Risk of Spreading Soft Rot Through Cutting Dips Against Whiteflies in Greenhouse-Grown Poinsettia.

Dipping is a quick and cost-effective technique to reduce pest infestations on unrooted cuttings of greenhouse ornamental crops. Large numbers of cuttings are immersed in an insecticidal treatment, e.g., biopesticides and/or insecticidal soap, before they are stuck in the growing medium and rooted. This research investigated the risk of cross-contamination of poinsettia cuttings with Pectobacterium carotovorum subsp. carotovorum, a potentially devastating pathogen causing soft rot, through the dipping process. Sampling at four commercial greenhouses showed that P. carotovorum subsp. carotovorum was present in all dip suspensions during and after processing poinsettia cuttings; concentrations up to 1 × 105 CFU/ml were detected. A laboratory experiment determined that P. carotovorum subsp. carotovorum-infected cuttings could contaminate clean dip suspensions to similar levels. These results indicated that there is potential for disease transfer during dipping. The potential for cross-contamination of healthy cuttings was evaluated by immersing poinsettia cuttings in dip suspensions artificially inoculated with P. carotovorum subsp. carotovorum (from 1 × 103 to 1 × 107 CFU/ml). Disease incidence increased as P. carotovorum subsp. carotovorum concentrations in the dip suspension increased and the variety 'Prestige Red' was more susceptible than 'Freedom White.' However, even at the highest P. carotovorum subsp. carotovorum concentration of 1 × 107 CFU/ml, the proportion of diseased cuttings was low at 6% for var. 'Freedom White,' but higher at 21% for var. 'Prestige Red.' We conclude that P. carotovorum subsp. carotovorum transfer among unrooted poinsettia cuttings through the dipping process is relatively low although some varieties are sensitive to high levels of inoculum. Even so, strict sanitation practices are still important to prevent build-up of inoculum in the dip treatment.

Amblyseius swirskii in greenhouse production systems: a floricultural perspective.

The predatory mite Amblyseius swirskii Athias-Henriot is a biological control agent that has the potential to play an important role in pest management in many greenhouse crops. Most research on this predatory mite has focused on its use and efficacy in greenhouse vegetables. However, an increasing number of growers of greenhouse ornamental crops also want to adopt biological control as their primary pest management strategy and find that biological control programs developed for vegetables are not optimized for use on floricultural plants. This paper reviews the use of A. swirskii in greenhouse crops, where possible highlighting the specific challenges and characteristics of ornamentals. The effects of different factors within the production system are described from the insect/mite and plant level up to the production level, including growing practices and environmental conditions. Finally, the use of A. swirskii within an integrated pest management system is discussed.

Optimizing Trap Design and Trapping Protocols for Drosophila suzukii (Diptera: Drosophilidae).

Drosophila suzukii Matsumura (Diptera: Drosophilidae) is a recent invasive pest of fruit crops in North America and Europe. Carpophagous larvae render fruit unmarketable and may promote secondary rot-causing organisms. To monitor spread and develop programs to time application of controls, further work is needed to optimize trap design and trapping protocols for adult D. suzukii. We compared commercial traps and developed a new, easy-to-use plastic jar trap that performed well compared with other designs. For some trap types, increasing the entry area led to increased D. suzukii captures and improved selectivity for D. suzukii when populations were low. However, progressive entry area enlargement had diminishing returns, particularly for commercial traps. Unlike previous studies, we found putting holes in trap lids under a close-fitting cover improved captures compared with holes on sides of traps. Also, red and black traps outperformed yellow and clear traps when traps of all colors were positioned 10-15 cm apart above crop foliage. In smaller traps, attractant surface area and entry area, but not other trap features (e.g., headspace volume), appeared to affect D. suzukii captures. In the new, plastic jar trap, tripling attractant volume (360 vs 120 ml) and weekly attractant replacement resulted in the highest D. suzukii captures, but in the larger commercial trap these measures only increased by-catch of large-bodied Diptera. Overall, the plastic jar trap with large entry area is affordable, durable, and can hold high attractant volumes to maximize D. suzukii capture and selectivity.

Host plant effects on the behaviour and performance of Amblyseius swirskii (Acari: Phytoseiidae).

