Be-Long Corporation’s Blog

Like many types of grass and cereal, maize is often attacked by mould fungi of the genus Fusarium. Some of these fungi produce mycotoxins . If maize contaminated with mycotoxins is fed to animals, these highly poisonous substances can lead to severe health problems in the animals, e.g. to reduced fertility or digestive problems. Mycotoxins can also be harmful to human health. EU-wide maximum limits have therefore been set for three different mycotoxins (see table).

Fusarium fungi, which produce these toxins, can enter a maize plant through the stigma of the female flower, but also through sites where the plant has been attacked by chewing pests. The fungi then spread inside the maize plant.

How severely a maize plant is infected with fungi and whether this leads to mycotoxins being produced depends on a large number of factors. Humidity and temperature during the growing season, soil cultivation and the susceptibility of the variety in question all play a role, as does the time chosen for harvesting. The complex process, which is not fully understood, makes it difficult to control mycotoxin formation in individual cases and to reduce contamination reliably. Studies in Germany, for instance, have shown that mycotoxin levels vary widely between individual maize plants, even on the same site. There are many indications that stress – both for the maize and for the fungus – results in higher mycotoxin production.

But it is also clear that a heavy infestation of chewing pests leads to higher mycotoxin contamination. In many maize-growing regions of Europe the European corn borer is the main maize pest: the larvae bore their way into the maize plants, leaving holes through which Fusarium and other fungi can enter. The more effectively the corn borer is controlled, the fewer chewing sites there are that can be used by the fungal pathogens to colonize the maize plant, in addition to the stigma route.

Although the results vary depending on the site, variety, trial design and type of mycotoxin, the general trend is clear (see diagrams)

     * There is a clear correlation between the severity of the corn borer infestation and the mycotoxin level.

     * Cultivation of the conventional maize variety without any measures to control the corn borer produced
         both the highest pest infestation and the highest mycotoxin levels. This effect is more pronounced on
         sites with high corn borer infestation.

     * Chemical and biological methods of controlling the corn borer, e.g. the use of insecticides or parasitic
         wasps (Trichogramma), can reduce both the number of corn borer larvae and the level of mycotoxin
         contamination.

     * On all sites, the Bt maize varieties used showed the best results: only isolated corn borers were found
         in the crops. On almost all the trial fields the mycotoxin values measured were lower in the Bt maize
         plants than in the conventionally grown control plants.

     * Ten out of thirteen studies on Bt maize came to the conclusion that Bt maize is less contaminated with
         mycotoxins than the conventional control variety in each case. This applies to the mycotoxins DON,
         ZEA and FUM.