Natural Resources and Volume 10, Issue 2, 2020 Sustainable Development DOI: 10.31924/nrsd.v10i2.049

POTENTIAL INTEGRATED MANAGEMENT PRACTICES AGAINST DESERT LOCUSTS (SCHISTOCERCA GREGARIA) IN NEPAL: A MINI REVIEW

Himal Adhikari*#

* Agriculture and Forestry University, Rampur, Chitwan, Nepal email: [email protected];

Abstract Desert locust (Schistocera gregaria) (: ) is an aggressive and voracious swarming grasshopper, a migratory pest that feeds on almost every vegetation on its way. In Nepal first desert locust incidence was reported in 1962 and major crop damage was reported in 1996. After 24 years, Desert locust was again reported on 27th June 2020 from Bara, Sarlahi, Parsa, and Rupendehi districts of Nepal. Until now, out of 77 districts, the incidence of locust has been reported from 55 districts and that had destroyed different crops in about 1118 hectares of land. This review highlights the biology of the pest species Schistocera gregaria and appropriate management practices and approaches that Nepalese farmers can afford and adapt. Mechanical measures like making a loud noise, generating smokes and fumes, digging trenches, net trapping could be done to control and monitor the pest for small scale farmers. Use of Nosema locustae, and combination of Paranosema locustae and Metarhizium anisopliae var. acridum were found as the best biological control agents. Neem, linseed oil, Allium cepa oil are effective botanicals whereas Malathion, chlorpyrifos, lamdacyhalothrin, and deltamethrin are effective chemical pesticides available now. The overall integration of mechanical, biopesticides, biological, chemical methods is the best combination of methods to reduce the impact of pest.

Key words: Metarhizium anisophilae var. acridum, Nosema locustae, Paranosema locustae, Schistocera gregaria, traditional control methods;

INTRODUCTION

Desert locust (Schistocerca gregaria) (Forskål, 1775) (Orthoptera: Acrididae) is a short-horned grasshopper that has a swarming process. It is the polyphagous mobile species that feed on any kind of plants i.e. crops, pasture, and fodder. In 1 km2, a swarm can consist of around 150 million locusts that fly in the direction of wind up to 150 km/day (Draper, 1980). An average locust swarm feed equivalent to 10 elephants, 25 camels, and 2500 people in one day (Aggarwal, 2020). If desert locusts appear and spread in similar ways in upcoming years then it will be serious threats to Nepal and Nepalese farmers. This pest is unknown to many and it has created fear for many farmers in Nepal. When there are excessive moisture conditions and green vegetation around, the locust's population increases rapidly (FAO, 2004; World Meteorological Organization & Food and Agriculture Organization of the United Nations, 2016). Due to heavy rainfall in the Arabian peninsula over that 18 months in spring 2019, the desert locust migrated to Iran, Pakistan,

# Corresponding author 115 India and Nepal, and south to East Africa (FAO, 2020; Stone, 2020). After 24 years, on 27th June 2020 desert locusts were first seen in Bara, Sarlahi, Parsa, and Rupendehi districts of Nepal (Mandal, 2020; Jha et al, 2020). Out of 77 districts, desert locusts have reached 55 districts of Nepal and it is estimated that around 7-8 million locusts have entered Nepal from India (Jha et al., 2020). The effective control of desert locusts is difficult. However, to mitigate the effect of desert locusts this review article can assist the farmers of Nepal to select the appropriate management practices and implement them wisely. This review article aims to assess the biology of desert locusts and also provide the management approaches to reduce the impact of the pest.

MATERIAL AND METHOD

This review article is based on information and facts from secondary sources. From Journal articles, reports of FAO, Books, Book section, and websites major information were collected, and findings were given a brief description in this review article. Nomenclature: Kingdom: Animalia Phylum: Arthropoda Subphylum: Uniramia Class: Insecta Order: Orthoptera Suborder: Family: Acrididae Subfamily: Genus: Schistocerca Species: Schistocerca gregaria (Forskål, 1775)

RESULTS AND DISCUSSION

1. Damage

The Desert locust is a phytophagous, polyphagous pest. The species damages the plant by eating leaves, flowers, fruits, bark, seeds, and the terminal portion of the plan (Steedman, 1990). Locusts consume the food equivalent to their body weight i.e. 2g/locusts/day and move 150 km/day (Murali Sankar, Shreedevasena, 2020). Desert locust feeds on more than 400 species crops (Uvarov, 1924). Desert locust damage both food and cash crops i.e. Bulrush millet, Maize, Cotton, Fruit trees, Grasslands and rangelands, Coffee, Sugarcane, Rice, Wheat, and Barley, Maize, Sorghum