Biological control in ornamental crops is challenging due to the wide diversity of crops and cultivars. In this study, we tested the hypothesis that trichome density on different host plants influences the behavior and performance of the predatory mite Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae). Behavioural observations of this predator in the presence or absence of prey (western flower thrips, Frankliniella occidentalis Pergande) (Thysanoptera: Thripidae) were done on leaf squares of ornamental plant species differing in trichome density (rose, chrysanthemum and gerbera) and compared to a smooth surface (plastic). Tomato leaves were used to observe the influence of glandular trichomes. The performance of A. swirskii was assessed by measuring predation and oviposition rate. Behaviour of A. swirskii was influenced by plant species. Up to a certain density of trichomes, trichome number had a negative effect on walking speed. It was highest on plastic, followed by rose. No differences were found among chrysanthemum, gerbera and tomato. Walking speed was slightly higher on disks without prey. Proportion of time spent walking was the same on leaf disks of all plant species, with and without prey. No effect of glandular trichomes on tomato leaves was seen. Most thrips were killed and consumed on gerbera, and least on rose. Predation rates on chrysanthemum and plastic were intermediate. In contrast, no differences in oviposition rate were found among plant species. The results of this study indicate that trichome density can explain some of the variability in efficacy of A. swirskii on different crops. Release rates of A. swirskii may need to be adjusted depending on the crop in which it is used.

Integration of the Generalist Predator Nabis americoferus (Hemiptera: Nabidae) in a Greenhouse Strawberry Biocontrol Program with Phytoseiid Predatory Mites and the Entomopathogenic Fungus Beauveria bassiana.

In strawberry production, western flower thrips (WFT) and two-spotted spider mites (TSSM) inflict feeding damage and reduce the yield. Biological control for these pests often includes phytoseiid predatory mites and entomopathogenic fungi. The hemipteran family Nabidae have been reported as prominent predators in open-field strawberry. Nabis americoferus Carayon is a new biocontrol agent developed in Canada. This study examined if this species was a good candidate for integration with biological control for greenhouse strawberry production. The laboratory trials showed that Phytoseiulus persimilis Athias-Henriot and Amblyseius swirskii Athias-Henriot were compatible with N. americoferus, especially when alternative food was available. In contrast, the nabid was not compatible with the Beauveria bassiana (Balsamo) GHA strain. A greenhouse cage study was conducted to determine if it was beneficial to add N. americoferus to the phytoseiid-mites-based biological control program for WFT and TSSM in greenhouse strawberry. The release of N. americoferus on a banker plant together with the placement of sachets of Neoseiulus cucumeris (Oudemans) and Neoseiulus californicus (McGregor) was beneficial, not only potentially reducing the number of sachet applications, but also providing better pest control than phytoseiid mites alone. Neither the phytoseiids nor the N. americoferus numbers were significantly affected by the presence of each other.

Laboratory Investigations on the Potential Efficacy of Biological Control Agents on Two Thrips Species, Onion Thrips (Thrips tabaci Lindeman) and Western Flower Thrips (Frankliniella occidentalis (Pergande)).

Thrips biocontrol research in greenhouse crops has focused primarily on western flower thrips (WFT; Frankliniella occidentalis). However, recent outbreaks of onion thrips (OT; Thrips tabaci) in Ontario, Canada, demonstrate that biocontrol-based IPM programs for WFT do not control OT sufficiently to prevent crop losses. A lack of comparative studies makes it difficult to determine which program components for WFT are failing for OT. We conducted several laboratory trials examining the extent to which commercial biocontrol products kill OT compared to WFT. These included phytoseiid mites (Amblyseius swirskii, Neoseiulus cucumeris, Amblydromalus limonicus, Iphiseius degenerans), a large generalist predator (Orius insidiosus), an entomopathogenic fungus (Beauveria bassiana strain GHA), and entomopathogenic nematodes (Steinernema feltiae, S. carpocapsae, Heterorhabditis bacteriophora). In no-choice trials, A. swirskii and O. insidiosus consumed more OT than WFT (first instars and adults, respectively). In choice trials, A. swirskii, N. cucumeris, and O. insidiosus consumed more OT than WFT. Steinernema feltiae caused higher mortality in OT than WFT. There was no difference in mortality between thrips species exposed to other biocontrol agents. This suggests available tools have the potential to manage OT as well as WFT. Possible explanations why this potential is not realized in commercial settings are explored.

Thrips Species Composition in Ontario Greenhouse Floriculture: Innovative Identification Tools and Implications for Integrated Pest Management.

