The prospect of applying chemical elicitors and plant strengtheners to enhance the biological control of crop pests

Abstract

An imminent food crisis reinforces the need for novel strategies to increase crop yields worldwide. Effective control of pest insects should be part of such strategies, preferentially with reduced negative impact on the environment and optimal protection and utilization of existing biodiversity. Enhancing the presence and efficacy of native biological control agents could be one such strategy. Plant strengthener is a generic term for several commercially available compounds or mixtures of compounds that can be applied to cultivated plants in order to 'boost their vigour, resilience and performance'. Studies into the consequences of boosting plant resistance against pests and diseases on plant volatiles have found a surprising and dramatic increase in the plants' attractiveness to parasitic wasps. Here, we summarize the results from these studies and present new results from assays that illustrate the great potential of two commercially available resistance elicitors. We argue that plant strengtheners may currently be the best option to enhance the attractiveness of cultivated plants to biological control agents. Other options, such as the genetic manipulation of the release of specific volatiles may offer future solutions, but in most systems, we still miss fundamental knowledge on which key attractants should be targeted for this approach.

Delivering sustainable crop protection systems via the seed: exploiting natural constitutive and inducible defence pathways

“…The greater investment in root systems will offer other advantages for water and nutrient utilization. However, more attention must be given to root protection and wider conservation and exploitation of the rhizosphere [13]. The stabilization of rural populations in genuinely increased intensification of sustainable food production will remove the persistent and progressive depopulation of rural regions to towns.…”

Tomato treatment with chemical inducers reduces the performance of Spodoptera littoralis (Lepidoptera: Noctuidae)

“…In this study, we used a relatively low concentration of 0.15 g/l (BTH) and 2 mM (PDJ), which corresponds to the recommended dose of the manufacturer for field application to induce pathogen resistance or fruit ripeness, respectively. These concentrations were previously used on a monocot (maize) and a dicot (cotton) plant with no observed phytotoxic signs (Mandour et al 2013;Sobhy et al 2012Sobhy et al , 2014Sobhy et al , 2015. In particular, a BTH concentration of 0.15 g/l is less than onefifth of the 0.8 g/l that was applied by Inbar et al (2001).…”

“…Our results demonstrate that BTH and PDJ can act synergistically when applied to tomato to reduce the performance of S. littoralis. Given the fact that these chemical inducers have low toxicity and potential compatibility with natural enemies (Sobhy et al 2014), we expect that they can be a benign and sustainable tactic for improved crop protection.…”

“…An accumulating body of studies shows that the exogenous application of chemical inducers could provide a novel strategy to protect crop plants against insect pests (Pickett et al 2014;Sobhy et al 2014). For instance, plant treatment with cis-jasmone, a catabolic derivative of JA, reduces the performance of various aphid species (Bruce et al 2003;Hegde et al 2012;Moraes et al 2008).…”

Achieving food and environmental security: new approaches to close the gap

“…Turlings and co-workers [24] explain the potential for improving plant performance by means of plant strengtheners or elicitors as agents that, when applied to crop plants, would boost their vigour, resilience and performance. Evidence from currently available compounds, such as the commercial compound acibenzolar-S-methyl and the natural product laminarin in increasing release of attractants for improved conservation biological control of herbivorous pests by parasitoids (i.e.…”