Miller Lime Sulfur Now Labeled for Bloom Thinning In NY
Mike Basedow, CCE-ENYCHP and Greg Peck, Cornell University
New for the 2025 thinning season, Miller has added apple bloom thinning to their lime-sulfur solution label. Research out of Pennsylvania, Virginia, and New York has found good efficacy with this material when used under optimal weather conditions, however there are some caveats to keep in mind with its use. A very helpful guide to bloom thinning with lime sulfur (LS) is available from Penn State here.
A few key highlights from the article and the label include:
- Thorough coverage is essential. For well-pruned dwarf and semi-dwarf trees, a spray volume of 80-100 gallons per acre via air-blast is typically used. For small trees with narrow open canopies, 50 gallons per acre may be enough, while older larger trees may require 200 gallons per acre to obtain thorough coverage. Avoid excessive spray volume to minimize leaf damage and fruit russeting. The action of LS is based on its concentration, not on the rate per acre. Do not concentrate the chemicals when spraying at a lower volume.
- When mixed with oil, use LS at 1.5 to 2% (v/v). Oil options include fish oil at 2% (v/v), dormant petroleum oil at 1%, or summer oil at 1 to 1.5% v/v. Trials in the mid-Atlantic indicate that an oil + LS combination is more effective than LS alone. The lower LS rate will also reduce the chance of fruit russeting.
- Two LS applications during bloom are suggested, if possible. If weather conditions are not conducive to a 2nd application, or if less aggressive blossom thinning is desired, a solitary application would still be of benefit in multi-step programs that include petal fall and fruitlet thinning (nibble approach).
- Before the Pollen Tube Growth Models (PTGMs) were developed, the timing of LS thinner was by visual estimates of the percentage of open blossoms. Typically, two sprays, one at 20-30% bloom followed by a second spray at 80-100% bloom. If you don’t have access to the models or choose not to use them, this method of timing can still be done with satisfactory results. The model just makes the timing more precise. To use the PTGM, average style length must be measured in each block. Additionally, the number of open blossoms must be actively monitored. Once the number of open king blossoms is equivalent to the desired crop load, the model is initiated. Detailed instructions with the NEWA interface are provided in the Using the Pollen Tube Growth Models on NEWA section of the Penn State article and in the following YouTube videos we have at Cornell. (click the titles below to view)
- The label carries a number of use restrictions, including not to apply for bloom thinning when temperatures are above 80 degrees, or will exceed 90 degrees within 24 hours of the application. It also states under the use precautions for bloom thinning section not to apply under slow drying conditions or wet weather. Take care not to overtreat the lower portion of the canopy nearest the nozzles. Applying at higher pressure and smaller nozzles can reduce phytotoxicity.
- Do not tank mix other spray materials when thinning with LS or LS plus oil. Additional applications of either oil or LS immediately after LS thinning sprays are very likely to increase thinning response. Oil and captan fungicide should never meet on your trees. To allow oil residues to weather, leave a 2 to 3-week interval between the last spray containing oil and the first captan spray. If there is a high risk of severe frost or freeze damage during the bloom period, consider delaying or avoiding application of LS as a bloom thinner.
The label is clear that the use of this product as an apple blossom thinner can potentially lead to crop injury, loss, or damage. This is mostly a concern for causing fruit russeting. Please see the Warranty and Limitations of Damages for Apple Bloom Thinning at the end of the label.
If you want to try lime sulfur for bloom thinning, we recommend starting on a small portion of your orchard, and make sure you have the right weather conditions for its application.