Out of all the vegetables grown in India, onions are probably the most important one of all. It is used throughout the country and therefore onions are cultivated thrice a year to meet the huge domestic and international demand. However, the returns from onion production are hampered by the fluctuating weather and price trends. Also, pests and diseases too hamper onion yields. Every year, onion harvests face a lot of damage and uncertainty due to pests and diseases.
Today, let’s learn about the six pests and diseases that harm onion crops.
1. Purple blotch disease
It is one of the most common diseases in onions caused by a fungus named Alternaria Porri. It usually starts out as purple lesions on old onion leaves before turning brown/yellow. As the disease progresses, the leaves turn dry and the bulbs will be affected leading to the rotting of onion bulbs in storage. Purple blotch can be controlled by using pathogen-free seed/sets. Proper spacing of onion bulbs to increase air circulation and regular weeding can help prevent this disease. Similarly, it’s recommended that onions be harvested in dry weather so that they can be cured properly before leaf removal.
2. Cervical Rot
This onion disease is caused by the Botrytis allii fungus. The bulbs are usually affected at the neck before the decay spreads to affect the whole bulb. The scales of diseased bulbs become soft and brown. This is followed by a dense grey mould growth and hard, black, crust-like structures on the bulbs. However, the onions may look perfectly healthy from the outside and the rot begins to show only after the affected onions have been in storage for a few weeks.
Cervical rot of onions can be prevented by the usage of good-quality seeds. Similarly, crop rotation, conservative use of nitrogen, and regular watering can prevent this disease. Make sure that the bulbs are dry while harvesting and cure them properly before storage.
3. Downy Mildew
A fungus named Peronospora Destructor is the cause of this disease. This disease manifests as a fine, furry, greyish-white growth on the surface of older leaves. It then affects the seed stalks and flower parts before proceeding to infect the bulbs.
To prevent this disease, choose healthy seeds and bulbs, to begin with. Ensure that the leaves dry between irrigation cycles. Similarly, ensure proper airflow between plants and proper drainage of fields to prevent dampness.
Thrips are a very common onion pest. They are very small in size and they cannot be seen easily. Thrips feed by punching through the leaf surface and then extracting the sap from plant cells. These puncture wounds lead to white or silvery patches that can weaken the immunity of the plants and make them susceptible to other diseases. They can also attack the crop after harvest or during storage, reducing the quality of the onions.
To reduce the infestation of thrips, plant barrier crops like maize or wheat around the onion fields. Also, do lab tests on the plants to ensure that you spray insecticides when the thrips population crosses 30 thrips/plant density. Reducing the usage of nitrogen and doing crop rotation too can help curb thrips.
Termites cause major losses to farms in general. When it comes to onions, termites attack onion plants grown in sandy or light soil. They attack the roots and stems of the plants. They also create termite hills near the fields, making them harder to kill. Termites can spread very rapidly and damage the harvests quickly.
It’s important to use healthy transplants and to plant seeds in well-irrigated soil to discourage termites. Proper irrigation and crop rotation can reduce termite attacks by allowing the soil to recover nutrients. Similarly, spreading organic matter or farm waste on the soil can distract the termites from attacking the plants.
Aphids are attracted to the strong scent of onions. They usually live on the onion plant leaves or on the bulbs in storage. Aphids suck the sap out of plants causing them to collapse and sometimes they also spread viruses. They can spread quickly to make the plants wilt, turn yellow, dry up, and collapse. Usually, aphids are kept in check by natural predators like birds. To discourage aphids, keep the plants well irrigated and fertilized. Similarly, inspect the crops and remove and burn plants infested with aphids before they spread. Do regular weeding as well. Ensure the health of your onions since aphids usually attack plants that aren’t robust.
As you have seen how much these pests and diseases are harmful to the onion crop. Due to this, the hard-grown crops of farmers get destroyed. By saving onion crops from these pests and diseases we can increase the production of onions. Better produce will make sure that mandis are getting a higher supply of good onions, and it will benefit the farmer, commission agent, and customer together. Bijak app has come forward to make onion trading better than ever for the farmer, commission agent, and customer. Bijak is India’s most trusted agri-trading app. It has a growing network of farmers, Buyers (commission agents), and Suppliers and sees daily trade in over 150 commodities. Bijak aims to learn from the agricultural ecosystem to create more trading opportunities for Indian traders. You can download the app from Google Playstore and Apple App Store.