Gut content analysis to study predatory efficacy of Nesidiocoris tenuis (Reuter) (Hemiptera: Miridae) by molecular methods

Nesidiocoris tenuis is considered to make significant contributions to the control of greenhouse pests such as whiteflies, thrips, leafminers, lepidopterans, and spider mites, although there is little information based on direct observation of the predation of N. tenuis on these target pests. We developed a method to perform gut content analysis of N. tenuis based on DNA in which specific PCR primers were designed to detect the DNA of target pests. By means of gut‐content analysis, we found that the percentage of N. tenuis preying on Bemisia tabaci and Thrips palmi was approximately 40% in the field.     

Ornamental pepper as banker plants for establishment of Amblyseius swirskii (Acari: Phytoseiidae) for biological control of multiple pests in greenhouse vegetable production

Silverleaf whitefly, Bemisia tabaci biotype B (Gennadius) (Hemiptera: Aleyrodidae), western flower thrips, Frankliniella occidentalis (Pergande), and chilli thrips, Scirtothrips dorsalis Hood (Thysanoptera: Thripidae), are key pests of vegetable crops in the US. The present study established ornamental peppers as banker plants supporting Amblyseius swirskii (Acari: Phytoseiidae) against the three pests. Specifically, this study (a) evaluated survival and population buildup of A. swirskii on three ornamental pepper varieties, Masquerade (MA), Red Missile (RM), and Explosive Ember (EE) in both laboratory and greenhouses and (b) determined the predation of A. swirskii reared on ornamental pepper plants to the targeted pests under greenhouse conditions. The results showed that the three pepper varieties were excellent banker plants and able to support at least ∼1000 of all stages of A. swirskii per plant in greenhouse conditions and allow them to complete their life cycle. A. swirskii dispersed or released from the banker plants to target plants, resulting in significant suppression of the three pests, i.e., after 14 d post-release, a significantly lower average of 2.75 B. tabaci and 13.4 all stages of thrips (chilli thrips and western flower thrips) were found per bean plant, respectively, compared to 379.5 B. tabaci and 235.4 all stages of thrips per plant in the control. Furthermore, our experiment observed that the sweet pepper seedlings closed to banker plants were healthy, whereas those without banker plants were heavily infested by chilli thrips; their growth seriously stunted or died. This is the first report of ornamental pepper as banker plants supporting A. swirskii against three notorious pests. This established banker plant system could be a new addition to the integrated pest management programs for sustainable control of these three pests in greenhouse vegetables.     

Control of <Emphasis Type="Italic">Bemisia tabaci</Emphasis> and <Emphasis Type="Italic">Frankliniella occidentalis</Emphasis> in cucumber by <Emphasis Type="Italic">Amblyseius swirskii</Emphasis>

Bemisia tabaci Genn. (Hemiptera: Aleyrodidae) and Frankliniella occidentalis (Thysanoptera: Thripidae) are major pests in greenhouse grown cucumber crops. Recently, Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae) was shown an effective biological control agent of both pests. Hence, perhaps both pests can be controlled simultaneously by this predator. However, with simultaneous infestation of both pests, synergistic effects, or interference could affect biological control and perhaps require changes in release rates of the predator. Thus, the aim of the present study was to evaluate different release rates of A. swirskii to control both pests under a worst case scenario of rapid immigration into a cucumber greenhouse. Two experiments were conducted, one simulating the influx of whiteflies alone (whitefly experiment) and the other immigration of whiteflies and thrips together (whitefly plus thrips experiment). Three treatments were compared in the whitefly experiment: (1) B. tabaci alone, (2) B. tabaci + 25 A. swirskii m⁻² and (3) B. tabaci + 75 A. swirskii m⁻². The high release rate was more effective than the low rate in controlling B. tabaci alone. The high rate was subsequently tested against B. tabaci and F. occidentalis for the whitefly and thrips experiment in which five treatments were compared: (1) B. tabaci alone, (2) F. occidentalis alone, (3) B. tabaci + 75 A. swirskii m⁻², (4) F. occidentalis + 75 A. swirskii m⁻² and (5) B. tabaci + F. occidentalis + 75 A. swirskii m⁻². This rate of A. swirskii controlled whiteflies and thrips either alone or together. Therefore, 75 A. swirskii m⁻² should be an adequate rate for controlling both pests either alone or simultaneously in cucumber greenhouses.     

