Biocontrol

Many insect herbivores rely on symbiotic bacteria for their survival. These ‘hidden players’ residing in insect tissues can affect fitness of the insect host. For example, some insect species show increased resistance to natural enemies when certain ‘protective’ symbiotic bacteria are present, which could make it more difficult to control pest infestations.

Under favourable conditions, parasitoid wasps can be effective natural enemies of aphids and they are frequently deployed to control infestations in glasshouses and polytunnels. Parasitoid wasps insert their eggs into the aphid body, from which a larva emerges that consumes and eventually kills the aphid. However, in the presence of certain protective symbionts, the parasitoid egg fails to develop.

Blackleg (including soft rot) of potato is a devastating disease for which there are no chemical treatments. Disease control is particularly important for the seed potato industry as the pathogen, once present, increases in population through seed generations. Since the 1960s, disease has been controlled by ventilated storage, seed certification, good hygiene and more recently by managing seed imports (safe haven scheme and Government legislation). While disease incidence is much reduced than 50 years ago, it still remains a major problem both in Europe and beyond.  Over the last 5 years blackleg disease appears to be on the increase although the reasons for this are not clear.  At the Institute we are focussing on 4 control measures to be included in the blackleg IPM strategy.

Reduction in the availability and quality of plant food resources through arable intensification and habitat fragmentation has been cited as a major cause of the decline in pollinators in the UK and worldwide, and is likely to have a negative impact on the activity and abundance of natural enemy species that rely on floral resources in their adult life stages. Many pollinator and natural enemy groups disperse over large distances in search of pollen and nectar, and this might be exacerbated in intensively-managed systems with low resource diversity. Alternative management systems that lead to increases in resource availability and quality for these insects are therefore likely to promote both diversity, through niche differentiation, and fitness, by reducing the need for insect foraging over large distances. Thus, management to increase within-field and farm-scale vegetation diversity is one option to combat declines in pollinator populations and promote numbers and activity of natural enemies.

We have been breeding raspberry varieties for Scotland, UK and Europe for > 40 years.  A key trait (conferred by one or more major resistance genes) is for resistance to the main aphid pest, the large raspberry aphid. This strategy has been very successful but over decades the pest has co-evolved resistance-breaking biotypes. We are now at a ‘tipping point’ where the pest can overcome resistance genes in the crop faster than plant breeders can introduce new types of resistance (typically taking  10+ years).

Bacterial pathogens pose a serious threat to either plant health or to food safety.  This has the consequence of financial impacts on crop production for pathogens that causes disease on plants, or human health impacts for food-borne pathogens transmitted into the food chain by plants.  One of the main challenges to producers is that there are few control options available for reducing or removing bacterial pathogens from plants, and growers have to resort to a limited set of biocides that can cause environmental damage, such as the active ingredient copper oxychloride.  This means that a pre-emptive approach is a more sustainable option, e.g. by reducing the risk of pathogens introduction from seeds or transplants and in irrigation water, or for endemic pathogens, using alternative strategies to keep their numbers at manageable, non-harmful levels.  These approaches require a degree of monitoring to ensure that the control levels are adequate, since the aim is to keep pathogen levels sufficiently low that they do not cause visible damage to crop plants, or for the food-borne pathogens, that they do not pose a food safety issue.