DISEASES SEEN IN MAIZE AND IT'S CONTROL MEASURES - बाराही अनलाइन खबर

Introduction
●Maize is the third important cereal crop in the world. And second important staple crop in Nepal.
●Maize is the staple food crop of hilly region of Nepal with 80%of total maize area (70%in mid hills and 10 %in high hills) in the country (MOAD, 2010).
●Maize has higher generic yield potential than others cereals because it has C4 photosynthetic pathway in which the LSP is higher than C3 plants so, maize is known as ‘Queen of cereals’.
●Maize contributes 3% to national GDP and 7% to AGDP (FAO, 2009).
● The male inflorescence of maize is known as the ‘tassel’ while the female inflorescence is the ‘ear’. The ear of the maize is a modified spike and there may be 1–3 per plant.
●Maize contains phytochemicals which plays important role in preventing chronic diseases.

Diseases can cause an average, about a 10 percent reduction in yield, which may go up from 50 to 90 percent in severe cases. Some of the diseases that are seen in maize are discussed below :

1.Northern leaf blight-caused by Exserohilum turcicum.

It is one of the most frequently occurring foliar diseases of corn in Ohio and the Midwest in general, according to Extension researchers at The Ohio State University.

During wet weather yield losses may be as high as 30-50% if the disease becomes establishes before tasseling. However, if leaf damage is only moderate or is delayed until 6 weeks after silking, yield losses are minimal.

Control measures:
We can manage northern corn leaf blight, including hybrid selection, scouting, cultural practices and fungicides. A combination of these crop protection practices provides optimum security to enhance corn yields and should be implemented to sustainably manage corn diseases.

2.Southern leaf blight -caused by plant pathogen Bipolaris maydis.
The infection can be confirmed microscopically. The sign (actual pathogen presence) of SCLB is its conidia. They are visible under a microscope and are usually brown and tapered with round edges. Northern corn leaf blight often occurs when southern corn leaf blight is present, and lesions distinguish between the two. SCLB lesions are more parallel sided, lighter, and smaller in comparison to NCLB.

Control measures:
Biocontrol with the competitive fungus Trichoderma atroviride SG3403 was used successfully against pathogen infection.

We can manage northern corn leaf blight, including hybrid selection, scouting, cultural practices and fungicides. A combination of these crop protection practices provides optimum security to enhance corn yields and should be implemented to sustainably manage corn diseases.

3.Head Smut – caused by fungus Sphacelotheca reiliana.
Leaf-like proliferations develop on the tassel and ears.Disease is most common in soils with nitrogen deficiencies. Ears may be aborted and replaced with a proliferation of leafy tissue. Plants also may be severely dwarfed.

Control measures :
Choose the best resistant varieties, such as silver king, fantasia, brilliant and seneca sensation, when available.Prevent damage from insects, such as corn borers, with Monterey® Garden Insect Spray or other organic insecticide.Fungicides are NOT an effective control option since the disease is so widespread and can persist in the soil for years.High nitrogen fertilizers may increase the severity of the disease — use a balanced organic fertilizer in the vegetable garden.Remove and destroy all garden debris after harvest and practice crop rotation the following year.

4.Downy mildew – caused by P. philippinensis.

It is one of the major maize diseases reported in some maize-growing countries, especially in the Philippines. High disease incidence has been reported in many parts of our country too,causing substantial losses to crop production.As the pathogen is able to survive in seeds, is able to spread rapidly and occasionally forms resting spores that can survive for more than 1 year.

Control measures :
Deep ploughing, crop rotation with pluses,rogue out infected plants, seeds should be treated with metalaxyl at 6g/kg. And spray the crop with metalaxyl+Mancozed @ 1kg on 20th day after sowing. And diseases resistant varieties and hybrids viz. CO1, COH1 and COH2.

5.Stalk rot – caused by Erwinia carotovora f. sp. zeae Sabet (re-designated as Pectobacterium chrysanthemi pathovar.
The bacterial stalk rot of maize is characterized by the discoloration of leaves, leaf sheath and the nodes of the stalk. The disease then develops rapidly along the stalk and spreads up to leaves.Affected plants have a foul odor. The stalk typically twists and falls over, but the plant may remain green for several weeks because the vascular tissue is not destroyed.It can occur any time during the season, particularly if conditions are very wet.

Control measures :
Always consider an integrated approach of preventive measures together with biological treatments. Chlorination of irrigation water or soil drenching with bleaching powder (33%chlorine @10kg/ha) at pre flowering stage is recommended. Formulations containing copper oxychloride can also be effectively applied aganist the disease.

6.Ear rot – caused by Fusarium species
This is the most serious disease of maize in most of the region of Nepal, not only because it reduces maize yield, but also because it reduces the nutritional value of infected grains and may induce the development of mycotoxins, threatening human and livestock health. Other fungal pathogens such as Diplodia spp., Penicillium spp., Aspergillus spp., Gibberella graminearum, and Fusarium moniliforme syn. F. verticillioides also inflict maize ear rots in the region.

Control measures :
Planting resistant hybrids, Rotating out of corn for at least a year, Burying or breaking down crop residue before tillage, Using insecticide to prevent wounds caused by insects, Harvesting early and storing in a dry condition (below 15% moisture).