Molecular Detection and Complete Genome Sequences of Tomato chlorosis virus Isolates from Infectious Outbreaks in China

Tomato chlorosis virus (ToCV) is a whitefly‐transmitted, phloem‐limited, bipartite Crinivirus. In 2012, severe interveinal symptoms characteristic of ToCV infections were observed in greenhouse tomato plants in the Shandong province of China. High levels of infestation by whiteflies (Bemisia tabaci), which transmit ToCV, were also observed on tomato plants in all the greenhouses investigated. The presence of ToCV was confirmed by specific RT‐PCR either in the sampled plants or in the whiteflies collected from the ventral surface of the leaves of diseased plants. The complete genomic nucleotide sequences (RNA1 and RNA2) of the Shandong isolate of ToCV (ToCV‐SDSG) were determined and analysed. ToCV‐SDSG RNA1 consisted of 8594 nucleotides encompassing four open reading frames (ORFs). ToCV‐SDSG RNA2 consisted of 8242 nucleotides encompassing nine ORFs. Phylogenetic analysis suggests that the Chinese ToCV‐SDSG isolate is most similar to the ToCV‐Florida isolate.     

Reduction of sooty mold damage through biocontrol of the greenhouse whitefly <Emphasis Type="Italic">Trialeurodes vaporariorum</Emphasis> (Hemiptera: Aleyrodidae) using selective insecticides in tomato cultivation greenhouses

The proliferation of sooty mold on tomato fruit, Solanum lycopersicum L.—as caused by the secretion of honeydew on the fruit by greenhouse whitefly, Trialeurodes vaporariorum (Westwood) (Hemiptera: Aleyrodidae)—has recently become a serious problem in estivo-autumnal greenhouse tomato cultivation in Japan. It is becoming increasingly difficult to control T. vaporariorum using insecticides because whiteflies have developed resistance to a variety of insecticides. As the first step towards integrated pest management, we examined whether the use of selective insecticides could prompt a cascade process in which an increase in parasitoids is followed by a decrease in whitefly occurrence and then a reduction in sooty mold damage. We compared greenhouses in which nonselective insecticides effective against T. vaporariorum and its parasitoids were used (hereafter denoted “nonselective insecticide greenhouses”) with greenhouses in which selective insecticides for T. vaporariorum were used (hereafter denoted “selective insecticide greenhouses”) in terms of the density and level of parasitism of T. vaporariorum as well as the degree of damage from sooty mold. The number of parasitized whiteflies increased with the number of whiteflies in the selective insecticide greenhouses, whereas it remained at low levels regardless of the number of whiteflies in the nonselective insecticide greenhouses. Furthermore, the selective insecticide greenhouses showed significantly higher parasitism levels, fewer whiteflies, and reduced sooty mold damage compared to the nonselective insecticide greenhouses. These results suggest that the use of selective insecticides causes an increase in parasitism, which in turn suppresses the number of greenhouse whiteflies and, eventually, sooty mold.     

Sharing a predator: can an invasive alien pest affect the predation on a local pest?

Invasive species can strongly affect biotic interactions in ecosystems, interacting both directly and indirectly with local species. In European tomato greenhouses, the invasive alien pest Tuta absoluta may impact the population dynamics of other pests like whiteflies. Besides inducing damages to the host plant and competing for resources with local pests, this alien species may exert a predator-mediated interaction on local pests sharing common natural enemies. Biocontrol agents usually used against whiteflies may also prey upon T. absoluta and this could alter the dynamics of local pest populations. We evaluated possible resource competition and predator-mediated interactions in a system involving one mirid predator Macrolophus pygmaeus and two pests, T. absoluta and a local whitefly, Bemisia tabaci, on greenhouse tomatoes. Results showed that both resource competition and predator-mediated interactions occurred simultaneously. In the presence of the shared predator, there was a short-term positive effect of T. absoluta on B. tabaci [up to 5.9-fold increase of B. tabaci juveniles (egg + larvae) after four weeks]. However, in the long-term there was a negative predator-mediated interaction of T. absoluta on B. tabaci, i.e., after ten weeks the density of B. tabaci was 7.3-fold lower in the presence of the invasive pest. We emphasize the critical role of generalist predators in managing both local and invasive alien pest populations and that the strength and direction of predator-mediated indirect interactions can depend on the time scale considered.     

