With the onset of warm weather after winter, and heavy rainfall across the country, the National Plant Protection Center (NPPC) under the ministry of agriculture is preparing to prevent an outbreak of armyworms which in 2013 affected 16 out of 20 districts in its first outbreak destroying maize and paddy nursery.
This year farmers and extension officers are in high alert and planning for advance measures to prevent an armyworm outbreak in the Country.
According to the official with the Entomology Department of NPPC, Loday Phuntsho, the outbreak can occur during the month of April and May after the periods of dry spells followed by heavy rainfall and evolving grassy weeds.
He said that the weather condition is becoming more favorable for the pest outbreaks and all extension officials are instructed to carry out regular monitoring of the pests, and assist farmers to implement control measures in time.
Hence the NPPC has instructed farmers to flood seedbeds as flooding drowns the swarming larvae can help get rid of the pests. Another measure is to plough a deep ditch and fill it with water so that the caterpillars found to be moving towards the field from the adjacent fields can be prevented from crossing over.
Further, farmers are advised to cut grass weeds from bordering fields regularly to reduce breeding sites and shelter for armyworm.
Digging a deep ditch with vertical sides to trap the caterpillars and prevent them from crawling out and drawing in the caterpillars to the holes and properly disposing the trapped caterpillars are another method advised to the farmers.
Meanwhile if there is high infestation of army worm the center has distributed chemicals to spray in the infested area late in the day since the armyworms feeds at night.
The Armyworms is known to feeds on paddy, maize, barley etc and other young seedlings at the plant’s base.
“They also cut off rice and maize panicles from the base” Loday Phuntsho said.
As per the literature adult armyworms survive better and produce more eggs when the temperature is at 15 °C maximum, and when plants are naturally fertilized.
Armyworms are nocturnal and feed on the upper portion of the rice and maize canopy on cloudy days or at night. The adult worms are known to feed, mate and migrate at night and during daytime take shelter at the base of the plant or under the soil clods.
There are three armyworm species which are the rice swarming caterpillar, common cutworm, and the rice ear-cutting caterpillar.
A single armyworm egg mass contains hundreds of eggs and each female lays 800−1000 eggs during its lifetime of about one week.
Last year the armyworm outbreak in the country was reported from Barp, Chhubu, Dzomi, Goenshari, Kbaisa, Lingbukha,Shengana, Talo, Toepisa and Toedwang under Punakha, Thetsho and Nahi under Wangdue, Tendrelthang paddy nursery in Thimphu, Khamey in Gasa and Menji and Gangzor and Khoma in Lhuntse.