Learned predators enhance biological control via organizational upward and trophic top-down cascades

Dietary experience alters predatory behavior of two ladybird species on tomato potato psyllid

The tomato potato psyllid, Bactericera cockerelli, is an invasive pest in Australia, which can cause severe economic loss in the production of Solanaceous crops. As an invasive pest, B. cockerelli may also modify biotic interactions in Australian agricultural and native ecosystems. Resident generalist predators in an area may have the ability to utilize invasive pest species as prey but this will depend on their specific predatory behavior. The extent to which generalist predators learn from their previous dietary experience (i.e., whether they have used a particular species as prey before) and how this impacts subsequent prey choice will influence predator and prey population dynamics after invasion. In this study, one nonnative resident ladybird, Hippodamia variegata, and one native ladybird, Coccinella transversalis, were investigated. Dietary experience with B. cockerelli as a prey species significantly increased preference for the psyllid in a short term (6 h) Petri dish study where a choice of prey was given. Greater suppression of B. cockerelli populations by experienced ladybirds was also observed on glasshouse grown tomato plants. This was presumably due to altered prey recognition by experience. The result of this study suggest the potential to improve the impact of biological control agents on invasive pests by providing early life experience consuming the target species. It may prove valuable for developing improved augmentative release strategies for ladybirds to manage specific insect pest species.

Overview of Updated Control Tactics for Western Flower Thrips

Frankliniella occidentalis Pergande (Thysanoptera: Thripidae), broadly known as Western flower thrips (WFT), are currently one of the most critical pests worldwide in field and greenhouse crops, and their management is full of yet unsolved challenges derived from their high reproductive potential, cryptic habit, and ability to disperse. The control of this pest relies widely on chemical control, despite the propensity of the species to develop resistance. However, significant advances have been produced through biological and ethological control. Although there has recently been a remarkable amount of new information regarding the management of this pest worldwide, there is no critical analysis of recent developments and advances in the attractive control tactics for WFT, constituting the present compilation's aim. Hence, this narrative review provides an overview of effective control strategies for managing thrips populations. By understanding the pest's biology, implementing monitoring techniques, accurately identifying the species, and employing appropriate control measures, farmers and researchers can mitigate the WFT impact on agricultural production and promote sustainable pest management practices.

Why are phytoseiid predatory mites not effectively controlling Echinothrips americanus?

The poinsettia thrips, Echinothrips americanus Morgan (Thysanoptera: Thripidae), is a key pest of various ornamental and vegetable greenhouse crops. As current biological control alternatives lack efficiency, applying chemicals remains the dominant control strategy, thereby heavily disturbing the biocontrol-based integrated management of other pests. For a range of other thrips pests, phytoseiid predatory mites have shown to be effective biocontrol agents, being able to overcome the thrips' physical and chemical defense armory. Here, we investigated potential underlying causes for the lack of phytoseiid efficacy in controlling E. americanus. First, we assessed the nutritional value of E. americanus for the predatory mite Amblydromalus limonicus (Garman and McGregor) (Acari: Phytoseiidae) when its physical or chemical defenses were eliminated by freezing the thrips. The phytoseiid could complete its immature development when frozen thrips instars were offered, but not when these were offered alive. Subsequently, we tested whether adult female A. limonicus had a higher predation rate on first instar E. americanus when they had been given experience with either live or frozen E. americanus during their immature development (i.e., conditioning). Conditioning significantly increased the predation capacity of the phytoseiid. Finally, we tested the control potential of conditioned A. limonicus versus naïve ones when exposed to E. americanus on sweet pepper plants. In contrast to the laboratory trials, at the plant level, conditioning did not yield better control. Possible factors explaining insufficient control of E. americanus by phytoseiids are discussed.

Tomato Potato Psyllid Bactericera cockerelli (Hemiptera: Triozidae) in Australia: Incursion, Potential Impact and Opportunities for Biological Control

Incursion and establishment of an exotic pest may threaten natural habitats and disrupt ecosystems. On the other hand, resident natural enemies may play an important role in invasive pest control. Bactericera cockerelli, commonly known as the tomato-potato psyllid, is an exotic pest, first detected on mainland Australia in Perth, Western Australia, in early 2017. B. cockerelli causes direct damage to crops by feeding and indirectly by acting as the vector of the pathogen that causes zebra chip disease in potatoes, although the latter is not present in mainland Australia. At present, Australian growers rely on the frequent use of insecticides to control B. cockerelli, which may lead to a series of negative economic and environmental consequences. The incursion of B. cockerelli also provides a unique opportunity to develop a conservation biological control strategy through strategically targeting existing natural enemy communities. In this review, we consider opportunities to develop biological control strategies for B. cockerelli to alleviate the dependence on synthetic insecticides. We highlight the potential of existing natural enemies to contribute toward regulating populations of B. cockerelli in the field and discuss the challenges ahead to strengthen the key role they can play through conservation biological control.

Egg Predation by Phytoseiid Predatory Mites: Is There Intraguild Predation Towards Predatory Bug Eggs?

Phytoseiid predatory mites are efficient biocontrol agents of important thrips pests, such as the western flower thrips, Frankliniella occidentalis Pergande (Thysanoptera: Thripidae). Until recently, it was believed that first instars, and to a lesser extent second instars, were the most vulnerable developmental stages of thrips to be attacked by phytoseiids. However, recent evidence showed that some phytoseiids can detect and prey upon thrips eggs inserted in the leaf tissue. As phytoseiid predatory mites often co-occur with other beneficial insects, such as mirid and anthocorid predatory bugs which also insert their eggs inside leaf material, this raises the question whether phytoseiid predatory mites may also feed on predatory bug eggs. Here we first tested the potential of Amblyseius swirskii Athias-Henriot, Transeius montdorensis Schicha, and Amblydromalus limonicus Garman and McGregor (Acari: Phytoseiidae) to kill eggs of F. occidentalis in leaf tissue. Secondly, we tested whether those phytoseiids were capable of killing eggs of Orius laevigatus Fieber (Hemiptera: Anthocoridae), Macrolophus pygmaeus Rambur and Nesidiocoris tenuis (Reuter) (Hemiptera: Miridae), three biocontrol agents that also insert their eggs inside plant tissue. Our results showed that A. swirskii and A. limonicus could kill thrips eggs, whereas T. montdorensis could not. Furthermore, we show that the presence of phytoseiid predatory mites does not affect the hatch rate of predatory bugs that insert their eggs inside leaves.

Spatiotemporal limitations in plant biology research

The way we currently capture biological processes in space and time often limits our understanding of plant development and stress responses, leading to an incomplete picture of plant life. Choosing the correct time frame for the study of every biological process, from seed germination to senescence or in plant stress responses, is essential, despite methodological limitations. A greater effort is needed in current plant biology studies to incorporate spatiotemporal approaches so that scientific knowledge meets the possibilities technological advances currently provide. From molecular, biochemical, and cellular approaches to (eco)physiological and population studies scaled up to the ecosystem level, there is an urgent need to link space and time using integrative and scalable data.