Management of downy mildew in sunflower

Management of downy mildew in sunflower
Sunflower crop is among the top five commercial oilseed crops grown all over India.
Its cultivation is mainly hindered by diseases and pests. Among the diseases downy mildew is a serious obstacle in sunflower cultivation due to its systemic nature of infection.
Typical symptoms occur in seedling stage. Infested seedlings die, but those that survive produce stunted plants with erect, platform heads with no flowers. Drought stress
If any flowers are produced they remain sterile and bear no seeds. The infested plants serve to perpetuate the fungus in the soil and are more prone to drought stress and lodging.
The disease is initiated by soil borne dormant structures called oospores or infected seeds.
Oospores germinate during spring in wet soils. They can survive in the soil for five to 10 years.
Cool, water-saturated soil during this period greatly favours the infection spread.
Plants become increasingly resistant to infection with age, so systemic infections occurs over a short period (two to three weeks) after germination.
Irrigation water running through an infested field also may carry mildew spores into a previously disease-free field. Management
— Plant high quality certified seeds free from downy mildew pathogen.
— Practise a five-year or longer crop rotation between sunflower crops with non-hosts such as corn and small grains.
— Eliminate weeds that can serve as alternate hosts of downy mildew.
— Avoid reuse of irrigation water from sunflower fields and provide adequate but not excessive irrigation, especially early in the season.
— Seed treatment with metalaxyl 6gm/kg seed will reduce the infection during the seedling stage. Spraying of rydomil MZ 3gm/lit or metalaxyl 3gm/lit water helps in controlling foliar infection.
— Using resistant varieties. is a good practice.
Mallikarjun Y, Kenganal, Hemavati, Ranebennur & Byadgi, A. S.
Department of Plant Pathology
University of Agricultural Sciences,
Dharwad, Karnataka

Mealy bug — a new threat to cotton cultivation

Mealy bug — a new threat to cotton cultivation
Cotton crops in Punjab, Rajasthan, Maharashtra, Andhra Pradesh, Gujarat and Tamil Nadu are being seriously infested with mealy bugs during the last 2-3 cropping seasons.
In Tamil Nadu the pest has been observed in Salem, Coimbatore, Perambalur, Erode, and Virudhunagar districts.
Mealy bugs are small, soft bodied sucking insects which suck the sap from the stem, twigs, leaves, flower buds and young bolls. Sooty mould
A sugary liquid secreted by these insects falls on the leaves and serves as a medium for the growth of sooty mould, a fungus that reduces photosynthetic ability of the plant.
Adult female lays 400-600 eggs in a thin bag called ovisac and within 3-9 days young mealy bugs called crawlers emerge from the ovisac.
The crawlers actively spread through various means and settle down in 25-30 days.
The pest causes premature leaf drop, dieback and death of plants if unchecked.
Serious attack of the pest results in bunchy growth, plants remain stunted and produce fewer bolls. Heavy clustering of mealy bugs can be seen on lower surface of leaves giving the appearance of a thick mat with waxy secretion.
The honeydew excreted by the mealy bugs attracts ants which help in spreading of the pest and provide protection from predators and parasites.Management
—Field borders should be free from weeds.
—Crop residues with infestation should be removed and burnt.
—Plough the infested fields to expose the immature stages in the soil to the biotic and abiotic factors.
—Discourage growing alternate host plants such as hibiscus, okra, custard apple, guava in nearby cotton fields.
— Encourage cowpea as border crop on bunds and irrigation channels to enhance the multiplication of predatory insects.
— Ant fences should be treated with chlorpyriphos 20 EC at 2.5 ml/lit through drenching (or) by application of malathion dust 5 per cent at 25 Kg/ha .
B. Dhara Jothi &
N. Gopalakrishnan
Central Institute for Cotton Research
Regional Station
Coimbatore, Tamil Nadu Mealy bug — a new threat to cotton cultivation
Cotton crops in Punjab, Rajasthan, Maharashtra, Andhra Pradesh, Gujarat and Tamil Nadu are being seriously infested with mealy bugs during the last 2-3 cropping seasons.
In Tamil Nadu the pest has been observed in Salem, Coimbatore, Perambalur, Erode, and Virudhunagar districts.
Mealy bugs are small, soft bodied sucking insects which suck the sap from the stem, twigs, leaves, flower buds and young bolls. Sooty mould
A sugary liquid secreted by these insects falls on the leaves and serves as a medium for the growth of sooty mould, a fungus that reduces photosynthetic ability of the plant.
Adult female lays 400-600 eggs in a thin bag called ovisac and within 3-9 days young mealy bugs called crawlers emerge from the ovisac.
The crawlers actively spread through various means and settle down in 25-30 days.
The pest causes premature leaf drop, dieback and death of plants if unchecked.
Serious attack of the pest results in bunchy growth, plants remain stunted and produce fewer bolls. Heavy clustering of mealy bugs can be seen on lower surface of leaves giving the appearance of a thick mat with waxy secretion.
The honeydew excreted by the mealy bugs attracts ants which help in spreading of the pest and provide protection from predators and parasites.Management
—Field borders should be free from weeds.
—Crop residues with infestation should be removed and burnt.
—Plough the infested fields to expose the immature stages in the soil to the biotic and abiotic factors.
—Discourage growing alternate host plants such as hibiscus, okra, custard apple, guava in nearby cotton fields.
— Encourage cowpea as border crop on bunds and irrigation channels to enhance the multiplication of predatory insects.
— Ant fences should be treated with chlorpyriphos 20 EC at 2.5 ml/lit through drenching (or) by application of malathion dust 5 per cent at 25 Kg/ha .
B. Dhara Jothi &
N. Gopalakrishnan
Central Institute for Cotton Research
Regional Station
Coimbatore, Tamil Nadu

