What to Do If It Rains After Applying Lime Sulfur

Heavy rain after applying lime sulfur may affect its efficacy, because it will be washed away by the rain, and you will need to reapply it after the weather clears; if the rain is relatively light, the impact is small, and you can skip reapplying or wait a while before applying again. The main methods of using lime sulfur are spraying and trunk painting. Spraying needs at least 12 hours to air-dry, while trunk painting needs 1-2 days. If it rains 12 hours after spraying or 1-2 days after trunk painting, you need to spray or paint the trunks again.

1. What is lime sulfur?

Lime sulfur is a fungicide, acaricide and insecticide used in agriculture, made by boiling quicklime, sulfur and water together. It kills fungi, pests and eggs by penetrating and corroding the bodies of pathogens and pests. It can control diseases such as powdery mildew, rust, brown rot, brown spot, scab, gummosis and resin disease, as well as pests such as spider mites, rust mites, red spiders, scale insects and aphids. It is mainly used on fruit trees such as apple, citrus, pear, peach, grape and jujube, and can also be used on flowers, alfalfa, legumes, wheat and tea trees. It is easy to source, low in price, highly effective, long-lasting, low in residue and does not cause pest resistance, so it is widely used by fruit growers.

2. Correct methods of using lime sulfur

The methods of using lime sulfur include spraying and trunk painting. Spraying is used most often, generally after the fruit trees have basically shed all their leaves and entered dormancy, or before the fruit trees bud, and it can also be used during the growing season. During the dormant period of fruit trees, spray a diluted lime sulfur solution of 3—5 degrees Baume; before spring budding of fruit trees, spray a diluted lime sulfur solution of 3—4 degrees Baume; during the growing season of fruit trees, spray a diluted lime sulfur solution of 0.2-0.5 degrees Baume.

3. Precautions for using lime sulfur

(1) Temperature: The water temperature for preparing lime sulfur should be below 30°C, otherwise its effectiveness will be reduced; an air temperature of 4-32°C is better. The higher the temperature, the better the efficacy. Use with caution above 32°C, and do not use above 38°C or below 4°C.

(2) Concentration: In winter, when the temperature is low and the plants are dormant, a higher concentration can be used; in summer, when the temperature is high and the plants are growing vigorously, a lower concentration should be used. For trees and flowers, use a higher concentration during the dormant period (early spring or winter) and a lower concentration during the growing season. Excessive concentration or excessively high temperature can easily cause phytotoxicity.

(3) Timing: Prepare and use it on the spot. It is best to use up the boiled lime sulfur in one go; it should not be left standing for long, otherwise its efficacy will decrease. For deciduous trees, the dormant period and before budding in early spring are the best times to use lime sulfur; for evergreen trees, use after picking and before flowering for the best effect. Rosaceae plants such as peach, plum, plum blossom and pear, and leguminous plants such as redbud and silk tree, are sensitive to lime sulfur, so use it with caution during the growing season and when flowering, otherwise it will inhibit flower bud differentiation and cause a reduction in yield the following year.

(4) Taboos: Lime sulfur must not be mixed with Bordeaux mixture, copper preparations, mechanical emulsifiable concentrates, rosin mixture, or pesticides that easily decompose under alkaline conditions; an interval of 15-20 days is required. Do not use it continuously over a long period; long-term use will cause pests and diseases to develop resistance, and the higher the concentration used, the faster resistance forms. It can be used alternately with other pesticides.