116 (Steeedman, 1990). In 2020, locusts swarmed in many countries including Ethiopia, Kenya, Congo, Sudan, Uganda, Somalia, Eritrea, India, Pakistan, Iran, Yemen, Oman, and Saudi Arabia, Nepal (Njagi, 2020; FAO, 2020). In Somalia and Ethiopia desert locust‟s outbreak was considered the worst in 70 years and has destroyed 70,000 ha of land (Peng et al., 2020). In India desert locusts have damaged was found worst in 27 years and destroyed crop states like Punjab, Maharashtra, Uttar Pradesh, Madhya Pradesh, Gujarat, and Ranajstan. (Goswami, 2020; Kiran, 2020) The desert locust is termed as “Salaha” in Nepal. In Nepal first locust infestation was experienced in 1962. The worst locust invasion took in 1996 when the swarms destroyed 80 % of crops in Chitwan and significantly, less damage was seen in Makwanpur, Mahottari, and Bara districts (Mandal, Prasain, 2020). In 2020 it has been reported that locust destroyed crops in 1,118 ha of land out of which 580 ha land in Dang, 283 ha damage in Pyuthana and Makwanpur, Arghakhanchi and Palpa (Figure 1.) sustained crop damage in 105, 100, and 50 hectares of land, respectively (GON, 2020; Mandal, 2020) 700 580 600

500 400 283 300

Surface(ha) 200 105 100 100 50 0 Dang Pyuthan Makwanpur Arghakhanchi Palpa Fig.1. Damage of desert locusts(ha) in different district of Nepal:2020

2. Biology of pest

The lifecycle of desert locusts consists of egg, hopper, and winged adults. During the copulation tip of the abdomen of male and female locusts come in contact and the male transform spermatozoa to the body of the female. The time for copulation varies from 3 to 14 hours (Steedman, 1990) Female store spermatozoa in the body and used to fertilize the eggs.

2.1. Egg: Females lay the eggs in moist and damp soil conditions by inserting its ovipositor 5- 10 cm below the soil surface (Cressman, Symmons, , 2001). In the gregarious phase, locusts lay 80 eggs while in the

117 solitarious phase 90 - 100 eggs (World Meteorological Organization & Food and Agriculture Organization of the United Nations, 2016). The egg hatches in about 2 weeks but the hatching period can vary between 10 - 60 days (Roffey, Popov, 1968; Ashall, Ellis, 1962). Size: Egg pod size varies from 6.2 - 7.5 mm in length (Maeno et al., 2013).

2.2 Immature stages: Hoppers: In gregarious and solitary locust, hopper goes from 5 and 5 - 6 instars, respectively (World Meteorological Organization & Food and Agriculture Organization of the United Nations, 2016). When they hatch, they have no wings and are called hoppers and after 5 - 6 molts, they become adults with well-developed wings (NRI, 1990). Hopper period is about 36 days on average but can vary between 24 - 95 days (Cressman, Symmons, 2001). Color of hoppers: Hopper color depends upon the density at which they are been living. In solitarious phase, they are usually green but larger one are yellowish or pale brown and in gregarious phase young hoppers are black and as they get old black markings develops in a yellow background (NRI, 1990) According to different instars the color development is listed in Table 1. Table 1 Characteristics of different instars of Hopper Instar Characteristics 1st Initially white and turns black in 1-2hours 2nd Large head and pale color pattern 3rd 2pairs wings develop at each side of the thorax 4th Color is black and yellow 5th The color is bright yellow with distinct black patterns Sources:(Joshi et al., 2020)

Size: Hoppers are 2 – 3 mm long in the fourth and about 6 – 8 mm in the fifth instar (NRI, 1990).

2.3. Adults: After 5th molting adults emerge and take 10 days to harden so that they can fly (World Meteorological Organization & Food and Agriculture Organization of the United Nations, 2016). It is 2.5 to 5 months for adults. Size: Each adult locust is the 7 – 8 cm length and about 2 g in weight (Showler, 2008). Color of adults: Generally, young swarming adults are pink in color varies from dark to light while older but immature ones are browner. On sexual maturity, they turn yellow which becomes bright in males (NRI, 1990). But non-swarming adults are sandy colored, brown or greyish.

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3. Control/Management

Complete eradication of desert locusts is not advisable and hard to achieve but certain management practices can be adopted to keep the population below the threshold level.

3.1 Monitoring and forecasting GIS, GPS, Remote sensing allows us to know about breeding, movement of the swarm on specific environmental conditions (Healey et.al., 1996). Use of LANDSAT and National Oceanic and Atmospheric Administration (NOAA) satellite images can be monitored to analyses green vegetation blooming and spreading in desert locusts breeding area based on NOAA Advanced Very high-Resolution Radiometer sensor (Tucker et al., 1985). Satellite data provides information in the detection of rainfall and vegetation area that are suitable for egg-laying, hatching, and development stages (Cherlet et al., 1991). By knowing the possible presence of desert locusts other management strategies can be adopted to control desert locusts. Similarly, all these tools and devices help to undertake necessary control operations on time, so that loss can be minimized.

3.2. Mechanical control Traditional mechanical control methods are effective in the place where there is low locust infestation, and labour is cheap. Making noise, generating smokes, digging trenches can disrupt, divert, and suffocate the locusts respectively (Waloff, Baron, 1973). Desert locusts are active at day but at night locust cluster on trees and open ground without dense vegetation (Khan, 2020) Till sunshine they are inactive so a mosquito net can be used for collecting the desert locusts.

