Gardeners across France are being urged to act quickly to protect their fruit trees from pests, with a narrow window of opportunity closing at the end of February. The call to action, issued as the country experiences a relatively mild winter, emphasizes preventative measures as more effective than treatments applied later in the growing season.
The Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement (INRAE) recommends applying a horticultural oil to the trunks and branches of fruit trees between February 15th and 28th, before buds begin to open. This treatment suffocates overwintering pests like aphids, scale insects, and mites, preventing them from damaging the trees during the spring and summer months.
The process involves spraying an emulsifiable vegetable oil, diluted according to the product’s instructions – typically 20 to 30 milliliters per liter of water – onto the tree until it runs off slightly. Before application, a gentle brushing of the trunk is advised to remove mosses and lichens, ensuring the oil reaches the pests hidden within the bark’s crevices. The treatment should be applied on a dry day with temperatures above 5°C (41°F) and no rain forecast for the following 24 hours.
Alongside this preventative oil treatment, February is also an optimal time for structural pruning. INRAE research indicates that winter pruning of pome fruits – apples, pears, and quinces – can increase yields by 10 to 15 percent compared to leaving trees unpruned. Yet, pruning should be avoided during periods of severe cold, snow, or when the wood is wet, as these conditions can weaken the tree.
For additional disease prevention, gardeners are advised to consider applying a Bordeaux mixture after pruning, ideally in early February, with two or three applications spaced two weeks apart. This copper-based fungicide, permitted in organic agriculture, should be used cautiously, as excessive copper accumulation can be toxic to the soil. Protective gear, including gloves, a mask, and eye protection, is recommended during application.
If the window for oil treatment is missed and buds begin to open, horticultural oil should not be applied, as it can damage the delicate modern tissues. In such cases, a lime wash applied to the trunk with a brush can help destroy larvae under the bark and reflect sunlight, reducing the risk of bark cracking during temperature fluctuations.
Untreated fruit trees can quickly become infested, leading to curled leaves, honeydew production, and reduced fruit quality or complete crop failure. A properly treated tree, however, is expected to maintain healthy foliage, flowers, and fruit development throughout the growing season.