Pest and disease management accounts for over 40% of the total cost of production. Therefore, knowing the precise growth stage when one can spray and get the most economical returns and yields is essential.
For instance, sap-feeding onion thrips causes a more than 60% yield reduction in bulb onion farming. To control these thrips, the general recommendation is to spray the crop with insecticides as soon as the pest appears and throughout the crop season, which is very expensive.
Most farmers ask the key questions: At what stage of onion bulb farming is the thrips infestation high? At what stage is the yield damage high? What happens if you skip spraying a particular growth stage and the next stage? Finally, at what stage is ideal for spraying, using fewer chemicals, and still getting high yields?
When should you spray?
Bulb onion thrips can affect the crop in all three stages: establishment, bulb formation, and bulb enlargement. However, the population varies with the weather. It tends to increase mainly in hot and dry seasons and decline in cold weather patterns regardless of the growth stages.
Data from trials and research shows that if the farmer doesn’t control sap-sucking thrips at bulb formation and bulb enlargement stages, it can lead to significant losses of up to 59%. In the trials, a considerable onion yield response to thrips infestation was observed during the second month (bulb formation stage) and third month (bulb enlargement stage) after transplanting, respectively.
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Therefore, spraying insecticides against sap-sucking thrips only at the bulb formation stage resulted in higher returns than full-season pesticide application.
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