गेहूं की फसल में रोग नियत्रण के उपाय
Disease and Insect pests of Wheat crop.

The major diseases of wheat in India are, three rusts - leaf, yellow and stem rust, Karnal bunt, foliar blights, powdery mildew and loose smut. Diseases of limited importance include head scab, foot rot and flag smut; these diseases though of lesser importance, may be important in certain pockets.

Leaf Rust /Brown Rust

Puccinia recondita tritici.

Distribution: Throughout wheat growing regions of India.

Development: Pathogen over-summers in low and mid altitudes of Himalayas and Nilgiris. Primary infections develop from

wind deposited urediospores in eastern Indo-gangetic plains in middle of January where it multiplies and moves westwards by March. Temperatures of 20 :t 5° C with free moisture (rain or dew) cause epidemics. Severe infection causes upto 30 percent yield losses.

Management: The presently recommended varieties in most of the wheat growing zones are rust resistant.

Stripe Rust /Yellow Rust

Puccinia striiformis tritici

Distribution: Hills, foothills and plains of north western India and southern hills zone (Nilgiri hills of Tamilnadu).

Development: Spreads through air-borne urediospores, when temperature are 10­20°C but the spread is checked above 25°c. Pathogen survives in the cool temperatures of hills ( Himalayas and Nilgiris ) and the primary infection takes places by middle of January in the foot hills and sub mountainous parts of north western India. Also, infection comes from across the western border, hence the probability of evolution of new races increases in this area. Yellow rust from Nilgiri hills cannot come out of the zone due to high temperatures in the Peninsular and Central India.

Management: Most of the presently recommended varieties are resistant. Major emphasis is on host resistance and cultivation of resistant varieties is the main strategy of management.

Stem Rust /Black Rust

Puccinia graminis tritici

Distribution: Mainly in Peninsular and I Central India, may occur in traces in Northern India too'

were the infestation comes late.

Development: Develops from air-borne urediospores, needs free moisture and temperature above 20° C for spread. It can cause severe grain losses if infection is early. The pathogen perpetuates in Nilgiri hills during off season and becomes air­borne. If Peninsular and Central India experience rainfall during November then epidemics are severe. Late infections cause less damage in north India.

Management: The presently re­commended varieties in most of the wheat growing zones are rust resistant, hence the old susceptible varieties be avoided.

Karnal Bunt

Tilletia indica (=Neovossia indica)

Distribution: Parts of Northern Plains, especially Punjab, parts of northern Haryana, foot hills of J&K and HP., tarai area of Uttranchal, in lesser severity in Rajasthan, Bihar and UP. The states of Gujarat, Maharashtra, Karnataka and several parts of M.P. are free of KB.

Development: Seed and soil-borne; infection occurs at flowering by means of soil-borne inoculum. The degree of disease development depends upon the weather conditions prevailing during spike emergence to grain filling stage of crop. If the rains occur during the month of February in north Indian plains (disease - prone areas), the disease is likely to come with higher severity.

Management: Among the present day varieties, PBW 502 is resistant while the others show various levels of susceptibility. For management of this disease, one spray of Propiconazole (Tilt 25EC@ 0.1 %) should be given at the time of anthesis. Integration of one spray of propiconazole with one spray of bioagent fungus, Trichoderma viride (0.4% suspension) gives almost cent per cent disease control. The bioagent spray should be done before earhead emergence (Crop growth stage 31- 39 on Zadoks scale), followed by the spray of chemical at start of earhead emergence (crop growth stage 41 -49 on Zadoks scale). Two sprays of T. viride, at these two critical growth stages also give non chemical control of the disease which is almost similar to one spray of propiconazole. Chemical control should be adopted mostly in seed production plots.

Black Point

Alternaria alternate

Development: Disease causes blackening of embryonic region of the seed (black point), discoloration of area beyond the embryonic region (black discoloration (Caused by Aalternata, Curvularia lunate, Epicoccum sp., Bipolaris sorokiniana, etc.) and eye-spot symptom (B. sorokiniana). The warm and humid weather at grain filling or near maturity favors this disease.

Management: This disease is of minor importance. Only when the disease percentage is high, it causes concern to the trader and the consumer. The discolored seeds are mostly shrivelled and they are separated out during processing.

Loose Smut

Ustilago segatum (U. tritici)

Distribution: North Indian plains and northern hills zone.

