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Melon thrips, Thrips palmi, represent a significant threat to plants, inducing necrosis and acting as vectors for numerous plant viruses. Entomopathogenic fungi present a promising avenue for the management of melon thrips populations resistant to conventional chemical treatments. In this work, an adult colony of melon thrips was exposed to Beauveria bassiana strain JEF-350, and the ensuing transcriptional response of the infected thrips was scrutinized to elucidate their reactions during fungal pathogenesis. Utilizing Illumina sequencing, RNA samples were extracted from untreated thrips as well as from thrips continuously infected for 2 and 4 days, each with three biological replicates. While no notable alterations in gene expression were observed between the untreated control and thrips infected for 2 days, those infected for 4 days exhibited a plethora of differentially expressed genes. Specifically, in the thrips infected for the extended period, pathways associated with lysosomal function and insect hormone biosynthesis were notably repressed, while others such as serine and glycine metabolism, Toll and Imd, and circadian rhythm pathways displayed heightened activity. Noteworthy downregulation was observed in numerous lysosomal hydrolase genes encoding glycosidases, sulfatases, and lipases, particularly glycosidases. Furthermore, certain genes related to hydrolase precursors within the Golgi apparatus exhibited heightened expression levels but failed to progress toward hydrolase biosynthesis. Upstream regulation of juvenile hormone biosynthesis was augmented, yet downstream genes were significantly downregulated, leading to a disruption in juvenile hormone production. Similarly, while cytochrome P450 genes in the downstream of ecdysone biosynthesis were upregulated, expressions of cholesterol desaturase and cytochrome P450 genes in the upstream were inhibited, consequently dampening ecdysone biosynthesis. The observed differential targeting of organs or pathways by B. bassiana JEF-350, in contrast to conventional chemicals primarily affecting neurotransmission and energy production, suggests its potential efficacy in managing resistant thrips populations. Consequently, integrating JEF-350 into the chemical spray regimen or incorporating it into tank-mix formulations with chemical insecticides emerges as a pragmatic approach within the realm of integrated pest management strategies. Key points: • Beauveria treatment inhibited lysosomal function and hormone synthesis in thrips. • Thrips serine/glycine metabolism, Toll and Imd, and circadian rhythm pathways were activated. • Upstream functions of thrips hormone biosynthesis increased, while downstream functions were suppressed. • Regarding biosynthesis of metabolites, this fungus targets other pathways with resistance management. [ABSTRACT FROM AUTHOR]

Different species of thrips can occur in the same location and on the same plant. However, variation among dominant thrips species in their susceptibility to insecticide remains unclear. In this study, we evaluated the susceptibility of Frankliniella occidentalis, Thrips palmi and Frankliniella intonsa, three common thrips on vegetables, to spinetoram, from 12 geographical areas across China. Thrips palmi showed the lowest susceptibility to spinetoram (LC50 ranged from 0.1192 to 117.6707 mg L−1), while F. intonsa showed the highest susceptibility (LC50 ranged from 0.0044 to 0.6476 mg L−1). Field-evolved resistance to spinetoram was found for T. palmi and F. occidentalis, resulting in 987.17-fold and 323.77-fold differences in toxicity within each of these species, respectively. The Shouguang populations of T. palmi and F. occidentalis had the highest overall levels of resistance, with LC50 values of 117.6707 mg L−1 and 11.4290 mg L−1, respectively. Levels of susceptibility in southern populations of F. intonsa were low compared to northern populations of this species in China. In conclusion, our study highlighted variation in susceptibility of thrips to spinetoram, both among species and among geographical areas. The results should help the implementation of management tactics, and they provide insights into the displacement of thrips species in fields. [ABSTRACT FROM AUTHOR]

Plant viruses can modify the performance and behavior of insect vectors to maximize their transmission rates. Whether viruses can evolve to mediate their insect vectors' interspecific competition is poorly understood. Here, we used two vectors of tomato zonate spot virus (TZSV), one native species (Thrips palmi) and one exotic species (Frankliniella occidentalis), to investigate this in laboratory and field experiments. TZSV infection increased the population growth of its insect vectors when the thrips species were isolated from one another. When both species coexisted, F. occidentalis displaced T. palmi on both TZSV-infected and uninfected plants. However, on TZSV-infected plant, F. occidentalis completely displaced T. palmi more rapidly (within 14 days) than on uninfected plants. Our results also revealed that reproductive interference occurred between the two thrips species, whereas TZSV-infected pepper significantly decreased the reproductive interference of T. palmi to F. occidentalis. When F. occidentalis and T. palmi co-occurred in Jinning County, Yunnan Province, we found a rising trend of natural proportions of F. occidentalis in the TZSV-infected pepper fields, suggesting that TZSV-infected pepper enhanced the competitive advantage of F. occidentalis over T. palmi in the field. Together, our findings demonstrate a plant virus that plays an important role in the competitive displacement of its insect vectors. [ABSTRACT FROM AUTHOR]

