Preventing and Monitoring for Stored Grain Pests

Excerpts from the Candian Grain Commission website

Insect pests in stored grain need certain living conditions to feed, reproduce and survive. In some cases you may have unwittingly provided an ideal living environment for insects even before grain is stored. The following measures are effective and simple ways of preventing pest development:

  1. Thoroughly cleaning the inside of the bin
  2. Removing spills or grain lying outside of bins
  3. Cleaning and treating structures before filling them. This is especially important prior to harvest.

Weed management around bins is as important as controlling weeds in the field. Weeds or volunteer cereal grains around bins, as in this photo, attract insect pests. Various weed seeds discovered in a grain shipment can result in a prohibition of export. Keeping areas around grain bins clean helps prevent insect infestations in stored grain.

 With the natural phenomena of convection currents in the bin, warm moist spots in the stored grain are not unusual.  These warm spots are ideal for the breeding and feeding of insect pests. 

Cold Weather Convection Currents Warm Weather Convection Curents

grain temperature graph

One of the best ways to prevent insect infestations is to monitor bin-stored grain every two weeks to detect early signs of deterioration or infestation.  There are several devices you can use to sample grain and check for insects.

As there is pressure world wide to reduce the use of pesticides associated with food, quality methods are necessary to achieve minimal, effective and judicious use of pesticides.  Trapping to determine the presence of insect pests in stored grains is a simple and cost effective way to monitor for infestations and identify insect pests so that you can make decisions about insect control.

Pit-fall traps are one variety of traps that have been developed for use in food.  These are two types of traps: Pheromone-baited pit-fall traps and pheromone baited probe pit-fall trap.  These traps are embedded in the grain at the top of the pile , near the center.  When grain becomes cooler, the insects tend to migrate to this area of the bulk.  These traps should be placed in the grain as early as possible  and removed ever 10-14 days to inspect for the presence of insects.  Once the grain temperature is below +150 C, monitoring can be reduced to monthly.  Suppliers of pesticides should be able to supply probe traps.

Pit fall traps

Use the following number of traps for different bin sizes:

  • 1 to 2 traps for bins that hold less than 25 tonnes (900 bushels)
  • 2 to 3 traps for bins that hold 25 to 50 tonnes (900 to 1800 bushels)
  • 3 to 5 traps for bins that hold more than 50 tonnes (1800 bushels). Place the first trap in the centre and insert the remaining traps in a radius approximately one metre from the centre.

If it is not possible to install and monitor traps, for example, when bins have limited access, probing, sampling and sieving grain are also effective ways to monitor grain.  A torpedo style probe can be used to sample grain to various depths.  Grain tier probes can also be used effectively as long as you have access to the complete bulk.

Samples collected should be sieved and the results of both trays inspected for insects.  The heat and light from a 60-100 watt bulb will cause mobile insects to move making detection easier.  Look for kernel damage and holes in the grain. 

Have any insects discovered identified so that the best control methods can be used.  Treatments of aeration, moving and turning the grain or fumigation and insecticides should be started immediately.

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