Acquisition of Tomato yellow leaf curl virus enhances attraction of Bemisia tabaci to green light emitting diodes

The light sensitivity of insects varies in response to different wavelengths of light. The change of light responses of vector insects plays an important role in the method of transmission and propagation of plant viruses. Here, we investigated whether the light attraction behaviors of whiteflies are altered by virus acquisition. Firstly, the light attraction rates of whiteflies were determined using LED light bulbs exhibiting different wavelengths in the visible and UV spectra. Whiteflies, Bemisia tabaci and Trialeurodes vaporariorum, were mostly attracted to green LEDs (526 nm). The attraction rate to green LED light was higher in B. tabaci than in T. vaporariorum, whereas it did not significantly differ between the B- and Q-biotypes of B. tabaci. Secondly, we investigated whether or not the green light attraction behavior of B. tabaci is influenced by the acquisition of Tomato yellow leaf curl virus (TYLCV). The attraction rate to green LED light was 2.5–3 times higher in TYLCV-infected whiteflies than in TYLCV-free whiteflies. However, this difference disappeared when the distance from the light source was greater than 0.5 m. Our results show that B. tabaci favors green light and its attraction is highly enhanced by the acquisition of the plant virus, TYLCV.     

Factors that affect the selection of tomato leaflets by two whiteflies,Trialeurodes vaporariorum and Bemisia tabaci (Homoptera: Aleyrodidae)

In Japan, although greenhouse whitefly, Trialeurodes vaporariorum (Westwood), and sweet potato whitefly, Bemisia tabaci (Gennadius), co-occur on tomato plants under greenhouse conditions, the two whiteflies are distributed differently with regard to leaf position. To elucidate the factors that determine the leaf position of these whiteflies, we investigated traits for leaflets collected from three positions on tomato plants. Furthermore, we examined leaflet selection by and fertility of the two whiteflies under choice and non-choice conditions. In addition, the effect on whitefly behavior of volatile compounds released from leaflets was evaluated by use of a Y-tube olfactometer test. Nitrogen and carbon content were highest for upper leaflets. In choice tests, more T. vaporariorum and B. tabaci adults selected upper and middle leaflets, respectively. Similarly, they oviposited more eggs on upper and middle leaflets. In non-choice tests, T. vaporariorum oviposited more eggs on upper leaflets, but B. tabaci oviposited equally on each leaflet. In Y-tube olfactometer tests, more T. vaporariorum adults moved to upper leaflets whereas more B. tabaci adults moved to middle leaflets. These results suggest that different leaflet selection by adults of these two whiteflies is likely to be associated with the different volatile compounds emitted by tomato leaflets at each position.     

Incidences and progression of tomato chlorosis virus disease and tomato yellow leaf curl virus disease in tomato under different greenhouse covers in southeast Spain

Epidemics of whitefly‐transmitted Tomato chlorosis virus, Tomato yellow leaf curl Sardinia virus and Tomato yellow leaf curl virus have been present in the south east of Spain since the 1990s. A survey was performed in 40 greenhouses and nethouses during 2003 to establish the relationship between the disease incidence and the quality of greenhouse or nethouse coverings, providing a physical protection of crops against whiteflies. For tomato chlorosis virus disease (ToCD), the incidence correlated with the type of greenhouse cover and was most reduced under higher quality covers. Control of tomato yellow leaf curl disease (TYLCD) was achieved only for crops grown in the highest quality greenhouses. TYLCD incidence in tolerant tomatoes remained below 100% within the 5 months of sampling, despite the disease progress rate at the initial stage of the cultivation being higher than that of ToCD, which did reach 100% incidence in many greenhouses. Linear regression analysis showed that the development of ToCD and TYLCD in most of the greenhouses was best described by the monomolecular model and the Gompertz model, respectively. Tomato infectious chlorosis virus was not detected in parallel surveys carried out during this study, although it has been described previously in the area studied.     

A Plant Virus Manipulates the Behavior of Its Whitefly Vector to Enhance Its Transmission Efficiency and Spread

