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Opinion now favours a shift away from the reliance on conventional insecticides towards the use of more natural, sustainable methods of protecting crops from insect damage. This bulletin considers alternatives which could be used as storage grain protectants, concentrating particularly on plants which have found other uses as food spices or for medical application.

Over 100 plant species are described in the review. Difficulty arose in defining what classified a plant as a spice as opposed to a herb or other edible material. All edible plant materials with potential as control agents have been considered to avoid confusion. At the current time, only a few plant species have been sufficiently tested in the laboratory to indicate their potential usefulness as protectants. These are all from the genera Azadirachta, Acorus, Chenopodium, Eucalyptus, Mentha, Ocimum, Piper, Tetradenia or are traditional vegetable oils.

Research which has been undertaken is described briefly and discussed but it is evident that far more research is required to critically evaluate most of the plants as stored product protectants, particularly with respect to mammalian toxicity and residual action. Very little information exists concerning actual use by farmers of botanical grain protectants, nor has the efficacy of the materials been assessed under real conditions of use on farms.

The situation for Azadirachta indica (Neem) is slightly different; commercial formulations of the product have recently been registered for application to horticultural and agricultural crops in the USA. Neem has been extensively studied in several forms against a wide range of storage pests on various commodities, but results from standardised long-term trials are still required. There is no evidence that any other spice or medicinal has been commercialised.

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