PROJECT RESULTS

Natural Insecticides Derived from Peas

Applicant: 

Dr. Paul Fields

Cereal Reseach Centre
Agriculture and Agri-Food Canada
Winnipeg, Manitoba  R3T 2M9  Canada

Table of Contents:

• Background and Objectives
• Procedure and Project Activities
• Results and Discussion
• Conclusions

ARDI Project:

#98-156

Project Status:

Completed January, 2001

Background and Objectives:

Insects in grain after harvest cause economic loss to producers and the grain industry. Canada maintains a policy to keep export grain insect-free to enjoy a reputation for quality, and thereby gain a preferred price for its grain. The three most common methods of insect control for post harvest are: aeration of grain, chemical treatment with malathion, or fumigation with phosphine.

In some years, fall temperatures are too high to control insects until well into November. Also, many farm bins and elevators do not have aeration equipment. Therefore, insect control through aeration can be problematic.

The Canadian Grain Commission and the Canadian Wheat Board discourage the use of malathion on grain as some customers require grain free of chemical residues. Resistance to malathion in populations of the rusty grain beetle is growing in Manitoba, and this may lead to control failures in the future.

Phosphine is the method of choice for many producers and elevator operators. However, it is an extremely toxic compound and must be handled with great care. In the past, producers could purchase phosphine at their local grain elevator and apply it themselves. However, there has been a change in the phosphine label, and now all people who use phosphine will have to be licensed by the province. In Manitoba, this will require successful completion of two courses, and until producers take the courses they will have to hire applicators to treat their grain for them. Also, because of the increased insurance liability for transporting and storing, some elevators no longer sell phosphine. These factors will make it more expensive to use phosphine to control insects in farm bins. Recent reports also indicate that insect resistance to phosphine is rapidly spreading throughout the world.

Previous work has shown that:

1. Commercially available protein-enriched pea flour acts a repellant, insecticide, antifeedant, and can reduce egg laying in stored-product insect pests.
2. We have developed a simple chemical extraction of the protein-enriched pea flour that increases the insecticidal activity a hundred-fold. This technique has been granted a USA patent (Bodnaryk et al. 1997) and a patent is pending in Canada.
3. There is a significant range of susceptibility within different species of stored-product insects.
4. The extracts have been tested against other insect pests and some have been shown to be susceptible.

The objectives of the project were to investigate applications of the pea derived insecticide/repellent that could be used to control stored-product insect pests in bulk grain, food processing facilities, and packaged cereal foods. This study will provide data needed to convince a pesticide company to develop this technology into a marketable product.

Procedure and Project Activities:

Granaries
The field trials where conducted at the Field Station of the Cereal Research Centre at Glenlea, Manitoba. Six 30-tonne capacity galvanized metal bolted-steel farm granaries were filled with 11 tonnes of barley in each granary. Barley harvested on August 19, 1999, with a moisture content of 12.9% was taken from the farm of the University of Manitoba at Glenlea, Manitoba. Barley was dusted with pea protein when loaded into granaries with a grain auger at a speed of 0.5 tonnes/minute. There were three treatments: all barley treated at 0.1% pea protein; the top half treated with 0.5% pea protein and the bottom half untreated; and untreated. There were two bins for each treatment.

Insects
The insects were reared in the laboratory at 30°C, 70% RH. The rice weevil and red flour beetle were laboratory strains, and had been cultured in the laboratory for over five years. The rice weevil was reared on whole kernels of wheat and the red flour beetle was reared on wheat flour mixed with 5% brewer’s yeast. The rusty grain beetle was a mixture of two-thirds of laboratory strain (reared in the laboratory for over five years) and one-third of a field strain, which was collected from the field in April, 1999. The rusty grain beetle was reared on wheat kernels, with 5% wheat germ and 5% brewer’s yeast.

