Anisum Essential Oil as a Natural Bio-molluscicide for Slug Control

Terrestrial molluscs (slugs, snails) feed on a wide range of crops, causing considerable crop losses worldwide. They can devastate crops in a short period of time. Furthermore, feeding damage increases crop susceptibility to pathogens. Both are heavily attacked by slugs. It is estimated that the total annual cost to the UK industry from not controlling slugs in arable crops is over £100 million.

Metaldehyde was the main pesticide used to control slugs in arable crops in the UK. It is often detected above the drinking water standard for pesticides. The withdrawal of metaldehyde and several other molluscicides has promoted an urgent search for safe alternatives. An essential oil from anisum seeds shows promise as a benign, sustainable molluscicide. This project focuses on: (1) recovery of the bioactive fraction of oil extracted using an inexpensive microwave-based method and (2) evaluating different formulations of the bioactive fraction. At least two formulations will be evaluated for delivery in drip irrigation, conventional sprayers and drilled during seed sowing or planting. Particular attention will be given to encapsulation of the AEO in inexpensive, proven matrices such as alginate, chitosan and cyclodextrin. Initial trials will be conducted in glasshouse studies with the optimised formulations and carefully selected controls being tested in experimental field trials, conducted on two important arable crops (oilseed rape, wheat). The commercial potential of the products for use as contact molluscicides, repellents and antifeedants will be evaluated by the industry partner, Crop IQ Technology, in field trials which determine optimum application rates and frequency of application.
Development of innovative molluscicides will be of immense benefit to growers in both the agricultural and horticultural sectors. Unlike current products, AEO is short lived, therefore, there should be no residues but this will be verified by GC-MS analysis of plant tissue and produce. This six month study will provide CropIQ the opportunity to determine if the formulations need improvement and for development of business plan with a clear route to market.

Invasive slugs are among the most important pests of home gardens and general commercial crops of agriculture, and horticulture including high-value crops. They incur direct losses in crop yield and quality and increase management costs. Slug damage to vegetable, cereal, grass and legume crops can be extensive near field margins. Grass seed, cereal, and vegetable crop plantings that immediately follow a perennial legume or pasture are likely to sustain slug damage. Thus, slugs constitute a serious menace to agricultural production resulting in a significant economic loss estimated at about £100 million per year as reported by the UK Agriculture and Horticulture Development Board. Slugs also play an important role in transmitting and spreading diseases to livestock, and humans. The current management of slugs relies almost exclusively on synthetic molluscicides, with metaldehyde, ferric phosphate, and methiocarb use currently being the standard practice. Although generally effective and efficient, synthetic molluscicides could be very toxic to pets and are being phased out of the market. Therefore, this project will develop a sustainable and environmentally friendly new molluscicide derived from anisum seeds. The natural molluscicide will be the anisum essential oil (AEO) extracted using microwave-assisted hydrodistillation optimised for the fraction that has the highest bioactive effect. The project will evaluate different formulations in liquid form and encapsulations in inexpensive and proven matrices. Initial trials will be conducted in glasshouse studies with the optimised formulations and carefully selected controls being tested in experimental field trials. The commercial potential of the products for use as contact molluscicides, repellents and antifeedants will be evaluated by the industry partner, Crop IQ Technology, in field trials which determine optimum application rates and frequency of application.