Manipulating fertilization: a management tactic against Frankliniella occidentalis on potted chrysanthemum

Fertilization during production of greenhouse chrysanthemum, Dendranthema grandiflora (Tzvelev), will influence Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae) populations as well as plant productivity and postproduction longevity. It is essential to include fertilization effects in the development of crop management practices that reduce thrips populations and maintain plant marketability. In this study, we lowered fertilization to reduce thrips population abundance while maintaining plant productivity. We tested fertilization levels below and above the recommended level (375 p.p.m. N) for commercial production. We reduced mean rate of change in F. occidentalis abundance from 0.05 to 0.03 (day⁻¹) and mean number of thrips per plant by 44% by fertilizing with either 188 p.p.m. N (50% of the recommended level) or 568 p.p.m. N (150%) and higher. Fertilization influenced not only the rate of change in thrips abundance but also the production time (from transplanting to flower opening). Lowering fertilization to 50% of the recommended level lengthened mean production time from 84 to 88 days. Plant height, flower size, and flower number were not adversely affected when fertilization was reduced to 50% of the recommended level. Mean postproduction longevity was shortened from 26 to 24 days when plants were fertilized with 50% of the recommended level. Two important advantages of lowering fertilization to 50% of the recommended level were (1) a 44% reduction in mean F. occidentalis abundance and (2) a significant reduction in fertilizer input for the production system. Manipulation of fertilization can be a useful management tactic against F. occidentalis .     

Reducing fertilization: a management tactic against western flower thrips on roses

Fertilization reduction could be a useful pest management tactic for floriculture crops if it reduced pest populations with minimal impact on crop yield and quality. We evaluated the response of the western flower thrips, Frankliniella occidentalis Pergande (Thysanoptera: Thripidae), to different fertilization levels for cut roses, Rosa hybrida L. cv. ‘Tropicana’, and quantified fertilization effects on (i) abundance of F. occidentalis on cut roses, (ii) biological control of F. occidentalis on cut roses and (iii) nutritional quality of the cut flower crop. We tested a commercially available fertilizer (Peters Excel 15‐5‐15 Cal‐Mag; The Scotts Company, Marysville, OH) at 100% and 33% of the recommended nitrogen level (150 ppm N) for rose production using liquid‐feeding and two control measures: no thrips control measure; release of a predatory mite, Amblyseius swirskii (Athias‐Henriot). To maintain equivalent ratios of macro‐ and micronutrients for all our fertilizer treatments, we varied only the concentration of the fertilizer to the levels specified in our experiments. Lowering fertilization rate from 100% to 33% of the recommended level reduced mean F. occidentalis abundance on cut roses by 30%. Combinations of both bottom‐up (fertilization) and top‐down (biological control) tactics provided better F. occidentalis control than either tactic alone. Flower production was not compromised on plants fertilized with 33% of the recommended level. Nitrogen, phosphorous and potassium content of the leaf tissue decreased at 33% of the recommended fertilization level, but all values were within optimal ranges for cut roses. We propose that fertility management may be an effective means of reducing thrips numbers on cut roses.     

Effects of tomato spotted wilt virus isolates, host plants, and temperature on survival, size, and development time of Frankliniella occidentalis

Tomato spotted wilt virus (TSWV) replicates in both its plant hosts and its thrips vectors. Replication of TSWV within thrips suggests the potential for pathological effects that could affect the fitness of its vectors directly, whereas infection of the plant may alter its suitability as a host for thrips development. This study was undertaken to examine the influence of TSWV isolate, host plant, and temperature on potential direct and host-mediated effects of virus infection of the thrips and the plant on Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), an important vector of TSWV. Neonate F. occidentalis were reared to adult eclosion on excised foliage of Datura stramonium (L.) (Solanaceae) or Emilia sonchifolia (L.) (Compositae) infected with either the CFL or RG2 isolate of TSWV, or not infected. Effects of the TSWV isolates and host plants on thrips were measured at 18.3, 23.9, and 29.4 °C. Results demonstrate significantly improved survival and a small but significant decrease in development time of F. occidentalis on TSWV-infected plants. These effects resulted from the combined influence of the direct effects of the virus on infected thrips and plant-mediated effects resulting from virus infection of the thrips’ host plant. Our results extend previous findings and help to explain inconsistencies among previously published reports by demonstrating that the manifestation and magnitude of effects of TSWV on F. occidentalis are dependent on host plant, virus isolate, and temperature.     

