Getting a “charge” from bugs in wheat

21-05-2007 | |
Getting a “charge” from bugs in wheat

How do you spot tiny insects that might be lurking inside grains? Give them a minor jolt, according to an Agricultural Research Service (ARS) engineer.

Thomas Pearson, who
works at the agency’s Grain Marketing and Production Research
, Manhattan,Kan., has found a novel and cost-effective way
to detect the pesky insect larvae that occasionally use kernels of our favourite
cereal grains as their homes.

agricultural researchers, including Pearson, are hard at work devising new and
improved methods for helping inspectors screen our nation’s grain supply. Why?
Despite rigorous scrutiny of grain at flour mills and loading docks for overseas
shipments, insects, in all their earthly abundance, remain persistent invaders
of stored grains.

Hard to find
Especially hard to find
are immature insects–tender pupae and larvae that metamorphose inside the
nutrient-rich cocoon of a grain kernel until they’re ready to emerge as

Pearson’s detection system relies on three

  • a roller system for crushing a sample of

  • a voltage source
    for sending a charge through the sample, and
  • a computer software program for measuring aspects of
    the sample’s electrical conductance.
  • Kernels infested with larvae cause a
    noticeable spike in electrical conductivity readings. Such increases are likely
    due to the hidden larvae’s moisture content.


    For his study, Pearson intentionally
    infested batches of hard winter wheat and soft winter wheat with two of the
    grain industry’s most insidious foes: the rice weevil and lesser grain

    He allowed the contaminated samples to
    “incubate” for several weeks so that stowaway insects had a chance to multiply
    and grow, and so that their unnerving presence could be independently

    Pearson’s specially adapted roller
    mill can impressively screen about 30,000 kernels–or one kilogram of grain–a
    minute, spotting 80 to 90% of those infested with insect

    The cost of the device is substantially
    less than other technologies for insect detection, including x-ray and
    near-infrared systems.

    More info can also be found in the article
    How wheat kernels “sing” is a sign of their

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