To develop an augmentative biological control programme for Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) and Thrips palmi Karny (Thysanoptera: Thripidae) using Nesidiocoris tenuis (Reuter) (Hemiptera: Miridae), we studied the life history traits of a Japanese strain of N. tenuis reared on B. tabaci and T. palmi in controlled environments. The lower developmental threshold during the nymphal period was far higher than those estimated for Spanish, Moroccan, and Iranian strains, indicating that the Japanese strain is better adapted to higher temperatures than the other three strains tested. The intrinsic rate of increase rm was highest at 30 °C and lowest at 20 °C. The rm value for individuals reared on T. palmi at 25 °C was lower than that for individuals reared on B. tabaci at the same temperature. Implications of these results for the biological control of B. tabaci and T. palmi in greenhouses are discussed. [ABSTRACT FROM AUTHOR]

Transmission efficiencies of capsicum chlorosis virus (CaCV) were investigated for four thrips species (Thysanoptera: Thripidae), Frankliniella occidentalis (Pergande), Frankliniella intonsa (Trybom), Thrips palmi (Karny), and Thrips tabaci Lindeman infesting green pepper in Japan. The first-instar larvae of the thrips were allowed to feed on CaCV-infected green pepper leaves for 24 h. The transmission of CaCV by thrips was examined using a petunia leaf disk assay. CaCV was transmitted by four male (8.70%) and four female (3.88%) T. palmi, but the virus was not transmitted by adults of any other species. In a second transmission assay, 10 adult T. palmi that had fed on infected leaves as larvae were released to healthy green pepper seedlings. After 21 days, the seedlings were examined and 50% of them showed symptoms of CaCV infection. RT-PCR confirmed that they were infected with the virus. The viruliferous rate of adult T. palmi was 60%, while CaCV was not detected in adults of the other three species. These results suggest that T. palmi is capable of being a new vector of CaCV. [ABSTRACT FROM AUTHOR]

Aggregation pheromones have been identified and tested in the field for Frankliniella occidentalis and Thrips palmi. These pheromones are produced by adult males and attract both males and females. They are likely to be widespread across the Thripidae and identification is in progress for several other pest species. Aggregation pheromones are used commercially for monitoring and activation. Field trials have shown they can be cost effective for mass trapping when used as part of an integrated pest management (IPM) programme. Use for other approaches, such as lure and kill and mating disruption have not yet been tested. A better understanding of the role of these pheromones in the mating behaviour of thrips is needed and this may suggest further ways of developing their potential for pest management. [ABSTRACT FROM PUBLISHER]

Ten entomopathogenic fungi were tested for the control of female adult Thrips palmi Karny in the laboratory. The most virulent fungus Purpureocillium lilacinum CKPL-053, two commercial bioinsecticides and a chemical insecticide were tested for control of T. palmi in two Dendrobium sp. orchid farms. Controls of T. palmi in both farms were highest with P. lilacinum CKPL-053. Purpureocillium lilacinum CKPL-053 and the Odashima strain P. lilacinum produced paecilotoxins A, B, and C when cultured in complete medium 1 but not in potato dextrose broth. Jasmonic acid contents in Dendrobium sp. petals after application of P. lilacinum CKPL-053, B.bassiana CKB-048, M. robertsii CKM-048, and P. lilacinum CKPL-012 spore suspensions were significantly higher than with imidacloprid and water control treatments. This suggests that jasmonic acid might assist in activating plant defense mechanism to exhibit the repellence and/or resistance effect of Dendrobium sp. against T. palmi. The LC and LT for P. lilacinum CKPL-053 against female T. palmi were 2.67 × 10 conidia ml and 2.6 days at the concentration of 1 × 10 conidia ml, respectively. [ABSTRACT FROM AUTHOR]

The population dynamics and in-farm distribution of Thrips palmi Karny were evaluated in two orchid farms, one in the Bangkok metropolitan area and the other in Ratchaburi Province, Thailand. Yellow sticky traps were hung above the orchid canopy (three traps/220 m), and the trapped adults were counted weekly from November 2009 to October 2010 at the first location and from January to December of 2012 at the second location. T. palmi nymphs and adults were both counted weekly on 300 orchid panicles in an area of 2,200 m at both locations. We found that the T. palmi population dynamics at the first location was represented by a W-shaped curve, with the distribution clumped throughout the year, whereas the curve was J-shaped at the second location, with the distribution mostly clumped. Qualitative surveys of thrips species were conducted on ten different orchid genera in ten locations and on 20 different Dendrobium hybrids in 20 locations. Five random sampling plots (1 × 4 m) were examined on each farm. The results indicated that only T. palmi was found on every farm. Moreover, quantitative comparison among five orchid types revealed that Dendrobium flowers with darker color are more attractive to T. palmi. However, this phenomenon does not coincide with Oncidium sp. and Mokara sp. because of their unfavorable morphology for thrips behavior. [ABSTRACT FROM AUTHOR]