Influence of salicylaldehyde and methyl salicylate on post-landing behaviour of Frankliniella occidentalis Pergande

This study investigates behavioural responses of adult western flower thrips (Frankliniella occidentalis Pergande; Thysan., Thripidae) females to direct contact with repellent phenylpropanoid plant compounds (salicylaldehyde and methyl salicylate) applied on bean and cucumber leaves. The residence time of F. occidentalis females until take off was significantly shorter on bean or cucumber leaf discs treated with salicylaldehyde at 1% concentration compared with control leaf discs. A methyl salicylate (1%) treatment of cucumber resulted in shorter time periods until thrips took off the treated leaf discs compared with the control leaf discs. In a choice experiment thrips avoided to settle on a 1% salicylaldehyde treatment of bean and cucumber leaf discs for a maximum of 3 h, on a 1% methyl salicylate treatment for a 5‐h period. Within a 24‐h period neither the egg‐laying nor the feeding activity of F. occidentalis was affected after salicylaldehyde application (0.1%, 1%) on bean or cucumber. In contrast, methyl salicylate (1%) applied on bean and cucumber significantly prevented thrips females from oviposition and reduced the percentage of damaged area caused by their feeding activity for 24 h. As olfactory repellent plant volatiles applied on crop plants may elicit diverse post‐landing responses of F. occidentalis, short‐ and long‐term effects should be considered when evaluating the factual applicability of secondary plant compounds in a successful thrips management strategy.     

Influence of plant species and plant growth stage on Frankliniella occidentalis pupation behaviour in greenhouse ornamentals

The influence of plant stage and plant species on the pupation behaviour of western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), was investigated in flowering and non‐flowering potted chrysanthemums and mini roses. On non‐flowering chrysanthemums and roses, 92–93% of the F. occidentalis pupated in the soil. On flowering roses, 87% pupated in the soil, and on flowering chrysanthemums only 60% chose the soil as a pupation site and 40% stayed on the plant. This means that, in the presence of flowers, especially complex inflorescences like chrysanthemums, a large proportion of F. occidentalis chooses stay on the plant to pupate.     

Influences of fertilization on Aphis gossypii and insecticide usage

Abstract: Fertilization levels for ornamental crops may influence pest population dynamics, crop quality, and pest management strategy. We examined the effect of fertilization on population growth and within‐plant distribution of melon or cotton aphid, Aphis gossypii Glover, on potted chrysanthemum, Dendranthema grandiflora (Tzvelev). In terms of pest management implications, we also investigated the effect of fertilization on the number of insecticide applications needed to control A. gossypii on potted chrysanthemum. Population growth rate of A. gossypii increased with fertilization levels from 0 to 38 ppm N and reached a plateau from 38 to 488 ppm N. Increased fertilization beyond 38 ppm N, 10% of the commercial standard, did not result in higher aphid number. Aphids responded to nutrient availability of plants by distributing themselves in areas with higher level of nitrogen. More aphids were found in the apical and middle strata of the plants than the basal stratum, which had the lowest nitrogen content. Leaf nitrogen content increased with increased fertilization level and was consistently higher in the apical and middle strata than the basal stratum. Increased fertilization from 0 to 375 ppm N did not result in higher number of insecticide applications. All three insecticides (bifenthrin, kinoprene or pymetrozine) were effective in keeping the aphid infestation below a pre‐determined level, five aphids per plant, but pymetrozine required the least number of applications. For chrysanthemum, a fast‐growing crop and heavy utilizer of nitrogen, increased fertilization shortened the time to flowering, which would allow growers to harvest their crop sooner and reduce the time for aphid population growth. Reduction in time to harvest could result in significant reduction of insecticide usage by reducing the time for aphid population growth. As a result, high fertilization together with minimal runoff may be a useful tactic to an integrated pest management (IPM) programme for managing A. gossypii on potted chrysanthemums.     

