Rice Swarming Caterpillar Infestation And Its Management

The Rice Swarming Caterpillar is considered a destructive pest that infests rice crops, causing significant threat to rice production. Rice swarming caterpillars feed on rice leaves, stem and panicles, leading to yield losses ranging from 20% in moderate infestation to 70% in severe infestation. This pest is particularly concerning because it has the ability to reproduce quickly and can migrate over large distances, making it difficult to control.  

Rice swarming caterpillars are polyphagous in nature which attacks various other gramineous crops and weeds, but upland rice is the preferred host of this caterpillar. Heavy rainfall favors the outbreak of rice swarming caterpillars. The mature larvae can be identified by their green, grey or brown color body with dark dorsal and sub dorsal longitudinal stripes. They also have two rows of black color C-shaped spots on their backs. 

Type of Infestation

The Rice Swarming Caterpillar can cause both sporadic and epidemic outbreaks. Sporadic outbreaks occur when small populations of the pest appear in localized areas, while epidemic outbreaks occur when large populations of the pest spread rapidly over a wide geographic area. These outbreaks can cause significant damage to rice crops by feeding on rice leaves and stems and result in reduced yields.  

Scientific Name: Spodoptera mauritia 

Most Affected States

The Rice Swarming Caterpillar is known to affect several states in India, particularly northern and eastern regions of the country, where rice production is a significant agricultural activity. The affected states include Bihar, Uttar Pradesh, West Bengal, Jharkhand and Odisha.  

Symptoms of Rice Swarming Caterpillar

The Rice Swarming Caterpillar can cause several damaging symptoms or infestation signs, including: 

• The caterpillars move in large numbers and cause damage to the paddy crop by cutting off leaf tips, margins and even entire plants at the base.
• The larvae feed on the leaves of the rice plants, making shot holes on the leaf blades.
• Skeletonization of leaves and dieback of stems.
• The damage is more severe on seedlings in nurseries and direct seeded crops, as well as during the early tillering stage in transplanted rice.
• Severely infested fields show cattle grazed appearance.

Control Measures

An integrated pest management technique which includes cultural, mechanical, biological and chemical methods is often necessary to effectively control rice swarming caterpillars. 

Cultural Measures

• Crop rotation with non-host crops helps to reduce the population of rice swarming caterpillars.
• Deep summer ploughing of fields exposes larvae and pupa of rice swarming caterpillar, which are located in the soil to birds.
• Flooding the nurseries and paddy fields will also expose the larvae to birds.
• Provide bird perches to facilitate predation by birds.
• Avoid using excessive amount of nitrogenous fertilizers.
• Allowing ducks into the field can feed on the larvae of rice swarming caterpillar.

Physical Measures

• As the moths of swarming caterpillars are attracted towards light, set up a Solar Light Trap which helps to catch the flying insects. It is recommended to install 1 trap per acre for effective trapping.

Mechanical Measures

• Hand picking and destroying the caterpillar is an effective way to control rice swarming caterpillar.
• In severe infestation cases, mix one litre of kerosene with 25 kg soil and broadcast in 1 hectare area.
• Tapas Yellow Sticky Trap can be used to trap adult moths. For effective trapping install 4 to 6 traps per acre.

Biological Measures

• Release natural predators such as an egg parasitoid Telenomus spp. and a larval parasitoid Apanteles spp. @40000 per acre for controlling rice swarming caterpillar.
• Greenpeace Neemol Bio Neem Oil Insecticide contains neem-based products azadirachtin which when used at the rate of 1-2ml per liter of water with 15days interval between each spray can effectively control swarming caterpillars in fields.

Chemical Measures

Chemical control methods involve the use of chemicals to manage the pest population. Insecticides that are commonly used to control the rice swarming caterpillars are mentioned in the table below, 

Product Name	Technical Content	Dosage
Shamrock Gold CP Insecticide	Chlorpyriphos 20% EC	2.5 ml/lit of water
Ekalux Insecticide	Quinalphos 25% EC	2 ml/lit of water
Starclaim Insecticide	Emamectin benzoate 5% SG	0.5 gm/lit of water
Plethora Insecticide	Novaluron 5.25% + Indoxacarb 4.5% SC	2 ml/lit of water