Change in pest scenario in the light of Bt cotton in India

Presented by:PARTHA DEBNATH

CAU/CPGS/ENTO/M14/04

Credit seminar

Cotton crop:• Cotton (Gossypium sp.) is designated as

“White Gold” and “King of fibres” among all the fibre crops.

• It belongs to the family Malvaceae.

• India ranks 2nd in world cotton production 6423 metric tons (Statista, 2015).

• It is cultivated in India in 126.55 lakh hectare area with a production of 401.00 lakh bale of seed cotton per year (Cotton Corporation of India, 2014).

• The pest spectrum of cotton is quite complex and as many as 200 species of insects have been reported to attack cotton at different stages of crop growth in India (Anon., 1981).

• But among these, the bollworm complex consisting of three notorious bollworms are considerd to be of great menace.

o American bollworm- Helicoverpa armigera Hub.

o Pink bollworm- Pectinophora gossypiela Sau.

o Spotted bollworm- Earias vitella and Earias insulana Fab. ( Patil et al., 2007)

• Cotton occupies 5 % of the total cultivable area however consumed 55 percent of the totally used pesticides in all crop cultivation in India (Barwale et al.,2004).

Insect pests present in cotton in India Sucking pests: Jassids- Amrasca biguttula

Red cotton bug- Dysdercus cingulatus

Aphid- Aphis gossypii

Mealybug- Phenacoccus soleneopsis

White fly- Bemesia tabaci

Damage symptoms of the bollworm complex• Pink bollworm:

Pin head size holes on the bolls.

Rosette flowers.

• American bollworm:

Bolls showing regular, circular bore holes.

Presence of granular faecal pellets outside the bore hole.

Yield loss upto 80% ( CICR, technical bulletin no-22).

• Spotted bollworm:

Drying and drooping of terminal shoots.

Flaring up of bracts during square and young boll formation stage.

Holes on bolls and rotting of bolls.

Bt cotton Bt cotton is a

genetically modified cotton crop.

It expresses an insecticidal protein which is derived from a soil bacterium, Bascillus thuringiensis var kurstaki.

Bt was first discovered by a Japanese scientist Isiwata in 1901.

The Bt gene cry1Ac was used to develop the first Bt cotton variety.

The acreage under Bt cotton was increased to 6.33 million hectares in 2007-08 from 3.69 million hectares during 2006-07(ISAAA, 2007).

Why do we need Bt cotton?

About 162 species of insects occur in cotton at various stages of growth of which 15 are key pests (Kannan et al., 2004).

About 9400 M tonnes of insecticides worth Rs 747 crores were used only for bollworm control in 2001 (Kranthi, 2012).

Before the introduction of Bt cotton, insecticide quantity applied on cotton was the highest, relative to other cultivated crops.

Cotton bolls are highly vulnerable to hidden insects such as the American bollworm, Pink bollworm and Spotted bollworm.

The pink and spotted bollworms are hidden feeders and generally do not come into direct contact with insecticide sprays.

The American bollworm comes into contact with insecticides, partially, has developed resistance to almost all the insecticides recommended for its control in all regions of the world.

About 50.0% of all insecticides in India were being unsuccessfully used for cotton pest control, until the year 2001, before Bt cotton was introduced.

Of these insecticides about 70.0% was for bollworm control and the rest for sap-sucking insects. (Kranthi, 2012).

Mode of action of Bt:• In the commercialized transgenic Bt-cotton plants, the protein

is expressed in all parts of the plant.

• When the larvae feed on Bt plants, they ingest Bt protein along with the plant tissues.

• If it is a susceptible insect like bollworms, the Bt protein gets activated in the mid-gut.

• The activated molecules bind themselves to certain receptors present on the gut membrane.

Bt strain active against various types of insects

Strain Target insects

Bt subsp. Kurstaki, sotto, aizwai Lepidopteran larvae

Bt subsp. israelensis Mosquito larvae

Bt subsp. tenebrionis Coleopteran larvae

Bacilus poppilae var. poppilae Japanese beetle larvae

Reddy, 2010

Classification of cry genes and their pathogenecity

Cry gene Toxic to the insect order

Cry1A(a), Cry1A(b), Cry1A(c) Lepidoptera

Cry1B, Cry1C, Cry1D Lepidoptera

Cry II Lepidoptera, Diptera

CryIII Coleoptera

CryIV Diptera

CryV Lepidoptera, Coleoptera

Prasad, 2004

Chronology of development and approval of Bt cotton in India

Year Development of bt cotton in India

1995 Mahyco applied to DBT for permission to import a small stock of Bollgard® (Bt-cotton) seeds from Monsanto Company, USA.