Plant viruses can produce direct and plant-mediated indirect effects on their insect vectors, modifying their life cycle, fitness and behavior. Viruses may benefit from such changes leading to enhanced transmission efficiency and spread. In our study, female adults of Bemisia tabaci were subjected to an acquisition access period of 72 h in Tomato yellow leaf curl virus (TYLCV)-infected and non-infected tomato plants to obtain viruliferous and non-viruliferous whiteflies, respectively. Insects that were exposed to virus-infected plants were checked by PCR to verify their viruliferous status. Results of the Ethovision video tracking bioassays indicated that TYLCV induced an arrestant behavior of B. tabaci, as viruliferous whitefly adults remained motionless for more time and moved slower than non-viruliferous whiteflies after their first contact with eggplant leaf discs. In fact, Electrical Penetration Graphs showed that TYLCV-viruliferous B. tabaci fed more often from phloem sieve elements and made a larger number of phloem contacts (increased number of E1, E2 and sustained E2 per insect, p<0.05) in eggplants than non-viruliferous whiteflies. Furthermore, the duration of the salivation phase in phloem sieve elements (E1) preceding sustained sap ingestion was longer in viruliferous than in non-viruliferous whiteflies (p<0.05). This particular probing behavior is known to significantly enhance the inoculation efficiency of TYLCV by B. tabaci. Our results show evidence that TYLCV directly manipulates the settling, probing and feeding behavior of its vector B. tabaci in a way that enhances virus transmission efficiency and spread. Furthermore, TYLCV-B. tabaci interactions are mutually beneficial to both the virus and its vector because B. tabaci feeds more efficiently after acquisition of TYLCV. This outcome has clear implications in the epidemiology and management of the TYLCV-B. tabaci complex.     

Field trials measuring the effects of ultraviolet-absorbing greenhouse plastic films on insect populations

Field studies were conducted to compare insect population levels in greenhouse crops covered with plastics that block the transmission of UV light in two wavelength ranges. Crops grown in greenhouses under a plastic that blocked UV light at wavelengths of 380 nm and below had lower numbers of aphids and thrips compared with a plastic that blocked UV light at wavelengths of 360 nm and below. This is consistent with the results found for thrips in previous studies using small, completely enclosed tunnels with no plant material. The effects were not as dramatic in the commercial greenhouses, perhaps due to unfiltered light entering through the open sides of those greenhouses. There was no reduction in greenhouse whitefly, Trialeurodes vaporariorum Westwood, populations under the <380 UV-absorbing plastic compared to <360 nm UV-absorbing plastic in these field trials. This is inconsistent with results found in small, completely enclosed tunnels, where sticky traps caught a significantly higher proportion (95 +/- 2%) of released greenhouse whiteflies inside tunnels covered with <360 nm absorbing plastic compared with the <380 nm absorbing plastic. The results of these studies suggest that the type of greenhouse plastic used in a structure can affect population levels of some insect species, and may be useful tools in developing integrated pest management programs for insect management. The design of the greenhouse and amount of unfiltered light that enters the system appear to be important factors in determining the level of effect.     

Prey suitability of western flower thrips,Frankliniella occidentalis,and onion thrips,Thrips tabaci,for the predatory mite Amblyseius swirskii

Western flower thrips, Frankliniella occidentalis, and onion thrips, Thrips tabaci, are both important polyphagous pests of vegetables and ornamentals in greenhouses. Difficulties in biological control of these pests have prompted a search for new natural enemies. Most recently, the predatory mite Amblyseius swirskii has been commercialised as biological control agent of whiteflies and thrips. However, little is known about the suitability of thrips as prey for A. swirskii. We therefore assessed prey acceptance and life history of A. swirskii when feeding on F. occidentalis and T. tabaci at 25±1°C. Amblyseius swirskii juveniles preyed upon first larval instars of both F. occidentalis and T. tabaci but suffered from high mortality (67 and 78%). Developmental time (egg to adult) of A. swirskii was 7.8 days with either prey species. Adult A. swirskii females readily accepted first larval instars of both thrips species, which were attacked in <20 min on a leaf and <10 min in an artificial cage. Oviposition rates (0.92 and 0.99 eggs/female/day) and offspring sex ratios (63 and 70% females) were similar with F. occidentalis and T. tabaci as prey. Less than one-third of juveniles reaching adulthood and oviposition rates below one egg/female per day resulted in relatively low intrinsic rates of increase (r _m) (0.056 and 0.024 per day with F. occidentalis and T. tabaci, respectively). Altogether, our study suggests that the recently reported superiority of A. swirskii to the widely used Neoseiulus cucumeris in suppression of thrips is due to other traits than its population growth capacity with thrips as prey.     