Proper species identification is the keystone of successful integrated pest management (IPM). However, efforts to identify thrips species in Canadian greenhouses have not been formally made since the 1980s. In response to recent increases in crop damage, we sampled thrips communities from eight commercial floriculture greenhouses in the Niagara region (Ontario, Canada) from May until August 2016. Selected sites were revisited in 2017, 2018, and 2019 to determine changes in species composition over time. Western flower thrips (Frankliniella occidentalis (Pergande)), along with onion thrips (Thrips tabaci Lindeman), constituted the majority of species found. Other pest species (less than 8% of specimens across all sampling years) included poinsettia thrips (Echinothrips americanus Morgan), chrysanthemum thrips (Thrips nigropilosus Uzel), and Frankliniella fusca (Hinds). Further investigations of thrips outbreaks in Ontario from 2016 to 2023 revealed other important species, including Thrips parvispinus (Karny), Hercinothrips femoralis (Reuter), and Scirtothrips dorsalis Hood. The current biocontrol strategies used in Ontario floriculture crops for western flower thrips do not adequately control onion thrips or other thrips pests in ornamental crops, making identification a fundamental step in determining whether biocontrol or chemical control strategies should be implemented. However, traditional taxonomic keys are inaccessible to non-specialists due to their technical difficulty. Using the data gathered in these surveys, we developed a simplified, illustrated identification key for use by growers and IPM consultants.

Oviposition Preference of the American Hoverfly, Eupeodes americanus, between Banker Plants and Target Crops.

Assessing the oviposition preferences of predatory hoverflies is a key factor in the prediction of the success of these biological control agents against aphids in greenhouses, especially when using banker plant systems or in mixed-crop contexts. In this study, two aspects of the oviposition preferences of the American hoverfly, Eupeodes americanus (Wiedemann, 1830) (Diptera: Syrphidae), were evaluated. Firstly, the preference between the banker plant and the target crop was evaluated for three banker plant species (barley, finger millet, or corn) and two target crops (cucumber or pepper). Secondly, the preference between the same two target crops was assessed. Female oviposition preferences were evaluated via two-choice experiments using different plant/aphid systems. The results showed that, for the cucumber crops, the species of banker plant used drastically influenced the oviposition preference of the hoverfly, with a preference for barley over cucumber, cucumber over finger millet, and no preference between corn and cucumber. Unlike cucumber, when used with pepper, barley engendered a preference for the target crop. We conclude that the barley banker plant could be adequate for aphid control in pepper but not in cucumber crops. In a mixed-crop context, the American hoverfly had no preference between cucumber and pepper, which means it has the potential to protect both crops in a mixed-crop greenhouse context. This study shows that the banker plant system should be carefully chosen according to the crops/aphids present in the greenhouse to optimize the impact of the hoverfly as a biocontrol agent. Further work is required to confirm this choice of banker plant in semifield or field testing.

Predation, development, and oviposition by the predatory mite Amblyseius swirkii (Acari: Phytoseiidae) on tomato russet mite (Acari: Eriophyidae).

Predation, development, and oviposition experiments were conducted to evaluate Amblyseius swirskii (Athias-Henriot) (Acari: Phytoseiidae) as a potential biological control agent for tomato russet mite, Aculops lycopersici (Massee) (Acari: Eriophyidae), which can be a serious pest of greenhouse tomatoes. Results showed that A. swirskii attacked all developmental stages of A. lycopersici and had a type II functional response at the prey densities tested. The attack rate and handling time estimates from the random predator equation were 0.1289/h and 0.2320 h, respectively, indicating that A. swirskii can consume 103.4 individuals per day. Predation rates of A. swirskii on A. lycopersici in the presence of alternative food sources such as pollen, first-instar thrips, or whitefly eggs were 74, 56, and 76%, respectively, compared with the predation rate on A. lycopersici alone. A. swirskii successfully completed their life cycle on either A. lycopersici or cattail (Typha latifolia L.) pollen. At 25 degrees C and 70% RH, developmental time of female A. swirskii fed on A. lycopersici or on cattail pollen was 4.97 and 6.16 d, respectively. For the first 10 d after molting to the adult stage, A. swirskii fed on A. lycopersici had higher daily oviposition rate (2.0 eggs per day) than on pollen (1.5 eggs per day). From this laboratory study, it can be concluded that A. swirskii has promising traits as a predator against A. lycopersici and that their populations can be maintained using alternative food sources such as cattail pollen. We suggest that the effectiveness of A. swirskii against A. lycopersici under field conditions needs next to be investigated.