Development: It is a seed borne disease; infection occurs during Loose Smut

flowering through wind-borne spores. The infection remains dormant inside the otherwise healthy looking seed but the plants grown from such seeds bear infected inflorescence. Infection is favored by cool, humid conditions during flowering period of the host plant.

Management: Disease can be easily controlled through seed treatment with systemic fungicides hence resistance breeding has not attracted much attention. Treat the seed with fungicides like carboxin (Vitavax 75WP @ 2.5g / kg seed), carbendazim (Bavistin 50WP @ 2.5g / kg seed), tebuconazole (Raxil 2DS @ 1.25g / kg seed) if the disease level in the seed lot is high. If it is low to moderate, treat the seed with a combination of Trichoderma viride (@4 g/ kg seed) and half the recommended dose of carboxin (Vitavax 75WP @ 1.25g / kg seed).

Foliar Blights

(Bipolaris sorokiniana ­(Spot blotch), Pyrenophora tritici repentis (leaf blotch or tan spot), Alternaria triticina (Alternaria leaf blight)

 Distribution: Mainly in eastern India but also occurs in Peninsular and Central Foliar blights India. This disease complex is emerging as a problem in the north western India too.

Development: The disease requires high temperature and high humidity. This disease is more severe in late sown crop and causes substantial yield losses through formation of shrivelled grains. Most of the varieties are susceptible or moderately susceptible. The disease can be controlled through one spray of propiconazole (Tilt 25EC @ 0.1 %).

Powdery Mildew

Erysiphe graminis tritici

Distribution: Mainly in the cooler areas and hilly region; foot hills and plains of north - western India and the southern hills (Nilgiris).

Development: Powdery mildew can easily be diagnosed by the white, powdery patches that form on the upper surface of leaves and stem. With age, the patches turn dull dirty white and may have small black specks embedded. This disease can spread to all aboveground

parts of the plant, including earhead and awns. The disease infects plants during periods of high humidity (not necessarily rain) and cool to moderate temperatures. Low light intensity, which accompanies dry weather and a dense crop canopy favours this disease.

Management: Present day varieties are not resistant to powdery mildew. Hence, the disease severity is more in some pockets. Avoid excessively dense, stands by using adequate seed. For chemical control, one spray of propi-conazole (Tilt 25EC@ 0.1 %) on disease appearance (which usually occurs during early March in northern plains) is highly effective.

Head Scab

Fusarium graminearum

Distribution: Parts of Punjab, especially in the sub mountainous regions. Bread wheat suffers lesser damage than the durum. It was first recorded in severe proportion in some parts of Punjab during 1995-96 crop season and again during 2004-05 crop season.

Development: Disease development is favoured by cool, moist weather with high humidity. Spores are produced on crop debris and reach the leaves through rain splash or wind. Apart from ear head infection, it can cause seedling blight and foot rot leading to lodging. In severe cases, it can cause shriveling of grains and low-test weights. At present, it is a disease of limited importance but has the potential to emerge as a major problem due to the production of toxins.

Management: Bread wheat are more resistant than durum. However, no resistant varieties are available. Hence, vigil is needed for this disease.

Cereal Cyst Nematode

Heterodera avenae

Distribution : This nematode is found In most of the cereal growing regions of the country, especially, the

dry and warmer areas of Rajasthan, Haryana and Punjab, but incidence is less in cooler climates.

Development: Larvae enter the roots near the growing point especially, at the seedling stage. Roots of infected plants become predisposed to various soil borne disease like root rots. In infected fields, the losses can be considerably enough.

Management: Most of the wheat cultivars are susceptible but some resist cyst formation. Chemical pesticides, some natural plant products and botanicals, coupled with improved cultural practices help in management of the CCN. For Rajasthan, one CCN resistant variety, CCNRV - 1 is available for the disease prone areas.

Seed Gall Nematode /Ear Cockle

Anguina tritici

Distribution: It is found mainly in some parts of northern India especially the states of Bihar, Jharkhand, eastern UP and Chhatisgarh.

Development: These nematodes are spread through seed galls in the seed lots during planting and harvesting. Wet weather favors larval movement and infestation. The nematode invades the crown and basal stem area, finally penetrating floral primordia. This leads to formation of nematode galls in ear heads.

Management: Use of clean seed (free of galls) is the only method to prevent this disease. For removal of galls, the seed lots are floated in 2 - 5 per cent brine solution. The galls, which float on the surface, can be easily separated and destroyed away from the fields. The seed thus cleaned should be washed with fresh water and used for planting.

