Onion Cultivation- Disease control - Insect pest control

Disease control
Both field and storage diseases reduce profitability. Field diseases include purple blotch, Stemphylium blight, anthracnose, downy mildew, Botrytis leaf blight, pink root, smut, smudge, and several basal rots. Storage diseases include some of the common field rots, black mold, botrytis neck rot, and bacterial soft rot.

Purple blotch (Alternaria porri) attacks onion, garlic, shallot and other Allium crops. Initially, small white sunken spots develop on the leaves. These enlarge, become zonate and under moist conditions, turn purple. These are also prominent on the inflorescence stalks. Infection can cause a semi-watery rot on necks of bulbs that turn yellow-red in color. Infected bulb tissues eventually become papery. This pathogen is widespread. The optimum temperature for disease development is 21 to 30°C. Therefore, it is most serious in hot, humid climates.
The fungus is seed-borne, but the relevance of this phase in initiating disease outbreaks in hot climates is not well documented. Infected onion debris has been implicated as an infection source.
Host-plant resistance is yet to be exploited. Some cultivars appear to be less susceptible, e.g. Red Creole. Taliana Red in Hungary is reported to be resistant.
Cultural control methods include long rotations with unrelated crops and good drainage. Lowering the density of transplanted crops will reduce infection, as will the application of high rates of calcium superphosphate and potassium fertilizer. Nitrogen fertilizer at low and high rates will incrase the prevalence of disease. Routine (weekly interval) field sprays with dithiocarbamate fungicides, particularly mancozeb and chlorothalonil have been reported to be effective.
Stemphylium leaf blight (Stemphylium vesicarium) has been reported from Europe, Africa, North and South America, and Asia. Foliage losses of 80 to 90 percent have been reported. Disease symptoms are very similar to purple blotch. Lesions are light yellow to brown, watersoaked and progress from the tip to the base of leaves. The conidia have up to six transverse septa, besides several vertical septa. Wet and warm conditions favor the disease spread. Control measures are similar to purple blotch. Anthracnose (Colletotrichum gloeosporioides) favors hot (24 to 29°C) and wet conditions. The disease overwinters in sets and soil, and spores are spread by wind, splashing water, and tools. The leaves become twisted due to infection. Downy mildew (Peronospora destructor) also attacks young plants, appearing as white specks, usually confined to the oldest leaves of young plants,. A white mold develops rapidly in cool damp weather and progresses down the sheath, and plants eventually fall over and dry up. The fungus overwinters in bulbs and sets and on plant debris. Spores are carried long distances by air currents. For control, young plants can be treated with mancozeb at weekly intervals until bulbing begins.Botrytis leaf blight, commonly termed blast, is caused by severalBotrytis species. The disease first appears as white specks on leaves, expanding to cause a dieback from the leaf tips. Tops may be killed completely within a week, and entire fields may be affected. Frequently, blight follows previous damage from insects, disease, mechanical damage, or air pollution. Control is achieved through mancozeb sprays at approximately 7-day intervals.Several bulb rots may occur either in the field or in storage. Basal rot, caused by Fusarium species, results in a breakdown of inner scales. Outwardly, the bulb may appear normal. It eventually becomes soft, however, and will develop a watery rot under moist conditions or a dry shriveled bulb in a dry environment. The disease is most severe in warm areas with poor soil drainage. Botrytis neck rot (shown) is an extension of the leaf blight disease and can become serious in storage. 

Insect pest control Thrips (Thrips tabaci) are minute insects that cut or "rasp" the epidermis of leaves or stems and suck the plant sap resulting in white blotches on leaves. Severe infestations result in leaf blasting and collapse. Bulbs become distorted and undersized. Infestations are more severe in dry seasons than in moist, and entire fields may be destroyed. The insect has many host plants. Adults and nymphs overwinter on plants or plant debris, or in weeds bordering the field. Most of the insects are female, which can reproduce without a male. Eggs are thrust into the leaves and will hatch in 5 to 10 days. Diazinon sprays at 7-10 day intervals are recommended to control thrips. Up to six applications may be necessary and good coverage is essential.

