Farmer's Weekly (South Africa)
The most important barley pests: Part 2
Barley is prey to some of the same insects that attack other small grains. One of these is false armyworm, which is found in most African countries and is a serious drain on profit, as it reduces yield.
CROPS
The false armyworm (Leucania is a moth of the family Noctuidae. It has a wingspan of 34mm to 44mm and the larva is reddish grey. False armyworm activity occurs throughout the year, but varies between the various production areas, according to Dr Goddy Prinsloo of the ARC-Small Grain, Bethlehem.
The female moths are attracted to lay their eggs by the smell of fermenting, rotten grass, a condition present in the last two or three weeks before harvesting.
“Barley plants at this stage are soft and vulnerable, and the larvae chew off the heads easily and feed on the grain itself,” notes Prinsloo.
The larvae feed from the edges of the leaves inward, doing so mostly at night; during the day they stay on the soil surface underneath plant material. The last three weeks before harvesting are the most critical time.
In the Western Cape, there is high moth activity between weeks 11 and 28 (mid-March to mid-July). This includes sowing time in this area.
“Larvae act the same way as cutworm by damaging the seedlings just after emergence,” says Prinsloo.
NEW MOTHS
New moths appear again between week 39 and week 46 (October to midNovember), coinciding with harvest time.
“This could give rise to many larvae just before harvest time, posing a potential threat. This doesn’t usually materialise, however, probably because the grain is swathed during this critical period. In the Western
Cape, therefore, this insect could be more of a threat during plant emergence than at the end of the growing season,” says Prinsloo.
Peak moth flight activity in the irrigation areas occurs between weeks 10 and 47. During this period, activity peaks during May and June and then again during September and October. This also coincides with the sowing and reaping of the grain.
In these areas, the larval activity is very low during winter, but increases from October onwards.
As the female moths lay eggs in fermenting or rotting grass, irrigated lands just before harvest could be an easy target when plants are drying out, says Prinsloo.
This could apply even more during drought conditions, as the moths have no other place to lay their eggs but in the irrigated lands.
This was the case in 2010, when an outbreak occurred in the Douglas and Vaalharts irrigation areas, notes Prinsloo.
It is therefore necessary to monitor moth flight patterns and pay attention to weather patterns, especially the occurrence of long, dry periods before harvest.
Source: Prinsloo G. 2022. ‘How to control relevant insect pests on barley’. SA Graan/Grain. bit.ly/3JeWEF1.