Background

Each year in North America, millions of dollars are spent protecting stored grain from insect pests. In Canada, there is zero tolerance for live insects in stored grain. Synthetic insecticides and fumigants are the main methods used to control stored-product insects, but consumer demands, pest resistance, problems with insecticide residues, and product withdrawal have prompted the search for alternative control measures.

The Technology

In response to the need for alternate approaches of insect control with safe and effective natural products, especially from food-grade materials, scientists at Agriculture and Agri-Food Canada’s Saskatoon and Winnipeg Research Centres, in co-operation with Parrheim Foods of Saskatoon, have studied the anti-insect properties of field pea flour and experimental extracts derived from protein-rich field pea flour. Protein-rich pea flour and its extracts were found to be toxic and repellent to several stored-product insects.

Air-classified pea flour produced by Parrheim Foods (Saskatoon) was used to examine the insecticidal properties and components of field peas. In granary trials, protein-rich pea flour at 0.1% controlled the rice weevil, one of the most damaging stored-grain insects in the world, and reduced by 70% the rusty grain beetle and the red flour beetle, the most common insect pests of stored grain in Canada. The insecticidal activity of the flour has good stability. Unlike most insecticides, it did not adversely affect two beneficial insects that attack the pest insect species.

Experimental extracts (referred to here as C8 extracts) have been isolated from protein-rich pea flour that were 20 to 100 times more toxic than the pea flour itself (US patent 5,955,082; Canadian patent 2,278,501). The isolation process employed chloroform defatting, aqueous methanol extraction and chromatography with C8 silica, and resulted in a complex mixture of natural products. The key natural products of C8 extracts have been separated and purified in the laboratory by thin layer, flash, ion exchange and high performance liquid chromatography (HPLC). Some of the components and mixtures derived from C8 extracts reduce the feeding and survival of the rice weevil. Insecticidal and synergistic components from C8 extracts were subsequently identified using various techniques including HPLC and mass spectrometry.

Research Plans

To facilitate product development and registration, additional research is needed on the large-scale production of crude insecticidal extracts from pea flour, eliminating the use of chloroform (a hazardous solvent) in defatting and C8 silica (an expensive chromatographic adsorbent) in the purification. Conditions of alcohol composition, temperature of extraction, time of extraction and flour to solvent ratios have been studied in laboratory-scale experiments with pea flour, omitting the chloroform defatting and C8 silica steps. The optimized conditions will be transferable to a pilot plant facility, starting with larger quantities of protein-rich pea flour.

The research will be facilitated by HPLC monitoring of the concentration of insecticides and synergists in large-scale isolates. Optimum ratios of insecticides to synergists are known from bioassays with rice weevil (determined by formulating and testing mixtures), but these ratios may be different for other insects. The crude, C8-like extracts will likely need to be further purified, but using techniques that do not rely on C8 silica, which is expensive. Once the standardized insecticidal pea extracts are available in quantity, appropriate end-use formulations need to be developed, and efficacy tests need to be expanded to granary trials with stored-product insects and other pest insects.

Economics

During the extraction of insecticidal components with alcohol, about 80% of the pea flour is left as an insoluble byproduct. Commercial applications for this byproduct also need to be exploited as an additional product with some value. Solvent recovery and reuse will be desirable from an economical viewpoint when insecticidal products are isolated in production-scale runs.

Advantages

This extract exhibits insecticidal properties against several pests of stored grains, and is a naturally occurring component of field peas – a food crop. Insect populations have developed resistance to malathion, and some buyers do not want to purchase wheat with malathion residues. Application of phosphine requires a specialized licence that many producers do not have.

Extracts derived from protein-rich field pea flour offer potential commercial applications in the control of insects attacking stored grains in home, farm, or elevator locations. As larger quantities become available, opportunities will exist to evaluate appropriately synergized pea extracts against other insect pests.

Opportunity to Collaborate and License

AAFC is seeking collaboration with an interested party or parties for further product development and to license this technology for commercialization.