1996 •A nucleus stock of the American variety Coker 312 containing the Bollgard® was received by Mahyco from Monsanto, USA.

•Mahyco initiated crossing Coker 312 with the Indian cotton breeding lines to introgress cry1Ac gene.

1996-1998 •Risk-Assessment Studies were conducted in laboratories and fields.

•These included pollen escape, aggressiveness and persistence, biochemical analysis, toxicity and allergenicity.

Year Development of bt cotton in India

1998-1999 Multi-location field trials at 40 locations in 9 states to assess agronomic benefits and safety. Data submitted to RCGM.

1999-2000 Field trials repeated at 10 locations in 6 states. Data submitted to RCGM

2000 Based on the recommendations of RCGM, the GEAC gave permission for large scale field trials in 85 ha and seed production in 150 ha.

2001 •Kharif 2001 – Large scale field trials covering 100 ha.

•Field trials were also conducted by All India Coordinated Cotton Improvement Project of the Indian Council of Agricultural Research (ICAR).

Year Development of Bt cotton in India

2002 •On 26 March 2002, GEAC approved Mahyco’s three Bt-cotton hybrids, viz. MECH 12Bt, MECH 162Bt and MECH 184Bt, for commercial cultivation in India.

Source: Manjunath, T.M., AICBA, 2007

How Bt cotton is developed For development of any transgenic crop, there are five

important steps:

Identification of effective gene or genes. Gene transfer technology. Regeneration ability from protoplast. Gene expression of the product at desired level. Proper integration of gene.

In case of cotton, Agrobacterium-mediated gene transfer technique has been essentially used (Firozabady et al., 1987).

Advantages of Bt cotton in India Bollworm control: Preventing yield losses from an estimated

damage of 30.0 to 60.0% each year in India thus far from 2002 to 2011.

Increased yield: Yields are estimated to have increased at least by 30.0% due to effective protection from bollworm damage.

Reduction in pesticide use for bollworm control: 46% in 2011, 26% after 2006 and 21% during 2011-12 (Kranthi, 2012).

Disadvantages of Bt cotton Small and marginal farmers of India can not afford the high

cost of Bt cotton seeds, Rs.1600 for 450 g of seeds.

Effectiveness up to 120 days, after that the toxin producing efficiency of the Bt gene drastically reduces (Jeyakumar et al., 2008).

Adverse effect on insecticide manufacturing companies due to reduced use of pesticides significantly by Bt cotton. 

• Ineffective against sucking pests like jassids, aphids, whitefly etc. 

• Adverse effect on the employment of those persons engaged in pesticide industries. 

• Promotes malpractices such as mixing of low-cost non Bt cotton seeds with high cost Bt cotton seeds for sale. This severely affects on cotton production and economic condition of the farmers using such fake seeds.

Bt cotton: Now and Then• Insecticide usage for bollworm control: From 1995 to 2004 was average 6767 M tonnes.

From 2005 to 2011 was average1089 M tonnes.

• Insecticide usage for sucking pests: From 1995 to 2004 was average 3335 M tonnes.

From 2005 to 2011 was average 4600 M tonnes. (Kranthi, 2012).

Over all , up to 69% reduction in usage of pesticides has been achieved through Bt transgenic cottons (Kranthi and Khadi, 2011).

• Insecticide use on cotton was 46% of the total insecticides used in India in 2001 and before.

• But soon declined to 25% within 4 years of Bt cotton introduction.

• Insecticide usage on cotton further declined to only 21% of the total usage in India during 2009 and 2010 (CICR, 2011).

Pest resurgance in Bt cotton:• Tobacco caterpillar S. litura has been noted as emerging pest

in BG-I genotypes in India (Jeyakumar et al., 2007) with advent of Bt genotypes.

Cotton mealybug: • A new pest, mealybug which was not familiar earlier started

destroying cotton crops.

