Antixenosis and antibiosis of common beans to Thrips palmi Karny (Thysanoptera: Thripidae)

Antixenosis and antibiosis in the resistance of common beans (Phaseolus vulgaris L.) to the melon thrips, Thrips palmi Karny, were investigated under laboratory and field conditions. Experiments were conducted for four moderately resistant genotypes ('Brunca', BH-130, EMP 486, and FEB 115) in comparison with one susceptible genotype (APN 18). Multiple-choice tests recorded most thrips on EMP 486 and least on FEB 115. Dual-choice tests conducted in both laboratory and field confirmed the antixenotic effect of FEB 115 and the attractant effect of EMP 486 on thrips. These results demonstrate the significance of antixenosis in the resistance of common beans to T. palmi. Life-table studies showed significant differences in egg duration, immature and adult survivorship, female body length and longevity, daily oviposition rate, and total fecundity among the bean genotypes. The intrinsic rate of natural increase (r(m)) and its associated population parameters varied significantly with the bean genotype on which T. palmi cohorts were reared. Based on mean r(m) values, the five bean genotypes can be divided into two groups, with BH-130 and 'Brunca' being less favorable for the population growth of thrips than EMP 486 and FEB 115; the latter were comparable to the susceptible genotype APN 18. These life-table results indicate the role of antibiosis in enhancing the resistance of common beans to T. palmi.     

Parameter estimation for a temperature-dependent development model of Thrips palmi Karny (Thysanoptera: Thripidae)

Development of immature Thrips palmi Karny was investigated at 12.5, 15, 17.5, 20, 22.5, 25, 27.5, 30, 32.5, and 35 °C, 20–40% RH and a photoperiod of 14:10 (L:D) h. Developmental time decreased with increasing temperature up to 32.5 °C in all stages. The total developmental time was longest at 12.5 °C (64.2 days) and shortest at 32.5 °C (9.2 days). The lower developmental threshold was 10.6, 10.6, 9.1, and 10.7 °C for egg, larva, prepupa, and pupa, respectively. The thermal constant required to complete the respective stage was 71.7, 59.2, 18.1, and 36.8DD. The lower threshold temperature and thermal constant were 10.6 °C and 183.3DD, respectively, for total immature development. The nonlinear relationship between developmental rate and temperature was well described by the modified Sharpe and DeMichele biophysical model (r² = 0.905–0.998). The distribution of developmental completion of each stage was described by the 3-parameter Weibull function (r² = 0.855–0.927). The temperature-dependent developmental models of T. palmi developed in this study could be used to predict its seasonal phenology in field and greenhouse vegetable crops.     

Potential of Metarhizium anisopliae and Beauveria bassiana to control Dinoderus porcellus (Coleoptera: Bostrychidae) infesting yam chips

The beetle Dinoderus porcellus Lesne is a serious storage insect pest that causes important losses by destroying stocks of yam chips. In the aim to found an alternative control method to the use of synthetic insecticides for its management, the virulence of the entomopathogenic fungi Beauveria bassiana (Balsamo) Vuillemin (isolate Bb115) and Metarhizium anisopliae (Metschnikoff) Sorokin (isolate Met 31) against adults of D. porcellus was evaluated under laboratory conditions (25 ± 2 °C and 70 ± 5% RH). Then, the effectiveness of the most virulent entomopathogenic fungus as biological agent against D. porcellus was assessed under farmer storage conditions. For each entomopathogenic fungus isolate, four conidial concentration (0, 10⁵, 10⁷, and 10⁹ conidia/mL) at the dose of 1 µL were inoculated topically on D. porcellus adults (3–5 days old). Observations focused on insect mortality, cadaver sporulation and weight loss of yam chips. Lethal dose and lethal time values were estimated using probit analysis. Both fungal isolates at all conidial dose caused more than 50% mortality on day 7, with the highest mortality (94.44%) achieved using B. bassiana at the 10⁹ conidia/mL. LT₅₀ values for B. bassiana and M. anisopliae isolates were 2.63 and 3.35 days, respectively, while their LT₉₀ values were 6.15 and 9.87 days, respectively. Yielding the lower LD₉₀ values and the highest rates of cadaver sporulation, B. bassiana isolate appeared as the most virulent against D. porcellus. After 3 months of storage, comparatively to the control, the B. bassiana isolate at the highest conidial dose (10⁹ conidia/mL) significantly reduced D. porcellus populations, and weight loss of yam chips. This study revealed the potential of B. bassiana and M. anisoplae isolates as biological control agent against D. porcellus for yam chips protection.     

