DIAMONDBACK MOTH &

ITS BIOLOGICAL CONTROL

Seminar Instructor:

Dr. P.K. Gupta, Prof. & Head Dr. A.K. Singh, Assoc. Prof.Dr. Umesh Chandra , Asstt. ProfDepartment Of Entomology Presented

by:Mun mun Mohapatra,M.Sc.Ag.(Entomology)A-8184/14

Scientific Name: Plutella xylostella

Order: Lepidoptera

Family: Yponomeutidae

Damaging Stage: Larvae

(Caterpillars)

DIAMOND BACK MOTH

It is one of the most destructive cosmopolitan pests of cruciferous crops such as cauliflower, cabbage, radish, knoll-khol & mustard etc.

It causes significant economic losses upto 52% approximately with an estimate of 4- 5 billion US $ per year globally.

It is most widely distributed pest among the other lepidopterans. The larvae feeds on the foliage at growth stage of the crop and

greatly reduce quality and yield as well. In past 50 years, it has becomes one of the most difficult insect in

the world because of resistance to every class of insecticides used extensively against it.

In India, it is one of the major constraints in the profitable cultivation of cole- crops.

INTRODUCTION

DBM has probably originated in the Mediterranean region.

Accidentally introduced from Europe in 1746, it was 1st reported in N. America in Illionis in 1854 & from Western Canada in 1885.

It is found over much of N. America, S. America, Southern Africa, Europe, India, S-E Asia, New Zealand and parts of Australia.

In India, DBM was reported in 1914 on cruciferous vegetables.

In India, it is also most devastating pest in the states of Punjab, Haryana, Himachala-Pradesh, Delhi, Uttar-Pradesh, Bihar, Tamil- nadu, Maharastra and Karnatak

DISTRIBUTION

The Diamondback moth feeds only on members of the family Cruciferae/ Brassicaceae.

Study on food plant preference of DBM revealed that the larvae have marked preference for cauliflower & cabbage among the 40 species of crucifers.

This is due to the fact that both plants posses fleshy & succulent leaves and provide olfactory & gustatory stimuli for successful host selection & development.

Alternate weed hosts are especially important in maintaining in DBM population in temperate regions in spring before cruciferous crops are planted.

The host range of DBM is limited to crucifers that contain mustard oil & their glucosides.

HOST PLANTS & HOST SPECIFICITY

The glucosides such as sinigrin, sinalbin & glucocheirolin act as specific feeding stimulants for DBM.

Certain chemicals such as sulfur-containing glucosinolates or its metabolites and allyl-isothiocyanates are present in crucifers & act as oviposition stimulants.

Sulfur deficient plants are not attractive to DBM for oviposition.

Allyl-isothiocyanates also stimulates egg production in diamondback moth adults.

Cont………

BIOLOGY (MARK OF IDENTIFICATION

• Flat, oval-shaped eggs, whitish – yellow & 0.5 mm in length & 0.26 mm in width

• Neonates are pale brown with dark head while full-grown are light green in color &10 mm in length

• 6 mm in length and light brown in color

• Small, grayish brown color moth ,the fore wings have 3 triangular, white spots along inner margin & at rest these give diamond shape & hind wings have fringed long hairs

EGG LARVAE

PUPAEADULT

EGG LARVAE

PUPAE ADULT

FEMALE MALE

Eggs are laid singly or in groups of 2-40 on the under surface of leaves. The eggs hatch in 3-9 days.

The larval period is completed in 8- 17 days.

Before pupation the larvae construct a barrel shaped silken cocoon, which is opened at both ends & is attached to leaf surface.

Pupal period lasts for 4 days in hot & rainy season and 5 days in cold season.

BIOLOGY (LIFE CYCLE)

Adult longevity ranges from 6-13 days, females live shorter than male.

Adults begin to mate at dusk on the same day of emergence and mating lasts only 1-2 hours, females mate only once.

Females lay eggs after mating and oviposition continues for 10 days with a peak on the first day of emergence.

2-4 generations occur in colder parts of India and 13-14 generations in South India.

Cont……..

