Maize: Subject-Matter and Major Diseases | Plant Diseases

In this article we will discuss about:- 1. Subject-Matter of Maize 2. Major Diseases of Maize and their Distribution 3. Major Epidemics 4. Biotic Stresses are Responsible for Lowering Yield 5. Changes in Diseases Spectrum Scenario.

Subject-Matter of Maize:

Maize (Zea mays L.) occupies an important place in world agriculture due to its high potential of yield and greater demand. Among cereals, maize in India ranks third in yield per hectare, fourth in total production and 5^th in total area. It is estimated that by the year 2020 demand for maize in developing countries will surpass demand for both wheat and rice.

Rising income in much of developing world and the consequent growth in meat and poultry consumption has resulted in rapid increase in demand of maize for livestock and poultry feed. In India 35% of the total produce directly consumed as a human food while the balance used in industry and poultry feed.

The total production during the year was 14.14 million tones, from the estimated area of 7.49 million hectare. The productivity during the year was 1887 kg/ha. The increase in the area has been reported mainly from the states of Gujarat, Bihar, U.R, A.R, M.R, Rajasthan, Chhatishgarh, Maharashtra and Tamil Nadu.

In Jammu and Kashmir, maize being the staple food of intermediate zone is grown in 3 m ha with an acreage of approximately 2 m ha in Jammu division. The district wise area in Jammu division under this crop in Udhampur, Doda, Rajouri, Jammu, Poonch and Kathua is 55.58, 48.19, 44.89, 26.77, 23.67 and 15.89 thousand hectares, respectively.

In recent years, the average yield of maize has declined and this is accounted by biotic, abiotic and nutritional stresses. Among the different stresses, biotic factors are the major constraints in the production and productivity of maize. Due to the attack of several plant diseases caused by fungi, bacteria, viruses and possibly nematodes, yields are often reduced considerably.

Diseases are important constraints to maize production, wherever the crop is grown. The importance and magnitude of damage depend on interaction between the host plant and the pathogen under a given set of environmental conditions Ahamad and Narain (2007). Losses due to corn diseases are estimated at 9.4 per cent per year worldwide, 12 per cent in Asia and 14 per cent in Africa.

On a country basis, losses are estimated at 12 per cent in the USA and 13.2 per cent in India. Several diseases, under favourable conditions, have the potential to completely destroy the crop or to render the produce unfit as human food or animal feed. The present findings are in accordance with Shurtleff (1980), Ullstrup (1977), De Leon (1984), Payak and Sharma (1982).

The incidence and economic impact of corn diseases in India vary from state to state (Table 2.1).

A large number of pathogens infest maize in the tropical lowland, subtropical, intermediate transition zone and high-land maize growing ecological zones covered by CIMMYT’s mandate.

In 1988, a study was conducted by CIMMYT where information was compiled on maize production along with perceived constraints for each of these defined zone (Tables 2.2 and 2.3). An attempt has been made to estimate losses caused by disease.

Outbreaks and incidence in the crop in terms of shelled grain. Potential loss that can be caused by diseases has been worked out individually for 10 diseases (Table 2.4). Based on experimental work and other observations, estimates have been prepared for India as a whole (Table 2.5).

Major Diseases of Maize and their Distribution:

About 72 pathogens have so far been reported causing substantial damage in maize, 16 have been identified as major ones and are given here.

These includes diseases which occur in both tropical and temperate environments:

i. Turcicum leaf blight (Exherohilum turcicum) occurs in Jammu and Kashmir (J&K), Himachal Pradesh (H.P.), Sikkim, West Bengal (W.B.), Meghalaya, Tripura, Assam, Rajasthan, Uttar Pradesh (U.P.), Bihar, Madhya Pradesh (M.P.), Gujarat, Rajasthan, Andhra Pradesh (A.P.), Karnataka, Tamil Nadu (T.N).

ii. Maydis leaf blight (Drechslera maydis), occurs in J&K, H.P, Sikkim, Meghalaya, Rajasthan, Punjab, Haryana, Delhi, U.P., Bihar, M.P., Gujarat, Rajasthan, A.P., Maharashtra.

iii. Common rust (Puccinia sorghi II, III stages only) occurs in J&K, H.P., Sikkim, W.B. Rajasthan, Punjab (winter), Haryana (winter), Delhi, U.P., Bihar, M.P., Gujarat, A.P., Maharashtra, T.N.

iv. Phaseospheria leaf spot (Phaseospheria maydis) is found in Sikkim, W.B., U.P., Karnataka, Maharashtra.

v. Erwinia stalk rot (Erwinia chrysanthemi pv. zeae) occurs in H.P., Sikkim, WB. Rajasthan, Punjab, Haryana, Delhi, U.P., Bihar, M.P, Rajasthan, A.P.