Effectiveness of insecticide-treated and non-treated trap plants for the management of Frankliniella occidentalis (Thysanoptera: Thripidae) in greenhouse ornamentals.

The effectiveness of trap cropping as an integrated control strategy against western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), was explored in potted chrysanthemum, Dendranthema grandiflora (Tzvelev), greenhouse crops. The efficacy of flowering chrysanthemum trap plants, either treated with the insecticide spinosad or untreated, to regulate F. occidentalis populations was tested at different spatial scales (small cage, large cage and commercial greenhouse) and for different time periods (1 or 4 weeks). It was demonstrated that flowering chrysanthemums as trap plants lower the number of adult F. occidentalis in a vegetative chrysanthemum crop and, as a result, reduce crop damage. In the 4 week large-cage trial and the commercial trial, significant differences between the control and the trap plant treatments started to appear in the third week of the experiment. Larvae were only significantly reduced by the presence of trap plants in the 1 week small-cage trials. There were no significant differences between treatments with spinosad-treated and untreated trap plants in the number of F. occidentalis on the crop. This suggests that there was minimal movement of adult F. occidentalis back and forth between the trap plants and the crop to feed and oviposit. It is concluded that the trap plant strategy is a useful tool for integrated pest management against F. occidentalis in greenhouses.

Reduced Drosophila suzukii Infestation in Berries Using Deterrent Compounds and Laminate Polymer Flakes.

Drosophila suzukii (Matsumura) is a recent invasive pest of soft fruits in North and South America and Europe. Control relies on frequent applications of synthetic insecticides. Additional tactics are needed for development of an effective integrated pest management program. Study objectives were to evaluate the repellency and oviposition deterrent capability of compounds in plant essential oils and the effect of select compounds on infestation rates in strawberries, using laminate polymer flakes as a carrier. Of 14 compounds from 5 essential oils, thymol was the most repellent to adult D. suzukii males and females for up to 24 h in the laboratory. Citronellol, geraniol and menthol were moderately repellent. In a choice assay, thymol on cotton wicks adjacent to ripe raspberries reduced female fly landings and larval infestation levels. In a no-choice assay, thymol reduced female fly landings by 60%, larval infestation by 50% and increased fly mortality compared to controls. Neither citronellol alone nor a blend of four repellent compounds was as effective as thymol alone at reducing fly landing, larval infestation, or increasing fly mortality. In a choice assay using polymer flakes, larval infestation was greater in raspberries near untreated flakes than in raspberries near flakes treated with thymol or peppermint oil. In the field, thymol and peppermint flakes reduced larval infestation levels by 25% in strawberries at 4, but not 7, days after application, compared to untreated flakes. With future improvements in application strategies, deterrent compounds may have a role in improving the management of D. suzukii.

How to Start with a Clean Crop: Biopesticide Dips Reduce Populations of Bemisia tabaci (Hemiptera: Aleyrodidae) on Greenhouse Poinsettia Propagative Cuttings.

(1) Global movement of propagative plant material is a major pathway for introduction of Bemisia tabaci (Hemiptera: Aleyrodidae) into poinsettia greenhouses. Starting a poinsettia crop with high pest numbers disrupts otherwise successful biological control programs and widespread resistance of B. tabaci against pesticides is limiting growers' options to control this pest; (2) This study investigated the use of several biopesticides (mineral oil, insecticidal soap, Beauveria bassiana, Isaria fumosorosea, Steinernema feltiae) and combinations of these products as immersion treatments (cutting dips) to control B. tabaci on poinsettia cuttings. In addition, phytotoxicity risks of these treatments on poinsettia cuttings, and effects of treatment residues on mortality of commercial whitefly parasitoids (Eretmocerus eremicus and Encarsia formosa) were determined; (3) Mineral oil (0.1% v/v) and insecticidal soap (0.5%) + B. bassiana (1.25 g/L) were the most effective treatments; only 31% and 29%, respectively, of the treated B. tabaci survived on infested poinsettia cuttings and B. tabaci populations were lowest in these treatments after eight weeks. Phytotoxicity risks of these treatments were acceptable, and dip residues had little effect on survival of either parasitoid, and are considered highly compatible; (4) Use of poinsettia cutting dips will allow growers to knock-down B. tabaci populations to a point where they can be managed successfully thereafter with existing biocontrol strategies.