به وبلاگ انجینر حسام الدین "حسام " خوش آمدید

Introduction to Crop Pest

Pest:

Any living organism that causes harm to man, his crops or animals or possession or simply cause annoyance to human being, qualifies to refer as pest

Pest Management:

It is the system in the context of associated environment & population dynamics of the pest, utilizes all possible techniques or practices to maintain the pest population that will not cause economic damage or losses. Pests will be dealt in respect with the following points.

Nomenclature: (Taxonomic Position):

Every living organisms are known by common name and scientific name. Particular insects are known by common name in certain area / locality & not all over the world. They are recognized in scientific community by scientific names which consist of two names, viz. Earias vitella the first name indicates genera & the second specify the species mime. This system of no­menclature is called as binomial system of nomenclature. Similarly, trinomial system of naming is in existence for some insects where in three names are given e.g.

Pyrilla perpusilla coimbatorensis
Pyrilla perpusilla pusana

Marks of Identification:

Description of different developmental stages for e.g. shoot fly egg, larva, pupa & adult is important for correct identification of pest.

Hosts:

These are the plants on which insect use lo feed upon for completion of its life cycle. When main host is not available insect can feed on other hosts for survival is called alternate hosts.

Life history:

Means the development of insect for instance in most of the insects development take place from egg to adult stages, e.g. Jowar shoot fly. The object to study the life history is to find out certain weak points of the insects viz. site of pupalation, carry over from one season to next, habit & habitat of pest. These are to be pointed out for deciding the control strategies of the pests.

Nature of damage:

There is hardly any plant which is not infested by the pest. Pests injure to host plants. They damage one or the other parts of the plant viz. roots (root feeders), Stem / shoot (stem borers) leaves (leaf feeders), buds, flowers, fruits (fruit borers) & grains also. Depending upon feeding habit, pests are categorized as sucking pests & chewing pests. Accordingly the symptoms are produced on damaged plant parts.

Management of the Pest:

While managing the pest there should be an integrated pest management (IPM) approach in order to keep pest population below a level of economically acceptable damage (ETL)

Jowar Shoot Fly & Jowar Stem Borer - Pests of Jowar

A. Jowar Shoot Fly

Scientific Name:  Atherigona soccata Rond.
Class & Order: Anthomyidae – Diptera

Economic Importance: It is one of the serious pests of sorghum in India. The Pest attacks the crop only in early stage of growth and infestation goes up to 80%. The high yielding hybrids are more susceptible to the attack of this fly. The total loss in yield is sometimes as high as 60%. The pest is very serious on kharif and Rabi crops in Maharashtra State.

Marks of Identification: Adult fly is dark grey, like the common house fly but much smaller in size, 6 & 4 dark spots on abdominal segments of female & male respectively (arranged in rows of two) Maggot are legless, tapering towards head, pale yellow, small ( 10- 12 mm in length ).

Host plants: Jowar and grasses like Andropogan sorghum, Cynodon dactylon and Panicum spp.

Life history: Eggs: Eggs are average 40 eggs are laid by a female singly on lower surface of leaves & tender stem. Incubation period is of 2-3 days. Larva: larval period 10 to 12 days. Four larval instars are present. Pupa: Pupation in stem. Pupal period is about a week. Adult longevity is 12-1 4 days. Life cycle completes in 2-3 weeks. Several generations in a year. Carry over -The pest over winters in adult stage on grasses.

Seasonal occurrence: The insect attacks the seedlings and late sown crops are attacked badly. The attack is severe during July to October. Cloudy weather favours multiplication of the insect. In rabi, early sown crop suffers more and hence sowing should be delayed possibly

Nature of Damage: Maggots on hatching from the eggs bore into the central shoots of seedlings and kill the growing point, producing "dead hearts". They feed on the decaying core of the shoots. Subsequently on death of central shoot, plant gives out tillers and plant gets bushy appearance.

Management Practices:

1. Sow the crop as early as possible i.e. immediately after the onset of rains or within 15 days after receiving of rains. Increase the seed rate to make up the loss.
2. Use the seeds treated with carbofuran 50 SP @ 5% a.i. by wt. of seed (Gum Arabic as sticker) or carbosulfan 25 STD @ 200 gm / kg of seed OR 3% carbofuran granuals @ 5 kgs /50 kgs of seed by using slurry of wheat flour as sticker. OR Application of phorate 10 gm @ 10 Kg / ha in soil at sowing OR Spray the crop with 0.05% endosulfan soon as 10% seedlings are infested or 1 egg / 10seedlings are noticed.
3. Removal and destruction of affected shoots along with the larvae.
4. Use resistant (Maldandi 35-1) or less susceptible varieties like R.S. V.9 R (Swati), S.P. V86 for planting.