Development of a sequence-specific real-time PCR to the melon thrips Thrips palmi (Thysan., Thripidae)

Abstract:  In recent years, the polyphagous pest Thrips palmi Karny has become a species of major quarantine concern, often intercepted on plant material in international trade. The ability to rapidly identify the species is a critical factor that will determine the success of any campaign to prevent its establishment in Europe or elsewhere. However, the immature stages cannot currently be identified to the species level with certainty by morphological methods. In this study, random amplified polymorphic DNA analysis was performed to identify putative markers, which were then screened by Southern blot analysis. One marker was sequenced and a real-time polymerase chain reaction assay developed. The assay was screened against 21 thrips species including 10 other species of the genus Thrips and were found to be specific to T. palmi . The assay is rapid, could be completed in as little as 45 min and can be used to aid the identification of T. palmi .     

Molecular differences in the mitochondrial cytochrome oxidase I (mtCOI) gene and development of a species-specific marker for onion thrips, Thrips tabaci Lindeman, and melon thrips, T. palmi Karny (Thysanoptera: Thripidae), vectors of tospoviruses (Bunyaviridae)

A quick and developmental-stage non-limiting method of the identification of vectors of tospoviruses, such as Thrips tabaci and T. palmi, is important in the study of vector transmission, insecticide resistance, biological control, etc. Morphological identification of these thrips vectors is often a stumbling block in the absence of a specialist and limited by polymorphism, sex, stage of development, etc. Molecular identification, on the other hand, is not hampered by the above factors and can easily be followed by a non-specialist with a little training. The mitochondrial cytochrome oxidase I (mtCOI) exhibits reliable inter-species variations as compared to the other markers. In this communication, we present the differences in the mtCOI partial sequence of morphologically identified specimens of T. tabaci and T. palmi collected from onion and watermelon, respectively. Species-specific markers, identified in this study, could successfully determine T. tabaci and T. palmi, which corroborated the morphological identification. Phylogenetic analyses showed that both T. tabaci and T. palmi formed different clades as compared to the other NCBI accessions. The implication of these variations in vector efficiency has to be investigated further. The result of this investigation is useful in the quick identification of T. tabaci and T. palmi, a critical factor in understanding the epidemiology of the tospoviruses, their management and also in quarantine.     

Advances in control of onion thrips (Thysanoptera: Thripidae) in cabbage

Onion thrips, Thrips tabaci Lindeman (Thysanoptera: Thripidae), feeding injury results in discoloration and a rough texture on cabbage, Brassica oleracea capitata (L.), leaves, and damage may occur deep inside the head. It has become a key pest of cabbage in the United States and many other countries. Previous studies have indicated poor control using insecticides. The present study identified imidacloprid drenches and sprays of acetamiprid, dimethoate, spinosad, and imidacloprid as insecticides that performed better than the industry standard, lambda-cyhalothrin. However, additional tests with foliar sprays of dimethoate and acetamiprid indicated there was not an ideal crop stage (precupping, cupping, or postcupping) at which either insecticide could be applied for reliable control of T. tabaci, possibly because of multiple flights of thrips into the crop or the asynchrony of flights and susceptible crop stages. In tests in a commercial field, a soil drench of imidacloprid 4 wk after transplanting reduced the number of damaged leaves in the head by 32%, whereas five sprays of acetamiprid reduced damage by 51%. Combining both insecticide regimes reduced damage by 85%, but resulted in a very costly management program. Cabbage varieties varied considerably in susceptibility with some having negligible thrips injury, regardless of being treated with an insecticide. Planting date affected susceptibility of cabbage to some degree, but not as much as other tactics. Overall, these studies indicate that increased emphasis should be placed on breeding cabbages to be resistant to T. tabaci as the foundation for its management.     