The biology significantly varies on cauliflower, cabbage, radish, turnip, knol-khol, beetroot, amaranthus and weed hosts.

There is no variation in egg period. Pupal- period is shorter and adult emergence is more on

cauliflower. Fecundity is higher on mustard(366eggs/female) followed by

cauliflower, cabbage, radish & knol-khol. The larvae consume and gain more weight on cauliflower than on

other host plants. The consumption index, growth rate, efficiency of conversion of

ingested food, efficiency of conversion of digested food and approximate digestibility are more on cauliflower than on other host plants.

COMPARATIVE BIOLOGY

DAMAGE SYMPTOMS

1st instars •They cause small mines & feed in these tunnels•At first their presence can be detected only from blackish excreta that appear at each mouth tunnel

2nd & 3rd instars •In 2nd instars the mines become more prominent•In 3rd instars the caterpillars usually feed outside the tunnels

4th instars •They feed from underside of the leaves leaving intact a parchment like transparent cuticular layer on the dorsal surface•They bite holes in the leaves & feed on curds

LETS HAVE A LOOKON

BIOLOGICAL CONTROLOF

DIAMONDBACK MOTH

Many countries are still continously plagued by P. xyllostella and there is strong evidence that this is due to lack of crucially important parasites.

Host plant availability and action of its natural enemies are two key biotic factors that regulate DBM populations in the field.

In countries, synthetic insecticides are used to control DBM, which often eliminates natural enemies.

This in turn, can lead to continued intensive use of insecticides, eventual insecticides resistance & control failure.

DBM was the 1st crop pest in the world to be reported resistant to DDT in 1953 in Java, Indonesia.

WHY IT IS NECESSARY

In addition, DBM have distinction of being the 1st insects to develop resistance in the field to bacterial insecticide, Bacillus thuringiensis.

This has prompted increased efforts worldwide to develop integrated pest management (IPM) programmes principally based on manipulation of natural enemies.

DBM populations native to different regions have genetic & biological differences and specific parasitoid strains may be associated with the specific DBM strains.

Therefore accurate identification based on genetic studies of both host & parasitoid is of crucial importance to attaining successful control of DBM through innoculative or innundative releases.

Cont………….

All stages of Diamondback moth are attacked by numerous parasitoids and predators.

Although over 90 parasitoids attack DBM, only about 60 of them appear to be important.

Among these, 6 species attack DBM eggs, 38 attack larvae and 13 attack pupae.

The majority of these species came from Europe where DBM is believed to have originated.

BIOLOGICAL CONTROL

NATURAL ENEMIES

PREDATORS PARASITOIDS

Among predators spiders, wasps, coccinellid beetles, pentatomid bugs, phytoseiulus mites, chrysopids, ophionea beetle and bird predators are important.

It has been observed to build up in later phase of the crop, causing as much as 68-70% larval mortality.

Although predators have been suggested as mortality factors, they have not been commercially exploited against DBM.

Larval parasitoids are most predominant and effective.

Egg parasitoids belonging to poly-phagous genera Trichogramma and Trichogrammatoidea contribute little to natural control and require frequent mass releases.

The most efficaceous larval parasitoids belong to two major genera, Diadegma insulare & Cotesia(=Apanteles) plutellae were found causing 16-70% larval parasitism in India.

STAGES OF DBM

PARASITOIDS ATTACKING THESE STAGES

Egg stage Trichogramma brasiliensis, T. minutum, T. pretiosum, Trichogrammatoidea armigera

Larval stage

Antrocephalus sp, Apanteles aciculatus, A. albipennis, A. halfordi, A. plutellae, A. ruficrus, A. sicarius, A. vestalis, Apanteles sp, Apanteles sp, Brachymeria phyta, D. eucerophaga, D. fenestralis, D. insularis, D. neocerophaga, D. plutelllae, Diadegma sp, Diadromus erythrostomus , Habrocytus sp, ltoplectis sp, Macrobracon hebetor, Macromalon orientale, Microplitis plutellae, Tetrastichus sp.

