The spring awakening of winter rapeseed marks not only the start of its active growth but also the time when the crop's main enemies appear. Stem weevils attack plants immediately after the weather warms up, which can lead to significant yield losses. How can farmers detect the threat in time, and what control methods are the most effective — let's explore in this article.
Spring Awakening: What Threatens Rapeseed?
It may seem that after winter the field is still "asleep." In fact, with the first warm days, not only rapeseed becomes active, but also those ready to feast on it. First and foremost — stem weevils. A sharp transition from winter to a favorably warm spring creates perfect conditions for the activation of these pests, who are particularly fond of feeding on winter rapeseed.
Main Enemies of Rapeseed in Spring
Stem (Large) Rapeseed Weevil (Ceutorhynchus napi)
Appears when the average daily temperature exceeds +6...+8°C. A single female lays up to 50 eggs inside the stem, and the larvae gnaw tunnels, which leads to stem cracking and plant lodging.
Black Rapeseed Weevil (Ceutorhynchus picitarsis)
Appears at +8°C, laying eggs in the leaf petioles. The larvae bore into the central vein, disrupting the plant's nutrient flow.
Before laying eggs, the beetles need to accumulate enough energy by actively feeding on young leaves, stems, and petioles of rapeseed. This period usually lasts several weeks, and it is during this time that they cause the most damage to the plants. Along with egg-laying, the period of harm to rapeseed begins. A typical symptom of rapeseed weevil infestation is S-shaped stem twisting, followed by stem cracking.
⚠️ Results of Weevil Damage in Early Spring:
◻️ Reduction of future yield by up to 30%.
◻️ Larvae penetrate the stem, creating tunnels that weaken the plant and cause lodging.
◻️ By gnawing through stem tissues, they create "entry points" for infections.
◻️ The damaged shoot thickens, becomes flattened, or cracks.
◻️ Plants become less resistant to temperature fluctuations and other stress factors.
◻️ Rapeseed flowers and ripens unevenly.
How to Protect Winter Rapeseed from Weevil Infestation? Farmers have long known the answer to this question — the use of pesticides.
💡 By the way, if anyone needs urgent insecticide application but cannot access the field, or if there are other issues with wheeled machinery — contact AGRONIX, and your crops will be protected with the help of spraying drones.
But how can early pest detection be implemented and addressed as effectively as possible? — We will discuss this further.
Phenology: When to Start Rapeseed Protection?
First Field Visit — When the Temperature Exceeds +6°C
As soon as the soil warms up, it is necessary to monitor the fields for the presence of weevils. Visual inspection (plants should be carefully examined, including inside the stems and leaf petioles) + yellow cup traps or containers with water will help determine the level of infestation.
How Do Yellow Traps Work?
◻️ Weevils are attracted to yellow color, which reminds them of rapeseed.
◻️ Beetles that have awakened after winter fly to the traps and fall into the liquid.
◻️ This allows for prompt detection of the pest's appearance and timely initiation of rapeseed protection.
How to Properly Set Up Yellow Traps?
◻️ As soon as the average daily temperature exceeds +6°C.
◻️ At the edge of the field (where pests usually appear first) and inside the crop.
◻️ Use yellow plastic bowls or containers (depth ~10 cm).
◻️ Fill with water + add a drop of detergent (to reduce water surface tension so beetles can't escape).
◻️ Place at a height of 10-15 cm above the soil surface (at the level of young plants).
◻️ Check every 1-2 days and count the number of beetles.
How to Interpret the Results?
◻️ 5 beetles in a trap over 3 days — threshold level indicating the need for insecticide treatment!
◻️ More than 10 beetles — high threat level, urgent protective measures are required!
In fact, this year, along with the active temperature increase, 8-10 weevils have already been recorded in Vinnytsia region and Southern regions. During the day, their number reached 12-15 specimens, although in the morning there were only 1-3.
The mating period has now begun, which means that in 5…10 days females will start laying eggs at the base of rapeseed stems and petioles.
What to do?
This week, it is necessary to actively monitor the fields and be ready to carry out insecticide treatment to prevent egg-laying. Once the eggs are laid, no insecticide can reach the larvae inside the stem.
Photo of a weevil detected on March 10, 2025, in the fields of Vinnytsia region.
Protection: Classic Scheme vs Innovative Approaches
Historically, farmers have relied on classic wheeled sprayers, but an overly wet spring makes this approach quite problematic. In such cases, spraying drones come to the rescue.
CLASSIC METHOD
✅ High-precision spraying
❌ Soil compaction, risk of plant damage
❌ High water consumption (100-200 L/ha)
AGRO DRONES
✅ Minimal water consumption (8-10 L/ha)
✅ Fast pesticide application regardless of soil moisture
✅ Ability to operate where wheeled machinery cannot reach
❌ Wind speed limitations (up to 3…4 m/s)
PRODUCTS FOR EFFECTIVE PROTECTION:
◻️ Lambda-cyhalothrin (0.2 L/ha)
◻️ Imidacloprid (0.15 L/ha)
RESULTS:
◻️ Timely treatment ensures healthy rapeseed development.
◻️ Drones enable fast action, reducing spraying costs.
◻️ Yield potential is preserved through timely monitoring and protection.
Early spring protection is not just the first treatment of the season. It is the foundation of the future harvest. Thanks to innovative approaches, such as spraying drones from AGRONIX, farmers can effectively combat pests and diseases without waiting for critical damage and loss of future yield potential.
The author thanks everyone who made it to the end! 🙂
