Eco-friendly management of fall armyworm in NE region

N Kennedy / R Karthik / R Harish / T Rojeet / S Mareena *

Fall Armyworm, Spodopterafrugiperda is a major economic pest of many agricultural and horticultural crops. It feeds on more than 350 plant species, causing major damage to economically important cultivatedgrasses such as maize, rice, sorghum, sugarcane, wheat and also other vegetable crops and cotton (Goergen et al., 2016).

It has become a serious pest on maize within a short time of its invasion with the pest infestation ranging between 6.00 to 100% on maize (Mallapur et al., 2018). Where larvae feed on vegetative and reproductive plant stages viz., leaves stems, buds, fruits and cobs which lead to substantial yield loss.

The yield losses in maize ranging from 8.3 M to 20.6 M tons per year from 12 maize producing countries, this pest can reduce corn grain yield up to 34% and estimated a loss of U$400 million annually in Brazil.

In Africa, recent invasion causes severe economic loss ranging from US$ 1-3 billion. The outbreak in Mizoram caused by S.frugiperda, has affected maize cultivation in 1,747.9 ha in 122 villages and causes drastic losses of 200 million rupees (www. thehindu businessline.com, May, 2019).

S.frugiperda was confined to American continents till 2015. The pest was reported for the first time out of American continents in 2016 from Benin, Nigeria, Togo and Sao Tome and Principe of Africa and in 2018 it has been spread into 43 African countries causing significant loss to maize production. This pest was reported for the first time in Asia in May 2018 from Shimoga of Karnataka, India (Kalleshwaraswamy et al., 2018) on maize.

Till June, 2019 this pest had been reported from 20 States viz., Karnataka, Maharashtra, Gujarat, Madhya Pradesh, Tamil Nadu, Andhra Pradesh, Telangana, Bihar, Rajasthan, Jharkhand, Chhattisgarh, West Bengal, Uttar Pradesh, Sikkim, Nagaland, Manipur, Assam, Arunachal Pradesh, Mizoram and Meghalaya. Favourable weather conditions play a major role in FAW dispersal and subsequent infestation.

The fall armyworm (FAW), S.frugiperda is a notorious pestiferous insect with high dispersal ability, wide host range and high fecundity that make it one of the most severe economic pests. And in management aspects it has already developed resistance against almost all kind of pesticides. In this case we need to go for natural control, where beneficial organisms play an important role.

The maximum per cent predation of Marucavitrata by Eocantheconafurcellata bug was 56% under laboratory conditions (Agnihotri et al., 2013). Andrallusspinidens reared on Spodoptera sp. which feed and kill as many as 100 larvae during their adult life (Shintani et al., 2010).

The farmers use a range of management tactics in American and African subcontinent, including host plant resistance, insecticide applications and biological control. However, ecofriendly management practices help to reduce the pesticide usage and reduce the hazardous effect on the environment.

PEST IDENTIFICATION

Larva: Fall armyworm can be easily identified with the presence of predominant inverted. Y-shaped suture between the eyes in the head and presence of black spots arranged square pattern on 8th and trapezoid on 9th abdominal segments. Adult: Male moth (A) has fawn coloured spot and white patch at the apical margin of the wing. Female (B) is dull with faint markings.

NATURE OF DAMAGE

The pest infestation can be easily recognised with the presence of large amount of faecal matter on the defoliated plants. In severe condition the pest totally feed on the central whorl of the plant leading to total economic loss. First instar larvae feeds by scraping and cause papery symptom. By the second or third instar, larvae begin to make holes in leaves and eat from the edge of the leaves inward. Older larvae cause extensive defoliation often leaving only the ribs and stalks of corn plants, or a ragged, torn appearance.

BIOLOGY

Life cycle of FAW - Egg:- Dome shaped, laid in lower surface of leaves, total eggs laid 1500-2000, duration 3-5 days. Larvae:- No. of instars 6, duration 14-20 days. Pupa:- Pupation: soil, duration 6-10 days. Adult:- Pre-oviposition 3-4 days sexual dimorphism duration 7-11 days.

PEST MONITORING

A. Agro-ecosystem analysis.

Agro-Ecosystem Analysis (AESA) is an approach, which can be gainfully employed by extension functionaries and farmers to analyse field situations with regard to pests, defenders, soil conditions, plant health, the influence of climatic factors and their-relationship for growing healthy crop. Such a critical analysis of the field situations will help in taking appropriate decision on management practices,. The basic components of AESA are:

(1) Climatic factors.(2) Soil conditions (3) Pest and defender population dynamics (4) Plants health at different stages. (5) Built-in-compensation abilities of the plants etc. Agro-Ecosystem Analysis of NER

o Climatic condition in North-east is subtropical type, where the mean temperature varies from 5 to 30oC and the mean relative humidity remains between 70% and 85%. Interaction of pest and pathogens (EPF) will be significant.
o Soil type is mostly acidic in nature; Therefore, it favours the growth of entomopathogenic fungi.
o North-Eastern States are considered as one of the mega Bio-diversity hotspots. Isolation and identification of native biocontrol agents will be beneficial and environmentally safe.
o Diversified cropping system showed beneficial in reducing major crop pest in the NE region specially FAW as monocropping of maize will increase the pest population significantly.

