OVER the years, the country’s grain production levels have been significantly reduced as a result of pests attacking crops in different farming regions.
Farmers have had to deal with pests including locusts, armyworm and maize stalk-borer, among others.
In recent times, the armyworm has proved to be a menace not only to local farmers, but also to those in the Southern African region such as Botswana, Namibia, Malawi, Mozambique and Zambia.
Last year the migratory pest hit five of the country’s eight farming provinces destroying hundreds of hectares of maize, sorghum and pastures.
Armyworm outbreaks have caused panic in the region, with rising fears that the continued plagues threaten food security.
The armyworm is a migratory pest, which, in eastern and southern Africa, displays a distinct migratory pattern.
The moth apparently starts breeding along the coast of East Africa and Mozambique further south.
A progression of outbreaks then follows two directions: one northerly, from Tanzania to Ethiopia and into Yemen, and the other to the south towards South Africa.
However, there are indications that initial breeding might also take place in Angola, leading to outbreaks spreading into Zambia and further south into Botswana and Zimbabwe.
The moth larvae, which derive their name from their feeding habits, march in large numbers across grasslands and grain fields ‑ eating everything on their path.
Their diet consists mainly of grasses and early stages of cereal crops like maize, rice, wheat, millet, and sorghum.
This season armyworm outbreaks have since been reported in Mashonaland Central, one of the country’s grain largest producer.
Plant Protection Research Services Institute deputy director in the Ministry of Agriculture, Mechanisation and Irrigation Development, Dr Godfrey Chikwenhere said the first reported case of armyworm was in Mbire.
“The pest destroyed 26 hectares of sorghum and pastures in Mbire and other affected areas include Muzarabani and Mount Darwin,” he said.
“The spread of the armyworm was, however, contained by the rains that resulted in floods in Mbire ad Muzarabani.”
Dr Chikwenhere said the distribution of chemicals to spray armyworms had begun.
“The department received US$$45 000 to buy chemicals and protective clothing from Government,” he said.
“We have stocks of Deltamethrin and Cypermethrin used to control armyworms in pasture grasses because they are less toxic to livestock.
“We also have Karate and Carbaryl to spray in maize and other crops because they have a long residual effect.”
Farmers have been urged to be on the lookout of the armyworm and ensure they have adequate chemicals.
Zimbabwe Farmers Union (ZFU) crop specialist, Simbarashe Muchena said the armyworm could be controlled through monitoring, chemical control and cultural control.
Under cultural control farmers do not use chemicals instead they might burn grass or dig trenches.
He said accurate monitoring of populations of armyworm is key to efficient and rapid control of armyworm.
“Farmers should constantly check for the presence of the moths, eggs and larvae,” he said.
“Moths are monitored using light and pheromones traps.
“Eggs are not easily found but searches can be made three to four days after a high trap catch by looking on the underside of leaves about one week after a high catch or after the first storm following a drought.”
Young larvae, Muchena said, maybe found by shaking grass or crops and checking for young larvae hanging on crops.
“Windowing of crop leaves is a sign of possible armyworm invasion,” he said.
“Searches for small or large larvae can be made using a sweep net.”
Muchena said it was the larvae that caused damage to crops and this was the only stage that is readily susceptible to pesticides.
“Carbaryl 85 or Thionex 50WP can be used to control armyworm and for one hectare 625g of Carbaryl is required and the application rate for a 15-litre knapsack is 37g,” he said.
“However, the major challenge is that armyworm is normally visible seven to 10 days after they have invaded and caused damage to the crop.
“This means there are only eight to 12 days to undertake control before the larvae puppet and each day delayed allows further damage to the crop.”
Muchena said traditional methods worked in controlling the spread of armyworms
“Farmers are advised to keep crops free of grass weeds to avoid infestation,” he said.
“However, if fields do become infested, grass weeds should be left as an alternative food source for the larvae and this will deter crop invasion.”
In Botswana another traditional method used involves digging 30 centimetre deep trenches around fields to curb the spread of the pests.
As the season goes on it is hoped that concerted efforts help minimise the levels of destruction by the armyworm.