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Armyworm -Rice armyworm, paddy armyworm, rice ear-cutting caterpillar

control: Parasitoids such as tachinids, ichneumonids, eulophids, chalcids, and braconid wasps parasitize this pest. Meadow grasshoppers, ants, birds and toads feed on the pest. Fungal diseases and a nuclear polyhedrosis virus also infect the larvae.

Chemical control may be needed when populations are extremely high. Pyrethroids can often kill the larvae but can also cause development of secondary pests, such as the brown planthopper.

symptoms:

• cutting off leaf tips, leaf margins, leaves and even the plants at the base
• cutting off rice panicles from the base
  The rice armyworm is present in all stages of the rice crop. It becomes very destructive when the population is high that it can totally devour the host plant. Mature panicles are cut off from the base of the plants.

Increased N2-fixation in Azospirillum

N2-fixation is one of the main characteristics of
Azospirillum cells, although it is probably a minor
mechanism in plant growth enhancement

Azotobacter-benefits in pulse crops

Azotobacter Vinelandii is a free-living bacterium that can fix atmosferic nitrogen into the soil, being a great source to obtain a natural biofertilizer that can be used in the cultivation of most crops. 
It is a great source of nitrogen to meet the needs of crops because also has the capabilities to cause a rejuvenation of soil microbiology to tap out the biological fixation of nitrogen.
Benefits:

It improves seed germination and plant growth

Azotobacter are tolerant to high salts.

It can benefit crops by Nitrogen fixation, growth promoting substances, fungi static substances.

Azotobacter is heaviest breathing organism and requires a large amount of organic carbon for its growth.

It is poor competitor for nutrients in soil and hence its growth promoting substances, fungistatic substances.

It thrives even in alkaline soils.

Azotobacter is less effective in soils with poor organic matter content.

Additional Benefits: Azotobacter also produces some substances which check the plant pathogens such as Alternaria, Fusarium and Helminthosporium. Hence Azotobacter also acts as a biological control agent.

Functions of Azotobacter: Azotobacter naturally fixes atmospheric nitrogen in the rhizosphere. There are different strains of Azotobacter each has varied chemical, biological and other characters. However, some strains have higher nitrogen fixing ability than others.. Azotobacter uses carbon for its metabolism from simple or compound substances of carbonaceous in nature. Besides carbon, Azotobacter also requires calcium for nitrogen fixation. Similarly, a medium used for growth of Azotobacter is required to have presence of organic nitrogen, micro-nutrients and salt in order to enhance the nitrogen fixing ability of Azotobacter.

Azotobacter also produces fixation of Thiomin, Riboflavin, Nicotin, indol acitic acid and giberalin. When Azotobacter is applied to seeds, seed germination is improved to a considerable extent, so also it controls plant diseases due to above substances produced by Azotobacter.

Phosphate solubilizing bacteria and their role in plant growth promotion

The use of phosphate solubilizing bacteria as inoculants simultaneously increases P uptake by the plant and crop yield. Strains from the genera Pseudomonas, Bacillus and Rhizobium are among the most powerful phosphate solubilizers. The principal mechanism for mineral phosphate solubilization is the production of organic acids, and acid phosphatases play a major role in the mineralization of organic phosphorous in soil. Several phosphatase-encoding genes have been cloned and characterized and a few genes involved in mineral phosphate solubilization have been isolated. Therefore, genetic manipulation of phosphate-solubilizing bacteria to improve their ability to improve plant growth may include cloning genes involved in both mineral and organic phosphate solubilization, followed by their expression in selected rhizobacterial strains. Chromosomal insertion of these genes under appropriate promoters is an interesting approach.