Thrips palmi Karny has recently been implicated in damage to eggplant fruits. This thrips causes cosmetic scars on and deforms fruits, thus lowering their market value. To investigate the relationship between the density of thrips and the resulting damage, experimental plots with initial release densities of 0, 20, 40, 70, and 100 adults thrips per plot were established under greenhouse conditions. Thrips density (for flower sampling = x; for sticky trap = x) was monitored using flower sampling and blue sticky trap counts, and was found to be directly related to the proportion of damaged-fruits (y) and the reduction in fruit yield: significant relationships were found for the flower samples ( y = 1.2261 x − 0.6232, r = 0.8582) and for the trap catches ( y = 11.667 ln( x) − 9.5, r = 0.8896). The proportion of damaged fruits that could be tolerated from an economic perspective, based on the cost of controlling the thrips population chemically and the market value of the fruit, was 6.67-11.76 %; this translated into economic thresholds of 1.05-1.5 adults and/or larvae of T. palmi per flower or 4.91-10.17 adults T. palmi per four-day sticky card count. [ABSTRACT FROM AUTHOR]

The life history of Thrips palmi Karny on eggplant ( Solanum melongena L.) leaves was studied based on the age stage and two sex-life tables at 16, 19, 22, 25, and 31 °C. The intrinsic rate of increase ( r) at these temperatures was 0.0427, 0.0566, 0.0979, 0.1738, and 0.2237 day, respectively. The relationship among the gross reproductive rate (GRR), the net reproductive rate ( R), and the pre-adult survivorship ( l) is consistent with R < l × GRR < GRR for all results at different temperatures. The mean generation time was 47.52, 38.33, 29.52, 19.81, and 13.88 days, respectively. The developments of pre-adult and adult stages were faster in males than in females. The means of developmental periods for each developmental stage decreased with increases of temperature. The maximum life span of female adults was noted at 56.67 days, whereas that of males was 50.66 days at 16 °C. The maximum female fecundity (64.18 eggs/female) was recorded at 25 °C and the lowest (23.38 eggs/female) at 16 °C. Life table data could be used to project population growth, to design mass rearing programs, and to establish management tactics to control insect pests. [ABSTRACT FROM AUTHOR]

Melon thrips, Thrips palmi Karny, is among the most destructive pests of vegetables in western Japan because of its development of insecticide resistance. To examine its resistance mechanisms against cypermethrin, a pyrethroid, we determined partial nucleotide sequences of the sodium channel gene and compared the deduced amino acid sequences of two strains (the KC and OK strains) of T. palmi. The KC and OK strains showed LC values of 3922.9 and 72.1 ppm, respectively. The LC values were thus above the agriculturally recommended concentration (60 ppm). Both strains had a resistant amino acid, Ile, at amino acid position 929. The synergist piperonyl butoxide caused 14.1- and 3.0-fold decreases in the resistance ratios of the KC and OK strains, respectively. These results suggest that the basal and differential resistance levels of both strains are conferred by reduced sensitivity of the sodium channel and cytochrome P450-mediated detoxification, respectively. [ABSTRACT FROM AUTHOR]

Surveys conducted in Melon yellow spot virus (MYSV)-affected cucumber greenhouses revealed that the incidence of MYSV disease on cucumber plants varied by crop management conditions. Because of temporal and spatial dispersal of viruliferous Thrips palmi in two greenhouses, MYSV was detected in 21.2% of the cucumber plants growing in a weedy greenhouse and in only 1.3% of the cucumber plants growing in a thoroughly weeded greenhouse at the end of the cropping period. MYSV was also detected in 13 weed species found outside the cucumber greenhouses. Viruliferous T. palmi adults were often found on Acalypha australis, Cerastium glomeratum and Lamium amplexicaule. T. palmi reared on MYSV-infected cucumber plants transmitted MYSV to C. glomeratum and L. amplexicaule. Moreover, T. palmi reared on MYSV-infected C. glomeratum rarely transmitted MYSV to cucumber seedlings. These results suggest that weed control is important for managing MYSV since weeds provide a habitat for the vector thrips and also serve as an initial inoculum source of the virus. [ABSTRACT FROM AUTHOR]

Little is known regarding non-chemical control measures against Thrips palmi Karny. Since entomopathogenic fungi and nematodes have been found to be active against thrips species such as Frankliniella occidentalis Pergande, comparative bioassays were conducted to determine the extent to which they also show activity against T. palmi. Significant mortality of the larvae of the species was recorded following treatment with Lecanicillium muscarium (Petch) Zare and Gams, and addition of the wetting agent Agral enhanced pathogenicity to T. palmi. T. palmi pupae were not affected by S. feltiae. The potential for use of these agents against T. palmi in the field is discussed in the light of these results. [ABSTRACT FROM AUTHOR]

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