Management of mango hoppers in orchards

Management of mango hoppers in orchards
Mango hoppers are the most serious pests of mango.
Hoppers have small sized wedge shaped body. Both nymphs and adults suck the sap from tender leaves, buds, flowers, flower stalk and fruits.
Severely infested leaves become curled and inflorescences get dried. In addition to direct damage, hoppers excrete honeydew on the infested plant parts which encourages the growth of fungal pathogen that form a sooty mould on the infested areas.
Favourable season
They are present throughout the year but are abundant only during the flowering season. The nymphs mature during June to October (feed and breed on the vegetative shoots) and January to March (breed on the flowers and inflorescence).
Egg laying
Adult female lays about 200 eggs singly by penetrating them into the midrib of the young leaves, shoots, flower stalks and unopened flowers.
Eggs are dull white in colour initially which later turn into light brown. The incubation period varies from 4 to 8 days.
After hatching from eggs, the nymphs are pinkish in colour which later turn into pale brown with prominent red bulged eyes along with long black coloured bristles on abdomen.
Nymphal period is 10-14 days. Female can be identified with the sickle shaped ovipositor. Adult longevity varies between three and four days.
Pest management
Avoid dense planting. Adopt resistant varieties and avoid susceptible varieties such as Baneshan, Chinnarasam, Bangalora, Khadar, Gaddemar, Rumani and Himayuddin ( Padiri, Neelam, Mulgoa, Peter and Sindura varieties are highly susceptible).
Orchards must be kept clean by ploughing and removal of weeds.
Remove over crowded, overlapping and infected branches.
Spray Phosalone 35 EC 1.5ml/ litre (or) Carbaryl 50WP 3gm/litre (or) Monocrotophos 36 WSC 1.25 ml/ litre.
Two rounds, first at the time of panicle emergence and the second two weeks later.
Spray 3 per cent neem oil or neem seed kernel powder extract 5 per cent.
M. KANNAN, M. KALYANASUNDARAM & P. SIVASUBRAMANIAN
TAMIL NADU AGRICULTURAL UNIVERSITY, COIMBATORE,

