By Jake Price
There are two types of rust mites, the citrus rust mite (CRM) and the pink citrus rust mite (PCRM). The CRM is one of the biggest citrus pests in Georgia on fresh fruit. I don’t know that I have seen the PCRM in Georgia, but it is probably here.
Every year, CRM is a problem at the J.L. Lomax citrus plot. Populations can build up very quickly. After spraying abamectin plus oil in early May for red spider mites and CRM (I saw very few CRM at this time), I was surprised to see a large CRM population on the foliage this week (late May). The abamectin/oil combination controlled the spider mites very well, so to see the CRM population this soon after the application was unexpected.
Rust mites can develop from egg to adult in six days at 81 degrees, and it was very warm this May. Each leaf that I examined on the Tango mandarins had at least 10 cream-colored mites. I didn’t see many on the Tango fruit. But with a high population on the leaves, they will surely move to the fruit.
CRM populations build from May until July and then decline in late August. They can build back up in October and November, but populations will not be as high.
CRM tends to prefer the lower parts of the tree on the north side, which tends to be the more shaded areas. When CRM feeds on growing fruit, it destroys epidermal cells which fracture, creating a rough surface. When the pest feeds on mature fruit, it creates a brown stain but does not destroy epidermal cells. This results in a polished brown look referred to as “bronzing.”
Rust mites are very small and hard to detect (even when magnified under a hand lens), so unless you know what you are looking for, they are easy to miss. Often, several miticide applications are needed to control CRM. Mixing an oil with miticide applications is recommended as oil helps control the eggs.
There are many miticides listed in the Florida Citrus Production Guide. Good tree coverage is necessary, especially if the tree foliage is dense. Make sure to use at least 150 to 200 gallons of water per acre and rotate miticides with different modes of action.
Jake Price is a Lowndes County Extension coordinator with the University of Georgia’s College of Agricultural and Environmental Sciences.
Share this Post