition, we found that they can both successfully overwinter in greenhouses in northern China, and the overwintering capacity of L. trifolii was higher than that of L. sativae. Moreover, the extreme low-temperature survival of L. trifolii was significantly higher than that of L. sativae, and the SCP of the former was lower than that of the latter. We thus conclude that the overwintering and cold tolerance capacity of L. trifolii is much better than that of L. sativae. Our findings indicate that L. trifolii has the potential to displace L. sativae and expand its range to northern China. Moreover, our results have important implications for predicting overwinter ranges and developing management strategies for invasive leafminers in China.

Avaliação da Eficácia de Produtos Orgânicos para Controle de Minerador de Folhas (Liriomyza sativae Blanchard) sobre Manjericão (Ocimum basilicum L.) / Evaluation of the effectiveness of organic products to control the leaf miner (Liriomyza sativae Blanchard) in basil (Ocimum basilicum L.)

Este trabalho foi conduzido para identificar espécies de leafminer e avaliar inseticidas orgânicos contra leafminer. Os danos causados ao leafminer foram tão graves que os cultivadores assumiram a presença de uma espécie diferente. As amostras foram retiradas de uma colheita de dinheiro perto de Todos Santos, Baja California Sur, México e a identificação foi feita com base no manual da Universidade da Califórnia (1985). As espécies identificadas foram Liriomyza sativae e Liriomizat trifolii. Cinco tratamentos e um controle foram comparados em um plantio comercial. A eficácia foi avaliada com base nas larvas mortas 48 h após a aplicação. A porcentagem de mortalidade na mistura Koch® + Ecoterra-Humipron® + Agro R® + Dipel® foi de 98,5%. A mistura Pire-Neem estava em segundo lugar, com 90,5% de mortalidade. A primeira mistura de quatro inseticidas mostrou um efeito sinérgico, enquanto a outra mistura (Solution®, Pireneem®, Ecot- Humipron®, Agro-R®) teve um efeito antagônico.

Does elevated CO2 affect the biological aspects of Liriomyza sativae in melon plants?

An increase in the carbon dioxide concentration (CO2) in the atmosphere has occurred in recent years, influencing the different biological aspects of herbivorous insects. The present study aimed to evaluate the effect of CO2 increase on the biological aspects of Liriomyza sativae Blanchard leafminer in melon plants. For this, two experiments were carried out: (i) to evaluate the effect of melon plants grown in CO2-enriched environments on the immature developmental stages of L. sativae and L. sativae adult longevity, and (ii) to verify the impact of increased CO2 concentration on L. sativae adult survival, feeding punctures, and oviposition. The experiments were carried out in growth chambers maintained in the temperature regime of 20-26-33 °C (simulating the minimum, average, and maximum daily temperature) and under two CO2 concentrations (400 ppm and 770 ppm). The immature stages and the egg-adult period of L. sativae were longer when they developed on plants grown in high CO2 levels (770 ppm), but no difference in adult longevity was observed. The viability of the immature phases was not different between the two CO2 concentrations. Furthermore, there was no difference in the number of eggs and feeding punctures between treatments. Thus, the increase in CO2 concentration prolongs the duration of the immature stages of L. sativae; however, it does not affect their viability. Adult survival, fertility, and feeding punctures were also unmodified by the environment enriched with CO2.

Monitoramento de mosca-minadora Liriomyza sp. (Diptera:Agromyzidae) em meloeiro e levantamento de seus possíveis inimigos naturais no município de Floresta, Pernambuco

Dentre os insetos-pragas que limitam a produtividade do meloeiro estão as moscas-minadoras do gênero Liriomyza. A maioria dos produtores adotam o controle químico para reduzir a incidência dessa praga nos plantios, porém o uso indiscriminado desse método pode causar vários problemas de ordem ecológica, econômica e social. Uma alternativa para o manejo desta praga é o controle biológico com o uso de parasitoides. Portanto, este trabalho teve como objetivos: identificar a espécie mais importante de mosca-minadora para o município de Floresta-PE; monitorar a sua densidade populacional durante todo o ciclo da cultura; verificar a ocorrência de inimigos naturais (parasitoides), bem como sua taxa de parasitismo para seleção dos mais promissores e verificar a melhor época de liberação conforme a fenologia da cultura. Os experimentos foram conduzidos em duas áreas comerciais de meloeiro localizadas nos arredores de Floresta-PE, onde selecionou-se de forma randomizada 30 plantas para amostragem de larvas presentes nas folhas. Foram analisadas 30 folhas para verificação da emergência tanto de Liriomyza quanto de parasitoides para posterior identificação e contabilização. Os levantamentos ocorreram semanalmente até a colheita e totalizaram sete por área. Os dados das amostragens de minadora foram submetidos à análise de variância e ao teste de Tukey (5%). Os dados da taxa de parasitismo foram sujeitos a uma fórmula específica. De acordo com os resultados obtidos, a espécie de mosca-minadora que predomina na localidade em questão é a Liriomyza sativae, sendo a sua maior ocorrência nos estágios iniciais da cultura do meloeiro. Dentre os inimigos naturais, os mais abundantes e com maior taxa de parasitismo foram os da família Eulophidae e a melhor época de liberação dos mesmos é entre a segunda e a terceira semana após o plantio.