Management of bacterial wilt in tomato

Management of bacterial wilt in tomato
Diseases are a major hurdle in tomato cultivation, both under controlled and field conditions.
Among them bacterial wilt is most devastating on tomato causing yield losses up to 90 per cent.
The disease is also known as southern bacterial blight or solanaceous wilt. Rapid and complete wilting of normal grownup plants is a characteristic symptom of bacterial wilt.
During warm and wet climatic conditions most conspicuous symptom of sudden drooping of leaves, without yellowing, often accompanied by rotting of the stem are seen. The roots appear healthy and well developed. Cultural management
The disease can be kept under check if crop rotations are followed with crops such as maize, ragi and okra, since they can reduce the pathogen population significantly.
Soil solarisation combined with fumigation reduces the pathogen considerably.
Destruction of weeds, collateral hosts and other off season hosts will reduce the innoculum potential. Application of sawdust
Application of sawdust, peatmoss are efficient in reducing the incidence.
Application of nitrite form of fertilizers is also capable of reducing the bacterial population.
Calcium concentration in soil should be increased to have better control of wilt disease.Chemical control
Soil treatment with chloropicrin, methyl bromide or mixture of both were found effective in retarding the wilt development.
Application of bleaching powder (15kg/ha) has also been found effective against this disease.
Seedling dip with streptocycline avoids early invasion and infection by the pathogen through wounds formed during transplanting.
Bacterinol-100 can be used as dry seed dresser, for nursery spray and field application. Streptomycin sulphate or oxytetracycline when sprayed at 200ppm at 7 days interval provides good control.
Tomato varieties such as Arka Abha, Sonali, DPT-38 and Arka Alok which are resistant to bacterial wilt can be used for cultivation.Biological management
Several biological control agents such as Pseudomonas fluorescens, Bacillus licheniformis, B. cereus, B. subtilis and mycorrihiza are very effective in delaying and reducing the wilt development.
Mallikarjun Y
, Kenganal
& Byadgi, A. S.
Department of Plant
Pathology, UAS, Dharwad

Suppression of rice leaf mite pest

Suppression of rice leaf mite pest
The rice leaf mite Oligonychus oryzae has attained pest status in the Cauvery delta regions of Tamil Nadu.
The infestation starts from the nursery till stem elongation stage. Leaf mites feed on upper and lower surface of rice leaves.
Usually they are more numerous on lower surface than upper surface.
The mites are small and microscopic and pierce the leaf tissues and suck the sap. They multiply very fast under congenial conditions and damage the entire leaf portion.Life cycle
The entire life cycle can take 8-12 days. The adults are sexually mature when they emerge and mate as soon as possible.
Egg laying begins in 1-3 days. Flattened spherical straw coloured eggs are laid singly in rows along the leaf midribs and veins. Incubation lasts 4-9 days.
This is followed by the three immature stages — larva, protonymph and deutonymph.
This mite is active and breeds throughout the year building large populations during hot weather when the life cycle lasts the shortest time.
The damage is most serious during summer months when the temperature is high and humidity is low compared to winter and rainy seasons.Management
Use chisel ploughing once in four years. Maintain the organic carbon content of the soil at optimum level.
Create a rice free period by ploughing down stubbles between crops or fallow crops with pulses and green manures in endemic areas. Maintain the bunds free from weeds.
Provide seed treatment/seedling treatment/main field application with pseudomonas flourescens at 10g/kg of seeds; 2.5 kg/ha seedlings; 2.5 kg/hectare of main field.
Top dress urea with neem cake (5:1) with LCC (leaf colour chart) based N to avoid excess nitrogen application and top dress with 50 per cent potash fertilizer.
In case of severity of mites foliar spraying of acaricides such as diafenthiuron 50WP 900 gm/ha or fenpyroximate 5SC 600ml/ha with wettable sulphur 40 WP 1.5 kg/ha if needed is recommended. .
S.M. Jalaluddin
Ravi G. & S. Jebaraj
Tamil Nadu Rice Research Institute, TNAU, Aduthurai , Tamil Nadu

