Symptoms and Signs
Crown gall appears as rough, abnormal galls on roots or trunk. Galls are soft and spongy. The center of older galls decay. Young trees become stunted; older trees often develop secondary wood rots.
Comments on the Disease
The bacteria survive in gall tissue and in soil. Crown gall is most damaging to young trees, either in the nursery or new orchard plantings. All nectarine rootstocks are susceptible to crown gall.
Management
The incidence of crown gall can be reduced by planting noninfected, "clean" trees. It is also important to carefully handle trees to avoid injury as much as possible, both at planting and during the life of the tree in the orchard. Preplant, preventive dips or sprays with a biological control agent are available and may be helpful in some orchards. Generally, by the time crown gall is evident in a nectarine orchard, it is usually best to tolerate the problem for the few remaining years of orchard life, which is about 12-15 years, or just remove the orchard and start anew.
When replanting a previously affected site, remove as many of the old tree roots as possible, grow a grass rotation crop to help degrade leftover host material and reduce pathogen levels, and offset the new trees from the previous tree spacing to minimize contact of healthy new roots with any infested roots that may remain.
| Common name | Amount per acre | REI‡ | PHI‡ | |
|---|---|---|---|---|
| (Example trade name) | (hours) | (days) | ||
| Not all registered pesticides are listed. The following are ranked with the pesticides having the greatest IPM value listed first—the most effective and least likely to cause resistance are at the top of the table. When choosing a pesticide, consider information relating to the pesticide's properties and application timing, honey bees, and environmental impact. Always read the label of the product being used. | ||||
| A. | AGROBACTERIUM TUMEFACIENS-84# | |||
| (Galltrol-A) | Label rates | 12 | 0 | |
| COMMENTS: Preventive preplant treatment only. | ||||
| B. | GALLEX | Label rates | 0 | 0 |
| COMMENTS: For removal of existing galls, apply winter through spring. | ||||
| # | Acceptable for use on organically grown produce. |
| ‡ | Restricted entry interval (REI) is the number of hours (unless otherwise noted) from treatment until the treated area can be safely entered without protective clothing. Preharvest interval (PHI) is the number of days from treatment to harvest. In some cases the REI exceeds the PHI. The longer of two intervals is the minimum time that must elapse before harvest. |