Les Shipp

Approaches to conserving natural enemy populations in greenhouse crops: current methods and future prospects

Biological pest control in greenhouse crops is usually based on periodical releases of mass-produced natural enemies, and this method has been successfully applied for decades. However, in some cases there are shortcomings in pest control efficacy, which often can be attributed to the poor establishment of natural enemies. Their establishment and population numbers can be enhanced by providing additional resources, such as alternative food, prey, hosts, oviposition sites or shelters. Furthermore, natural enemy efficacy can be enhanced by using volatiles, adapting the greenhouse climate, avoiding pesticide side-effects and minimizing disrupting food web complexities. The special case of high value crops in a protected greenhouse environment offers tremendous opportunities to design and manage the system in ways that increase crop resilience to pest infestations. While we have outlined opportunities and tools to develop such systems, this review also identifies knowledge gaps, where additional research is needed to optimize these tools.

Intra-guild vs extra-guild prey: effect on predator fitness and preference of Amblyseius swirskii (Athias-Henriot) and Neoseiulus cucumeris (Oudemans) (Acari: Phytoseiidae)

The relationships between the predatory mites, Amblyseius swirskii (Athias-Henriot) and Neoseiulus cucumeris (Oudemans) (Acari: Phytoseiidae), and their prey, western flower thrips (Frankliniella occidentalis Pergande) (Thysanoptera: Thripidae), were investigated to determine the effects of predation on intra-guild or extra-guild prey and predator preference. Life history characteristics of both predatory mites were measured when fed eggs and larvae of the other predator species and compared to data obtained when the predators were fed thrips larvae. In addition, choice tests were conducted to determine if the predators had a preference for different prey or if they were indiscriminate predators. Amblyseius swirskii appears to be an important intra-guild predator of N. cucumeris juveniles because of a high predation rate and a preference for N. cucumeris juveniles over thrips. Neoseiulus cucumeris is also an intra-guild predator of A. swirskii juveniles; however, it has a lower predation rate than A. swirskii. Contrary to intra-guild predation theory, intra-guild prey was an equally good or better food source than thrips (extra-guild prey) for both predators, based on high oviposition rates and fast development times. The results of this study indicate a high potential for negative interactions between A. swirskii and N. cucumeris when used together in biological control of thrips.

Effect of reduced risk pesticides for use in greenhouse vegetable production on Bombus impatiens (Hymenoptera: Apidae).

BACKGROUND Bumble bees [Bombus impatiens (Cresson)] are widely used for supplemental pollination of greenhouse vegetables and are at risk of pesticide exposure while foraging. The objective of this study was to determine the lethal and sub-lethal effects of four insecticides (imidacloprid, abamectin, metaflumizone and chlorantraniliprole) and three fungicides (myclobutanil, potassium bicarbonate and cyprodinil + fludioxonil) used or with potential for use in Ontario greenhouse vegetable production to B. impatiens. RESULTS Imidacloprid, abamectin, and metaflumizone were harmful to worker bees following direct contact, while chlorantraniliprole and all fungicides tested were harmless. Worker bees fed imidacloprid-contaminated pollen had shortened life spans and were unable to produce brood. Worker bees consumed less pollen contaminated with abamectin. Metaflumizone, chlorantraniliprole and all fungicides tested caused no sub-lethal effects in bumble bee micro-colonies. CONCLUSION We conclude that the new reduced risk insecticides metaflumizone and chlorantraniliprole and the fungicides myclobutanil, potassium bicarbonate and cyprodinil + fludioxonil are safe for greenhouse use in the presence of bumble bees. This information can be used preserve greenhouse pollination programs while maintaining acceptable pest management.

