Thrips Susceptibility Research Articles

Using Sentinel Plots to Monitor for Changes in Thrips Susceptibility to MON 88702 Cotton Containing the Cry51Aa2.834_16 Bt Protein.

Transgenic Bt crops are important tools for growers to manage insect pests, but their durability is threatened by the evolution of insect resistance. Implementing a resistance monitoring program is essential to detect and mitigate resistance. For non-high-dose Bt crops, resistance monitoring is challenging, because insect control is not complete, so targeted insects and insect damage will be present even without resistance. Given these challenges, sentinel plots have been used to monitor for insect resistance to non-high-dose crops by assessing changes in the efficacy of a Bt crop over time relative to a non-Bt control. We optimized a sentinel plot resistance monitoring approach for MON 88702 ThryvOn™ cotton, a new non-high-dose Bt product targeting two sucking pest taxa-Lygus (L. lineolaris and L. hesperus) and thrips (Frankliniella fusca and F. occidentalis)-and report here on the thrips monitoring methods and results. Quantifying thrips immatures was the best metric to characterize the impact of the trait, with at least a 40-60% average reduction of thrips immatures on ThryvOn relative to the control cotton at all sites with higher thrips densities. These data can be used within a ThryvOn resistance monitoring program and represent a case study for establishing a resistance monitoring approach for a non-high-dose trait product.

Bioefficacy of insecticides against Thrips palmi in cotton (Gossypium hirsutum)

Various species of arthropod have been recorded as cotton pests at various stages of its growth as defoliators, tissue borers and sap-suckers, causing considerable yield losses. Among these, thrips are one of the most devastating early-season sucking pests limiting cotton (Gossypium hirsutum L.) productivity directly by feeding and transmitting viruses. So far, scanty information is available on the efficacy of insecticide against thrips in cotton. Thus the present study was carried out at Research farm of CCS HAU, Hisar, Haryana during rainy (kharif) season 2019–20 and 2020–21. The efficacy of 14 label-claimed insecticides against Thrips palmi was evaluated under field and laboratory conditions. Under field conditions, profenofos was the most effective insecticide against thrips at three days after spray, while spinetoram recorded the highest thrips reduction after seven days of spray. The following efficacious chemistries against thrips were fipronil and cypermethrin, whereas flonicamid and buprofezin recorded higher thrips population than other treatments. Under laboratory studies, the leaf dip bioassay was conducted to revalidate the field results, and it was found that profenofos, fipronil and spinetoram were highly effective, causing maximum thrips knockdown, whereas lower mortality was recorded in flonicamid. The study provided baseline data on thrips susceptibility to different insecticides, which can be used to develop an effective management strategy by altering different chemistries to avoid selection pressure.

Regional variation in susceptibility of thrips (Thysanoptera: Thripidae) to insecticides on onion in the Rift Valley of Ethiopia

The responses of thrips to commonly used insecticides were studied in onion fields with the aim of detecting presence or absence of thrips resistance to insecticides in the Central Rift Valley of Ethiopia. Thrips populations were collected from area with heavy pesticide use history Meki and Melkassa and less use areas of Werer and Minjar. Collected adult thrips populations were exposed to various concentrations of λ -cyhalothrin, dimethoate, profenofos, diazinon and spinetoram treated vial and thrips mortality was assessed after 24 h. The percent mortality was significantly lower in Meki and Melkassa collected thrips populations than in Minjar and Werer populations to λ –cyhalothrin and diazinon at recommended field rate. On the other hand, differences were insignificant for the insecticides spinetoram and profenofos at recommended field rate. Of the five tested insecticides λ –cyhalothrin had higher resistance ratios to Meki (10.8-fold) and Melkassa (6.78- fold) collected thrips population, while resistance ratio was intermediate to diazinon and lowest to dimethoate and profenofos insecticides. Results of this study suggest that thrips affecting onion in Meki and Melkassa areas have developed resistance to λ –cyhalothrin and diazinon insecticides. Periodic assessment of efficacy of registered insecticides and deploying a pesticides resistance management strategy are useful for sustainable use of pesticides in integrated thrips management program.

