### Rosemary (*Rosmarinus officinalis*)

1.  **Powdery Mildew** (*Erysiphe* spp.)
    *   **Integrated Management Strategies:**
        *   **Cultural & Preventive:** This is the most important factor. Ensure excellent air circulation by pruning dense growth and providing adequate spacing. Plant in a sunny location. Avoid over-fertilizing.
        *   **Biological:** Some strains of *Bacillus subtilis* have shown efficacy.
        *   **Chemical:** For edible rosemary, use OMRI-listed products like horticultural oil, neem oil, or potassium bicarbonate. Apply thoroughly, covering all plant surfaces. For ornamental use, systemic fungicides like myclobutanil can be used.

2.  **Root Rot** (*Phytophthora* & *Pythium* spp.)
    *   **Integrated Management Strategies:**
        *   **Cultural & Preventive:** This is almost entirely a cultural problem. Plant in very well-drained soil, such as a sandy loam or a pot with large drainage holes. Amend heavy soils with compost and grit. Water deeply but infrequently, allowing the soil to dry out significantly between waterings. Rosemary is highly drought-tolerant.
        *   **Biological:** Incorporating beneficial microbes like *Trichoderma* into the potting mix can help suppress root rot pathogens.
        *   **Chemical:** Fungicide drenches are available but will not save a plant with advanced rot. They are best used preventively in nursery settings. Active ingredients include mefenoxam (*Pythium*) and phosphorous acid (*Phytophthora*).

3.  **Botrytis Blight** (*Botrytis cinerea*)
    *   **Integrated Management Strategies:**
        *   **Cultural & Preventive:** Prune to open up the plant canopy and improve air circulation. Water at the base of the plant in the morning. Remove any dead or decaying plant material immediately.
        *   **Biological:** *Bacillus subtilis*-based products can be used preventively.
        *   **Chemical:** Check labels carefully for use on herbs. Potassium bicarbonate is an organic option.

(The final two diseases, **Aerial Blight** and **Bacterial Leaf Spot**, are less common and are managed with the same principles: improve air circulation and avoid wet foliage.)