Efficacy of biorational insecticides against chilli thrips,Scirtothrips dorsalis (Thysanoptera: Thripidae), infesting roses under nursery conditions

We evaluated biopesticides based on entomopathogenic fungi, azadirachtin and horticultural oils for the management of the chilli thrips, Scirtothrips dorsalis Hood, an economically significant invasive pest in the United States. Insecticides were applied four times at 7‐ to 10‐day intervals against established S. dorsalis infestations on shrub roses KnockOut^®, Rosa x ‘Radrazz’ under simulated nursery conditions. When applied as stand‐alone treatments, Beauveria bassiana GHA (BotaniGard^® ES), Metarhizium brunneum F52 (Met‐52 EC), a horticultural oil (SuffOil‐X^®) and azadirachtin (Molt‐X^®) at label rates provided significant control, reducing populations of S. dorsalis by 48–71% compared with control over 4–6 weeks. Similar results were observed when the biopesticides were applied in rotation with each other. A conventional standard, spinosad (Conserve^® SC), was consistently the most effective treatment in these studies, reducing thrips populations by >95% overall. In another study, more effective control (87%–92%) was achieved in biopesticide rotation programmes that included spinosad, when compared with those that did not. Results also showed that these biopesticides can be tank‐mixed. However, there was no evidence that B. bassiana or M. brunneum combined with azadirachtin resulted in additive or synergistic control, as neither tank‐mix treatment improved control compared with azadirachtin alone. These findings highlight the potential use of biopesticides in rotation programmes with conventional insecticides to manage S. dorsalis on roses. Biopesticides evaluated in this study can be incorporated into an IPM programme for roses.     

An observation on the embryonic development in Thrips palmi (Thysanoptera: Thripidae) eggs obtained by an artificial oviposition setup

Thrips palmi is an important insect pest of vegetables and ornamental crops worldwide. Besides direct damage caused by feeding, it transmits several tospoviruses in a persistent-propagative manner. Eggs of T. palmi are microscopic and embedded within plant tissue by the sharp ovipositor of adult female. In the present study, an artificial oviposition setup has been standardized for T. palmi. Eggs of T. palmi were harvested in sterile water between two thin membranes. The developmental stages of T. palmi embryo were studied starting from oviposition up to hatching by inverted and confocal reflection microscopy. Energids were homogeneously distributed at an early stage of development. The anterior end of the egg curved with a constriction post 38 h. Initiation of tissue organization, mouthparts, appendages, compound eyes were observed at different time points. Appendages were well developed and segmentation was prominent post 70 h. The embryo was completely developed at around 80 h and hatched by 86 h post oviposition at 28 °C temperature. The study first time reports the embryonic development of T. palmi that would be helpful in detailed investigations of thrips developmental biology and evolution.     

Potential of a strain of the entomopathogenic fungus Beauveria bassiana (Hypocreales: Cordycipitaceae) as a biological control agent against western flower thrips,Frankliniella occidentalis (Thysanoptera: Thripidae)

Five Beauveria bassiana strains were evaluated for control of western flower thrips. Strain RSB was the most virulent, causing 69–96% mortality at concentrations of 1×10⁴–1×10⁷ conidia mL^?1, 10 days after inoculation of first instars. In greenhouse trials, RSB applied to broccoli foliage significantly reduced adult and larval populations.     

Mechanisms of resistance to spinosad in the western flower thrip, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae)

Cross‐resistance, resistance mechanisms, and mode of inheritance of spinosad resistance were studied in the western flower thrip, Frankliniella occidentalis (Pergande). Spinosad (naturalyte insecticide) showed low cross‐resistance to prothiophos (organophosphorus insecticide) and chlorphenapyr (respiratory inhibitor) showed some cross‐resistance to thiocyclam (nereistoxin). The synergists PBO (piperonyl butoxide), DEM (diethyl maleate), and DEF (s, s, s‐tributyl phosphorotrithioate) did not show any synergism on the toxicity of spinosad in the resistant strain (ICS), indicating that metabolic‐mediated detoxification was not responsible for the spinosad resistance, suggesting that spinosad may reduce sensitivity of the target site: the nicotinic acetylcholine receptor and GABA receptor. Following reciprocal crosses, dose‐response lines and dominance ratios indicated that spinosad resistance was incompletely dominant and there were no maternal effects. The results of backcross showed that spinosad resistance did not fit a single‐gene hypothesis, suggesting that resistance was influenced by several genes.     

Resistance to cypermethrin in melon thrips, Thrips palmi (Thysanoptera: Thripidae), is conferred by reduced sensitivity of the sodium channel and CYP450-mediated detoxification

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 LC₅₀ values of 3922.9 and 72.1?ppm, respectively. The LC₅₀ 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.     