High Concentrations of Very Long Chain Leaf Wax Alkanes of Thrips Susceptible Pepper Accessions (Capsicum spp)

The cuticular wax layer can be important for plant resistance to insects. Thrips (Frankliniella occidentalis) damage was assessed on 11 pepper accessions of Capsicum annuum and C. chinense in leaf disc and whole plant assays. Thrips damage differed among the accessions. We analyzed the composition of leaf cuticular waxes of these accessions by GC-MS. The leaf wax composition was different between the two Capsicum species. In C. annuum, 1-octacosanol (C28 alcohol) was the most abundant component, whereas in C. chinense 1-triacotanol (C30 alcohol) was the prominent. Thrips susceptible accessions had significantly higher concentrations of C25-C29n-alkanes and iso-alkanes compared to relatively resistant pepper accessions. The triterpenoids α- and ß-amyrin tended to be more abundant in resistant accessions. Our study suggests a role for very long chain wax alkanes in thrips susceptibility of pepper.

Identification of Thrips Species and Resistance of Frankliniella occidentalis (Thysanoptera: Thripidae) to Malathion, Spinosad, and Bifenthrin in Blackberry Crops

Mexico is among the most important blackberry producers in the world. In this crop, thrips damage is associated with poor fruit set. The objectives of this study were to identify the main thrips species associated with the flowers of cultivated blackberries, and to determine the resistance level of 13 field-collected populations of western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), to the insecticides malathion, bifenthrin, and spinosad in the states of Michoacan and Jalisco, Mexico. Verification of F. occidentalis was conducted by morphology and PCR amplification of the cytochrome oxidase I (COI) partial gene using LCO and HCO primers The susceptibility of adult thrips to insecticides was determined using residual contact exposure on bean (Phaseolus vulgaris L.; Fabaceae) leaf sections dipped into aqueous solutions of 8 different concentrations of malathion, bifenthrin, and spinosad. The morphological identification of thrips from 8 different sampling zones confirmed that the main thrips species associated with blackberry flowers was F. occidentalis. However, Retanathrips funestus (Hood), Frankliniella insularis (Franklin), Frankliniella tolucensis Watson, Taenothrips frici (Uzel), and Isoneurothrips australis Bagnall (all Thysanoptera: Thripidae) also were found. Most of the evaluated populations of F. occidentalis showed significant differences from the susceptible population in terms of the level of resistance to bifenthrin, malathion, and spinosad. The resistance ratios (RR50) for malathion varied from 36 to 2,458, followed by 4 to 974, and 2 to 248 in bifenthrin and spinosad, respectively. These results suggest the need to establish insecticide resistance management programs, particularly in zones that resulted in the highest levels of insecticide resistance.

Geographical and interspecific variation in susceptibility of three common thrips species to the insecticide, spinetoram

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.

Monitoring Onion Thrips (Thysanoptera: Thripidae) Susceptibility to Spinetoram in New York Onion Fields.

Onion thrips (Thrips tabaci Lindeman) is a severe pest of onion (Allium cepa L.). Their management relies on frequent applications of foliar insecticides, including spinetoram (Radiant® SC), which has a novel mode of action and is effective at controlling large populations. However, despite being widely used for the past 10 yr, susceptibility to spinetoram has not been evaluated formally in New York state, where nearly 3,000 hectares of onion are planted annually. Over 2 yr (2017-2018), the susceptibility of onion thrips to spinetoram was assessed from populations collected in commercial onion fields in New York. LC50s for adults were generated from feeding assays and ranged from 2.07 to 5.08 ppm, but grower reports indicate that onion thrips populations continue to be susceptible to spinetoram. Moreover, both regional and temporal variations in susceptibility were similar among these populations based on survival at individual concentrations tested, despite significant differences in LC50s. These results suggest some genetic heterogeneity among onion thrips populations and serve as a valuable reference for the continued monitoring of onion thrips susceptibility to spinetoram, contributing to ongoing efforts to manage insecticide resistance in this system.