Distributions of western flower thrips (Thysanoptera: Thripidae) and its predatory bug Orius niger (Hemiptera: Anthocoridae) assessed by coloured sticky traps and plant samplings in cotton

The capturing efficiency of four coloured (yellow, green, white and blue) sticky traps, placed at the top, middle and bottom strata of cotton plants, was tested for the western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), and its predatory bug, Orius niger (Wolff) (Hemiptera: Anthocoridae), as well as spatial distributions of both insects on the plant in years 2006 and 2007. The white coloured trap was the most attractive to F. occidentalis and O. niger in the 2-year study. The blue coloured trap was the least attractive for Orius. The mean numbers of F. occidentalis and O. niger on the top plant parts (flowers and leaves) and in all coloured traps positioned on the upper parts of the plants were greater than those found in the lower two strata. Taylor's power law analysis showed that F. occidentalis and O. niger adults aggregated in the flowers or on the leaves. This study suggests that top flowers could be preferentially sampled to determine population densities of Frankliniella flower thrips and Orius species in cotton, and thus, sticky traps should be placed on the top level of plants. F. occidentalis: O. niger ratios in the flowers varied from 4 to 60 thrips per Orius adult in the three plant strata. This result may indicate that F. occidentalis experiences more predation from Orius.     

Biotic resistance limits the invasiveness of the western flower thrips,Frankliniella occidentalis (Thysanoptera: Thripidae), in Florida

The spread of the western flower thrips, Frankliniella occidentalis (Pergande), has resulted in the world‐wide destabilization of established integrated pest management programs for many crops. It is hypothesized that frequent exposure to insecticides in intensive agriculture selected for resistant populations, which allowed invasive populations in the eastern USA to overcome biotic resistance from the native community of species. Research conducted in Florida to understand the role of biotic factors in limiting the abundance of the western flower thrips is reviewed. Orius spp. (Hemiptera: Anthocoridae) are effective predators that suppress populations of thrips on crop and non‐crop hosts in southern and northern Florida. Orius are more effective predators of the western flower thrips than the native flower thrips, F. tritici (Fitch) and F. bispinosa (Morgan). The native species are competitors of the western flower thrips. Excessive fertilization and the use of broad‐spectrum insecticides in crop fields further enhances populations of the western flower thrips. Interactions with native species clearly limit the abundance of western flower thrips in Florida, but populations are abundant in fertilized crop fields where application of insecticides excludes predators and competitor species.     

Erratum

Abstract: Fertilization levels for ornamental crops may influence pest population dynamics, crop quality, and pest management strategy. We examined the effect of fertilization on population growth and within‐plant distribution of melon or cotton aphid, Aphis gossypii Glover, on potted chrysanthemum, Dendranthema grandiflora (Tzvelev). In terms of pest management implications, we also investigated the effect of fertilization on the number of insecticide applications needed to control A. gossypii on potted chrysanthemum. Population growth rate of A. gossypii increased with fertilization levels from 0 to 38 ppm N and reached a plateau from 38 to 488 ppm N. Increased fertilization beyond 38 ppm N, 10% of the commercial standard, did not result in higher aphid number. Aphids responded to nutrient availability of plants by distributing themselves in areas with higher level of nitrogen. More aphids were found in the apical and middle strata of the plants than the basal stratum, which had the lowest nitrogen content. Leaf nitrogen content increased with increased fertilization level and was consistently higher in the apical and middle strata than the basal stratum. Increased fertilization from 0 to 375 ppm N did not result in higher number of insecticide applications. All three insecticides (bifenthrin, kinoprene or pymetrozine) were effective in keeping the aphid infestation below a pre‐determined level, five aphids per plant, but pymetrozine required the least number of applications. For chrysanthemum, a fast‐growing crop and heavy utilizer of nitrogen, increased fertilization shortened the time to flowering, which would allow growers to harvest their crop sooner and reduce the time for aphid population growth. Reduction in time to harvest could result in significant reduction of insecticide usage by reducing the time for aphid population growth. As a result, high fertilization together with minimal runoff may be a useful tactic to an integrated pest management (IPM) programme for managing A. gossypii on potted chrysanthemums.     

