Certain insect pests, including aphids, beetles, flies, locusts, mites, moths, true bugs, are so destructive that they cause billions of pounds’ worth of damage to the agricultural and horticultural sectors and to other industries, across the UK and worldwide.
Traditionally, pest management has been handled by growers reaching for the most available or the cheapest chemical pesticide to kill a pest. Although modern chemical pesticides are generally highly effective and safe when used properly, there is widespread public concern about their use in terms of their effects on the environment in general and the presence of chemical residues on produce. As a result, chemical pesticides are heavily regulated so that the cost of bringing a new product to market is high, and the number of active ingredients permitted for use by growers is reducing rapidly. Equally important for growers is that continued use of pesticides, whether applied as synthetic chemicals or in the form of genetically modified crops, can lead to resistance to the insecticide in the target pest.
Alternative approaches to controlling insect pests are being developed that minimise or avoid the use of chemical pesticides. These include cultural approaches, use of resistant crop varieties, application/enhancement of pathogens, predators and parasites of the pests, and use of behaviour-modifying chemicals (e.g. pheromones). These can be combined in an ‘integrated pest management’ (IPM) approach, which is now mandatory in EU countries under Directive 2009/128/EC.
What is NRI's solution?
NRI's Chemical Ecology Group was one of the pioneering groups in research on insect pheromones in the 1960s and was the first to develop one of the key research techniques. Pheromones are chemical compounds used for signalling between members of the same species. Insects rely heavily on chemical signals such as pheromones for many vital functions including finding food, mates and suitable places to lay eggs. By identifying and synthesising the pheromones used by pest species of insect, it’s possible to produce powerful tools to interfere with these functions and develop new approaches to pest control.
Pheromones are natural products and generally without toxic effects on animals, plants or the environment. They are often highly biologically active, and so only small amounts are required to have an effect. Their biological activity is also often highly specific, so they act only on the target species.
The Group has identified and synthesised the pheromones of over 50 pest species, and, more importantly, worked with a wide range of collaborators worldwide to exploit their use in management of insect pests. Although the Group produces synthetic pheromones and formulations for research purposes, transferring the technology to commercial suppliers is essential for uptake by growers. The Group has always worked closely with agrochemical companies who specialise in this type of approach and four examples are highlighted below.
Innovations and outcomes
Pine sawyer beetle (Monochamus provincialis) is a vector of the pine wood nematode (PWN), an invasive pest from China introduced into EU through Portugal in 1999. Eighty million Euro has been spent attempting to eradicate PWN in Portugal; Three million Euro was spent to contain three isolated outbreaks in Spain.
The institute participated in the EU projects ‘PHRAME’ and ‘REPHRAME’ which aimed to prevent the spread of PWN into the rest of Europe. The team identified and synthesised a male-produced aggregation pheromone attracting both male and female beetles. In collaboration with University of Valladolid, Spain, the team developed a lure consisting of pheromone and kairomones in controlled-release dispensers, which was used to monitor beetles and the presence of PWN. Control by mass trapping was demonstrated. The pheromone was found to attract twelve other species of Monochamus beetles in Europe, China, US and Canada; it is now known as ‘monochamol’. The lures were patented and sold in Europe by SEDQ, Barcelona, Spain. In 2017, trapping beetles was proposed for surveillance as part of the UK Contingency Plan for the PWN (Bursaphelenchus xylophilus) and its longhorn beetle (Monochamus spp.) vectors.
Capsids, or capsid bugs (Heteroptera, Miridae, Mirinae) are common and important pests of many horticultural and some agricultural crops worldwide, causing severe economic losses, especially in strawberries, raspberries, blackcurrant, apple, pear, and cotton. In conventional crops they have been controlled by sprays of broad-spectrum insecticides, but their use is increasingly restricted. In organic crops they cause high levels of damage because the insecticides available are inadequate and of short persistence. Capsids have few natural enemies and effective biocontrol methods have not been developed for them. They present a bottleneck in the development of IPM programmes.
The institute identified and synthesised female-produced sex pheromones of four species of capsid in the UK and developed a slow-release dispenser. This was the first time that reliable attraction of capsids to a synthetic lure had been achieved in over 30 years of research worldwide on these pheromones. Subsequently, the institute has identified pheromones for the three main species of capsids in the US and shown the new dispensing system is effective. The institute supplies lures for sale in the UK through Agralan for monitoring the pest and over 22,000 lures have been supplied during the last five years. The institute has also provided many thousands of lures to collaborators, particularly NIAB-EMR, with whom the institute demonstrated control of capsids using a push-pull system combining the pheromone with a repellent which they identified. The institute has also provided lures to the Strawberry Commission and Cotton Growers in California, USA.
Thrips, sometimes known as thunderbugs, are minute, slender insects with fringed wings and unique asymmetrical mouthparts. Different thrips species feed mostly on plants by puncturing and sucking up the contents, although a few are predators. Frankliniella occidentalis, known as the western flower thrips (WFT) causes bronzing of fruit and has become difficult to control because of resistance to insecticides and lack of effective alternative biological controls. Financial losses can be high, exceeding £15m to the UK industry alone. Except for Spotted wing drosophila, WFT is currently the most serious pest of UK strawberry and financial losses can be high. WFT is difficult to control because it is resistant to all pesticides available to UK strawberry growers and because biocontrol with the predatory mite Amblyseius cucumeris sometimes fails.
The team has identified and patented a pheromone for the WFT that is sold through Syngenta Bioline (now Bioline Agrosciences Ltd.). This was taken up by Russell IPM in Optiroll for control of thrips. Russell IPM were awarded the Queen’s Award for Innovation 2018.
Midges are a group of insects that include many kinds of small flies. There are many different species of midge, some of which are vectors of diseases and others are pests of a wide range of horticultural crops. Examples include the Apple leaf curling midge (Dasineura mali), a monophagous pest of apples in northern Europe, New Zealand, North America and Argentina, and the Raspberry cane midge (Resseliella theobaldi) larvae, which feed on raspberry canes and are associated with the disease complex known as ‘midge blight’ in much of Europe.
The institute has identified pheromones for: Raspberry cane midge, Apple leaf midge, Pear leaf midge, Pear midge, Blackcurrant leaf midge, Blackberry leaf midge, Blueberry midge, Saddle gall midge, Chrysanthemum gall midge, Honey locust gall midge, Rice gall midge and Canola flower midge. The institute jointly patented the novel structural motif of pheromone of apple leafcurling midge and raspberry cane midge. Over the last five years, the institute has provided the following numbers of lures to Agralan and Russell IPM: Raspberry midge – 5,636, Blueberry midge – 25,169, Blackcurrant midge – 331, Blackberry midge – 16,405, Apple midge – 637, Pear midge – 45.