High temperature and high humidity favor the emergence of the false rust mite

The Phyllocoptruta oleivora mite, also known as the false rust mite, is considered one of the main pests of citrus farming in Brazil and several other countries, affecting all varieties of citrus, such as sweet oranges, tangerines, lemons and sour limes. .

Infestation in orchards occurs throughout the year, but reaches the largest populations between the months of December and June, a favorable period for the development of the pest, due to the high temperature and high humidity. Under these climatic conditions, the mite completes the biological cycle (egg to adult) in just seven days, whereas, in periods of drought and low temperatures, it can take more than 14 days to complete the cycle.

Symptoms and damage caused by the false rust mite

The false rust mite is found mainly on leaves, branches and young fruits, and is spread by wind. On affected fruits, the pest causes the appearance of dark, rusty-looking spots on the skin, which vary in intensity according to the level of infestation. On the leaves, the mite causes the appearance of irregularly shaped dark spots mainly on the leaf edges, known as “grease spots”.

Mite infestations reduce the photosynthetic capacity of the plant, which directly impacts the quality and productivity of the orchard. In oranges, the peels become thicker, causing them to lose their commercial value both for fresh consumption and for industry, as it causes damage to extraction machines. Furthermore, high populations of this mite alter the flavor of the juice, cause a drop in the amount of vitamin C and weight loss.

Mite control

In the rainiest and hottest periods of the year, citrus growers must pay even more attention to monitoring the false rust mite to avoid major losses caused by the pest, as the level of economic damage, estimated in orange fruits, is 70 to 80 mites per cm2 of fruit.

According to professor at the Faculty of Agricultural and Veterinary Sciences at Unesp-Jaboticabal Daniel Andrade, mite monitoring must be carried out periodically. “Due to its small size and high reproductive capacity, monitoring the population development of this pest is not always an easy task. A frequency of inspections between 7 and 15 days using a pocket magnifying glass is recommended. The citrus grower must evaluate four fruits per plant around the crown and, in the absence of fruits, analyze six leaves per plant. The level of action varies depending on the citrus species and the final destination of the fruits, for example, juice or fresh consumption”, explains Andrade.

Control must be carried out with acaricides – and, in addition to chemical products, the market also has biological products with good performance in controlling rust mites. There are some active ingredients indicated to combat the pest, however, the most used are products based on sulfur and abamectin.

Application must be made when the pest is found in 20% of the inspected leaves or fruits, in the case of the fresh fruit market, and 30% when the production is destined for industry. However, it is necessary to make the correct choice and rotate products to avoid the risk of developing resistant populations.

Furthermore, the citrus grower must pay attention to the application technology used and the condition of the sprayers. “The volume of syrup must be adjusted so that it provides sufficient coverage on all parts of the plant for efficient mite control”, comments the expert.