Rust Mite Damage and Management

Josh McGillBrazil, Pests

Phyllocoptruta oleivora, known as the false rust mite in Brazil, is one of the country’s main citrus pests, Fundecitrus reported. In the United States, the pest is known as citrus rust mite or silver mite. It affects all varieties of citrus.

rust mite
Russeting damage induced by Phyllocoptruta oleivora on grapefruit
(Photo by Emilie Demard, University of Florida)

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

The false rust mite is found mainly on leaves, branches and young fruits, and it is spread by wind. In affected fruit, the pest causes the appearance of dark spots with a rusty appearance on the skin. This can vary in intensity according to the level of infestation. On leaves, the mite causes the appearance of dark spots of irregular shape, mainly on the leaf edges, known as “grease spot.”

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 juice; it causes damage to the extraction machines. In addition, high populations of this mite change the flavor of the juice, causing a drop in the amount of vitamin C and weight loss.

In the rainiest and hottest periods of the year, the citrus grower must be even more attentive to the monitoring of the false rust mite to avoid heavy damage.

According to Daniel Andrade, São Paulo State University professor, monitoring of the mite should occur at a frequency of every seven to 15 days with a pocket magnifying glass.

“The citrus grower must evaluate four fruits per plant around the canopy and, in the absence of fruits, analyze six leaves per plant,” advised Andrade. “The level of action varies depending on the citrus species and the final destination of the fruits.”

Control must be done with acaricides. In addition to chemical products, the market also has biological products with good performance in controlling the rust mite. The most used active ingredients to combat the pest are sulfur and abamectin.

An application should occur when the pest is found in 20% of the inspected leaves or fruits for the fresh market, or 30% when the production is destined for juice. It is necessary to rotate products to avoid the risk of developing resistant populations.

Source: Fundecitrus

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