Chris Smedley, Wayne County Extension IPM program assistant
Our recent string of days of unseasonably warm temperatures is resulting in perennial plants, including fruit trees and brambles, beginning to break dormancy. For fruit growers, this means that dormant spray applications targeted to reduce incidence of some disease and insect pests need to be made much earlier this year. Fruit growers need to monitor and be aware of when plants break dormancy and growth stage development to determine if and when early season dormant applications can be made.
In brambles (raspberry and blackberry), a delayed dormant (when tips of buds show green) application of Sulforix can help to prevent anthracnose, spur blight (red raspberries) and cane blight. Peach and nectarine growers can control peach leaf curl by applying an effective fungicide before bud swell in the spring. Effective fungicides include Bravo (chlorothalonil), copper hydroxide, Bordeaux mixture, copper oxychloride, Ferbam or Ziram.
Dormant oil is regularly used on apple, pear, and plum trees to aid in control of scale and aphid pests, at a rate of 2%, which means 2 gallons of horticultural oil per 100 gallons of water. This should be made as a dilute application, with plenty of water so that all bark is treated. As the word “dormant” implies, this spray should be applied before the buds swell or before new growth (green tip stage) starts in the spring. If applied after growth starts, the new tissue can be damaged by oil at this rate. Application should be done when temperatures have been above freezing (above 35 degrees F) the day before the application and when the weather forecast calls for non-freezing temperatures for at least 24 hours after application. For this area, usually late February to early March is a good target period. This is why it is critical right now and you do not want to miss out on this window of opportunity.
In orchards where either scales or aphids are a consistent problem from year to year, oil can be improved by the addition of Lorsban (chlorpyrifos). Beware that Lorsban is allowed only once per year.
Oil can also be used for control of mites, but for best control of mites, it is more effective if application is delayed until late in the delayed dormant stage. When oil is applied at the half-inch green bud stage or no later than the tight cluster bud stage, the rate can be dropped to 1%, meaning 1 gallon of horticultural oil per 100 gallons of water. Oil at this time should still be applied in dilute form so that all of the bark surface is treated.
In pear and apple orchards where fire blight is a problem applying a fixed copper fungicide at the swollen bud stage is recommended.
According to Melanie Ivey, fruit pathologist at the OARDC, current weather conditions are conducive for the development of powdery mildew on apples. Growers should be monitoring their trees carefully. Fungicides (sulfur) are applied at tight cluster through the end of new shoot growth to aid in the control of powdery mildew.
An important note: for all fruit crops, if liquid lime-sulfur is used, it should not be sprayed with, or in close timing (1 week) with an oil spray as tissue damage can result.
Remember to always read and follow the label directions for proper use of any pesticide. For more information call the OSU Extension Office- Wayne County at 330- 264-8722