Slugs and snails assignmen tviki

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Slugs and SnailsASSIGNMENT Submitted To :- Submitted By :- Dr. O. P. Chaudhary Vaibhav Dept. of Entomology

Transcript of Slugs and snails assignmen tviki

Page 1: Slugs and snails assignmen tviki

Slugs and SnailsASSIGNMENT

Submitted To :- Submitted By :-

Dr. O. P. Chaudhary Vaibhav

Dept. of Entomology

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Phylum Mollusca

• 2nd largest phylum of animal kingdom.

• Includes slugs and snails.

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Characteristics :-

• Unsegmented, without appandages.

• Mostly aquatic in habit.

• Respiration takes place through gills.

• Circulatory system is open.

• Development may be direct larvel.

• Snail posses a shell but slug doesn’t.

Mollusca

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• Order : Stylommatophora

• Class : Gastropoda

• Without backbone.

• Asymmetrical, unsegmented and spirally coiled body.

• Hermaphrodite in nature.

• Lack of good protection against dehydration, hence avoid direct sunlight.

• Mostly nocturnal.

• During day time, hide in moist place or under debris.

Slugs and snails :-

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Snail secrete light

yellow SLIME and

Slugs secrete colourless

SLIME which become

Silvery after drying.

Slugs and snails :-

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• In India, about 1500 species of land snails occurs but the no. of species of slugs are limited.

• Among these 9 species of snails and 12 species of slugs have been reported as pests of ornamental plants, fruits, vegetables, and field crops.

Slugs and snails (THE PESTS)

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SNAILS -

• Found in different parts of world including India and islands of the Andaman and Nicobar group.

• Pests of paddy, vegetable, fruits and plantation crops like banana and papaya etc.

• Paddy crop is seriously damaged by them in Kashmir and some parts of U.P. and South India.

• They feed on leaves and stems of plant.

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Important species of snails -

• The common snail (Helix spp.)

• Giant african snail (Achatina fulica)

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The common snail (Helix spp.)

• Helix is a genus of large air-breathing land snails.

• This genus is native to Europe and the regions around the Mediterranean Sea.

• Helix is the type genus of the family Helicidae.

• The best-known species include Helix aspersa, the common, or brown garden snail, and Helix pomatia, the Roman snail, Burgundy snail.

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Biology :

• A hard calcareous shell that covers and protects the internal organs.

• The head and foot region can be observed when the snails are fully extended.

• When they are active, the organs such as the lung, heart, kidney and intestines remain inside the shell, only the head and foot emerge.

• The head of the snail has two pairs of tentacles: the upper and larger pair contain the eyes, and the lower pair are used to feel the ground in front.

• The mouth is located just underneath the head.• The mouth has a tongue called a "radula" that

is composed of many fine chitinous teeth. This serves for rasping and cutting food.

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Life cycle :

• The snails produce both eggs and sperm in the ovotestis (also called the hermaphrodite gland), but it is later separated into two divisions, a sperm duct and oviduct.

• Mating takes several hours, sometimes a day.

• The eggs are usually 4–6 mm in diameter.• After snails hatch from the egg, they mature

in one or more years.• The size of the adult snails slightly varies

with species. H. aspersa grows up to 35 mm in height and width, whereas H. pomatia grows up to 45 mm.

• The life span of snails in the wild is on average two or three years.

• The garden snail is a relatively fast snail. It has been observed to reach speeds of up to 1.3 cm/s.

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Giant African snail (Achatina fulica)

• The giant African snail is native to East Africa.

• Each individual has both testes and ovaries and is capable of producing both sperm and ova.

• Although both snails in a mating pair can simultaneously transfer gametes to each other (bilateral mating).

• Snails of similar size will reproduce in this way. Two snails of differing sizes will mate unilaterally (one way), with the larger individual acting as a female.

• The number of eggs per clutch averages around 200.

• A snail may lay five to six clutches per year with a hatching viability of about 90%.

• Adult size is reached in about six months, after which growth slows, but does not cease until death.

• The snails can live for up to ten years.

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Slugs -

• Feed on either dead or living vegetation.

• Live in most damp places.

• They have been observed to damage vegetable crops and banana etc. in U.P., Maharashtra, Assam, and M.P.

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Important spp. Of Slugs -

• The common garden slug (Laevicaulis alte).

• The black/ brown slug (Filicaulis alte).

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The common garden slug (Laevicaulis alte)

• This species is probably indigenous to Africa (western Africa and eastern Africa).

• Laevicaulis alte is a round, dark-coloured slug with no shell,

• 7 or 8 cm long.

• Skin is slightly tuberculated.

• The tentacles are small, 2 or 3 mm long.

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• Larger specimens are active during the day sometimes.

• This slug can grow up from 0.5 cm to approximately 4 cm in length in 7 months.

The common garden slug

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The black/ brown slug (Filicaulis alte).

• Dirty, creamish, white, spongy eggs in masses on damp soil.

• 74-80 eggs/ mass.• Newly hatched juvenile resembling

adults in colour.• Starts laying eggs at the age of about

8-9 months.• Lay eggs twice a year.• Adult is 8.0-8.5 cm in length, 1.5-2.0

cm in breadth, 7-8 g. in weight.• Average life span of about 390 days.

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Damage (Slugs and snails)

• They appear as sporadic pests in those places where damp conditions prevail.

• They may also appear on roads, creating problem during taking off or landing of the aircraft.

• Polyphagous in nature.

• Giant african snail is known to feed on 227 host plants..

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• They completely devour the small leaves.

• Mature leaves show holes on them.

• Mine like holes and tunnels are bored in tubers, roots and bulbs.

• Sown seed of wheat in soil are completely hollowed out startling from embryo.

• Completely pericarp is eaten away in case of tomato.

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Act as carriers of propagules of plant pathogens -

• Spores of Alternaria sp., Phytopthora sp. and Fusarium sp.found in SLIMES.

• Phytophthora palmivora (black rot disease).

• Economic damage to crops of cucurbitaceae(46%), basellaceae(39%), by A. fulica.

• Damage to seedlings of margild(97%), cabbage(75%), brinjal(51%), spinach(48%).

Cabbage

Tomato

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Management :

• Handpicking of snails during midnight and both snails and slugs before dawn and after dusk.

• Should be destroyed in 10% common salt solution.

• Keep area free from weeds.

• Smooth copper or zinc sheets can be used as mechanical barriers.

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Chemical control

• Poison baits consists of 10% carbaryl 50WDP in wheat bran.

• Spray copper sulphate (3%) @12 kg dissolved in 400 ltrs. Of water/ ha.

• Dust 15% metaldehyde @ 50 kg/ha.

• Spray 50% metaldehyde powder @10 kg/ha.

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Thank you