Aphids

Sitobion avenae, Rhopalosiphum padi and various other species

Distribution: All wheat growing areas, especially in NWPZ and Peninsular India.

Development: The aphids exist in different stages, viz., winged (alates), wingless (apterous) sexual and asexual forms. The rapid spread takes place through asexual reproduction where females give rise directly to nymphs rather than eggs. Infestation usually occurs during second fortnight of January till crop maturity.

Management: When feeding in sufficient numbers, they can cause considerable damage, but under normal conditions, losses are not much. Chemical pesticides are recommended for this pest in wheat if the level of aphids per tiller crosses 10 during vegetative phase and 5 during reproductive phase. However, there is need to keep watch on this pest. The spray of imidacloprid @ 20 g a.i. per ha initially on border rows and if infestation is severe then in entire field will give good protection against this pest. Generally, natural enemies present in the field help in controlling the population of this pest.

Brown Wheat Mite

Petrobia lateens

Distribution: In most of the wheat growing areas, under rainfed conditions, especially in the states of Rajasthan, Haryana and M.P. Sometimes, it is a pest in humid and warm conditions of irrigated

areas also.

Development: They Brown wheat cause damage through mite infestation

sucking mouth parts. When present in large numbers, mites cause a silvery flecking on leaves. Individual mites are too small to be visible with naked eye without 'effort. These can be seen by shaking the infested leaves on a white paper.

Management: Most of the times, mites do not cause any production constraint in wheat so no management practices are required. However, there is a need to keep vigil on this pest so that it may not become important in changing cropping sequence of future.

Army Worm

Mythimna separate

Distribution: Mostly in the warmer climates of central India and to some extent in northern plains.

Development & Management: The larvae are found in the cracks of soil and hide during the day but feed during night or early morning. In wet and humid weather, they may feed during day time also. They survive during summer on the subsequent crops like rice and also continue to exist in rice stubbles before wheat crop comes in the field. Recently, this pest is catching attention in the northern India under Rice-Wheat rotation and where rice stubbles / straw remain in the fields.

Legume Pod-borer

Helicoverpa armigera (= Heliothis armigera)

Distribution and Importance: This is a polyphagous insect that attacks various legumes as a pod border. It is seen damaging wheat ear heads at grain development stage when major hosts are not available. However, the damage is below economic threshold level. It is found mostly in northern and central parts of India. Wheat can serve as a bridge host for carry over of this polyphagous pest.

Termites

Odontotermis obesus, Microtermis obesi

Distribution: Mainly in the northern and central India, but also in some pockets of peninsular India.

Early Symptoms of Damage: Termites attack the crop at various growth stages,

from seedlings to maturity. The severely damaged plants can be easily uprooted and look wilted and dried. In case roots are partially damaged, the plants show yellowing.

Management: For effective management, chemicals like endosulfan, chlorpyriphos and carbosulfan can be used both for seed treatment and for broadcast of treated soil in standing crop.

रोग	नियंत्रण
करनाल बन्‍ट Karnal bunt	यह फफूंद रोग है। इसके बचाव के लिए बीज को 2.5 ग्राम थीरम अथवा बावस्‍टीन प्रति किलो बीज के हिसाब से उपचारित करके बोऐं।
अनावृत कन्‍डुआ Loose smut	बीज बोने से पूर्व कॉबाक्सिन (बिटावेक्‍स) की 2.5 ग्राम दवा प्रति किग्रा बीज से उपचारित करें।
सेंहू Ear cockel	यह एग्‍वीना ट्रिटिसाई निमेटोड (सूत्रकृमि) से होता है। इससे बचाव के लिए बीज को 2 प्रतिशत नमक के घोल में उपचारित करके बुआई करें।
अल्‍टरनेरिया ब्‍लाईट (झुलसा) Alternaria blight	किसी भी फफूंदी नाशी जैसे मैन्‍कोजेब आदि को 2 किग्रा प्रति हैक्‍टेयर को 800 लिटर पानी में घोलकर छिडकें।
गेरूआ या रतुआ Rust	किसी भी फफूंदी नाशी जैसे मैन्‍कोजेब आदि को 2 किग्रा प्रति हैक्‍टेयर को 800 लिटर पानी में घोलकर छिडकें।