The Ministry of Agriculture, Forestry and Fisheries has alerted farmers to the destructive potential of fall armyworms on rice fields, vegetables and industrial crops, and has cautioned farmers to remain vigilant, as the pests are rapidly spreading across farmland in around 10 provinces. 

Armyworms are the larvae of several species of moths known for their destructive feeding habits, primarily on grasses and cereal crops, and can cause severe agricultural damage. They are called "armyworms" because they tend to move in large groups, much like an army, consuming nearly all vegetation in their path.

They have become a global concern in recent years, wreaking agricultural havoc across multiple continents. Originally detected in the Americas, fall armyworms (Spodoptera frugiperda) were first reported in Africa in 2016. By 2018, they had spread to Asia, severely impacting countries such as India, China, Thailand and Cambodia.

Their rapid proliferation is facilitated by the moths' strong migratory abilities, international trade and the movement of infested plant materials.

According to data from ministry spokesman Khim Finan, obtained by The Post on June 20, five districts in Takeo province and three in Kampong Thom are the worst affected, with leaf roller and clothes moth larvae affecting 5,859ha and 3,873ha of farmland, respectively.

However, it noted nearly 2,000ha of farmland in Kampong Thom have been saved from the pests. 

"Pailin province is affected by armyworms on 2,240ha of industrial crops, while Preah Vihear province has 505ha of industrial crops and 386ha of farmland affected,” the report said.

Four districts in Siem Reap province are also infested, with 333ha of rice and 150ha of industrial crops affected. 

In Steung Treng, armyworms have destroyed 114ha of rice, 52ha of mixed crops and 95ha of industrial crops.

Other infected areas include 10ha of industrial land in Kampong Cham’s Stung Trang district, 2ha of farmland in Kampong Chhnang’s Teuk Phos district and 120ha of rice and 64ha of industrial crops in Tbong Khmum province. 

"This year's hot and prolonged weather has shortened the life cycle of the worms, causing the eggs to hatch and the worms to grow faster. They are born at a fast pace,” Finan explained. 

He noted that weather conditions have not only reduced biodiversity but also led to the loss of species that control armyworms, resulting in a rapid and significant increase in their population.

Finan stressed that officials from the ministry are rushing to monitor the outbreak and take direct action if necessary. 

Finan recalled a similar incident in 2016 when invasive pests destroyed crops in Preah Vihear and Kampong Cham provinces.

"Farmers should regularly monitor their crops and take timely action to avoid serious losses," he advised.

Finan recommended preventive measures such as clearing weeds in and around fields, which are habitats for worms and other pests. He also suggested digging ditches with a diameter of 30cm and a depth of 20cm, then sprinkling ash or bran at the bottom to interrupt the worms' movement.

The ditches act as physical traps, preventing the worms from moving freely across farmland. Ash is abrasive to the worms and they are attracted to bran. Worms and larvae can fall into these ditches, making it difficult for them to climb out and continue their path to crops. 

For eradication, Finan suggested releasing ducks into the fields to eat the worms or flooding the fields to drown the larvae and pupae. He also mentioned that using a mosquito or fishing net to skim the surface of the water after flooding, to remove and destroy the worms, can also be effective.

Dy Saman, deputy director of the ministry’s plant protection, sanitary and phytosanitary department, addressed farmers in a video message. 

He explained that these swarms of worms originate from moths, adding that their lifespan is between 35 and 55 days, during which they consume various crops, including rice, vegetables, beans and cassava.

To control the spread, Saman suggested starting with sweet-sour traps to catch moths, which are capable of laying between 700 and 3,600 eggs each. 

"Farmers should make a sweet-sour trap with a mixture of water, white wine, vinegar and sugar, let it sit for 3-4 hours, then add one cc of Fipronil per litre," he advised.

If mechanical measures are insufficient, Saman recommended certain pesticides, including Thuricide or Dipel at a dose of 1kg per hectare, Pyrethroid group pesticides like Cypermethrin or Deltamethrin at a dose of 1 litre per hectare or Carbomate pesticides such as Carbaryl at the same dosage.