Pathogenicity of Beauveria bassiana ANU1 to the red imported fire ant,Solenopsis invicta workers in Korea

The red imported fire ant (RIFA), Solenopsis invicta, is one of the globalized invasive pests. This study focused on pathogenicity and virulence of entomopathogenic fungi as one of the biological control agents to RIFA workers under different temperatures. The fungal pathogen, Beauveria bassiana ANU1 was isolated from Korea in 2015 and showed the pathogenicity to RIFA workers. A conidial suspension (1 × 10⁷ conidia/ml) induced a low mortality from day 2 after treatment and reached to 100% mortality at day 7 and day 8 after treatment for major and minor workers, respectively. The median lethal concentrations of B. bassiana ANU1 were calculated as 3.9 × 10³ for major and 4.6 × 10³ for minor workers at day 7 after treatment. Low temperatures decreased a virulence of B. bassiana ANU1 (1 × 10⁷ conidia/ml) to RIFA and showed mortality of 26.6% for major and 20% for minor workers. Based on bioassay results, this study provides one of possibilities of effective and successful strategy for controlling RIFA by entomopathogenic fungi.     

Precision application of aldicarb to enhance efficiency of thrips (Thysanoptera: Thripidae) management in cotton

Field studies were conducted during 1999-2001 in two climatic/edaphic areas of Georgia (Southern Piedmont and East Gulf Coastal Plain) to test the hypothesis that precision placement of aldicarb with cotton seed in hill planting at spatially specific intervals could decrease insecticide use for management of tobacco thrips, Frankliniella fusca (Hinds). Precision-placed aldicarb controlled thrips during cotton seedling stages using per ha amounts of one-half or less than standard in-furrow application rates with no significant differences in yield. Residual analysis of cotton plants showed that plants in precision placement plots had as much or more aldicarb and aldicarb metabolites present as compared with cotton treated with conventional in-furrow treatments. Higher rates of precision-placed aldicarb did cause phytotoxic burning early in the growing season, but no significant impact on yield was observed.     

Evaluation of potential entomopathogenic fungus,Beauveria bassiana,for controlling the coffee berry borer Hypothenemus hampei (Ferrari) (Coleoptera: Curculionidae) in Taiwan

Hypothenemus hampei (Ferrari) (Coleoptera: Curculionidae: Scolytinae), a coffee berry borer (CBB), is a serious pest of coffee fruits and causes economic losses in the coffee industry. With the concerns of chemical control, an alternative eco-friendly management strategy such as microbial control has emerged as the times require. Herein, a total of thirty-three fungi were isolated from CBB cadavers. Two entomopathogenic fungal isolates, NCHU-271 and NCHU-272, which showed fast insect-killing activity, were subjected to molecular identification and named “Beauveria bassiana-NCHU-271” (Bb-NCHU-271) and “Beauveria bassiana -NCHU-272” (Bb-NCHU-272). Moreover, a virulence test of Bb-NCHU-271 and Bb-NCHU-272 against CBBs was also performed. Both Bb-NCHU-271 and Bb-NCHU-272 caused 100% mortality at 8 days post inoculation (d.p.i.) and a LT₅₀ of Bb-NCHU-271 by spraying 10⁸ conidia/ml was less than Bb-NCHU-272. Therefore, histological evidence of Bb-NCHU-271 infected CBBs was provided to proven the infection process of B. bassiana in CBBs. Furthermore, an infestation test was performed to evaluate the differences in CBB control efficacy between the treatments of “Borers exposed to EPF first” or “Berries exposed to EPF first”. The results revealed that the “Borers exposed to EPF first” of Bb-NCHU-272 caused significantly lower survival rates and higher mycosis rates than those of Bb-NCHU-271. Only slight control effects of Bb-NCHU-271 and Bb-NCHU-272 were also observed in the “Berries exposed to EPF” treatment. In conclusion, Bb-NCHU-271 and −272 showed controlling ability to the CBBs either before or after CBB infestation into coffee berries, while application of EPFs before the CBBs bored into coffee fruits could enhance the control effect.     

