No abstract

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.

Fungus gnats (FG) (Diptera: Sciaridae: Bradysia spp.) are economically important pests of greenhouse flowers. Larvae feed on root tissue and transmit a variety of phytopathogens. Atheta coriaria (Kraatz) (Coleoptera: Staphylinidae) is a new biological control agent (BCA) for FG. To support its successful use by the greenhouse industry, its compatibility with current integrated pest management (IPM) programs used in floriculture was assessed. This included investigations of prey preference, possible detrimental interactions with other soil-dwelling BCAs, and the toxicity to A. coriaria of registered and novel insecticides. Atheta coriaria showed little preference among eggs of different pest species or between pest eggs and eggs of the intraguild predator Hypoaspis aculeifer (Canestrini) (Acari: Mesostigmata: Laelapidae). It preferred FG 1st-instar larvae to larvae and pupae of other soil-dwelling pests. The entomopathogenic nematode Steinernema feltiae (Filipjev) (Rhabditida: Steinernematidae) was compatible with A. coriaria, but H. aculeifer mites fed on A. coriaria larvae. Insect growth regulators with limited contact activity (e.g., diflubenzuron) were compatible with adult A. coriaria and had minimal effects on larvae compared with other insecticides. Atheta coriaria can be incorporated into an IPM program for FG if harsh insecticides are avoided, but interactions with predatory mites, as well as its effectiveness against other greenhouse pests when FG are present, require further investigation.

No abstract

Western flower thrips, Frankliniella occidentalis (Pergande) (Thysanoptera: Thripidae), is a serious pest of greenhouse vegetable and ornamental crops across Canada (Broadbent et al. 1987). Upon completing larval development, F. occidentalis either pupates on their host plant or drops to the ground before pupation occurs (Lewis 1973). Because several soil-dwellers prey on or infect F. occidentalis pupae (Gillespie and Quiring 1990; Helyer et al. 1995), assessing the proportion of individuals that pupate on the ground is of critical importance for developing pest management strategies. The present study provides the first quantitative assessment of the pupation behaviour of F. occidentalis.

Bemisia tabaci (Gennadius) is an economically important pest of agricultural and ornamental plants worldwide and is now widely recognized as a cryptic species complex. In North America, B. tabaci is a particularly important pest of greenhouse poinsettia. In poinsettia production, two cryptic species from the B. tabaci complex, Mediterranean and Middle East Minor 1, often infest crops simultaneously. Differences in pesticide susceptibility between these two cryptic species have the potential to influence growers' management decisions, including the use of biological control or insecticides, and the choice of insecticide active ingredient. However, the demographic behavior of mixed-species infestations in commercial greenhouses has yet to be investigated. We conducted a survey of B. tabaci populations in commercial greenhouses in Ontario, Canada, and provide evidence that under biological control-based management, Middle East Minor 1 can displace Mediterranean, whereas under insecticide-based management Mediterranean populations will persist. Furthermore, we comment on implications of this behavior on the management of B. tabaci, and comment on methods used to identify B. tabaci cryptic species.

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.

(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.