False armyworm responsible for up to 50% losses of the barley harvest

The insect responsible for the loss ofup to 50% of barley harvests in the Vaalharts irrigation scheme in the Northern Cape has been identified as the false armyworm (Leucania loreyi).
Issue date: 31 December 2010

It’s found on maize from time to time, but has never been observed on wheat or barley before, said Dr Goddy Prinsloo of the Agricultural Research Council (ARC’s) Small Grain Institute in Bethlehem. The worm can remain dormant in the soil for up to five years, and destroys the ears and, sometimes, the leaves. It’s nocturnal, which made it virtually impossible to detect. The moths are also nocturnal and females can lay as many as 550 eggs.

The insects were detected in an area stretching from Viljoenskroon to Douglas. “This might be a once-off, but one never knows when it might occur again,” said Dr Prinsloo.Barley producer Kobus Human said he and other producers had been unaware of the crisis that unfolded under their noses.

“We started harvesting and were astonished by the low yields. The crops looked in excellent condition, but upon closer inspection, we found that the ears were gone. We initially ascribed it to wind damage. I expected a yield of at least 7t/ha, but only realised 6t/ha. Some producers’ yields decreased to 4,5t/ha. I lost some 10%, but there are cases of 50% losses.”Early ripening barley cultivars such as SSG585 and Coctail were the hardest hit, said South African Breweries Maltings agriculturalist Burrie Erasmus.

They received 7 087t of an expected total yield of 9 183t SSG585 and 9 952t of the 14 101t Coctail expected. “There was also a slight decline in the production of the Puma cultivar. Just over 12 000t of the expected 14 127t was delivered,” noted Erasmus.

“Metomax, with Methomyl as the active ingredient, can be used to prevent false armyworm outbreaks in barley. In the case of wheat, the insecticide Karate Zeon can be used,” he said, adding that the maize BT gene isn’t resistant to the worm. Dr Prinsloo said pheromone traps will be put out in the affected areas as soon as possible to determine the moth activity.

“This will enable us to warn producers of possible outbreaks,” he explained.