Rice

1.  Seed treatment

•      Seed treatment with Pseudomonas @ 8g/ kg seed or wet seed treatment with Carbendazim @ 1g/kg seed for 24 hours or
• Dry seed treatment with Carbendazim        2.5g/ seed to protect the crop from soil borne diseases 

2.  Adoption of Alley Ways
For every 2mts leave 20 cm alley ways in east-west direction to penetrate better light which reduces BPH population. It also facilitates other cultural practices (Fertilizer application, spraying etc)

3.  Maintenance of Optimum population and age of the seedlings

Duration	Spacing	Plant population	Age of seedlings
Long duration	20 x 15 cm	33 hills sq mt	35 days
Medium duration	15 x 15 cm	44 hills / sq. mt	30 days
Short duration	I5 x 10 cm	66 hills / sq_mt	25 days

4.  Fertilizer Management

• Avoid Phosphatic fertilizer application as top dressing
• Micro nutrient deficiency
  •   Adoption of green manure cultivation
  •   Application of Zinc to control zinc deficiency based on Soil test results @ 20 kg/ acre as basal application or zinc sulphate (0.20%) spraying ice at 3-4 days intervals on standing crop as soon as symptoms observed.

5.  Plant Protection in nursery

• Application of Carbofuran granules @ 160 g/cent nursery at wet condition to protect main crop from gall midge & stern borer attack
• Clipping leaf tips of aged seedlings to check the Stem borer incidence before transplantation

Groundnut

1.  Seed treatrnent

• Seed treatment with Mancozeb @ 3g / kg of seed
• For Root grub control, seed treatment with Chlorphyriphos @ 6ml / kg seed
• For PSND control, Imidacloprid @ 2ml / kg seed (particularly for Anantapur)
• For Stem rot, Trichoderma viride @4 gm/kg seed
• Soil application of Trichoderma viride @ 2kg+180 kg FYM+20 kg Neem cake
       incubated for 10 days / per acre. (should be applied 3 years continuously).

2.   Plant Population
Maintenance of optimum plant population of 33 plants / sq. mt

3.  Weed control
Pendimethalin @ 1 liter / ac as pre-emergence weedicide within 72 hours after sowing

4.  Plant protection : Control of PSND

• Border crops such as Bajra, Maize & Jowar (4 rows) should be maintained to
       control PSND with application of nitrogen when moisture is available
• For control of PSND, removal and destruction of weeds such as Parthenium,
       which acts as alternate host for the virus
• Intercropping with Redgram (7:1)
• Avoid growing, of Marigold and sunflower in the vicinity of Groundnut fields

Sunflower

• Use optimum seed rate of 2 Kg/ac with a spacing of 60 x 30 cm. Thin out the plants leaving a single seedling per hill.
• Treating the seed with Imidacloprid 5 gm/kg seed.
• Raise boarder crop of Sorghum or Maize 4-6 rows around the main field.

Maize

1. High Density Plant Population:

• Adoption of recommended seed rate i.e. 8 kg/acre
• Maintenance of optimum plant population i.e. 25,000 per acre.

2. Seed treatment
Seed treatment with Dithane M 45 or Dithane Z 78 @ 2.5 gm/kg of seed

3. Weed control
Spraying of pre emergence weedicide i.e. Atrazine @ 2-2.5 kg/ha in 600 liters of water immediately after sowing under moist conditions for control of broad leaved weeds

4. Plant Protection Measures
Control of Post Flowering Stalk Rot (PFSR)

• Seed treatment with Dithane M-45 or Dithane-Z-78@2.5 gm/kg seed
• Adoption of Crop rotation
• Non cultivation of same hybrid continuously
• Application of Potash @80 kg/ha as basal application
• Avoid stagnation of water
• Only preventive measures are effective and there is no control measures after attack of the incidence

Control of Stem borer
Spraying of Endosulan @ 2 ml/lt of water at 12 to 15 days after sowing or carbofuran granules after 25 DAS

Black gram and Green gram -seed treament

• Growing of Resistant Varieties (Yellow Mosaic)

- Green gram : LGG 460, LGG 407, WGG 37, MGG 347, MGG 295
- Black gram : LBG-752, T9, PU 31, TU 94-2

