Management of Fall Armyworm - An alarming agri crisis in NE India

Arup Kumar Sarma *

Fall Armyworm (Spodopterafrugiperda) is a pest native to tropical and subtropical regions of the America. The incidence of this pest was first observed in our country at Shivamogga, Karnataka on 18th May, 2018. Recently, it has also entered and attacked maize crop in several states of North East India.

The ICAR Manipur Centre for the first time reported the incidence of fall armyworm in Manipur state in the month of May, 2019 (Firake et al., 2019). It has also alerted that the pest has already caused extensive damage to maize cultivation at Chandonpokpi, Chandel district. Accordingly, Manipur agriculture department has constituted three joint action teams to combat the spread of FAW.

In Arunachal Pradesh, the pest has been identified in the campus of College of Horticulture and Forestry (CAU, Imphal), Pasighat during May itself. Mizoram government has informed the ICAR Centre about an estimated crop loss of Rs. 20 crore caused by an outbreak of FAW in the state. ICAR-NEH centre also expressed its concern and in its advisory stated that in addition to Mizoram, Nagaland, Tripura and Manipur, it has also been detected infesting maize fields in Meghalaya and also suspected to be in Sikkim too (Firake et al., 2019).

Food and Agriculture Organization (FAO) of the United Nations in its report has emphasized the invasiveness of Fall Armyworm (Spodopterafrugiperda) in recent times. It can attack more than 80 plant species, causing remarkable damage to economically important cultivated cereals such as maize, rice and sorghum, and also to vegetable crops and cotton. It is the larval stage of the insect that causes the damage of crops.

It is high time to disseminate the techniques of controlling the pest. Agricultural officers, extension workers, farmers, agro-based NGOs and policy makers should be well aware of the biology and management tactics of the pest.

Why it is so invasive? FAW is highly invasive for its short life cycle with several generations per year, high reproductive potential with high fecundity and strong flight capacity. It reproduces several generations per year. A female moth can lay up to 1000 - 1200 eggs in her life time. Being strong fliers, the moths can fly up to 100 km per night and can invade a large area within a small span of time.

Identification of Fall Armyworm: Identification of FAW is the first step for management.

a) The moth is 3 to 4 cm wide. Its front wings are dark brown while the rear wings are grey white. It will live 2 to 3 weeks and lay about 1000-1200 eggs before dying.
b) Eggs are pale green or white at the beginning, get covered in scales, and turn clear brown to brown before hatching. They hatch within 2-3 days.
c) Half-grown or fully-grown caterpillars are the easiest to identify. The larvae are generally characterized by 3 yellow stripes on the back, followed by a black, then a yellow stripe on the side. Look out for four dark spots forming a square on the second to last segment. Each spot has a short bristle (hair).

The head is dark; it shows a typical upside down (inverted) Y-shaped pale marking on the front. A larva sheds off its skin five times and passes through six stages before pupation. Young larvae are pale colored. They become brown to pale green, and then turn darker at the advanced stages. Depending on the season, the larval duration lasts for 12 to 20 days.

d) Pupae are dark brown and remain hidden in the soil, more rarely in the stalk. Pupae live for 12-14 days before they emerge as adults.

Symptoms of attack: The caterpillars prefer to feed inside the whorl of a maize plant, where it feels protected and chews tender maize leaves. As they chew away, the leaves continue to grow out, and thus, leave a ragged/ halfchewed leaves that are typical symptoms of FAW infested maize fields. At very high population levels, FAW can also penetrate maize ears, causing direct damage to the harvest. They do not produce dead-heart (drying away of central leaves) as the stem borers do.

Management strategies against FAW: A strategic crop management practice along with systematic plant protection is essential in an area where FAW has established. Such practices should be applied in wide manner through community approach in order to manage FAW population below economically damaging levels. An integrated pest management (IPM) approach is to be followed as described below:

1. All farmers of a locality/community should plan to sow at same time (within 2-3 days of same week) to get uniform planting. The pest attacks crop with staggered planting more.

2. Deep ploughing of the crop field before planting in every crop season is essential to expose the hidden FAW pupae to sun light and predators. If zero-tillage is practiced, spread neem cake @ 500 kg ha-1.

3. Plant napier grass in the border rows to act as FAW trap crop.

4. Single cross maize hybrids with tight husk cover should be selected for planting. Seed treatment might prevent early damage of the seedlings after germination.

5. Hill planting of maize is to be avoided; one plant should be maintained per hill by thinning.

6. Intercropping of maize with suitable pulse crops of particular region should be done for maximizing plant diversity. For example: Maize + pigeon pea/black gram /green gram.

7. Maintain the crop field clean, weed free and follow balanced fertilizer application.

8. After control measures, apply nitrogen and irrigation to boost the crop growth.

9. Spray the crop with 5% NSKE or azadirachtin 1500 ppm @ 5 ml l-1 at weekly intervals. Also release Trichogramma- pretiosum @ 50,000 or Telenomusremus @ 10,000 adults acre-1 at weekly intervals, starting within a week of germination till harvest. Commercial formula- tion of Bt (Bacillus thuriengiensis variety kurstaki) is also effective if applied @ 2 g l-1 water. These control measures are important for organic states of North East Indian states.

10. Install FAW pheromone traps @ 2 bigha-1 on or before germination of the crop to monitor pest arrival and population build-up.

11. Use pheromone trap @ 6 bigha-1 cropped area for mass trapping of male moths to keep population buildup under control.

12. Erect bird perches @ 10 acr-1 as soon as sowing is completed.

13. Follow weekly scouting and adopt symptom-based control measures. One should follow the action thresholds for right timing of the chemical spray.

14. While scouting, hand pick and destroy egg masses and neonate larvae by crushing or immersing in kerosene water.

15. Timing of chemical control measures is based on action threshold. Action threshold determined is determined by leisure walking in “W” pattern in the field after leaving 4-5 border rows. Observe 10 plants in each of the five stopping points of “W” pattern (starting point+3 vertices of the three angles in the “W” + the finishing point) and record the number damaged plants of the 50 plants observed in one”W” scout to find out percent of plant infested.

At early stage the spray should be done at 5-10% infested plant and at later stage, at 10-20% damage. Insecticides like spinectoram 11.7% SC @ 0.5 ml l -1 or chorantraniliprole @18.5 SC @ 0.4 ml l-1 or thiamethoxam 12.6% + lamda cyhalothrin 9.5% ZC @ 0.25 ml l-1 of water may be applied.

16. Poison baiting of large size FAW larvae: Pesticides sprays often fail to control 5th and 6th instar larvae and poison baiting is the most effective at this stage. To prepare the bait:
a) Mix 10 kg rice bran and 2 kg jaggery in 2-3 litres of water.
b) Keep the mixture for 24 hours for fermentation.
c) Add 100 g thiodicarb 75% WP.
d) Roll the mixture into small balls of 0.5 - 1 cm diameter just half an hour before application in the field. Add some sand while rolling if the balls are too sticky.

The above mixture is sufficient to cover about 2.5 bigha of cropped area. The bait should be applied into the whorl of the plant in the evening.

Precautions

1. Use gloves and mask while preparing and application of poison bait and pesticide spray.
2. All the pesticides spray and poison bait should be applied only to the whorls.
3. Enter the field only after a minimum period of 48 hours followed by a pesticide spray.
4. Avoid cattle grazing in pesticide sprayed and poison baited fields at least for a month.
Sound policy at state level should be formulated and implemented to prevent its entry and management should be done before it causes enormous damage to crops.


For further details contact: -
Public Relations & Media Management Cell,
CAU, Imphal.
Email: prmmcell@gmail.com