A biopesticidal lease of life for crop protection : additive manufacturing for tailored timing of biopesticide release by natural triggers

The need to meet the increasing demand for food while growing crops more sustainably is a major global challenge. For more sustainable crop production, there is an urgent need to reduce reliance on synthetic chemical pesticides on farms, as these have led to impoverished soils, widespread pest and disease resistance, water contamination and a significant loss of biodiversity. In the UK, there are presently around 2,400 authorised plant protection products (PPPs) based on synthetic chemistry, but far fewer sustainable options such as biopesticides, e.g., naturally occurring microorganisms that inhibit spread of crop pests. Of the latter, only a small handful are permitted on arable crops. This absence of effective, alternative options means growers are presently unable to meet demands from consumers, environmental bodies and policy makers, for a more sustainable approach to farming. This is exacerbated by poor efficacy of existing biopesticides. One fundamental reason for their poor efficacy is that biospesticides generally do not maintain the necessary concentrations in the environment for suitable amounts of time. Therefore, they may no longer be active when they are most needed, as pests proliferate; and it is not feasible for farmers to try to time their deployment through ongoing crop monitoring. This project will establish an interdisciplinary community to redress this problem.

The timeliness for the project is clear: if we are to change our farming habits to help create healthier soils, cleaner water and safer, more sustainable farming we need action to give growers the correct tools to make it happen. To provide such tools, we will introduce additive-manufacturing capability to engineer the encapsulation and delivery of biopesticidal fungal spores via concepts similar to those used for 3D printed 'polypills' in biomedicine. That is, the pest controlling organisms will be incorporated into polymeric 'capsules' and their release controlled and driven by the very same environmental triggers as those that signal the growth of the pests - the controlling organisms would emerge at the same time as the pests, giving rise to a timely biological competition during which the biopesticide can act optimally and plant growth can thrive.

For proof-of-concept in this project, we will focus on fungal release from manufactured capsules using moisture and pH triggers (each of which is a common indicator coincident with pest proliferation), tested using selected fungi representative of a range having biopesticidal potential against important pests such as cyst nematodes (which are responsible for significant losses of arable crops in the UK and globally). Our technical work will deliver optimisation of fungal-spore encapsulation and environmentally-triggered release in conjunction with biological assay of fungal viability and outgrowth pre- and post-release. This work will be complemented by close engagement with key industry partners and stakeholders to guide development towards application of the proposed technology. The investigators comprise a new, inter-disciplinary collaboration of scientists based at academic and non-academic organizations, with expertise encompassing fungal biology, additive manufacturing and biopesticides. Positive progress in this project will crystallize the focus of a community of key players and beneficiaries around development of the biopesticidal capsules and the common mission to slow or reverse the deterioration of our crop production by pests.

Our goal is to develop an additive manufactured capsule with a multi-fungi payload, each of which can be timed to deliver when most needed, providing an alternative to synthetic pesticides.

Work Package 1
We will use extrusion-based additive manufacturing systems to create capsules that will package biopesticides in a way that allows them to be released at some predetermined time after planting or under specific conditions. We will develop formulations that a) allow for additive manufacturing via extrusion, requiring the development of pastes of suitable rheology, b) package the biopesticides such that they are protected and remain viable when they are released from the capsule and c) are triggerable, either via an external stimulus or via changes in the environment, such as a change in hydration or pH.

Work Package 2
We will use five known pest / disease pathogens from different genera and representing a range of morphologies and physicochemical characters. This diversity will be important for informing optimal capsule design which, depending on results, might be tailored for different fungal biopesticide species. The results of viability assessment, undertaken post printing, will allow us to gauge and optimize the relative performance of different encapsulation agents and decomposition protocols in offering the greatest recovery, on cue, of viable biopesticide.

Work Package 3
WP3 will evaluate the performance of the capsules and condition of released fungi in soil conditions, enabling us to assess the level of efficacy of our approach for controlled release of biopesticides in soils, before moving to true field-like conditions in follow up work. We will assess the compatibility of combining biopesticide and plant growth-promoting strains within the same capsule, allowing us to optimise the combinations which are likely to be successful in the field.