Pupal stage

Diadromus plutellae, D. subtilicornis, Dibrachys cavus, Euptromalus viridescens , Celis tenellus, Habrocytus sp, Itoplectis maculator, Phaeogenes sp, Spilochalcis albifrons, Stomatoceras sp, Tetrastichus ayyari, Tetrastichus sokolowskii, Thyraeella collaris

STAGES OF DBM

PREDATORS ATTACKING THESE STAGES

PATHOGEN ATTACKING THESE STAGES

Egg stage

Chrysoperla carnea

Larval stage ANTS:

Componatus sericus, Tapinoma melanocephalumPheidole sp

BIRDS:Yellow wag tail (Motacilla flava)Cattle egret (Bulbueus ibis)

Bacillus thuringiensis var. KurstakiNuclear polyhedrosis virus (NPV) Granulosis virus (GV)Paecilomyces farinosus (Fungus)Beauveria bassiana (Fungus)Zoophthora radicans (Fungus)Metarhizium anisopilae(Fungus)Variriomorpha sp. (Protazoa)\Nematode

PRINCIPAL BIOCONTROL AGENTS OF Plutella xylostella

• Five commercially available are Trichogramma pretiosum, T. ostriniae, T. plationeri, T. minutum, T. brassicae.

• These wasps cause mortality by laying eggs in them & also by host feeding.

• T. bactrae, T. pretiosum & T. minutum causes 95-98% mortality.

• T. bactrae & T. pretiosum causes highest rate of mortality (69-72%)

EGG PARASITOID

• Diadegma insulare is most important larval-parasitoid as it is an efficient host searcher & has ability to avoid multi-parasitism & superparasitism.

• It is solitary, host-specific & larval endoparasitoid of DBM.

• It can parasitize 70-90% of DBM larvae & parasitized larvae consume 35-70% less food than non-parasitized larvae.

• It pupate inside the cocoon of mature DBM larvae & these cocoon turns into white instead of green.

• Depending upon the food sources, the no. of DBM larvae parasitized vary from 0-150.

• Microplitis plutellae is also an important & efficient parasitoid as D. insulare .

• But there is exception that, D. insulare is better in large scale infestations whereas M. plutellae is better in small scale infestations.

PUPAL PARASITOID

•Diadromus collaris is a solitary endo-parasitoid that supplements the control achieved by other parasitoids.•It spends its egg, larval and pupal stages inside the DBM pupa while the adult is free-living.•The presence of a silken cocoon surrounding the host pupa plays an appreciable role in the acceptance and parasitization of a particular host.•This species exhibits superparasitism but not multiparasitism.

LARVAL PARASITOID

Trichogramma pretiosum

Trichogramma minutum

Diadegma insulare

Cotesia plutellae

Oomyzus skolowski

If naturally occurring bio-control agents fail to colonize infested fields, or colonize too late in the season to provide effective pest control, augmentive/innundative releases of natural enemies may be effective for reducing pest damage.

In contrast, innoculative releases entail the release of relatively low numbers of bio-control agents early in the season allowing them to establish successfully for pest control later on.

This strategy may prove to be an effective tool where DBM is known to overwinter and causes predictable infestations and damage later in the season

RELEASES OF PARASITOIDS

Bt, Bacillus thuringiensis is a bacterium that is highly effective against larvae of DBM.

Among Bt strains, Bt var. aizurai & Bt var. kurstaki are effective particularly against DBM

Bt products are registered for use on brassica crops that kills only caterpillars and are very valuable in managing diamondback moth (DBM).

These products include Dipel®, Delfin®, Halt®, Xentari®, Novosol®, Agree®, Biobit® and Thuricide®.

Bt is applied at 500gm a.i /ha. at 10 days interval.

ENTOMOPATHOGENS: BACTERIA

•The caterpillars eat the Bt, which contains spores and crystals.

•The crystal toxin is activated by gut enzymes.

•The toxin binds to receptors on the gut lining.

•The caterpillar stops feeding 20 to 30 minutes after eating the Bt.

•The gut lining is destroyed.

•Spores move into the body cavity and start to multiply.

