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Biorational alternatives to conventional pesticides based on insect hormones - PS2116

Insect pests of agricultural crops cause damage largely through their feeding activity (larvae of Lepidoptera, Coleoptera, Diptera), but are also responsible for the transmission of plant viruses (aphids), resulting in significant losses in crop yield. Currently, in the UK, the control of these insect pests is achieved primarily through the use of broad-spectrum, neurotoxic insecticides, (organophosphates, carbamates and synthetic pyrethroids). These insecticides are believed to be harmful to the environment, hazardous to humans and wildlife, responsible for biodiversity loss, and toxic to beneficial insects and other invertebrates. There is now a clear recognition to reduce the usage of these broad-spectrum pesticides by introducing less harmful, non-neurotoxic alternatives. Peptides from the insect endocrine system are involved in the regulation of almost all physiological processes including feeding, growth and development, and are seen as an important basis for alternative strategies for biorational insect pest control. By applying peptides at inappropriate times it may be possible to disrupt the physiological processes they normally regulate, resulting in feeding suppression, retarded growth and development, and ultimately death. However, due to the chemical nature of peptides, which are comprised of amino acids, there are problems associated with their stability and delivery to the insect. To exert its effects, the peptide must reach the insect blood, but to do this has to overcome physical and chemical barriers. Insecticides are usually applied topically and therefore must penetrate the insect exoskeleton (cuticle), or are ingested with the food, and therefore must pass through the gut wall to reach the blood. Peptides do not readily penetrate either the insect cuticle or the tissues of the gut. In addition, after oral ingestion, peptides are susceptible to degradation by digestive enzymes in the gut that will render them inactive and hence prevent then exerting their desired effects.This project aims to address these issues to demonstrate that neuropeptides involved in the regulation of feeding can offer viable alternatives to conventional pesticides, using methods to enhance enzyme resistance and peptide delivery across the physical barriers of the gut and cuticle. From previous work we have identified the regions (specific amino acids) of selected feeding suppressive peptides from a UK lepidopteran (moth) pest that are susceptible to gut and/or blood borne enzymes. To counteract this, susceptible amino acids in these moth peptides will be replaced with neutral amino acids or amino acid mimics, which will offer resistance to degradation by enzymes. To enhance the ability of a peptide to penetrate the insect cuticle and/or gut, molecules will be incorporated into the peptides to make them more lipophilic, (or more soluble in oil). These peptide analogues will be created without affecting the ability of the peptide to exert its physiological actions (regulate feeding), which will be evaluated using established procedures on moth larvae (caterpillars). Delivery of peptide analogues with enhanced stability to the insect blood via the gut or cuticle can be used to target the physiological processes the native peptide normally regulates (feeding) as an effective means of control. The effectiveness of orally delivered insect peptides/analogues may also be increased by using compounds, such as enzyme inhibitors to reduce peptide degradation, and biological agents (Bacillus thuringiensis) or growth regulators (chitin synthesis inhibitors) to increase gut permeability thereby promoting peptide uptake into the blood. The wider application of these moth peptides/analogues to reduce conventional, broad spectrum, neurotoxic pesticide use will also be evaluated by testing on other UK pest species such as aphids, fly and/or beetle larvae.
The primary aim of the proposed work is to further our understanding of the endocrine factors (neuropeptides) that regulate feeding, growth and development in insect pests and the key elements affecting their potential use. The oral and/or topical delivery of these peptide hormones to selected UK agricultural pest species will be investigated as a means of biorational pest control. The project will identify ways of enhancing uptake and bioactivity of peptides to demonstrate that insect peptide hormones offer a viable alternative to conventional chemical pesticides. The specific objectives are:

1. To design and synthesise peptide hormone analogues to enhance their stability and/or their hydrophobicity, thereby increasing their effectiveness. Assess the activity, stability and uptake of selected insect peptide analogues as potential anti-feeding factors.

2. To investigate antifeedant/myoinhibitory peptides and/or peptide analogues in a UK pest aphid species.

3. To demonstrate the wider applicability of selected peptide hormones/hormone analogues and their potential to reduce broad-spectrum pesticide usage.

The project as outlined is based on a two year work plan with a break point at the end of the first year to review scientific progress and likelihood of being taken up by LINK or other matched funding at the end of the second year.
Project Documents
• Final Report : Biorational Alternatives to Conventional Pesticides Based on Insect Hormones   (304k)
Time-Scale and Cost
From: 2006

To: 2008

Cost: £335,534
Contractor / Funded Organisations
Central Science Laboratory
Crop Pests              
Pest and Weed Control              
Pest Control              
Pesticide use              
Plants and Animals              
Fields of Study
Pesticide Safety