The insects were sieved out of the rearing medium and placed 4,400 rice weevil, 4,400 red flour beetles, and 3,000 rusty grain beetles per 4-L jar containing 2.5 kg barley taken from bins until the insects were released into boxes placed in the bins. Five boxes (30´30´30 cm) with a plastic screened bottom (2 mm² openings) were buried so that the top edge of the box was level with the top surface of the grain mass. One box was located in the centre of the bin and the other four boxes were placed half way between the centre and the bin wall at each of the compass points. The screened bottom allowed insects to move freely between the release boxes and the grain mass. Boxes and the grain in the boxes were removed 10 days after insects had been released. The number of insects remaining in the boxes was counted after the grain was sieved with a dockage tester. For the rice weevil and the red flour beetle, there were approximately 2 insects/kg of barley or 22,000 insects per species per bin. For the rusty grain beetle, there were about 1.4 insects/kg of barley or 15,000 insects per bin.

Temperature
A data logger (CR10, Campbell Scientific (Canada) Corp.) was used to record the temperature. In each bin there were 12 thermocouples: three depths (just below the surface, midway and just above floor, 4 cm, 30 cm and 155 cm from the top surface, respectively) at four locations (20 cm from the north granary wall, 93 cm from the north granary wall, the granary centre, and 93 cm from the south wall). Temperature was recorded every hour.

Sampling
There were ten sample points in each bin, five at the surface and five one metre below the surface. About one kg barley was taken from each point on September 9, September 23, October 7 and October 21, 1999. A 0.3-L torpedo probe sampler was used for the one metre samples and a cup was used for the surface layer samples. In the laboratory, the grain samples were sieved using a sieve with two mm² openings. The adult insects were removed and the species and number living and dead were noted. The rest of the sample was placed in a 4-L jar and held at 30^oC, 70% RH for five weeks, when the grain was sieved a second time and the insects counted to give an estimate of immature stages in the grain at the time of sampling.

Insect populations were also monitored by checking the number of insects in four kinds of traps: surface pitfall traps, flight traps, probe pitfall traps, and sticky bar traps (Figure 3, 4). Surface pitfall traps (Storgard Flit-Trak M², Trécé Inc.) with corn oil and flight traps (25 cm diameter paper plates covered with TangleFoot®) were placed on the surface of the grain bulk at the five sampling points. Pitfall probe traps (Storgard WB Probe II) were inserted into the grain surface or 1 m deep at each sample point. A wooden board (5 cm by 10 cm by 250 cm long) smeared with TangleFoot®, was marked in five equal sections and placed underneath the entirely perforated floor of the granaries. Insects caught by all traps were counted and removed every week.

Results and Discussion:

Insecticide-Repellant In Bulk Grain

Grain temperature
There were no differences in mean grain temperature among bins (13.7 ± 0.1^oC, range 36.0 to -5.8 ^oC). The maximum head space temperature was 40.4^oC. During the first three weeks, the temperature was between 25 to 20^oC, 20 to 15^oC in the third to fifth weeks, 15 to 10^oC in sixth and seventh weeks, and 10 to 5^oC in the eighth to eleventh weeks.

Grain samples
There were fewer live adults, of all species, in the treated grain than the untreated grain (Table 1). There was no difference between 0.1% pea protein (all grain treated) and 0.5% pea protein (top half of the grain bulk treated). No rice weevils were found alive in grain samples in the bins treated with 0.1% pea protein on September 23 and after. There were few live rice weevils in the untreated lower level in the bin treated with 0.5% pea protein in the top half on October 21 and later. The red flour beetle and the rusty grain beetle had reduced numbers, but were not eliminated by the end of the trials.

There were fewer immatures in the grain in the treated grain than the untreated grain (Table 1). There was no difference between 0.1% and 0.5% pea protein treatments.

Table 1. The mortality of insects found in grain samples taken from bins with 11 t barley treated either by mixing 0.1% pea protein throughout the entire grain bulk, or mixing 0.5% pea protein in the top half compared with a control with no pea protein. Offspring response was measured by incubating samples for five weeks at 30^oC and counting live adults.

