Vine Crop Edition - by Elaine Roddy, Vegetable Crop Specialist, OMAFRA, Ridgetown (elaine.roddy@ontario.ca)

Downy Mildew in Cantaloupe
Downy Mildew in Cucumbers
Powdery Mildew and White Mould in Squash and Pumpkins
Simcoe Vegetable and Alternative Crop Open House

Downy Mildew in Cantaloupe

Downy mildew has been identified in cantaloupe plants in the sentinel plots near Chatham.  Downy mildew symptoms in cantaloupe can be quite different than those seen in cucumbers.  The lesions are often irregular in shape and lack the distinct angles seen on infected cucumber leaves.  Spores are not always readily apparent on infected cantaloupe plants.  We often find that the spores are much smaller and can only be seen at the edges of the lesions under a microscope.

Downy mildew in cantaloupe can be easily confused with other foliar diseases such as alternaria and scab.  Alternaria lesions commonly have concentric rings of darker tissue in the lesion while scab usually has a bright yellow halo around the lesion.

 Figures 1 and 2; Downy Mildew Lesions on Cantaloupe Leaves.

A fungicide program in cantaloupes should take into account both downy mildew and the other foliar diseases.  Alternaria, scab and anthracnose must be controlled as these diseases can infect the fruit, resulting in harvest rots and a loss of marketable yield.  Unfortunately, the most effective downy mildew products (Ranman and Tattoo C) will not control other foliar diseases.

Rotate broad spectrum products with the downy mildew products.  Broad spectrum products include mancozeb (Manzate, Dithane, Penncozeb), chlorothalonil (Bravo) and pyraclostrobin (Cabrio). Tattoo C does contain chlorothalonil, however it is a much lower rate than would normally be applied for broad spectrum disease control.

Downy Mildew in Cucumbers

Downy mildew infections have now been confirmed in pickling cucumber fields in Elgin and Norfolk counties. Nevertheless, levels of downy mildew remain considerably lower than those seen in 2007 and 2008.

Growers should maintain the 7 day preventative spray program during harvest.  Keep in mind that Ranman has a one day pre-harvest interval and Tattoo C has a two day PHI.  Always rotate between chemical groups.

Powdery Mildew and White Mould in Squash and Pumpkins

Powdery mildew was found in a squash field earlier this week.  Powdery mildew fungicides are most effective when they are used preventatively.  Do not wait until the disease is established in the field to begin spraying.

Monitor fields regularly for signs of infection.  Inspect the upper and lower leaf surfaces of at least 100 leaves across the field.  Infections usually appear as a pale yellow spot on the upper leaf surface with powdery white growth on the corresponding lower leaf surface. Powdery mildew control products include: Bravo and Cabrio.

Figures 3 and 4; Powdery Mildew Upper and Lower Leaf Surfaces

White mould is an occasional problem in pumpkins and squash.  Some of the specialty types of gourds and mini pumpkins seem to be particularly susceptible to white mould infections, especially when these crops are grown in rotation with soybeans.  Varieties with deeply recessed handles appear to be most susceptible to infection.

The initial infection commonly occurs at flowering or during fruit expansion.  Lance fungicide is registered for white mould control.  Thorough spray coverage of the blossoms and fruit is essential.  Unfortunately, with many vine crops this is difficult to achieve.  Use high water volumes and aim for medium sized spray droplets.

Research trials indicate that when Lance is applied for white mould control it will also control powdery mildew.

Simcoe Vegetable and Alternative Crop Open House

New Crops, Old Challenges - Tips and tricks for managing these new crops!

Date:  Tuesday, August 18, 2009 (Rain Date:  Thursday, August 20, 2009)
Time:  1:30 p.m. - 5:00 p.m.
Place:  Simcoe Research Station, 1283 Blueline Road, Simcoe
Please RSVP by August 14th by calling 519-426-7127 ext. 323

Crops featured include:  Chia (Salvia grain), Bitter Melon, Kohlrabi, Luffa, Celtuce, Gobo (Japanese Burdock), Goji, Tomatillo, Gourds (bottle, hairy, winter), Yard long beans, Edamame, Skullcap, Fenugreek, Calendula, Edible Chrysanthemum, Tahtsai, Ethnic varieties of eggplant, peppers, cucumber, basil, Sweet potatoes.

Other plots and hands-on demonstrations on alternative crops:

• Pest management and sprayer technology:  discuss with provincial specialist
• Cover crops:  oppportunities to save your nitrogen dollars
• Current nitroge research conducted by the University of Guelph

Enjoy refreshments, meet with other producers and take the opportunity to talk with University of Guelph staff and OMAFRA specialist.

Attention CCA's:  2 CEU's have been requested.

Funding for this field day was generously supplied by the Ontario Soil and Crop Improvement Association (OSCIA), the Norfolk Soil and Crop Improvement Association (NSCIA), OMAFRA, University of Guelph, Agrium Inc., and A & L Laboratories.