•The caterpillar dies in 1 to 3 days

HOW BT WORKS:

Bt and fungi are quite dissimilar in their mode of action.

The spores of the bacterium must be ingested by a larva to elicit an effect.

while conidia of the fungus must contact insect cuticle, germinate, and penetrate it through enzymatic action and mechanical pressure, and initiate mycelial growth, resulting in death of insect in a few days.

Zoopthora radicans and Beauveria bassiana are two most effective fungus against larvae of DBM.

FUNGI

It is an important entomo-pathogenic fungus isolated from DBM, reported to cause epizootics under favourable environmental conditions and can reduce local populations to zero.

The moths infected contaminated with Z. radicans can serve as a source of fungal innoculum in the field and airborne conidia lead to epizootics as a result of auto-dissemination in DBM populations.

Although infected insects can survive for sometime, a reduction in feeding damage may occur sooner as the fungus is robust & long-lived.

For example, third instars infected larvae consumed 44% less foliage than healthy larvae.

Zoophthora radicans

There is increasing interest in the use of myco-insecticides based on B. bassiana for the control of DBM.

This pathogen applied at the rate of 3-106 conidia ml-1 gives 100% DBM mortality after 3-7days.

Those contaminated moths effectively transmit (horizontal/ passive transmission) this fungus to healthy moths and larvae foraging on plants.

Sporulating cadavers producing Z. radicans or B. bassiana conidia result in similar transmission rates.

Beauveria bassiana

Myco-insecticides are useful tools that are compatible with IPM of DBM depending on their target specificity.

It involves the attraction of male moths in response to synthetic female sex pheromone into specially designed inoculation chambers containing infective fungal spores.

Once inside the chamber they become contaminated with conidia and then return to the crop, disseminating the pathogen in the local population.

MYCOINSECTICIDES

A number of baculoviruses have been reported to infect P. xylostella.

Granulo-viruses (GVs) showed promising levels of pathogenicity.

A Kenyan isolate of PlxGV (Nyathuna, Nya- 01) applied in the field at 3.0-1013 occlusion

bodies (OB) ha-1 controlled DBM on kale with 82 and 90% infection rates for second and 1st

instars, respectively.

The NPVs isolated from Anagrapha falcifera (AfNPV), Autographa californica (AcNPV), and Galleria melonella (GmNPV) were also infectious to DBM but their potency was moderate to low.

VIRUS

Bio-control of DBM is an important measure that can be integrated into modern IPM programs, particularly when the pest complex is simple and DBM is the dominant species.

Crucifer growers should choose cultivars that are partially resistant to DBM and more attractive to its natural enemies. Ex. Cabbage (All season, Red drum head), Cauliflower ( Early patna, KW-5, KW-8).

They should avoid unnecessary use of fertilizers as it results in higher infestations of DBM and other crucifer pests such as Delia species.

Bt-transgenic crops grown in conjunction with refugia may also enhance sustainable pest management.

INTEGRATION OF BIOCONTROL AGENTS WITH OTHER TACTICS IN IPM

Intercropping should be done which also provide sufficient resorvoir for natural enemies. Ex. cabbage+carrot, cabbage+tomato/mustard.

During application of insecticides ETL should be considered (10 larvae/plant at seedling stage) & also safe to both host & natural enemies. Ex. Phosalone, Permethrin, Deltamethrin, Fenvalerate, NSKE etc.

Different traps should be used using sex pheromone for attracting male moth , which is also helpful in successful establishment of natural enemies.

CONT…….

REFUGIA THAT ATTRACT NATURAL ENEMIES

NASTURTIUMSWEET ALLYSUM

PHACELIA

Diamondback moth is most devastating pest of cole-crops. As it shows resistance to every class of insecticides, its control is

most difficult job. So, modern IPM programme is developed principally based on

natural enemies. But only single biological control or chemical control can’t be

effective against this devastating pest. So by keeping biological control in our mind we should also use

other tactics such as resistant variety, trap crops, intercropping, safer insecticides that will act as synergists for natural enemies.

CONCLUSION

OUR MOTTO is

Prosperity to farmers

&

health for

all