Traps
The interpretation of the trap data are complicated as there are several factors that can effect trap catch: the number of live insects in the grain, the rate of movement of the insects which is reduced at low temperatures and which increases when insects are exposed to repellants.

In many cases, the traps caught more insects in the treated bins than the untreated bins, even though the number of live insects decreased over the experiments. For the probe pitfall traps the rice weevil initially was caught more in the treated grain, but by the end of the trial there were more caught in the control. A significant number of rusty grain beetles left the bin via the perforated floor. Averaging the number caught per surface area and extrapolating this to the entire bin, we estimate that 5,760, 7,410 and 6,210 rusty grain beetles (control, 0.1% and 0.5% pea protein treated bins, respectively) left the bin through the perforated floor. Splitting the bin into a inner and outer section, our estimations were: 6,420, 11,050 and 9,501 rusty grain beetles leaving the bins. This is significant considering only 15,000 insects were released into the each bin.

Conclusions:

Rice weevil
Treating barley with 0.1% pea protein controlled the rice weevil in farm sized grain stores. Treating the top one metre of the grain bulk did not prevent insects from reaching the untreated grain, and although the mortality levels were similar between the two treatments, we feel that it would be safer to treat the entire grain mass.

The rice weevil is one of the most damaging stored-product insects in the world. Although it is only found occasionally in Canada, it and the lesser grain borer are the most serious pests in the United States, Australia, and much of southeast Asia and Africa. Preliminary work with our colleagues at the USDA Grain Marketing and Production Research Center in Manhattan, KS has shown that a common parasite of the rice weevil, Anisopteromalus calandrae, is not killed by pea protein at 0.1%. Thus, pea protein could allow the parasites to further reduce stored-product insect populations, whereas most insecticides wipe out the natural enemies as well as the target pests.

Rusty grain beetle and red flour beetle
The rusty grain beetle is responsible for over 90% of insect infestations at the terminal grain elevators. The red flour beetle is the second most common insect pest found, although it is mainly seen in stored grain in farm bins. Both these insects had the adult populations reduced by over 50% and their offspring reduced by over 70%. Given that these insects must colonize the grain and build up their populations over 1-2 generations before they reach levels that are detectable in grain, pea protein may be useful in reducing the populations of these insects if the grain is treated at harvest. The field test conditions used in these trials use high initial levels of infestation so that it would be possible to detect changes in the insect populations. A natural infestation in grain bins would start with much lower initial numbers of insects. Given that pea protein increases emigration from the grain and reduces the number of offspring, the population increase of pest populations would be greatly reduced. We were unable to test the pea protein on natural infestations because it would require the treatment of at least 20 bins to insure that we tested bins that were infested.

• Pea protein is a food product, and could probably be sold as a registered organic insecticide.
• Pea protein would offer longer protection than a fumigation.
• Tests done after the work detailed in this report have shown that pea protein has little effect on the parasites of the rice weevil and the rusty grain beetle.
• In the USA, there is significant pressure from the EPA to reduce or eliminate the use of organophosphate insecticides in stored grain.

• Pea protein has low activity against the lesser grain borer, a pest that is often found in grain along with the rice weevil.
• There are some tropical strains of rice weevil that are not affected by pea protein, although these strains have not been seen in the USA or Europe.
• Combination formulations may address the problem of limited spectrum of activity and resistant rice weevil strains. Mr. Hou will be continuing this work as part of his Ph.D.

Acknowledgements:

This project was made possible due to funding from the Governments of Manitoba and Canada through the Canada-Manitoba Agri-Food Research and Development Initiative (ARDI) and the University of Manitoba. Ken Fulcher of Parrheim Foods provided the pea protein used in the tests.

References:

Bodnaryk, R, Fields, P, Xie, Y, and Fulcher, K. 1999. Insecticidal factors from field pea. United States Patent 5,955,082.

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