Evaluation of Susceptibility of Western Flower Thrips (Frankliniella occidentalis ) and Garden Thrips (F. intonsa ) to 51 Insecticides

Evaluation of Susceptibility of Western Flower Thrips (Frankliniella occidentalis ) and Garden Thrips (F. intonsa ) to 51 Insecticides

Effects of Bt maize on Frankliniella tenuicornis and exposure of thrips predators to prey‐mediated Bt toxin

AbstractAs a part of a risk assessment procedure, the impact of Bt maize expressing Cry1Ab toxin on the thrips Frankliniella tenuicornis (Uzel) (Thysanoptera: Thripidae) was investigated, and the potential risks for predators feeding on thrips on Bt maize were evaluated. The effects of Bt maize on F. tenuicornis were assessed by measuring life‐table parameters when reared on Bt and non‐Bt maize. The content of Cry1Ab toxin in different stages of F. tenuicornis reared on Bt maize and the persistence of the toxin in adults where determined in order to evaluate the possible exposure of predators when feeding on thrips. In addition, Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae) was used as a model predator to assess how the behaviour of prey and predator may influence the exposure of a natural enemy to the Bt toxin. Life‐table parameter results showed that F. tenuicornis was not affected when it was reared on Bt maize. This indicates that the potential for prey quality‐mediated effects on predators is low. Bt content was highest in thrips larvae and adults, and negligible in the non‐feeding prepupal and pupal stages. The persistence of the Cry1Ab toxin in adult F. tenuicornis was short, resulting in a decrease of 97% within the first 24 h. Predation success by young C. carnea larvae varied among the thrips stages, indicating that exposure of predators to Bt toxin can additionally depend on the prey stage. When combining the current knowledge of the susceptibility of major thrips predators with our findings showing no potential for prey quality‐mediated effects, relatively low toxin content in thrips as well as short persistence, it can be concluded that the risks for predators when feeding on thrips in or next to Bt maize fields are negligible.

Decreased preference and reproduction, and increased mortality of Frankliniella occidentalis on thrips‐resistant pepper plants

AbstractThe effect of thrips resistance in pepper (Capsicum annuum L.) – previously shown to result in impeded thrips population development (Maris PC, Joosten NN, Goldbach RW & Peters D (2003a) Restricted spread of Tomato spotted wilt virus in thrips‐resistant pepper. Phytopathology 93: 1223–1227. Maris PC, Joosten NN, Goldbach RW & Peters D (2003b) Spread of Tomato spotted wilt virus and population development of Frankliniella occidentalis in pepper resistant to thrips. Proceedings of the Section Experimental and Applied Entomology Netherlands Entomological Society (NEV) Amsterdam 14: 95–101.) – on thrips’[Frankliniella occidentalis Pergande (Thysanoptera: Thripidae)] reproduction, mortality, host preference, and behaviour was investigated. Reproduction, studied by oviposition and larval survival, was negatively affected by the thrips‐resistant (TR) phenotype, whereas the offspring's developmental rate did not differ on TR and the thrips‐susceptible (TS) phenotype. While thrips’ behaviour was hardly affected by thrips resistance, a significant preference for TS plants over the TR plants was found in different tests. When released on either a TR or a TS plant, thrips dispersed at significantly higher rates from the TR plants, demonstrating that not only an impeded reproduction, but also a reduced residence time adds to the reported lower thrips numbers on TR plants.

Factors influencing the population of the onion thrips on onion

The onion thrips (Thrips tabaci Lindeman) has been known for a long time as a pest of onion. The damage hinders the development of the onion, causing the plant to end its development earlier than usual, so there may be a decrease in crop yield, too. Control of the onion crop against the onion thrips is the basis of its protection. The chemical protection is difficult owing to the hidden lifestyle of the pest and the wax cover on the leaf of the onion. The natural enemies of the onion thrips can reduce the population only to a small degree. One of the efficient and environmentally friendly protection methods could be the production of thrips resistant onion varieties. The thrips susceptibility of onion varieties (dry onion, leek, green bunch onion and chive) produced in Hungary is unknown. Our aim was to investigate the thrips susceptibility of commercially produced onion varieties and to work out the methods of a large-scale investigation.