• Reducing yields up to 40-50% in affected fields since 2006 (Compendium of Cotton Mealybugs, 2011).

Mealybug infestation were recorded in 2006 on G. hirsutum in all the nine cotton-growing states of India- Punjab, Haryana, Rajasthan, Gujarat, Madhya Pradesh, Maharashtra, Tamil Nadu, Andhra Pradesh and Karnataka. (Dhara Jothi et al., 2008).

Nearly 2000 acres of cotton crops were destroyed by mealybug (Goswami, 2007).

Outbreak is serious in both Bt and non Bt cottons.

Whitefly: a black story

• Whitefly became a major pest on cotton in India only after 1984.

• It feeds on more than 500 plant species and by sucking sap from under surface of leaves causes yellowing and upward curling of the leaves.

• Cotton losses were estimated to be in the range of 15-20% and sometimes up to 30% (Cotton Statistics and News, 2015).

• In August, 2015, a whitefly outbreak devastated the bt cotton crop in Bathinda, Faridkot districts of Punjab and Sirsa district of Haryana.

• The insect infestation and whitefly incidence were higher than the previous three years.

• Whitefly incidence ranged from 1.6 to 90 adults /3 leaves during July-August in Sirsa. Thus far, high levels of whitefly infestation were noticed in the second week of August in both the two states.

• Fields sprayed with repeated insecticide sprays, insecticide mixtures, fipronil and pyrethroids had the highest levels of whitefly infestation.

• 15 farmers committed suicide due to failure of crop. (TOI, 2015).

Causes of outbreaks

• Synthetic pyrethroids and acephate induce bollworms and whiteflies where spinosad induces mealybugs infestations (Cotton Association of India, 2015).

• The natural enemies of whitefly are generally more susceptible to insecticides than the insect pests. For example, the whiteflies have a waxy coating over the body which protects against insecticides, but its natural enemies are not protected.

• The whiteflies feed from under surface of the leaf where insecticides do not easily reach.

• The natural enemy predators and parasites are generally present all over the plant and get exposed to insecticides.

• Insect pests become resistant quickly to insecticides whereas natural enemies take a longer time for resistance development.

• There is a phenomenon reported with whiteflies and American bollworms, called ‘Hormoligosis’ which causes insects to rapidly reproduce and multiply when the surviving insects perceive chemical stress.

• Some reports also describe insecticide-induced physiological changes in the plant which become more favourable to insect pests. Thus more the insecticide sprays -more the problem.

• This season insecticides such as fipronil and synthetic pyrethroids were used frequently also as mixtures with organophosphate insecticides (monocrotophos, acephate and triazophos) in north India right through July-August (CAI, 2015).

• These insecticides severely induce pest populations leading to resurgence and outbreaks.

• This year, in many parts of the north, there was delay in sowing by 15-20 days, which helped the whitefly with rainfall less than 100 mm and cloudy weather with high humidity.

Insecticide resistance of Whitefly

• Studies conducted by CICR showed that whiteflies in north India have developed resistance to all the commonly used insecticides.

• ‘Neonicotinoid’ group insecticides are most commonly used in north India. Whitefly resistance to the neonicotinoid insecticides is high in north.

• This led to the severe whitefly outbreaks and further development of resistance.

• CICR showed that high level of insecticide resistance to acetamiprid, thiomethoxam, imidacloprid, monocrotophos, cloropyriphos, triazophos and acephate is there in north India.

• So, for effective management of this pest, crop natural ecosystem should be least destroyed.

Is it true that Bt cotton is responsible for emergence of new pests: Controversy

• Pests like mirid bugs, mealybugs, dusky and red cotton bug used to occur even before the advent of Bt-cotton, but used to be controlled due to repeated spraying mainly against bollworms.

• In case of Bt-cotton, the insecticide usage has been drastically reduced and since Bt does not control such minor pests and if no suitable control measures are taken against them in time, they multiply and cause damage ( Manjunath and Mohan, 2015).

Conclusion

To get the full benefit of Bt cotton, the ideal approach is integrated pest management (IPM) where Bt-cotton is relied upon to control bollworms while it is necessary to be watchful and take appropriate control measures against those pests not controlled by Bt-cotton.

THANK YOU FOR YOUR ATTENTION