Managing fruit borer menace in pomegranate

Managing fruit borer menace in pomegranate
Pest incidence is more during rains
Pomegranate faces a serious set back due to infestation by insect pests. The most obnoxious is Anar butterfly(Deodorex isocrates.)
The larvae of this insect directly bore into the pomegranate fruit. There are no satisfactory control measures for the pest after it enters into the fruits. Peak infestation
The incidence of the pest is at its peak during the month of August during monsoon season, while in winter crop it is more during November/December.
The female butterfly lays eggs on flowers-buds and the calyx of developing fruits; in a few days the caterpillars enters the fruit and feed on the pulp.
The conspicuous symptoms of damage are offensive smell and the excreta from holes. The fruits rot and drop off.
The fruit borers may cause loss of an entire crop unless the flowers are sprayed two times 30 days apart.
All the pomegranate varieties are susceptible to the pomegranate butterfly infestation.Management
— Bagging of fruits with butter paper before maturity should be done in isolated and smaller scale.
— Remove and destroy all the affected fruits (fruits with exit holes).
— Removal of flowering weeds, should be carried out on a regular basis.
— Frequent release of egg parasitoid Trichogramma species was found effective in controlling the pest.
— Spray Deltamethrin at 0.002 per cent at the time when more than 50 per cent of fruits are set. Repeat after two weeks with Carbaryl at 0.2 per cent or Fenvalerate at 0.005 per cent in non-rainy season. Quinalphos at 0.06 per cent is also effective.
— Malathion (0.1 per cent) spray and covering the fruits with butter paper bags recorded the highest fruit yield per tree.
D. N. Kambrekar S. B. Kalaghatagi & S. B. Jagginavar Regional Agricultural Research Station, Bijapur Karnataka

Management of false smut infestation in paddy

Management of false smut infestation in paddy
False smut of rice, once considered as a minor disease, has now become a serious disease in Tamil Nadu and also other rice growing states of India.
For the past three years, the disease incidence has been reported in many places in an alarming proportion.
The disease is caused by a fungus also known as Lakshmi disease of rice. Yield loss is not only due to the occurrence of the smut balls but also due to increased sterility of kernels adjacent to the smut balls. Affects grain quality
Usually, only a few grains in a panicle get infected. At severe infection, most of the grains in the panicles are affected by the disease. The disease not only reduces the yield but also affects the quality of grains or seeds.
Prominent high yielding rice varieties such as CO:43, CR:1009, ADT:38, ADT:39 and BPT:5204 are also found to be affected by the this infestation.
Due to fungal infection, individual grains of the panicles transform into greenish spore balls of velvety appearance.
Spore balls are small at first growing gradually to reach one cm or more in diameter and enclosing the floral parts. High moisture or rainfall accompanied by cloudy days during the period between flowering and maturity of grains favour the development of false smut. Management
Healthy seeds or seeds free from sclerotia should alone be used.
Early planted crop has less smut balls than the late planted crop.
At the time of harvesting, diseased plants should be removed and destroyed so that sclerotia do not fall in the field.
This will reduce primary inoculum for the next crop. Field bunds and irrigation channels should be kept clean to eliminate alternate hosts.
Excess application of nitrogenous fertilizer should be avoided.
Regular monitoring of disease incidence during rabi season is very essential.
Spraying of copper oxychloride at 2.5 g/litre or Propiconazole at 1.0 ml/litre at boot leaf and milky stages will be more useful to prevent the fungal infection.
A. Karthikeyan
& S. Jebaraj
Tamil Nadu Rice Research Institute, Aduthurai
Thanjavur , Tamil Nadu