• Seed treatment of seed with Imidacloprid @4 gms / kg or Thiomethaxam @5 gms / kg of seed
• Optimum Plant Population : 6 Kg /acre - Green gram, 8 Kgs/ acre - Black gram
• Optimum Time of Sowing : June 15th - July 15th
• Sowing in lines at 30 x 10 cms to facilitate inter cultivation at 20-25 days to conserve soil moisture and arrest weed growth
• Weed Management
  • Pr-emergence - Pendimethalin 1 ltr / acre immediately after sowing
  • Post - emergence at 20-25 days after sowing spray Quizalbethyl @ 400 ml/ acre or Fenoxoproethyl @ 250 ml for Grass weeds and Imazethapyr @ 200 ml / acre for Broad leaved and grass weed
    • Maruca Pod borer control (Preventive) : Spraying with neem products at
      flower bud initiation stage spray NSKE 5% or Neem oil (Azadarachtin)
      5rnl / liter

false smut control with kocide

Kocide—A New Chemical Against
Bacterial Leaf Blight
THE efficacy of a copper hydroxide fungicide,
Kocide 2000 54 DF (35% metallic copper) from M/
s Dupont, for controlling the bacterial leaf blight was
evaluated under field condition using a susceptible
variety (Tapaswini). The incidence of bacterial leaf
blight was the lowest (32%) in case of Kocide spray at
3 g lit-1, as against 88.6% incidence in the untreated
control. The grain yield was also the highest (4.9 t ha-1)
in this treatment. The new chemical molecule was also
effective against false smut.

Vandana—A Pre-cyclone Rice for the Benefit of Coastal Farmers

Coastal part of Orissa frequently faces cyclone of different intensities, particularly in the months of September to November resulting in the damage of wet season’s rice and other field crops to varying degrees.  In the end of October 1999, the super cyclone devastated the coastal districts of Orissa, specially Ersama block of Jagatsinghpur district causing total damage of field crops and animals besides, houses and human lives to greater extent. In such unpredictable, adverse situation, the growing of contingent field crops before cyclone will be an appropriate approach for providing food and nutritional security to the farm families. Keeping this in view and also with an aim of restoration of the devastated farming sectors in the super cyclone affected areas of two blocks, Ersama in Jagatsinghpur district and Astaranga in Puri district of Orissa, a project entitled “Management of Coastal agro-ecosystem in super cyclone affected areas in Orissa” was initiated in June 2001.  This project for a period of 3 years with funding from NATP to the extent of Rs 195.62 lakhs, is a multidisciplinary and multi institutional activity with CRRI, Cuttack as lead centre and eight other cooperating centers, involving all the ICAR Institutes/Regional Stations and Orissa University of Agriculture and Technology located at Bhubaneswar.

The concept of pre-cyclone rice was conceived for the first time, in addition to many other programmes, especially with the growing of early rice variety ‘Vandana’ (90 days duration) in upland and medium land situations.  A total of 100 kg quality seed of this variety was distributed to 19 farmers including the seed production farmers (10) in both target areas.  One among these farmers was Mr Seikh Mohammad, about 60 years old, in the village of Chaulia, Ersama block.  He belongs to marginal group of farmers with 3 acres of land.  He cultivated rice ‘Vandana’ in the wet season of 2002, in 252m² area of medium land. The nursery was raised on June 8, 2002 and the healthy rice seedlings of 20 days old were transplanted on June 28, 2002. This rice crop was raised with a fertilizer schedule of 60 kg N, and 30 kg each of P₂O₅ and K₂O per ha. The nitrogenous fertilizer was given in two splits, 50% at basal and the rest after 30 days.  The major insect pest was gundhibug, at flowering stage of the crop. He controlled the pest of gundhibug by two sprays with the insecticide monocrotophos @ 0.5 kg ai/ha.  The rice crop was harvested in the first of September, after 90 days of seeding.  Mr. Mohammad realized a rice grain yield of 167 kg in 252 m² area, that was with an estimated yield of 6.6 t/ha. Other farmers in the project areas obtained a grain yield in the range of 4 to 5 t/ha with in a 3 month period.  These farmers were benefited by growing rice ‘Vandana’ and harvesting good quantity of rice within a short period of 90 days.  This strategy would held the farmers to escape the bad effects of a possible cyclone in the months of September to November, which occur frequently in Orissa.

