You certainly don't want these Fall Armyworms in your farms

Since the past few months, the Fall Armyworm pest has been sighted in many states of the country affecting the corn crop. If not identified and controlled in time, this pest shall cause immense harm in the future

Divendra SinghDivendra Singh   12 Sep 2019 7:34 AM GMT

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You certainly dont want these Fall Armyworms in your farms

After destroying the corn crops of African countries three years ago, the Fall Armyworm has made a foray into many states of India and if not identified and controlled in time, shall cause immense harm in the future.

Fall Armyworm has been detected in the corn crops of Karnataka, Tamil Nadu, Bastar district of Chhattisgarh followed by Uttar Pradesh's Kannauj and Sitapur districts. Farmer Nand Kishore of Barbata Zalimpur village in Sitapur, Uttar Pradesh has sown corn in his one-acre farm. He said: "I have grown corn for many years, but this time it has been infested by a newer type of pest that I know nothing about. It is fast destroying the crop."

Prior to this, the Fall Armyworm had been detected by the scientists of the Regional Central Integrated Pest Management Centre, Lucknow during their surveying and monitoring of corn crops in Kannauj district.

The Indian Corn Research Institute, Ludhiana's scientist Dr Mukesh Chaudhary informed: "Since past few months, this pest is sighted in many states of the country affecting the corn crop from South India's Karnataka and Tamil Nadu, thereafter Chhattisgarh, West Bengal, Mizoram, Uttar Pradesh and more recently in Bihar where the farmers are yet to be made aware of this pest."

He added: "Presently we have sighted it in Punjab too—it covers a distance of up to 100kms in a night. If sighted in a farm and left chemically uncontrolled, it travels hundred kilometers further. An adult pest produces 1,000 eggs at one go and even if 10 survive, they would further produce 10,000 eggs."

This has even affected crop production. Regarding this, he said: "It also has affected the production, this time farmers in South India have sown less corn as it seems to be the pest favoured crop. In the absence of the corn crop, the pest will move on to the sugarcane crop. Even in the absence of sugarcane, it will thrive on jawor, bajra etc. Corn being its primary target, it can harm over 190 different types of crops."

The ill-effects of this pest were first noticed in Karnataka's Shivamoga on May 18, 2018. Thereafter, the Fall Armyworm was reported in dangerous level in the fields of Tamil Nadu, Andhra Pradesh, Telangana, Maharashtra, Madhya Pradesh, Odisha, West Bengal, Gujarat, Chhattisgarh, Kerala, Rajasthan, Jharkhand, Mizoram, Manipur, Nagaland, Tripura, Meghalaya, Arunachal Pradesh and Sikkim.

Krishi Vigyan Kendra's crop protection Scientist, Dr Daya Srivastava informed, "This pest is known as 'Fall Armyworm', it was first sighted in May 2018 upon the corn crops of Shivamoga district in Karnataka. Thereafter it has rapidly spread across Tamil Nadu, Maharashtra, Andhra Pradesh and even Mizoram. Uttar Pradesh cultivates sugarcane and corn in a large scale so now the pest's presence in the state is an extremely grave issue."

It is primarily a corn-based pest. If the corn crop is not available then it attacks jowar. If both aren't available then it feeds upon other crops such as sugarcane, rice, wheat, ragi and even fodder grass. It also causes harm to cotton and vegetables. Fall Armyworm adult moths are rapid flyers which can fly over 100kms in search of host crops.

What is fall armyworm?

Fall armyworm (FAW), a destructive pest native to the Americas, recently invaded India and presently causing economic damage in maize.

Which crops in danger?

It is primarily a pest of maize. If maize is not available it will look for sorghum. If both are not available, it will attack other crops belonging to poaceae, the family of grasses, such as sugarcane, rice, wheat, ragi, fodder grasses etc. It may attack cotton and vegetables as well, which is not reported yet.

How to recognize if FAW has arrived in your field?

The adult moth is a strong flier. It can fly over 100 km in search of host plants. Pheromone traps specific to FAW will attract male moths. Male moth has two characteristic markings -- a fawn-coloured spot towards the center and a white patch at the apical margin of the forewing. Forewing of the female is dull with faint markings.

How to ascertain the larva feeding your crop is FAW?

Larvae of many species of Armyworm belong to the genus Mythimna and Spodoptera look the same for a layman and cause similar symptoms in maize.
FAW larvae appear in shades of green, olive, tan and grey with four black spots in each abdominal segment and has three creamy yellow lines running down its back.
It is easily identified from any other armyworm species by its tail end, where the black spots are bigger and arranged in a square pattern on abdominal segment 8 and trapezoid on segment 9. The head has a predominant white, inverted Y-shaped suture between eyes.

What are the symptoms of FAW damage in maize and what are the management measures to be taken with the progression of symptoms?

A symptom-based treatment is very much essential in FAW management because of two reasons -- the stage of symptom progression indicate the stage of larval growth, and the stage of larval growth decides the choice of pesticide/ control measure.

(1) Elongated papery windows

Start observing the maize crop from the seedling stage. If elongated papery windows of all sizes are seen spread all over the leaves in a few adjacent plants the crop might have been infested with FAW. This symptom is caused by 1" and 2™ instar FAW larvae which feed by scrapping on the leaf surface. Early identification of this symptom is a must for effective management of FAW.

What measure to be taken at this stage?
It is easy to manage the larvae at this stage with botanical and microbial pesticides. The choices are:

(1) 5% Neem Seed Kernel emulsion (NSKE) or azadirachtin 1500ppm @ 5ml/I water.

(2) Bacillus thuringiensis variety kurstaki formulations (Dipel 8 l @ 2ml/I of water or Delfin 5WG @ 2g /l water).

(3) Entomopathogenic fungi Metarhiziumanisopliae (1 x 108 cfu/g) @ 5g/l and /or Nomuraearileyi rice grain formulation (1 x 108 cfu/g) @ 3 g/l water.

However, when the infestation is more than 10% in the field, it is better to resort to chemical pesticides which are recommended below for the bigger larvae. Apart from pesticide sprays, put some sand/soil alone or mixed with lime/ash (9:1) into the plant whorl when the whorl is well-formed to withstand its weight. This will directly harm larvae and increase the effectiveness of pesticides sprayed, especially by acting as a reserve for microbial pesticides.

2. Ragged-edged holes:

Once the larva enter 3rd instar, its feeding cause ragged-edged round to oblong holes on leaves. The size of holes increases with growth of larvae.What measure to be taken at this stage?

Damage at this stage needs the application of chemical pesticides. The choices are,
Emamectin benzoate 5 SG @ 0.4 g/l
Spinosad 45 SC @ 0.3 ml/l
Chlorantraniliprole 18.5 SC @ 0.4 ml/I

3. Extensive leaf damage:
Once the larva enters 5th instar, it feeds voraciously, losing larger areas of leaves. Sixth instar larva extensively defoliates the leaves and produce large amount of faecal matter.

What measure to be taken at this stage?
Pesticides sprays fail to control 5th and 6th instar larvae. Only effective measure at this stage is poison baiting. Mix 10 kg rice bran and 2 kg jaggery in 2-3 liters of water and keep the mixture for 24 hours to ferment. Add 100g Thiodicarb 75% WP and roll into 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 bait should be applied into the whorl of the plant in the evening. The above mixture is sufficient to cover one acre.

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