- White rust and Anthracnose have been reported in spinach in southern New Jersey this week.
- Symptoms of white rust include yellow lesions on the upper leaf surface and white blister-like pustules on the underside of the leaf. Generally, the upper surface of the leaves remain chlorotic, however in advanced stages, white lesions may form on the upper side of the leaf. White rust caused by Albugo occidentalis is an oomycete, or ‘water mold’, and its development is favored by cool, wet weather with extended periods of leaf wetness. Spinach leaf surfaces must remain wet for at least 2 to 3 hours or longer to allow infection to occur, with the optimum temperature for spore germination at 54°F. The disease develops most rapidly during periods of cool, humid nights and mild daytime temperatures.
- Anthracnose in spinach is caused by Colletotrichum dematium. Symptoms of anthracnose are small, circular, water‑soaked lesions on young and older leaves. Lesions enlarge, turn brown to tan in color, and become thin and papery. In severe cases, lesions coalesce and result in severe blighting of foliage. Diagnostically, tiny black fruiting bodies (acervuli) which look like small black hairs form profusely in diseased tissue and are a characteristic feature of the disease. The presence of acervuli distinguishes anthracnose from Cladosporium and Stemphylium leaf spot diseases, which also form circular lesions on infected spinach.
- Importantly, the fungicides to control White rust will be different for those used to control Anthracnose in spinach
- Anthracnose crown rot, caused by Colletotrichum gloeosporioides, has been reported in strawberry this week. Symptoms of anthracnose crown rot include the “marbling” of the crown tissue. Cutting the crown lengthwise reveals white and reddish brown streaks, creating a marbled effect, with a dry rot-like appearance. Initial symptoms include plant stunting and flagging of young leaves due to lack of water. Initially plants wilt in the heat of the day, which is often over-looked as drought or heat stress. In advanced infections, the entire plant will die.
- For more information on White rust, Anthracnose in spinach, and Anthracnose crown rot control in strawberry please the 2020/2021 Mid-Atlantic Commercial Vegetable Production Recommendations guide. The new guide is now available FREE on-line or can be purchased in hardcopy form through your county agricultural office in New Jersey. The complete 2020/2021 Vegetable Production Recommendations guide or specific sections can be downloaded depending on your production needs.
April 2, 2020 Andy Wyenandt
