What to Spray for Cane Rust on Blackberries

Fungicide Types

• Only certain fungicides have been registered in the U.S. for use on blackberries -- Cabrio 20EG, Pristine 38WG, Nova 40W and Rally 40 WSP -- help control rust on the plants. The fungicides should be applied in the spring, before the blackberry plant begins to exhibit signs of rust infestation. Cane rust can also occur late in the summer and may require additional fungicide applications to will help control the late season cane rust fungi.

Signs

• Begin a blackberry spray program in the spring, before the yellow pustules form on the blackberry plant's leaves. Wild blackberry plants usually begin to show signs of cane rust before cultivars, so they can be a reliable indication of when to start the spray regime, according to the North Carolina State University. If rust occurs in late summer or early fall, begin the fungicide treatment at the first indication of infestation.

Timing

• Apply the fungicide throughout the spring months at 10 to 14 day intervals. Cease using the fungicide when the temperature tops 77 degrees Fahrenheit. Consider alternating fungicide types for the best control and so the rust fungi do not build up an immunity to a specific fungicide. Apply the fungicide at 14 day intervals in the late summer or early fall if rust occurs. Continue the spray program, throughout until winter.

Application Amounts

• Apply Nova 40W at a rate of 1.25 to 2.5 ounces per acre of blackberry plants. Avoid using more than 10 ounces per acre for the growing season. Use 14 ounces of Cabrio 20EG per acre for each application. Apply Pristine at a rate of 18.5 to 23 ounces per acre. The Southern Region Small Fruit Consortium suggests only using Cabrio 20EG and Pristine for two consective applications and then use another fungicide type. Both fungicide types -- Cabrio 20EG and Pristine -- should not be used more than four times per growing season. Apply Rally 40WSP at a rate of 1.25 to 2.5 ounces per acre.