Potential of Haplothrips brevitubus (Karny) (Thysanoptera: Phlaeothripidae) as a predator of mulberry thrips Pseudodendrothrips mori (Niwa) (Thysanoptera: Thripidae)

The predation potential of Haplothrips brevitubus (Karny) for thrips was evaluated in the laboratory. When second stage larvae of Pseudodendrothrips mori (Niwa) were presented to an adult H. brevitubus at densities of 10, 20, 30, and 40 larvae per cage at 25 °C over 24 h, the number of larvae consumed per day increased with an increasing density up to 30. Predation of H. brevitubus exhibited the type II functional response. The mean development time of the egg, larva, and pupa of H. brevitubus were 4.5, 9.6, and 4.8 days, respectively, at 25 °C. The survival rate from egg to adult emergence was 94.7%. One H. brevitubus larva consumed 41.6 P. mori larvae on average during the total larval period. Adult longevity was 35.2 days in females and 34.6 days in males. The pre-oviposition period was 2.7 days and the oviposition period was 31.5 days. The lifetime fecundity was 120.1 eggs and the mean daily oviposition rate was 3.6 eggs. Calculated mean generation time (T) was 29.5 days, intrinsic rate of natural increase (r_m) was 0.162, and net reproductive rate (R₀) was 56.5. The r_m value of H. brevitubus was higher than that of Thrips palmi Karny and almost equal to that of Frankliniella occidentalis (Pergande). These results indicate that H. brevitubus has good potential as a predator of P. mori and is likely to be useful for controlling thrips.     

Role of cuticle-degrading enzymes of Beauveria bassiana and Metarhizium anisopliae in virulence on Plodia interpunctella (Lepidoptera,Pyralidae) larvae

Entomopathogenic fungi (EPF) are important biological control agents in pest management programs in agroecosystems against insect pests. EPF such as Beauveria bassiana (Bals.) Vuillemin and Metarhizium anisopliae (Metchn.) Sorokin produce a wide range of extracellular enzymes involved in disturbance of the first barrier in the insect cuticle comprising proteins, chitin, and lipids. Realizing relationships between the expression of these enzymes and fungal virulence might aid in development of effective mycoinsecticides. The virulence of B. bassiana (isolates TV and OZ1) and M. anisopliae (isolate CS1) were investigated on Plodia interpunctella (Hübner) larvae in this study. The third instar larvae were immersed in a suspension containing 1 × 10⁸ conidia mL^?1 of fungal conidial inoculum. The results revealed that all three fungal isolates caused mortality in larvae, but there was a considerable variation in their virulence. Total proteinase, exochitinase and lipase assays were done for these isolates. The TV isolate with the highest mortality with 41.7%, had the highest level of specific activity of exochitinase, protease, and lipase with 0.148, 0.654, and 0.190 U. mg^?1 protein, respectively. In the current study, a positive correlation was determined between the virulence of fungal isolates and the activities of protease and lipase, but this link was not significant for exochitinase. Our results demonstrated that extracellular enzymes, particularly protease and lipase, may play a crucial role in the virulence of these fungal isolates against P. interpunctella larvae.     

三种花蓟马触角感器的超微结构

采用扫描电子显微镜对花蓟马Frankliniella intonsa (Trybom)、 禾花蓟马F. tenuicornis (Uzel) 和西花蓟马F. occidentalis (Pergande) 3种国内危害严重的农业害虫的两性成虫触角感器超微结构进行观察和比较, 旨在明确3种花蓟马两性成虫触角上的感器类型、 数量、 分布及超微形态特征, 明晰3种花蓟马触角感器差异, 进而补充蓟马感器详细资料、 完善蓟马形态学研究。结果表明： 3种花蓟马两性成虫触角上均有8种感器类型, 即Böhm氏鬃毛、 钟形感器、 毛形感器、 刺形感器、 锥形感器、 腔锥形感器、 腔形感器和特殊结构感器。触角各节上感器的分布和数量并不均匀。分析结果显示, 各类感器在触角上的分布相对稳定, 具有一定规律; 近缘种间和同种两性间触角感器的形态及分布无明显差异。     

New Neotropical Species of the Genus Frankliniella Karny (Insecta: Thysanoptera: Thripidae)

Four new species of the genus Frankliniella Karny are described, two from Chile, F. rahakana sp. n. and F. otites sp. n.; one from Costa Rica, F. senckenbergiana sp. n. and one from Argentina, F. amigoi sp. n. F. rahakana sp. n. belongs to the ‘intonsa group’ and the other three to the ‘minuta group’ of Frankliniella.