Effect of reduced risk pesticides on greenhouse vegetable arthropod biological control agents

BACKGROUND Arthropod biological control agents (BCAs) are commonly released for greenhouse vegetable insect pest management. Nevertheless, chemicals remain a necessary control tactic for certain insect pests and diseases and they can have negative impacts on BCAs. The compatibility of some formulated reduced risk insecticides (abamectin, metaflumizone and chlorantraniliprole) and fungicides (myclobutanil, potassium bicarbonate and cyprodinil + fludioxonil) used, or with promise for use, in Canadian greenhouses with Orius insidiosus (Say), Amblyseius swirskii (Athias-Henriot) and Eretmocerus eremicus (Rose & Zolnerovich) was determined through laboratory and greenhouse bioassays. RESULTS Overall, the insecticides and fungicides were harmless as residues to adult BCAs. However, abamectin was slightly to moderately harmful to O. insidiosus and A. swirskii in laboratory bioassays, whereas metaflumizone was slightly harmful to E. eremicus. CONCLUSIONS In general, these products appear safe to use prior to establishment/release of these adult BCAs.

Predation, Development, and Oviposition by the Predatory Mite Amblyseius swirkii (Acari: Phytoseiidae) on Tomato Russet Mite (Acari: Eriophyidae)

ABSTRACT 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°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.

Dispersal of Adult Western Flower Thrips (Thysanoptera: Thripidae) on Chrysanthemum Plants: Impact of Feeding-Induced Senescence of Inflorescences

Abstract The current study investigated the interaction among density, feeding impact, and dispersal of western flower thrips, Frankliniella occidentalis (Pergande), on potted flowering chrysanthemum plants. In cage experiments using chrysanthemum plants infested with either 0, 400, 800, or 1,200 thrips, the proportion of senescent inflorescences increased with time and with the number of thrips released on chrysanthemum plants. Positive correlations between the proportion of senescent inflorescences and the density of thrips per inflorescence for different time periods indicate that the feeding activity of thrips causes a premature senescence of inflorescences. On plants infested with 0 or 400 thrips, population density slightly increased for 10–14 d and then leveled off; on plants infested with 800 or 1,200 thrips, in contrast, population density remained high for 7–10 d and then steadily declined to very low levels. A high proportion of senescent inflorescences was positively correlated with the proportion of females that dispersed on blue sticky cards for different time periods, whereas the rate of dispersal by males was not consistently impacted by the quality of inflorescences. Releasing adult thrips marked with fluorescent powder in greenhouses indicated that the quality of inflorescences meditates the dispersal behavior of adult thrips up to a distance of 4 m: females are more likely to disperse from senescent than healthy inflorescences and preferentially colonize healthy inflorescences over senescent inflorescences. The dispersal behavior of adult thrips has important implications in terms of sex-specific optimal reproductive strategies, sampling procedures, and population dynamics.

Density, dispersal, and feeding impact of western flower thrips (Thysanoptera: Thripidae) on flowering chrysanthemum at different spatial scales

Abstract.  1. This study evaluated the effect of dispersal on the density and feeding impact of a phytophagous insect in relation to the spatial distribution of its host plants.

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.

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.

Evaluation of various types of supplemental food for two species of predatory mites, Amblyseius swirskii and Neoseiulus cucumeris (Acari: Phytoseiidae)

Although phytoseiids are best known as predators of phytophagous mites and other small arthropods, several species can also feed and reproduce on pollen. In laboratory assays, we assessed the profitability of two types of dietary supplements (three pollen species—cattail, maize and apple—and eggs of the Mediterranean flour moth, Ephestia kuehniella) for the two species of predatory mites most commonly used as biocontrol agents in horticulture in Canada, Neoseiulus cucumeris and Amblyseius swirskii. We measured the effects of each diet on phytoseiid fitness parameters (survival, development, sex ratio, fecundity) and, as a means of comparison, when fed larvae of the common targeted pest species, western flower thrips Frankliniella occidentalis. A soluble protein assay was also performed on the alternative food sources as protein content is often linked to high nutritive value according to the literature. All food sources tested were suitable for N. cucumeris and A. swirskii, both species being able to develop from egg to adult. The dietary supplements had a beneficial impact on biological parameters, mostly resulting in shorter development times and higher survival rates when compared to thrips larvae. Amblyseius swirskii exhibited a wider dietary range than N. cucumeris. Overall, flour moth eggs, cattail pollen and apple pollen are food sources of equal quality for A. swirskii, whereas apple and cattail pollen are better when it comes to N. cucumeris. In contrast, maize pollen is a less suitable food source for N. cucumeris and A. swirskii. Soluble protein content results did not match the prediction under which the most beneficial food source would contain the highest concentration in protein.