Colour preference and potato cultivar oviposition choice by onion thrips,Thrips tabaci (Thysanoptera: Thripidae)

Thrips tabaci (Lindeman) is an important polyphagous pest, and vector of Tomato spotted wilt virus responsible for sporadic, but devastating epidemics in potato. T. tabaci shows significant preferential differences between potato cultivars that may be important for field resistance. To investigate the role of visual cues in host choice we tested colour preference using two-choice assays. Thrips tabaci showed a significant preference for mid-green over red, blue, and white coloured cards, a preference for both light-green and mid-green over dark-green, and light-green over yellow, but no preferential difference between mid-green and yellow, and between light-green and mid-green. Analysis of the spectral reflectance of potato cultivars differing in thrips preference, revealed significant differences within the 400–700 nm wavelengths. In most cases cultivars preferred by T. tabaci had lighter green foliage and higher reflectance at 552 nm, and thus colour preference may be important for host selection. Oviposition choice of T. tabaci for potato cultivars was determined from counts of larvae and unhatched eggs from leaf disks under choice and no-choice conditions. In contrast to the colour choice experiments, onion thrips showed oviposition preference for cultivars with darker green foliage and lower reflectance at 552 nm.     

Laboratory and greenhouse evaluation of a new entomopathogenic strain of Beauveria bassiana for control of the onion thrips Thrips tabaci

Abstract

The onion thrips Thrips tabaci is one of the most important pests of greenhouse and open-field broccoli, onion and other crops. However, the current strategy of using synthetic pesticides for its control is inadequate and unsustainable, leading to a growing interest in novel and effective biological control alternatives such as entomopathogenic fungi. Among 20 isolates of Beauveria bassiana tested for virulence against T. tabaci in laboratory bioassays, we found strain SZ-26 as the most potent, causing 83–100% mortality in adults at 1×10⁷ mL^?1conidia after 4–7 days. Further experiments in greenhouses showed the strain SZ-26 significantly lowered the numbers of adult and larval stages.     

Biological control of thrips [Thysanoptera: Thripidae] on greenhouse cucumber byAmblyseius cucumeris

The predatory miteAmblyseius cucumeris (Oudemans) [Acarina: Phytoseiidae] was evaluated as a biological control forThrips tabaci Lindeman andFrankliniella occidentalis (Pergande) [Thysanoptera: Thripidae] on greenhouse grown seedless cucumber.A. cucumeris spread throughout the greenhouses and provided control of both species of thrips.A. cucumeris adults persisted on plants for 7 weeks in the virtual absence of prey, and increased numerically in response to increases in prey population. On the basis of these resultsA. cucumeris is recommended as a useful biological control forT. tabaci andF. occidentalis on greenhouse cucumber. Publication No. 361, Agassiz Research Station, Agriculture Canada, Agassiz, B.C. Canada VOM 1AO.     

Evaluation of the indigenous parasitoid Encarsia transvena (Hymenoptera: Aphelinidae) for biological control of the whitefly Bemisia tabaci (Hemiptera: Aleyrodidae) in greenhouses in India

The efficiency of the native parasitoid, Encarsia transvena Timberlake for the management of greenhouse whitefly, Bemisia tabaci (Gennadius) was studied in cages and a greenhouse in India. Parasitism by Enc. transvena of B. tabaci on Lycopersicon esculentum L. (tomato), Solanum melongena L. (eggplant) and Nicotiana tabacum L. (tobacco) was evaluated in cages to compare the utility of each species as potential banker plants. B. tabaci populations were consistently present on all three host plant species for almost two months providing sufficient hosts for parasitoid multiplication. Significantly more B. tabaci nymphs/unit leaf area were found on N. tabacum (77.7) and on S. melongena (76.5) than L. esculentum (45.9) in the initial growing period of the plants, that increased more on L. esculentum as the crops grew older. A greater proportion of B. tabaci were parasitised by Enc. transvena on L. esculentum than on N. tabacum and S. melongena. Rate of parasitism on L. esculentum was 25.19 and on N. tabacum was 24.70 in greenhouse. Parasitism, although occurring throughout greenhouses, was greatest on plants within 3 metres of introduced banker plants. The results suggest the utility of the three plant species as potential banker plants for the management of whiteflies in greenhouses.     

Specific Insect-Virus Interactions Are Responsible for Variation in Competency of Different Thrips tabaci Isolines to Transmit Different Tomato Spotted Wilt Virus Isolates