The effect of background plant odours on the behavioural responses of Frankliniella occidentalis to attractive or repellent compounds in a Y‐tube olfactometer

The western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), causes major losses in agricultural and horticultural crops worldwide. The volatile compounds methyl isonicotinate, p‐anisaldehyde, eugenol, and linalool are known as olfactory attractants, and salicylaldehyde is known as a repellent for F. occidentalis under clean‐air conditions in laboratory experiments. In the present study we assessed the responses of F. occidentalis to these compounds when presented alone, in combination, and in the presence of background odours emanating from cucumber (Cucumis sativus L., Cucurbitaceae), capsicum (Capiscum anuum L., Solanaceae), chrysanthemum (Chrysanthemum morifolium Ramat., Asteraceae), clove basil (Ocimum gratissimum L.), and lavender (Lavandula angustifolia L., both Lamiaceae) plants in a Y‐tube olfactometer. In the presence of any background plant odour, the attractiveness of pure methyl isonicotinate to F. occidentalis proved to be consistently significant. Compared to clean‐air conditions, a slightly lower percentage of thrips chose the Y‐tube arm loaded with 10% p‐anisaldehyde in the presence of cucumber leaf odour. With non‐flowering clove basil plants in the background, F. occidentalis responses to 1% eugenol, a constituent of clove basil essential oil, were neutral, and the same applied to responses to pure linalool, a constituent of lavender essential oil, in the presence of flowering lavender plants. Also, thrips responses to pure or diluted salicylaldehyde were clearly influenced by plant background odours. We simulated a push‐pull situation and found a trend indicating that the percentage of F. occidentalis choosing the airflow loaded with the attractant methyl isonicotinate was higher when the airflow in the other arm of the Y‐tube was loaded with the repellent salicylaldehyde compared to clean air, and vice versa. We showed interactions between attractive or repellent volatile compounds and the environmental odours in the chemical ecology of F. occidentalis and the potential of a combined use of these compounds in thrips pest management.     

Effects of tomato spotted wilt virus (TSWV) isolates, host plants, and temperature on survival, size, and development time of Frankliniella fusca

The effects of different isolates of the tomato spotted wilt tospovirus (TSWV), host plants, and temperatures on Frankliniella fusca (Hinds) (Thysanoptera: Thripidae), the most important vector of TSWV in North Carolina, were measured in the laboratory. Thrips were reared at either 18.3, 23.9, or 29.4 °C until adult eclosion on excised leaves of Datura stramonium L. or Emilia sonchifolia (L.). Plants were either infected with the TSWV isolates CFL or RG2, or left uninfected (control). The results revealed a positive relationship between larval survival and temperature, regardless of host plant or TSWV isolate. Both survival to adult and percentage transmission of TSWV by F. fusca were significantly affected by the interaction between host plant and TSWV isolate. The consequence of this interaction was that the cohort‐based percentage transmission from infected E. sonchifolia plants for CFL was 1.3‐fold greater than that of RG2, whereas the percentage transmission from infected D. stramonium plants for RG2 was twice that of CFL. Both host plant and TSWV isolates showed significant effects on thrips development time to adult and head capsule width of adult thrips, as well as on the incidence of thrips infection with TSWV. The infection status of these thrips was determined by ELISA for the NSs viral protein. Infected thrips reared on infected host foliage took longer to develop to adult and were smaller than non‐infected thrips which had also been reared on infected host foliage, demonstrating a direct effect of the TSWV on thrips. However, non‐infected thrips reared on non‐infected leaves took longer to develop than non‐infected thrips reared on infected leaves, suggesting an effect of the plant tissue on thrips. In addition, adult thrips reared on TSWV‐infected D. stramonium at 29.4 °C developed smaller head capsules than thrips developing on infected foliage at lower temperatures and on non‐infected leaves of D. stramonium or E. sonchifolia. Both TSWV isolates and host plants differentially affected females more than males. In conclusion, both the infection of thrips by TSWV and TSWV‐mediated changes in host plant quality were found to have significant biological effects on F. fusca.     