This strategy of the project has created greater awareness among the farmers for growing the early rice variety ‘Vandana’. All the adopted farmers are keeping the seeds of this variety for use of the Wet season of 2003.  Mr. Seikh Mohammad grew this variety, even in the dry season 2003, to produce more quantity of seeds.  About 100 farmers will grow this rice variety ‘Vandana’, by collecting seeds from the adopted farmers. By the end of this project period, it is expected that a large number of farmers will accept this rice variety ‘Vandana’.  The cultivation of ‘Vandana’ and similar varieties with early duration will facilitate in the built up of enough reserve food before cyclone occurs in the months of September-November.

This practice was also suitable in coastal andhra

Bael and Tulsi aqueous control blast disease in farmers field

Severe leaf blast occurred in the rice field of a farmer from village Bhairpur in Cuttack district. The intensity of the disease ranged between 65% and 75% on rice variety Lalat. The environmentally safer technology, developed at CRRI to control rice blast disease, comprising of the aqueous extract of Bael leaf @ 25 g/litre of water and steamed aqueous extract of Tulsi leaf @ 25 g/litre of water was sprayed in the blast infested field. The farmer repeated this spray after 10 days. On the subsequent visit after 15 days, it was observed that the blast disease was successfully and effectively controlled. The rice crop had registered, an 80% to 85% recovery as compared to 45% recovery in ediphenphos (Hinosan) sprayed field.

Symptoms - False Smut-paddy

The disease occurs in the field at the hard dough to mature stage of the crop. The fungus transforms individual grains of the panicle into greenish spore balls that have a velvety appearance. The spore balls are small at first and visible in between glumes, growing gradually to reach 1 cm or more in diameter and enclosing the floral parts. They are covered with a membrane that bursts as a result of further growth. The color of the balls become orange and later yellowish green, or greenish black. At this stage, the surface of the ball cracks. The outermost layer of the ball is green and consists of mature spores together with the remaining fragments of mycelium.

The outer soporiferous region is three-layered. The outermost layer is greenish black with powdery spores; the middle layer, orange; and the innermost layer , yellowish.

Infections are of two types. One type takes place at the very early flowering stage when the ovary is destroyed while the style, stigmas, and anther lobes are buried in the spore mass. The second type occurs on the mature grain when spores accumulate on glumes, absorb moisture, swell, and force the lemma and palea to come apart. The fungus finally contacts the endosperm; ultimately the whole grain is replaced and enveloped by the fungus.

Chlamydospore

a thick- or double-walled asexual spore formed directly from a vegetative hyphal cell that functions for overwintering or as a resting stage.

formed on the spore balls are born laterally on minute sterigmata on radial hyphae, and are spherical to elliptical, warty, olivaceous, 3-5 x 4-6 µm. Younger spores are smaller, paler, and almost smooth.

Chlamydospores germinate in culture by germ tubes that become septate and form conidiophores bearing conidia at the tapering apex. These conidia are ovoid and very minute.

Some of the green spore balls develop one to four sclerotia in the center. These sclerotia overwinter in the field and produce stalked stromata the following summer or autumn. The stromata form a swelling at the tip of the stalk, are more or less globose, and contain perithecia around the periphery. Each flask-shaped perithecium contains about 300 asci. The asci are cylindrical with a hemispherical apical appendage, 180-220 x 4µm, and 8-spored. Ascospores are hyaline, filiform, unicellular, and 120-180 x 0.5-1µm.

In temperate regions, the fungus survives the winter by means of sclerotia as well as chlamydospores. It is believed that the primary infections are initiated mainly by the ascospores produced from the sclerotia. Chlamydospores play an important role in secondary infection, which is a major part of the disease cycle.

Studies in India and China showed that there are varieties/ lines/accessions that are resistant to false smut. Spraying with

• jinggamycin + Bordeaux mixture or chlorothalonil + metalaxyl combinations
• triadimefon, or
• carbendazim

at late booting to heading stage gave good control of false smut.