3.3. Botanical methods Fungi used for biological control need high moisture and time to become effective while chemical pesticides are harmful to the human environment and other species. In this case, pesticides prepared from botanical plants represent a better alternative. Studies have shown that the use of linseed oil/bicarbonate emulsion caused 80 % mortality of desert locusts (Abdelatti, Hartbauer, 2020). In the 3rd nymph stage of desert locusts, the use of 1.11 and 1.42 ppm, of Allium cepa oil was found more toxic than 1.34 and 1.61 ppm Petroselinum sativum oil (Mansour et al., 2015). Neem (Azadirachta indica)

119 shows antifeeding action against various instars causing a mortality rate of 80 % in 5th instar larvae (Bashir, El Shafie, 2017).

3.4. Biological Method This category of control methods is based on the use of biological natural enemies to control the desert locusts. Several entomopathogens are used to control immature stages and adults of the desert locusts. These are listed in table 2.

Table 2 Pathogens controlling Desert locusts Pathogens Organism Sources Metarhizium anisophilae (Metschnikov) Sorokin Fungorum Lomer et al., 1883(Hypocreales: Clavicipitaceae) 2001 Metarhizium flavoviridae (Gams, Rozypal, 1956) Fungorum Bateman et al., (Hypocreales: Clavicipitaceae) 1993 Paranosema locustae (Canning, 1953) Fungorum Tounou et al., (Microsporidia: Nosematidae) + Metarhizium 2008 anisopliae var. acridum) (Driver & Milner; Bisch., et al., 2009) (Hypocreales: Clavicipitaceae) Nosema locustae (Canning,1953)(Microsporidia: Fungorum Fu et al., 2010 Nosematidae)

Metarhizium kills about 70 – 90 % of locusts within 14 - 20 days (Lomer et al., 2001). Several egg parasitoids and predators like oligophagous Scelio (Hymenoptera: Platygastridae), Stomorhina lunate (Diptera: Rhiniidae), Systoechus somali (Diptera: Bombyliidae), Trox procerus (Coleoptera: Trogidae) lay their minute eggs inside the egg of desert locusts (Steedman, 1990). predators and vertebrates prey on adults and hoppers of desert locusts which are listed in table 3.

Table 3 Predators controlling Desert locusts Predators Prey on Ant (Hymenoptera : Formicidae) Young hoppers Otis tarda (Otidiformes : Otididae) 5th instar hopper Milvus migrans(Accipitriformes : Accipitridae) 1st and 2nd instar hoppers Ciconia abdimii(Ciconiformes : Ciconiidae) 3rd intsar hoppers Ciconia ciconis (Ciconiiformes: Ciconiidae) 1st instar hoppers Glenurus gratus ( Neuroptera : Myrmeliontidae) Hoppers and adults Anas platyrhynchos (Anseriformes : Antidae) Adults Sources: (Steedman, 1990; Redigolo, 2020)

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3.5. Chemical control This is an effective method of locusts control as it kills the majority of locusts. The most effective means to control the locusts is the use of 0.5 - 1.0 l/ha of ultra-low volume pesticide spray (ULV) (Dobson, 2001). Due to less effectiveness of water-based spraying i.e., emulsifiable concentrate (EC) and wettable powder (WP) formulation ULV spraying is generally carried out. In Nepal, ULV formulation insecticides and equipment to spray ULV spray are not readily available. The government of Nepal (GON) has released the name of insecticides along with its appropriate doses which are listed in the table below (Table 4).

Table 4 Insecticides that control desert locusts

Insecticides (g)a.i./ha Insecticides/ Insecticides/ Pesticide Liter of water ha solution (liter)/ha Malathion 50%EC 125 g 3 ml 1850 ml 600 L Lamdacyhalothrin 20 g 0.77 ml 400 ml 600 L Chloropyrifos 20%EC 225 g 1.88 ml 1125 ml 600 L Deltamethrin2.8%EC 12.5 g 0.75 ml 450 ml 600 L Deltamethrin 11% EC 12.5 g 0.20 ml 120 ml 600 L Source: (GON, 2020)

CONCLUSIONS

According to FAO, 45 million km2 of land in 90 countries are potentially prone to locust attacks, if not controlled in time. Desert locusts attack in Nepal is a serious threat to Nepalese farmers as it can raise food insecurity and create a havoc condition. Due to its polyphagous nature, all crops are in a vulnerable condition of being attacked. This review article helps to create awareness among the farmers so that timely management practices can be adopted and loss can be minimized. There is no immediate threat to Nepal as the rainy season is going to end in September but locusts can cause damage to crop on the onset of next year monsoon. Therefore, for the effective management of desert locusts the integration of monitoring, mechanical, biological, botanical, chemical pesticides are best.

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Received: September 17, 2020 Revised: October 7, 2020 Accepted and published online: November 30, 2020

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