Life history characteristics of Frankliniella occidentalis on cucumber leaves with and without supplemental food

The development time, fecundity, longevity, and resultant intrinsic growth rate of the western flower thrips Frankliniella occidentalis (Pergande) [Thysanoptera: Thripidae] encaged on a cucumber leaf were compared among seven types of food supplied: six pollen species and a mixture of milk powder and yeast. The rationale was to find a food source that offers the least benefit for thrips and could therefore be considered as a food source for the preventative introduction of thrips predators. With the exception of the mixture of milk powder and yeast, all the food sources tested offered a nutritional benefit for the thrips. The addition of pollen increased fecundity and reduced development time, mainly during the larval stage. Betula pubescens and Corylus avellana pollen also increased adult longevity. The nutritional benefit of Pinus sylvestris pollen was greater than that of the other five pollen species, as manifested by its significantly greater positive effect on fecundity. The other pollen species could not be ranked in terms of nutritional benefit to F. occidentalis. The negative effect of the milk powder plus yeast mix on the life‐table parameters of F. occidentalis probably only occurs in an encaged situation where thrips cannot escape from the unfavorable environment. The crude estimate of the intrinsic growth rate of F. occidentalis increased from 0.163 on the plain cucumber leaf to 0.240 when P. sylvestris pollen was added to the leaf. The differences in intrinsic growth rate mainly reflect the differences in fecundity among the food sources. Thus, the peak oviposition rate may be used as a measure of the nutritional benefit F. occidentalis can obtain by feeding on supplemental food sources. The positive effect of a supplemental food source on thrips does not necessarily mean it is unsuitable for the preventative introduction of thrips predators, because the supplemental food can also affect the population dynamics of the predator and the predator–prey interaction and, hence, the outcome of biological control.     

Cross‐resistance of chrysanthemum to western flower thrips,celery leafminer,and two‐spotted spider mite

Chrysanthemum [Chrysanthemum × morifolium Ramat. (Asteraceae)] is one of the economically most important greenhouse ornamentals worldwide. A major constraint in chrysanthemum production is adequate pest management, requiring the use of different tactics, such as improving host plant resistance, in the framework of an integrated pest management (IPM) approach. In this study, we investigated cross‐resistance of chrysanthemum to its three major pests: western flower thrips [Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae)], celery leafminer [Liriomyza trifolii (Burgess) (Diptera: Agromyzidae)], and two‐spotted spider mite [Tetranychus urticae Koch (Acari: Tetranychidae)]. We quantified resistance to each pest by performing greenhouse bioassays with a broad range of chrysanthemum types from commercial germplasm provided by Dutch breeding companies. Considerable variation was detected among the chrysanthemum cultivars in thrips silver damage and growth damage, leafminer damage, measured as number of mines and pupae, and spider mite numbers and damage. We observed significant positive correlations between thrips damage (both silver and growth damage) vs. leafminer numbers (both mines and pupae), and between leafminer numbers (both mines and pupae) vs. spider mite numbers. Our results indicate an overlap in resistance to all three herbivores. The important implications of this result for chrysanthemum breeding are discussed.     

Abundances of thrips on plants in vegetative and flowering stages are related to plant volatiles

Western flower thrips (WFTs), Frankliniella occidentalis Pergrande, and onion thrips (OTs), Thrips tabaci Lindeman, are two cosmopolitan insect pests of agricultural and horticultural plants. Understanding the occurrence and development of thrips on plants is crucial for identifying suitable plants that can be used for developing a “push-pull” strategy against thrips. In this study, the dynamics of WFTs and OTs on plants (Allium fistulosum L., Medicago sativa L., Luffa cylindrica (L.) Roem., Ocimum basilicum L., and Schizonepeta tenuifolia (Benth.) Briq.) were investigated for two consecutive years (2018–2019). Throughout the survey, the abundances of both thrips species were strongly associated with plant species and plant phenology; both thrips species were present at relatively high densities on M. sativa but very low densities on O. basilicum and S. tenuifolia. Populations of both thrips species greatly increased during plant flowering. A Y-tube olfactory test was used to study the effects of plant volatiles in mediating thrips behaviour and showed that volatiles of M. sativa were attractive to both thrips species whether emitted by the plant in the vegetative or flowering stage, while volatiles of O. basilicum and S. tenuifolia were repellent to thrips. Additionally, because of the presence of a high number of floral chemicals, both thrips species exhibited a greater preference for volatiles emitted by plants in the flowering period over those emitted by plants in the vegetative period. Our observations indicate that plant species and flowering status play an important role in the abundance dynamics of thrips and that the volatiles of flowering plants attract thrips more strongly than volatiles emitted by vegetative plants. These findings can facilitate the screening of attractive/unattractive plants for developing push-pull strategies to control thrips.     