Regional and temporal variation in susceptibility to lambda-cyhalothrin in onion thrips, Thrips tabaci (Thysanoptera: Thripidae), in onion fields in New York.

Populations of onion thrips, Thrips tabaci Lindeman, from commercial onion fields in New York were evaluated for their susceptibility to the commonly used pyrethroid, lambda-cyhalothrin (Warrior T), using a novel system called the Thrips Insecticide Bioassay System (TIBS). To use TIBS, thrips are collected directly from the plant into an insecticide-treated 0.5-ml microcentrifuge tube that has a flexible plastic cap with a small well into which 0.08 ml of a 10% sugar-water solution with food colorant is deposited. The solution is sealed into the well with a small piece of stretched parafilm through which the thrips can feed on the solution. Thrips mortality is assessed after 24 h with the help of a dissecting stereoscope. In 2001, onion thrips populations were collected from 16 different sites and resistance ratios were >1,000 in five populations. Percent mortality at 100 ppm, a recommended field rate, varied from 9 to 100%, indicating high levels of variation in susceptibility. Particular instances of resistance appeared to be the result of practices within an individual field rather than a regional phenomenon. In 2002, we also observed large differences in onion thrips susceptibility, not only between individual fields but also between thrips collected in a single field at mid season and late season, again suggesting that insecticide-use practices within an individual field caused differences in susceptibility. Additional tests indicated no differences in susceptibility between adult and larval onion thrips populations and only relatively minor differences between populations collected from different parts of the same field. Using TIBS, several populations of onion thrips with different susceptibilities to lambda-cyhalothrin were identified and then subjected to lambda-cyhalothrin-treated onion plants. There was a highly significant positive relationship between percent mortality of thrips from TIBS and percent mortality from the treated onion plants, indicating that results from TIBS could be used to predict spray performance. These data suggest that use of TIBS for evaluating susceptibility to particular insecticides could be instrumental for developing a resistance management strategy for onion thrips.

Thrips (Thysanoptera: Thripidae) Injury to Cabbage Cultivars in Ohio

Cabbage cultivars were evaluated for thrips damage over a 3-yr period. During this time, the correlation between damage ratings and amount of cabbage trimmed to remove thrips-damaged tissue was variable. Differences in susceptibility between cultivars were also variable, although some cultivars (‘Bravo’, ‘Titanic 90’, ‘Superkraut’) consistently had little damage and others (‘Krautpacker’, ‘Superdane’) were consistently and heavily damaged. Time required to trim thrips injury from cabbage heads was a linear function of amount of tissue removed. Slopes and intercepts for trimming time predicted by the amount of tissue removed were significantly different among cultivars. Data suggest that the mechanisms that govern susceptibility of a given cabbage cultivar to thrips injury are variable in time. Cultivars should be examined for thrips susceptibility for > 1 yr, and a combination of quantitative and qualitative measures of thrips injury should be used in cultivar evaluations.

ミナミキイロアザミウマのオキサミル粒剤に対する薬剤感受性簡易検定法

ミナミキイロアザミウマのオキサミル粒剤に対する薬剤感受性簡易検定法

Resistance to Thrips Damage in Cassava1

Part of the germplasm bank of cassava in the Centro Internacional de Agricultura Tropical (CIAT) was evaluated at the end of each of 2 successive dry seasons for resistance to thrips, Frankliniella sp. and Corynothrips stenopterus Will. Clones were classified in 6 resistance groups on the basis of damage symptoms. About 20% of the 1254 clones evaluated showed no symptoms of thrips damage. Thrips damage and the number of thrips present in the terminal buds were related. A strong relationship existed between pubescence of unexpanded leaves and thrips resistance; plants with pubescent leaves were resistant to thrips attack. At flowering, leaf pubescence decreased and thrips susceptibility increased. Resistance was not associated with plantcyanide content. Thrips may cause similar symptoms as viral or mycoplasmic organisms.