This weekly update provides information on the timing of apothecia (mushrooms) development from mummified overwintering berries in Washington’s Snohomish, Skagit, and Whatcom Counties.
The first table shows the percentages of floral and vegetative buds at different developmental stages and indicates when susceptible tissue is available on the plants. The second table shows the apothecial developmental stages from mummies and when ascospores are produced.
Development of mummies and host reflect conditions occurring in one field from each of the three counties that are currently being monitored. There may be differences in the stages of development in other blueberry fields in these same counties, in different counties, or for different blueberry cultivars.
Host Developmental Stages
| Week Beginning | County | Cultivar | Floral, Bud Swell | Floral, Bud Break* | Floral, Tight Cluster* | Vegetative, Bud Swell | Vegetative, Early Green | Vegetative, Late Green* |
|---|---|---|---|---|---|---|---|---|
| 3/15/24 | Snohomish | Blueray | 80 | 16.7 | 0 | 0 | 33.3 | 63.3 |
| 3/15/24 | Snohomish | Bluecrop | 50 | 50 | 0 | 90 | 10 | 0 |
| 3/15/24 | Skagit | Duke | 73.3 | 26.7 | 0 | 0 | 40 | 60 |
| 3/15/24 | Whatcom | Rancocas | 100 | 0 | 0 | 46.7 | 53.3 | 0 |
| 3/15/24 | Whatcom | Bluecrop | 56.6 | 43.3 | 0 | 3.3 | 50 | 46.7 |
Percentages represent data collected from 30 plants per each cultivar.
*Red indicates a susceptible stage for infections.
Reference: Blueberry Growth Stages [Michigan State University]
Pseudosclerotial (mummy) Developmental Stages
| Week Beginning | County | Dormant | Germination | Emergence | Differentiation | Sporulation** | Finished |
|---|---|---|---|---|---|---|---|
| 3/15/24 | Snohomish | 76 | 2 | 1 | 4 | 0 | 0 |
| 3/15/24 | Skagit | 83 | 0 | 0 | 2 | 0 | 4 |
| 3/15/24 | Whatcom | 65 | 8 | 4 | 25 | 9 | 0 |
**Red indicates release of ascospores.
- Dormant: Pseudosclerotia that have shed the host exocarp, revealing melanized hyphae, overwinter on the soil surface.
- Germination: Pseudosclerotia develop stipe initials, which are dark brown hardened protrusions smaller than 5 mm.
- Emergence: Stipe initials continue to elongate and grow to between 5 mm and 15 mm
- Differentiation: Stipe initials elongate, become fleshy, turn a light brown color, and produce a tip indentation that may expand to a diameter up to 2 mm.
- Sporulation: The tips of the stipes have expanded wider than 2 mm, to become cup-shaped apothecia.