Asthma: This is the most likely diagnosis given the symptoms of wheezing, chest tightness, and nighttime cough, which are classic for asthma. The triggers mentioned, such as mowing grass and inhaling smoke, along with positive allergy tests to tree, grass, and ragweed pollen, further support this diagnosis as allergic asthma.

Allergic Rhinitis: While the primary symptoms are respiratory, the positive allergy tests suggest that the patient may also suffer from allergic rhinitis, which could contribute to or exacerbate her respiratory symptoms.
Chronic Obstructive Pulmonary Disease (COPD): Although less likely in a 44-year-old without a significant smoking history mentioned, COPD could be considered, especially if the patient has had significant exposure to smoke or other lung irritants. However, the presence of allergy symptoms and specific triggers makes this less likely than asthma.
Hypersensitivity Pneumonitis: This condition is caused by an allergic reaction to inhaled substances, which could fit with the patient's symptoms after inhaling smoke or mowing grass. However, it typically requires more prolonged exposure to the allergen.

Pulmonary Embolism: Although the patient's symptoms do not strongly suggest pulmonary embolism, it is a potentially life-threatening condition that must be considered, especially if there are any risk factors for thromboembolism (e.g., recent travel, immobilization, family history).
Cardiac Ischemia: Chest pain (described as sternum pain) could also be indicative of cardiac ischemia, particularly if the pain is exertional or has other characteristics of angina. Given the potential for fatal outcomes, this diagnosis must be ruled out.

Eosinophilic Granulomatosis with Polyangiitis (Churg-Strauss Syndrome): This is a rare autoimmune condition characterized by asthma, eosinophilia, and vasculitis. It could be considered if the patient has systemic symptoms or if asthma symptoms are particularly severe and resistant to treatment.
Occupational Asthma: If the patient's symptoms are specifically related to her work environment (e.g., mowing grass as part of her job), occupational asthma could be a consideration. This would involve exposure to specific allergens or irritants in the workplace.