B. Field scouting

o Monitoring of larval damage symptom per plant growth stages.
o Weekly scouting (W-shape); Select 10 plants from each stopping point.
o Monitor the crop by using pheromone trap, 1 acre-1.
o For effective control measures we should go for early detection and early adoption methods.

C. Action threshold/economic threshold level (ETL)

The Economic threshold level (ETL) is an attempt to improve decision making practices by using partial economic analysis on the impact of the control practice such as spraying a pesticide. At the ETL, the benefit of spraying is equal to the losses caused by the insects in the field. The farmers are advised to take appropriate control measures when the incidence crosses ETL.

D. Eco-friendly management of law

Detecting fall armyworm infestations before they cause economic damage is the key to their management. On maize, if 5% of seedlings are cut or 20% of whorls of small plants (during the first 30 days) are infested with FAW, it is recommended to apply an effective control measure to prevent further damage (Fernandez, 2002).

Strategies used to manage FAW including cultural practices, biological control using parasitoids: Trichogramma-pretiosum, Cotesia sp., Chelonusblackburni; predators: birds, rodents, beetles, earwigs; and pathogens: Metarhiziumanisopliae, Nomuraearileyi, Beauveria-bassiana (Gross and Pair, 1986). The proper timing for applying the above management options is very important for effective pest control, also taking into consideration the FAW larval stages cycle and the time of day for application.

CULTURAL CONTROL

Cultural control is an important component of a pest management strategy for FAW. The monocropping of maize offers a favourable environment for FAW to spread fast. The cultural control includes avoiding late planting since the maize ears would be heavily attacked by a higher FAW infestation than those of the early plantings. Also, intercropping and rotating maize with non-host crops like sunflower and bean may be useful to minimize the invasion of FAW (FAO,2018).

Cultural control methods such as maize intercropping, handpicking and killing of caterpillars, application of wood ashes and soils to leaf whorls gives maximum reduction in pest population if taken up in early stages (Abate et al., 2000). A survey conducted in Ethiopia and Kenya showed that 14% and 39% of the farmers practiced cultural methods such as handpicking and killing of caterpillars, used for the management of FAW (Kumela et al., 2018).

BIOLOGICAL CONTROL

Biological control can be considered as a powerful tool and one of the most important alternative control measures providing environmentally safe and sustainable plant protection. The success of biological control depends on understanding the adaptation and establishment of applied biological control agents in agricultural ecosystems. Microbial pathogens and arthropod biocontrol agents have been successfully used in agricultural systems (Pilkington et al, 2010).

Their production costs have been significantly reduced in recent times as they are mass produced in liquid media (such as; bacteria, fungi and nematodes) (Mahmoud, 2016). Even though biological control may not replace conventional insecticides, a number of parasitoids, predators and pathogens readily attack larval and adult stages of FAW.

Release of egg parasitoids: Trichogramma-pretiosum, Telenomus spp. Provides significant reduction in pest population at the dosage 5 lakh ha-1. Larval parasitoids: Glyp-tapanteles-creatonoti Campoletis- chlorideae Apanteles creatonoti Cotesia spp. Tachinidfly etc., for the reduction of larval population.

Use of predators: Innundation of Eucantho-conus bug, stink bug, reduvid bug, wolf spiders and conservation of wasps, predatory beetles like Cicindella sp. ground beetle, rove beetle. Ear wig (Forficula spp.) and Chrysoperla spp. will be useful in reducing the FAW population.

Entomopathogens: Application of Entomo- pathogens like Metarhi-ziumanisopliae talc formulation (1x108cfu g-1) @ 5 g 1-1 whorl application at 15-25 days after sowing, Nomuraearileyi (1x108cfu g-1) @ 3 g 1-1 whorl application at 15-25 days after sowing and Bacillus thuringiensisvarkurstaki formulations @ 2 g 1-1 (or) 400 g acre-1 will be effective on controlling FAW. Botanicals like Neem based products will be effective in controlling the FAW.

CHEMICAL CONTROL

The proper timing and selection of insecticides with recommended dosage are the prerequisite for effective management of the pests. Inappropriate use of chemical controls could lead to resistance development, plant damage, and risks to human health and the environment (Togola et al., 2018).

Seed treatment: Cyantraniliprole 19.8% + Thiomethoxam 19.8% FS @ 4 ml kg-1 seed reported to offer protection up to 2 week after germination.

Pesticide spray: Emamectin benzoate 5 SG @ 0.4 g 1-1Spinosad 45 SC @ 0.3 ml 1-1; Chlorantra-niliprole 18.5 SC @ 0.4 ml 1-1 etc.

CONCLUSION

The fall armyworm (S.frugiperda) has recently been reported in India and caused huge damage to maize crop in 2018-2019 cropping season. In the short period of time, the pest spread throughout the country including NE region of India. Moreover, monoc-ropping and planting of maize during the warmer and moister summer season provides a favourable environment for the insect to quickly multiply and spread to more areas.

Therefore, effective control should focus since it is impossible to avoid this pest unless developing sustainable management. Furthermore, there is an urgent need to increase awareness among the farming communities about the life stages of thepest, scouting for the pest (as well as its natural enemies), understanding the right stages of the crop on which high economical damage may occur by FAW, and the time for management application and implementing low-cost agronomic practices and other landscape management practices for sustainable management of the pest.

At the same time, it is important to introduces, validate, and deploy low-cost, environmentally safer, and effective technological interventions with the help of extension workers is theneed of the hour.


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