Dr. Moanaro Progm. Asstt.
Ms. E. Lireni Kikon ACTO, Plant Protection
Fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) is a destructive pest native to tropical and subtropical regions of the Americas, recently invaded India and presently causing economic damage in maize. In India, this pest was first observed in Shivamogga, Karnataka on 18th May 2018. FAW was later reported in Tamil Nadu, Andhra Pradesh, Telangana, Maharashtra, Madhya Pradesh, Odisha, Bihar, West Bengal, Gujarat, Chhattisgarh, Kerala and Nagaland at mild to alarming levels in farmer's fields.
Adult moth is a strong flier, can fly over 100 km in search of host plants. Male moth has two characteristic markings, viz., a fawn coloured spot towards the centre and a white patch at the apical margin of forewing. Forewing of female is dull with faint markings. Female moth lays its eggs on plants, from which larvae hatch and begin feeding. Female moth can lay up to a total of 1000 eggs in her lifetime. Eggs of FAW are white in color and later turn into brown. They hatch in 2-3 days. Larvae has six stages initially are brown in color and later turn into dark green. Initial stages of FAW larvae are seen in group which later disperses in the field. Larva of FAW can be identified by four characteristic spots on the last second segment forming a square and an inverted “Y” mark on the head region.
Fig.- Life cycle of FAW Spodoptera frugiperda
Larva is the damaging stage of the insect. It generally prefers maize, but can attack more than 350 plant species, causing major damage to economically important cultivated grasses such as rice, millet, sorghum, sugarcane wheat, vegetable crops and cotton and can persist in an area throughout the year where there is availability of alternative hosts. Due to the strong flying ability, it has spread to most of the tropical countries and if the eradication and management of the pest is delayed, it can cause huge loss to crop yield.
Crop management practices along with systematic plant protection in an area wide manner can manage FAW population below economically damaging levels. An integrated pest management (IPM) approach is to be followed as described below:
- Selection of single cross maize hybrids. Choose cultivars with tight husk cover, especially for sweet corn.
- Deep ploughing before every crop season to open up the soil to expose FAW pupae to the sunlight and predators. If zero-tillage is practice, spread neem cake @ 500kg/ha. Maintain fields weed free and follow balanced fertilizer application.
- Plan for maximizing plant diversity by inter cropping of maize with suitable pulse crops like maize + pigeon pea/black gram /green gram/Soybean. Plant Napier grass in the border rows to act as FAW trap crop.
- Plan the sowing time at community level to follow synchronous planting.
- Seeds treated with Cyantraniliprole 19.8% + Thiomethoxam 19.8% @ 4 ml per kg seed reported to offer protection up to 2-3 weeks after germination.
- Avoid staggered sowing and if it is unavoidable spray the crop with 5% NSKE or azadirachtin 1500 ppm @ 5ml/l at weekly interval or release Trichogramma pretiosum or Telenomus remus @ 50,000 per acre at weekly intervals, starting within a week of germination till harvest.
- Install FAW pheromone traps @ 5/acre on or before germination of the crop to monitor pest arrival and population build-up or 15 traps/acre for mass trapping of male moths to keep population build-up under control.
- Erect bird perches @ 10/acre as soon as sowing is completed.
- Follow weekly scouting and adopt symptom based control measures on action thresholds.
- While scouting, hand pick and destroy egg masses and neonate larvae by crushing or immersing in kerosene water.
Symptom based treatment is essential in FAW management because the stage of symptom progression indicates the stage of larval growth, and the stage of larval growth decides the choice of pesticide/ control measure. Management as per different stages of symptoms are as follows:
- Elongated papery windows
Start observing the maize crop from 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 1st and 2nd instar FAW larvae which feed by scrapping on leaf surface. Early identification of this symptom is a must for effective management of FAW. At this stage it can be managed with botanical and microbial pesticides. Apply anyone of the following treatments:
- 5% Neem Seed Kernel Emulsion (NSKE) or azadirachtin 1500ppm @ 5ml/L water.
- Bacillus thuringiensis variety kurstaki formulations (Dipel 8 l @ 2ml/I of water or Delfin 5WG @ 2g /l water).
- Entomopathogenic fungi Metarhizium anisopliae (1 x 108 cfu/g) @ 5g/l and /or Nomuraea rileyi rice grain formulation (1 x 108 cfu/g) @ 3 g/l water.
However, when 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 the larvae and increase the effectiveness of pesticides sprayed, especially by acting as reserve for microbial pesticides.
- Ragged-edged holes:
Once the larva enter 3rd instar, its’ feeding cause ragged-edged round to oblong holes on leaves. Size of holes increases with growth of larvae. Damage at this stage needs application of chemical pesticides. Choices are,
i. Emamectin benzoate 5 SG @ 0.4 g/L of water
ii. Spinosad 45 SC @ 0.3 ml/L
iii. Thiamethaoxam 12.6% + lambdacyhalothrin 9.5% @ 0.5 ml/L
iv Chlorantraniliprole 18.5 SC @ 0.4 ml/L
- Extensive leaf damage:
Once the larva enters 5th instar, it feeds voraciously, loosing larger areas of leaves. Sixth instar larva extensively defoliates the leaves and produce large amount of faecal matter. 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 litres 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. Apply the bait into the plant whorl at evening hour. The above mixture will be sufficient to cover one acre.
- Damage to tassel and corn ear
In reproductive stage of the maize crop, tassel and cob ears are the vulnerable parts. Chemical control measures are not advisable in reproductive stage of maize crop since tassel damage may not cause economical loss and spraying on corn ears are futile as larvae hiding inside the ear would not be exposed to sprays. Moreover spraying chemicals especially in sweet corn and baby corn is strictly not advisable, since it is often consumed with less processing. Choosing a variety with tight husk and husk covering the tip could offer some protection against FAW.