As an environmental factor, temperature impacts the distribution of species and influences interspecific competition. The molecular chaperones encoded by small heat shock proteins (sHsps) are essential for rapid, appropriate responses to environmental stress. This study focuses on Hsp20.8, which encodes a temperature-responsive sHsp in Liriomyza trifolii, an insect pest that infests both agricultural and ornamental crops. Hsp20.8 expression was highest at 39℃ in L. trifolii pupae and adults, and expression levels were greater in pupae than in adults. Recombinant Hsp20.8 was expressed in Escherichia coli and conferred a higher survival rate than the empty vector to bacterial cells exposed to heat stress. RNA interference experiments were conducted using L. trifolii adults and prepupae and the knockdown of Hsp20.8 expression increased mortality in L. trifolii during heat stress. The results expand our understanding of sHsp function in Liriomyza spp. and the ongoing adaptation of this pest to climate change. In addition, this study is also important for predicting the distribution of invasive species and proposing new prevention and control strategies based on temperature adaptation.

Liriomyza trifolii is a significant pest of vegetable and ornamental crops across the globe. Microwave radiation has been used for controlling pests in stored products; however, there are few reports on the use of microwaves for eradicating agricultural pests such as L. trifolii, and its effects on pests at the molecular level is unclear. In this study, we show that microwave radiation inhibited the emergence of L. trifolii pupae. Transcriptomic studies of L. trifolii indicated significant enrichment of differentially expressed genes (DEGs) in ‘post-translational modification, protein turnover, chaperones’, ‘sensory perception of pain/transcription repressor complex/zinc ion binding’ and ‘insulin signaling pathway’ when analyzed with the Clusters of Orthologous Groups, Gene Ontology and the Kyoto Encyclopedia of Genes and Genomes databases, respectively. The top DEGs were related to reproduction, immunity and development and were significantly expressed after microwave radiation. Interestingly, there was no significant difference in the expression of genes encoding heat shock proteins or antioxidant enzymes in L. trifolii treated with microwave radiation as compared to the untreated control. The expression of DEGs encoding cuticular protein and protein takeout were silenced by RNA interference, and the results showed that knockdown of these two DEGs reduced the survival of L. trifolii exposed to microwave radiation. The results of this study help elucidate the molecular response of L. trifolii exposed to microwave radiation and provide novel ideas for control.

Heat shock proteins (HSPs) participate in diverse physiological processes in insects, and HSP70 is one of the most highly conserved proteins in the HSP family. In this study, full-length cDNAs of three HSP70 genes (Lthsc70, Lthsp701, and Lthsp702) were cloned and characterized from Liriomyza trifolii, an important invasive pest of vegetable crops and horticultural crops worldwide. These three HSP70s exhibited signature sequences and motifs that are typical of the HSP70 family. The expression patterns of the three Lthsp70s during temperature stress and in different insect development stages were studied by real-time quantitative PCR. Lthsp701 was strongly induced by high- and low-temperature stress, but Lthsc70 and Lthsp702 were not very sensitive to temperature changes. All three Lthsp70s were expressed during insect development stages, but the expression patterns were quite different. The expression of Lthsc70 and Lthsp702 showed significant differences in expression during leafminer development; Lthsc70 was most highly expressed in female adults, whereas Lthsp702 was abundantly expressed in larvae and prepupae. Lthsp701 expression was not significantly different among leafminer stages. These results suggest that functional differentiation within the LtHSP70 subfamily has occurred in response to thermal stress and insect development.

In recent years, the serpentine leaf miner Liriomyza trifolii (Burgess) has become a major pest of cotton (Gossypium spp.) in India, with high levels of incidence observed at the seedling stage, particularly in transgenic Bt cotton. We monitored the severity of infestation and damage by L. trifolii to transgenic and non-transgenic genotypes of Gossypium arboreum L. and G. hirsutum L. between 2002 and 2007. Overall, significantly lower L. trifolii damage occurred in G. arboreum varieties than in G. hirsutum varieties and hybrids. Among the G. hirsutum genotypes, damage was significantly lower in varieties than in hybrids. However, no significant differences in damage were observed between Bt and non-Bt cotton hybrids. Abiotic factors had a major influence on the severity of damage; there was a significant and negative association of L. trifolii damage with open pan evaporation (E), maximum temperature, solar radiation and sunshine, and a significant and positive association with relative humidity and rainfall (RF). Multiple stepwise regression analysis indicated that 99% of the variation in L. trifolii damage was accounted for by RF, open pan E and relative humidity.

The incidence of the American serpentine leafminer, Liriomyza trifolii (Burgess) (Diptera: Agromyzidae) was studied in cotton-growing tracts of Tamil Nadu State, India. The incidence was higher on summer than on winter cotton and the cropping pattern was found to have an impact on the incidence of the leafminer on cotton. Biological studies on L. trifolii conducted on cotton, Gossypium hirsutum L., tomato, Lycopersicon esculentum Mill., and cowpea, Vigna sinensis (L.) Walp., revealed that its life cycle varied with different hosts. The duration of the pupal stage of L. trifolii was the longest in the leafminer's life cycle. Lycopersicon esculentum was the preferred host—females of L. trifolii survived the longest and had the highest fecundity on this host. Sex discrimination was possible at the pupal stage, on the basis of size; female adults were found to emerge from larger-sized pupae and males from smaller ones.

The serpentine leaf-miner Liriomyza trifolii is a new proliferous and polyphagous agricultural pest in Mauritius, attacking crops, ornamentals and weeds. Urgent chemical control measures had to be developed in order to save total crop loss, in particular potato, tomato, haricot beans, crucifers and onions. This insect is resistant to most insecticides. In view of formulating an integrated management programme, this paper reports on some aspects of practical importance concerning the biology and ecology of the leaf-miner, the incidence of damage, and the possibility of its control by natural plant products such as extracts of neem (Azadirachta indica). Steam distillates of neem leaves seriously affect larvae and pupae upon treatment by contact at as low a dose as 0.3% of the extract. Field treatments of onion plantations with aqueous neem extracts (0.5%) gave good protection to the crop. The current control measures are briefly considered.

The leafminer, Liriomyza trifolii Burgess, a polyphagous agricultural pest, can attack crops at different stages of development; some are attacked at the beginning of the crop cycle and others at the end of the cycle. Experiments on the differential susceptibility of the bean Phaseolus vulgaris and the potato Solanum tuberosum plants were done to get some information about factors which influence host selection by the leafminer. The distribution and density of leaf trichomes, as well as the nutritional status of the host plants, were found to be important in host selection. High trichome density acts as a physical deterrent to Liriomyza flies, just as senescing primary bean leaves induce non-acceptability. When given a choice, flies prefer bean to potato leaf discs, though the latter possess less trichomes. Other factors (chemical attractants and some nutrient components) might therefore also be involved in the complex host selection behaviour of L. trifolii.