Province sees average year for corn ear moulds, mycotoxins

Mycotoxin and ear mould levels in this year’s Ontario corn crop are in line with long-term averages, says the annual survey of corn in the province.

The survey is conducted by OMAFRA field crop specialists with help from Grain Farmers of Ontario and members of the Ontario Agri-Business Association. 

Mycotoxins, especially deoxynivalenol (DON) are especially a problem when fed to livestock, particularly hogs. DON is formed mostly by gibberella or fusarium ear moulds.

The 2021 survey found 89 per cent of samples tested had less than two parts per million of DON, which is acceptable for feeding to animals. This is the same result as last year. 

Why it matters: The survey provides a baseline for moulds and mycotoxins present in Ontario corn, which can affect feeding quality for livestock. 

A total of 205 ear corn samples were randomly selected across the province from Sept. 21 to Oct. 2, 2021. Five consecutive ears were collected from four random locations throughout a field and placed into high temperature driers (80 C) as soon as possible after collection. Pictures were taken to document moulds and insect and bird feeding damage. Dry ears were shelled and coarse ground and mixed for sub-sampling consistency. Sub samples were collected and finely ground for DON analysis at the University of Guelph Ridgetown Campus mycotoxin lab.

The survey found that some samples had clear evidence of ear moulds. The severity was generally low with infections often appearing to be in very early stages (e.g. light mycelium growth between tip kernels). Many also displayed no symptoms, and only two samples tested over five ppm. 

As in recent surveys, insect feeding was low. Ear feeding by pests, particularly western bean cutworm (WBC), corn earworm (CEW) or birds can open husks, damage kernels and present opportunities for greater ear mould infection and DON. Survey authors say that low feeding damage was possibly because most corn tasseling occurred prior to peak WBC moth flights (period of Jul. 29 to Aug. 4 on average for Ontario in 2021). Where feeding damage was present, visual mould symptoms were usually apparent.

Sixty-three per cent of samples tested lower than 0.5 parts per million of DON, 26 per cent from 0.5 per cent to two per cent and 10 per cent from two to five parts per million. There were only two samples over five parts per million.

Although the growing season remained dry across most parts of the province from April through to late June, survey authors say heavy and frequent rains started for many parts of Southern and Eastern Ontario in July that created moist, humid conditions in corn canopies.

While good for yield, the moist air created favourable conditions for ear mould establishment at fresh silk stage, and persisted for several weeks. However, they say drier conditions in August and September likely limited ear mould progress in fields where infection had become established. 

Although nearly 90 per cent of samples tested below the two ppm threshold, study authors say growers should still remain vigilant and review management options in fields with higher DON concentrations. Very wet weather has delayed harvest in many areas, and most ear rot fungi will continue to grow until grain moisture is below 15 per cent. Above this level, the fungi could potentially produce mycotoxins. 

The authors advise growers who have fields with significant ear moulds (10 per cent or more ears with mould symptoms) to collect a representative sample prior to harvest and test for mycotoxins before storing or feeding to livestock.