Cucurbit powdery mildew (PM) is a fungal disease that typically develops around mid-summer every year. Now that we are a little past the halfway point, it is becoming and more evident in our field walks. PM leads to extensive defoliation increasing the likelihood of sunscald on fruit and will weaken stems on pumpkins and winter squash. Early intervention is very important.

Scout fields regularly and apply fungicides early in disease development. Protective fungicides (e.g. sulfur, horticultural oils, chlorothalonil, copper, mancozeb) should be applied before the first sign of disease as powdery mildew spreads rapidly and cannot be controlled once it is well established.

See the New England Vegetable Management Guide for currently labeled fungicide options.

Blossom end rot is a very familiar abiotic disorder for many growers. It is commonly identified on peppers and tomatoes, but can affect squash too. Stressful growing conditions, especially dry spells, are to blame. In peppers, blossom end rot can be confused with sunscald. Water management aimed at keeping the soil moisture consistent is the best strategy to reduce BER. Removing fruit with BER can reduce further losses as even damaged fruit will continue to mature and compete for the plant’s nutrients.

Bacterial Spot: The most common often destructive disease of peppers in the northeast. It is present wherever these solanaceous crops are grown. Spot lesions on leaves are generally water-soaked, brown and circular and coalesce into dark long streaks. Spots can also form on stems and fruit. Scout fields weekly to look for small brown leaf spots on plants.

Bacterial Speck: Lesions on leaves are round and dark brown to black with a halo that develops over time. Spots can coalesce, killing large areas of tissue. On unripe fruit, small dark spots or specks develop with the tissue around them more intensely green. This disease is generally a minor concern.

Bacterial Canker: The most destructive bacterial disease of tomatoes in our region. Initial symptoms are leaf curling, wilting, chlorosis, and shriveling of lower leaves. In advanced stages, the pathogen spreads throughout the plant and causes poor growth, wilt and plant death. Stems break easily and cankers form. Small raised white to yellow spots with a brown center (“bird’s eye spots”) form on fruit.

Similar management strategies can be applied when any of these three bacterial diseases have been identified in your field:

• Work infected fields last and try to avoid working in fields when they are wet. Do not use high pressure, air-blast sprayers which cause increased leaf infection in rows adjacent to spray alleys spreading the disease across rows. Destroy crop residue after harvest to encourage rapid decomposition.
• Effective management requires rotating to fields where solanaceous crops and weeds in the nightshade family have not existed for at least two years.
• Use a hot water treatment on seeds. Diseases-resistant varieties can also be found.
• Chemical controls by themselves are not sufficient to control a bacterial disease once it has been established.
• Bacterial diseases can overwinter in crop debris in the field or on wooden stakes. Disinfect before reusing.

Similar to June, July and early August have seen ozone level surges reaching toxic levels for crops in Connecticut, with severity varying depending on exact location within the state. Ozone injury in susceptible vegetable varieties develops when ozone levels are over 80 ppb for four or five consecutive hours, or 70 ppb for a day or two when vegetable foliage is at a susceptible stage of growth. Typically, the most susceptible vegetable crops include cucumber, potatoes, watermelon, cantaloupe, snap beans, pumpkins, and squash.

The best recommendation for managing susceptible crops in when ozone levels are high is to whatever extent possible, avoid additional stresses on plants. Do not apply unwarranted pesticides or nutrients during this period. Note which varieties show fewer symptoms and plan to select varieties that are less susceptible in the future.

For more information on the relationship between the Air Quality Index (AQI) and Ozone levels, visit the Air Quality Guide for Ozone and Particle Pollution. For example, ozone concentrations would be 71-85 ppb when AQI is 101-150. To monitor local trends, visit airnow.gov.