vi. Pythium stalk rot (Pythium aphanidermatum = P. butleri) is found in Sikkim, WB. Rajasthan, Punjab, Haryana, Delhi, U.P., Bihar.

vii. Fusarium wilt and stalk rot (Fusarium moniliforme) occurs in Rajasthan, U.P., Bihar, M.P, A.P, Karnataka, T.N.

viii. Late wilt (Cephalosporium maydis) is reported from Rajasthan, U.P., Bihar, A.P.

ix. Charcoal rot (Macrophomina phaseolina) occurs in J&K, Punjab, Haryana, Delhi, U.P., M.P., A.P., Karnataka, T.N.

x. Brown stripte downy mildew (Sclerophthora rayssiae var. zeae) occurs in J&K, H.P., Sikkim, W.B., Rajasthan, Punjab, Haryana, Delhi, U.P., Bihar, Meghalaya, M.P., Gujarat.

xi. Phillipine downy mildew (Peronosclerospora phillipinensis) occurs in Punjab, Haryana, Delhi, U.P., M.P, Bihar.

xii. Sorghum downy mildew (Peronosclerospora sorghi) occurs in Rajasthan, A.P, Maharashtra, Gujarat, Karnataka, T.N.

xiii. Sugarcane downy mildew (Peronosclerospora sacchari) is found in U.P., Bihar.

xiv. Brown spot (Physoderma maydis) occurs in J&K, H.P., Sikkim, Rajasthan, Punjab, M.P., W.B., Rajasthan, Maharashtra, Karnataka.

xv. Banded leaf and sheath blight (Rhizoctona solani f.sp. sasakii) occurs in J&K, Sikkim, Rajasthan,Punjab, M.P., Haryana, Rajasthan, U.P. and Delhi.

xvi. Cyst nematode (Heterodeara zeae) occurs in Rajasthan, M.P., Bihar, U.P.

Some Major Epidemics of Maize:

Six major diseases out breaks have been recorded in India since the sixties:

i. Bacterial stalk rot (Erwinia chrysanthemi pv. zeae) appeared in the foothills (tarai) area of U.P. in 1959 and in 1969 in H.P on Hybrid Ganga5.

ii. Brown stripe downy mildew (Sclerophthora rayssiae var. zeae) appeared in 1962 and 1964 in WB hills, 1964 in -Western M.P. and south-eastern Gujarat, 1964 in north Bihar and in 1965 in the tarai region of UP and parts of Himachal Pradesh.

iii. There was an out break of Sorghum downy mildew (Peronosclerospora sorghi) in Rajasthan, Karnataka and Tamil Nadu from 1968 to 1973.

iv. Common rust appeared from 1973 onwards in the winter (Rabi) season on hybrids GS-2 and Hi-starch in Bihar.

v. Turcicum leaf blight (Exherohilum turcicum) virulent strain of E. turcicum appeared in 1974 on hybrid Ganga5, Deccan, Piox104, X114 and Kisan and in 1989- 90 in Bihar.

vi. Banded leaf and sheath blight (Rhizoctona solani f.sp. sasakii). In the late sixties there was an outbreak of this disease in HP, and other areas of western Himalaya.

Biotic Stresses are Responsible for Lowering Yield of Maize:

Among the factors adversely affecting productivity, ubiquitous incidence of diseases in the pre-harvest stage is prominent. Since there is practically no possibility of increasing maize area, the productivity can only be raised by providing seed replacement with improved cultivars, better agronomic practices and protection against diseases and pests.

Changes in Diseases Spectrum Scenario of Maize:

There is a major shift in disease pattern during the past years as the major diseases like TLB, MLB, BSDM and ESR are gradually becoming diseases of lesser economic importance now a days due to availability and use of sources of resistance in the newly developed hybrids and varieties. On the other hand the disease of minor importance became increasingly severe and assumed epidemic proportion in coming years.

In early sixties the diseases like BLSB, Late wilt, Polysora Rust and Preharvest cob rots were considered as a disease of minor importance only, but due to changing the weather condition and pattern of disease spectrum these diseases are considered as major diseases not only in India but other countries of Asian region wherever maize is grown.

One of the cheapest and best method of disease control is the use of resistant varieties but the break down of resistance year after year resulting problem in gene pyramiding has restricted this approach.

Chemical control is practically feasible but non judicious and untimely application has made this approach ecologically and economically unsuitable on the other hand biological control is ecologically and socially acceptable but difficulty in having an effective bio-control agent as well as lack of awareness among the farmers has limited its inclusion in regular disease management schedule of crop.

Considering all these constraints it is imperative formulate an IDM programme incorporating all the conventional disease management approaches in such a way so that the limitation of one approaches can be neutralized with other one.