Does natural deposition of pine pollen affect the ovipositional behavior of Frankliniella occidentalis and Frankliniella fusca?

Tree pollen, especially Pinus spp. (Pinaceae), is shed in large quantities every spring in North America. Pine pollen deposition onto leaves was found to significantly influence the ovipositional behaviors of certain thrips species (Thysanoptera: Thripidae) in peanut and tomato leaf choice and no‐choice tests. Pine pollen (Pinus elliottii Engelm.) increased the oviposition rate 2.9‐fold for Frankliniella occidentalis (Pergande) (western flower thrips) and 1.6‐fold for Frankliniella fusca (Hinds) (tobacco thrips) in choice tests averaged over both plant species. These results support the idea that pollen has a greater impact on F. occidentalis behavior than on F. fusca behavior. The most dramatic increase was in peanut, where F. occidentalis only oviposited on leaves dusted with pollen, suggesting that the addition of pollen stimulated this flower thrips to lay eggs on a poor host‐plant part. The impact of pollen on the rate of oviposition by thrips is important because it is the early‐instar nymphs that acquire tomato spotted wilt virus (TSWV), which these two thrips species vector. In a laboratory bioassay, the addition of pine pollen to TSWV‐infected peanut foliage increased the percentage of infected F. fusca after one generation.     

Genetic variation in chrysanthemum for resistance toFrankliniella occidentalis

In a choice-experiment, 42 chrysanthemum cultivars were screened for resistance toFrankliniella occidentalis (Pergande). Oviposition preference, two types of feeding damage and thrips numbers per flower were recorded as measures of resistance. A large genetic variation in thrips resistance was found among the cultivars screened. The amount of feeding damage was strongly determined by oviposition preference. Besides, a positive correlation was found between the oviposition preference in non-flowering chrysanthemums (number of eggs) and flowering chrysanthemums (number of thrips per flower). Thrips feeding on young, developing tissues, causes growth damage because affected cells are unable to expand and leaves become distorted. Thrips feeding on older, expanded leaves causes cells to become filled with air, resulting in ‘silver’ damage. The amounts of growth-and ‘silver’ damage were negatively correlated suggesting that thrips chose either young or older leaves to feed on. The order of resistance among cultivars did not change during the experiment. In order to get more insight in resistance mechanisms the influence of some plant- and flower characters on resistance was examined. The plant characters height, number of leaves, flower production and flower weight were all negatively correlated with resistance. It is suggested that tall chrysanthemum cultivars with many and large flowers may invest less in defence than smaller cultivars, and therefore are more damaged by thrips.     

Thrips-induced damage of chrysanthemum inflorescences: evidence for enhanced leakage of carotenoid pigments

The present study quantifies the leakage of carotenoid pigments in senescing inflorescences of chrysanthemum, Dendranthema grandiflora Tzelev (Asteraceae), infested or not with western flower thrips, Frankliniella occidentalis Pergande (Thysanoptera: Thripidae). The extractability of pigments was evaluated at repeated intervals by measuring the absorbance of immersion and crude extracts of inflorescences, using 447 nm as a diagnostic wavelength (absorption peak of lutein, a predominant carotenoid pigment in chrysanthemum with yellow inflorescences). The absorbance of immersion extracts increased over time and was higher for inflorescences infested with thrips than control inflorescences; the opposite trends were observed for crude extracts of inflorescences. These results suggest that both natural and thrips‐induced senescence of chrysanthemum inflorescences are characterized by enhanced extractability of pigments in organic solvents, most likely resulting from a disruption of cellular membranes. Thin layer chromatography analysis confirmed the presence of lutein in immersion extracts of thrips‐infested inflorescences, providing further support to the hypothesis that the mechanical damage caused by thrips is linked with a leakage of cellular content. An enhanced extractability of pigments in organic solvents may be a widespread phenomenon characterizing floral senescence in non‐climacteric plants.     