B. Jowar Stem Borer

Scientific Name: Chilo partellus S.
Class & Order: Pyralidae – Lepidoptera

Economic Importance: It is one of the major pests of Jowar and has a wide distribution. The infestation is noticed till harvest and the grown up plants when damaged loose their vigour and put forth week ears. The infestation is more pronounced on rabi and hot weather crops.

Marks of Identification: Moths - medium sized, straw coloured, yellowish grey forewings. The hind wings are whitish. Caterpillar - ditty white, brown head, many dark spots on the body, 12- 20 mm in length.

Host plants: Although principle hosts are Jowar and maize, it has also been recorded on Sugarcane, Ragi and certain grasses.

Life history: Eggs - about 300 eggs are laid, on leaves in clusters, incubation period about 6 days larval period:  3-4 weeks. Pupa: pupation in stem. Pupal period 7-10 days. Before pupation larva prepare a hole on stem at ground level for the moth to escape / come out. Adult longevity 2-4 days

Life cycle: completed in 6-7 weeks. About 4-5 generations are completed in a year.

Carry Over: The pest hibernates in the larval stage in stubbles. Seasonal occurrence: The pest is generally active from July to November. The infestation is more on rabi & summer crops.

Nature of damage: On hatching from the eggs, the larvae initially feed on tender leaf whorls causing series of holes in the leaf lamina and later bore into the stems, feed on the central shoots causing their death, commonly known as “dead hearts”
 
Management Practices: Preventive and curative measures.

Preventive:

1. Collection and destruction of stubbles after the harvest of crop to kill hibernating larvae
2. Increase the seed rate to compensate the loss.
3. Follow proper crop rotation (with non host crop).
4. Use of light traps.

Curative:

1. Removal & destruction of affected shoots along with the larvae.
2. Spraying with 0.05% endosulfan or 0.2%carbaryl OR whorl application of endosulfan 4G @ 10kg/ha, when 10% plants are infested.

3.        Aphids & Delphacids - Pests of Jowar

4.        A. Aphids:

5.       Scientific Name: i) Rhophalosiphum maidis F. ii) Aphis sacchari Z
Class & Order: Aphididae: Hemiptera

6.       B. Delphacids:

7.       Scientific Name: Peregrinus maidis A.
Class & Order: Delphacidae: Hemiptera.

8.       Economic Importance: They are the most important pests of Jowar. The infestation is usually high on rabi crop. The yield is adversely affected and the fodder quality also deteriorates.

9.       Marks of Identification: Aphids-Adults are minute, soft bodied, oblong, light green or pale yellow Cornicles: They are characterized by the presence of 2 tubes like structures on the dorsal side of abdomen. They are generally wingless but winged forms are often noticed usually in the beginning and towards end of season for migration to other crops.

10.    Nymphs: Smaller and greenish. Aphids are found in large numbers on lower surface of leaves and leaf whorls and do not move unless disturbed.

11.    Delphacids: Adults: Wedge, pale yellow, walk diagonally. Nymphs -like adults but wingless. Delphacids found mostly in the whorl of the plant.

12.    Host plants: Jowar, bajara, other cereals and sugarcane.

13.    Life history: Aphids - only females are noticed in Maharashtra. Reproduction parthenogetically on an average each female produce about 42 young ones within period of 5 days. Nymphs moults 4 times in a period of 5 days. A generation is completed in about 2 weeks.

14.    Delphacids: Eggs - about 150 eggs are laid in tissues incubation period 7-8days nymphal period 15-19 days (moults 5 times) Life cycle completed in about a month time.

15.    Nature of damage: Both nymphs and adults suck the sap from plant especially from the leaves. As a result the leaves turn yellow and in case of heavy infestation the plants remain stunted. Their injury causes oozing of sap which crystallizes on evaporation forming sugary material called "Chikta" OR ""Sugary Disease". Due to sugary material oozing out of the plant and honey due excreted by the insects, the sooty mould develops and the leaves turn blackish. The yield is adversely affected and the fodder quality also deteriorates.

16.    Management Practices: Spraying with dimethoate / quinalphos at 0.03% or formothion / monocrotophos /methyl demeton at 0.02%OR dusting the crop with endosulfan 4D / quindphos 1.5 D @20kg'lia. Spraying is more effective than dusting.