Knowledgebase

Lime-Sulfur Alternatives #305138

Asked March 06, 2016, 8:22 PM EST

OSU Extension Service's leaflet, "Managing Diseases and Insects in Home Orchards," recommends use of Polysul or similar lime-sulfur sprays for, among other applications, powdery mildew in apple and pear trees and blister mites in pear trees. However, lime-sulfur spray has now been withdrawn from the market by the manufacturers. The only alternative for the above applications mentioned in the leaflet is thiophanate-methyl (Halt), but its manufacturer's web site cautions against its use on fruit trees. What is OSU now recommending for these applications in place of lime-sulfur?

Josephine County Oregon

Expert Response

Copper-based pesticides and fungicides are a popular dormant spray and lime sulfur alternative. Copper is a harsher chemical and can be damaging to ponds and waterways, so take care to use copper dormant sprays according to the indications on the label. Copper is a potent anti-fungicide, insecticide, and is even effective against plant-borne bacterial infections.

Horticultural oil is a dormant spray that is used to coat old growth vines and woody plants. The oil coats the surface of the plant tissue and deprives pests and fungus of oxygen, preventing their overwintering in the woody portions of the plant. Horticultural oil is frequently used on grape varieties that might be sensitive to harsher chemicals such as sulfur and copper.

I hope this helps.

Chris Rusch Replied March 07, 2016, 11:45 PM EST
I am familiar with copper and horticultural oil sprays, and I use them for the winter dormant season.  Also, for apples, I use copper post-harvest for anthracnose.  My understanding, however, is that copper is not meant to be used while blossoms or fruit are present on the trees, and also that oil sprays are primarily for use during the dormant season.  What I am looking for is a replacement for lime-sulfur during the pre-pink, pink, and petal fall periods.  I can use Captan to control scab on apple trees, but I have found no recommended alternative to lime-sulfur or thiophanate-methyl for powdery mildew in the spring season.
The Question Asker Replied March 08, 2016, 12:56 AM EST

Below is a publication that will help.

http://extension.psu.edu/plants/tree-fruit/insects-mites/insecticides-and-miticides

Chris Rusch Replied March 08, 2016, 1:15 AM EST
Thank you.  I'm sure that this will be helpful in reviewing options for insect and mite control.  If, in addition, you can recommend a similar source of information on growing-season fungicides, that would also be very much appreciated.
The Question Asker Replied March 08, 2016, 1:30 AM EST

Neem oil is a great organic pesticide.

Neem oil is pressed from the fruit and seeds of the neem tree

(Azadirachta indica). At a 70 percent concentration, neem oil

kills powdery mildew spores, virus vectors (such as aphids and

white fly), and the eggs of numerous insect pests. It is less effective

against rose black spot (caused by Diplocarpon roseae) and

other fungal diseases.

Bicarbonates

Baking soda (sodium bicarbonate) has been used as a can also be used against powdery mildew.

Hope this helps.

Chris Rusch Replied March 08, 2016, 10:27 PM EST
Indeed it does.  Thank you.
The Question Asker Replied March 09, 2016, 2:09 AM EST

Loading ...