Local adaptation between sympatric host and parasite populations driven by vector genetics appears to be a factor that influences dynamics of disease epidemics and evolution of insect-vectored viruses. Although T. tabaci is the primary vector of Tomato spotted wilt virus (TSWV) in some areas of the world, it is not an important vector of this economically important plant virus in many areas where it occurs. Previous studies suggest that genetic variation of thrips populations, virus isolates, or both are important factors underlying the localized importance of this species as a vector of TSWV. This study was undertaken to quantify variation in transmissibility of TSWV isolates by T. tabaci, in the ability of T. tabaci to transmit isolates of TSWV, and to examine the possibility that genetic interactions and local adaptation contribute to the localized nature of this species as a vector of TSWV. Isofemale lines of Thrips tabaci from multiple locations were tested for their ability to transmit multiple TSWV isolates collected at the same and different locations as the thrips. Results revealed that the probability of an isofemale line transmitting TSWV varied among virus isolates, and the probability of an isolate being transmitted varied among isofemale lines. These results indicate that the interaction of T. tabaci and TSWV isolate genetic determinants underlie successful transmission of TSWV by T. tabaci. Further analysis revealed sympatric vector-virus pairing resulted in higher transmission than allopatric pairing, which suggests that local adaptation is occurring between T. tabaci and TSWV isolates.     

Infection of tomato by Tomato Yellow Leaf Curl Virus alters the foraging behavior and parasitism of the parasitoid Encarsia formosa on Bemisia tabaci

Encarsia formosa Gahan is a solitary endoparasitoid that is commercially reared and released for augmentative biological control of whiteflies including Bemisia tabaci (Gennadius). Bemisia tabaci biotypes B and Q are two most invasive species that greatly reduce crop yields in China by feeding on plant sap and by transmitting Tomato Yellow Leaf Curl Virus (TYLCV). The effects of TYLCV infection of tomato on E. formosa foraging on B. tabaci B and Q are unknown. In Y-tube olfactometer assays in the present study, E. formosa significantly preferred TYLCV-infected tomato plants over TYLCV-free plants. The wasp females also significantly preferred TYLCV-infected tomato plants infested with 3rd-instar nymphs of B. tabaci biotype Q over TYLCV-free plants with biotype Q nymphs. However, no significant differences were observed when B. tabaci biotype B was infested on tomato plants. The oviposition bioassays confirmed that TYLCV infection on tomato plants resulted in the recruitment of parasitoids. These results indicate that TYLCV-infection of tomato increase the foraging of E. formosa on B. tabaci, as differs on the B and Q biotypes.     

Evaluation of efficacy of Neoseiulus cucumeris for control of western flower thrips in spring bedding crops

Western flower thrips, Frankliniella occidentalis (Pergande), is the principal insect pest of spring flower crops grown in the northeastern United States for use as bedding plants. Neoseiulus (=Amblyseius) cucumeris (Oudemans) is a predacious mite reared commercially that is recommended for control of western flower thrips in various vegetable and flower crops at a rate of ca 53 mites/m²/week. Efficacy on spring flower crops, however, is not well demonstrated, reports being either from other crops or extension demonstration trials. In two trials (each replicated), we compared suppression of western flower thrips in spring bedding plants provided by (1) N. cucumeris at the recommended rate, (2) spinosad (at the labeled rate), the most widely used thrips-control pesticide, and (3) both combined. Trial No. 1 was run in mixed bedding plants in commercial greenhouses and Trial No. 2 in impatiens monocultures in University greenhouses. We found that in commercial greenhouses, variation in species composition of crops and movement of plants during crop production made it difficult to detect any significant effects. In an impatiens monoculture (Trial No. 2), we found better evidence of partial suppression of thrips larvae and adults by treatments. Spinosad alone provided the best control, with mites alone usually providing control intermediate to that of spinosad alone and the untreated control. Control from spinosad plus mites was not significantly different from that of spinosad alone (all treatments evaluated as counts of thrips per plant, in flowers). In another University-based trial (Trial No. 3), we compared the commercially recommended rate of N. cucumeris (53 mites/m²/week) to a 3- to 4-fold higher rate (190 mites/m²/week) in impatiens monocultures. This trial was replicated twice in the fall of 2004 and once in spring of 2005 in Amherst, Massachusetts. We found that the higher release rate, while not resulting in statistically significantly more mites per plant (in flowers) than the standard rate, did suppress thrips larvae per plant (in flowers) by 50–75%, a higher level than that achieved by the recommended standard rate. No reductions, however, were found in counts of adult thrips, either as numbers per plant (in flowers) or as numbers caught per yellow sticky card, except for one replication in which thrips counts were lowered compared to controls by mites (at both release rates). We conclude that N. cucumeris, especially at the higher rate, provides partial control of western flower thrips in impatiens bedding plants, but that control from spinosad is better. Biological control of western flower thrips with this predator is not a complete thrips IPM program, but may be used together with spinosad or other materials to prevent development of pesticide resistance. This approach is most likely to be of value in crops grown as continuous relay plantings or a series of different, but thrips-susceptible, crop species.