嗜食植物与非嗜食植物对西花蓟马成虫寄主选择性的影响

【目的】西花蓟马是世界性害虫,利用西花蓟马对寄主植物嗜食性的差异,通过驱避作用防控西花蓟马,能够为绿色治理提供依据。【方法】在西花蓟马嗜食的甘蓝和非嗜食的大蒜上互喷汁液,采用黄瓜+甘蓝、黄瓜+大蒜2种相间种植方式,研究它们对西花蓟马寄主选择性的影响。【结果】在甘蓝上喷洒大蒜汁液后,甘蓝叶片上西花蓟马的虫量和产卵量均明显减少。大蒜汁液浓度越高,减少得越多;在大蒜上喷洒甘蓝汁液后,大蒜植株上西花蓟马的虫量和产卵量明显增加,且增加程度与甘蓝汁液的浓度呈正相关。黄瓜和甘蓝相间排列时,西花蓟马在黄瓜叶片上的数量与单作黄瓜叶片上无明显差异;但黄瓜和大蒜相间排列时,西花蓟马在黄瓜上的数量明显高于单作黄瓜上的虫数,多52.4%。【结论】在嗜食寄主植物上喷洒非嗜食植物汁液或间作非嗜食的寄主可以明显减少西花蓟马的选择性。研究结果为利用非嗜食植物挥发物防控西花蓟马提供了理论依据和新的方法。     

Effect of spinosad and predatory mites on control of Frankliniella occidentalis in three strawberry cultivars

Western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), is a major pest of strawberry, Fragaria × ananassa Duchesne (Rosaceae). Spinosad is highly efficacious against F. occidentalis, and spinosad is believed to be compatible in an integrated pest management program. This study determined whether F. occidentalis could be controlled with predatory mites [Typhlodromips montdorensis (Schicha), Neoseiulus cucumeris (Oudemans) (both Acari: Phytoseiidae), and Hypoaspis miles (Berlese) (Acari: Laelapidae)] and spinosad in strawberry. In the glasshouse, three strawberry cultivars (Camarosa, Camino Real, and Albion) were sprayed once with spinosad at the recommended rate (80 ml 100 l^?1 rate, 0.096 g a.i. l^?1) or with water (control). Thrips adults were released onto plants 24 h after spraying and predatory mites released 6 days later. Spinosad significantly reduced thrips numbers compared with water. All three mite species reduced F. occidentalis numbers, and spinosad had no effect on predatory mites. Though H. miles could not be counted, the numbers of thrips in treatments with H. miles were lower than those in treatments without the mite. Thrips numbers were lowest on Camino Real and highest on Camarosa. These results suggest that the use of Camino Real with spinosad applications followed by releases of predatory mites can significantly reduce thrips numbers.     

A global invasion by the thrip,Frankliniella occidentalis: Current virus vector status and its management

Western flower thrip, Frankliniella occidentalis (Pergande), is among the most economically important agricultural pests globally, attacking a wide range of vegetable and horticultural crops. In addition to causing extensive crop damage, the species is notorious for vectoring destructive plant viruses, mainly belonging to the genera Orthotospovirus, Ilarvirus, Alphacarmovirus and Machlomovirus. Once infected by orthotospoviruses, thrips can remain virulent throughout their lifespan and continue transmitting viruses to host plants when and wherever they feed. These irruptive viral outbreaks in crops will permanently disrupt functional integrated pest management systems, and typically require a remedial treatment involving insecticides, contributing to further development of insecticide resistance. To mitigate against this continuing cycle, the most effective management is early and comprehensive surveillance of the pest species and recognition of plant viruses in the field. This review provides information on the pest status of F. occidentalis, discusses the current global status of the viruses vectored by this thrip species, examines the mechanisms involved in transmitting virus‐induced diseases by thrips, and reviews different management strategies, highlighting the potential management tactics developed for various cropping systems. The early surveillance and the utilization of potential methods for control of both F. occidentalis and viruses are proposed.