Sunday, June 9, 2013
How do I control Downey Mildew in vegetable seedlings?
Please click on the image to view a quick video of next week's spec load.
Winter weather suits plants like the beautiful Primrose Marlies above but it 'aint ideal for everything. Many of the perennial herbs: Mint, Thyme, Sage, etc. are starting to look worse for wear. They become particularly susceptible to Botrytis (Grey mould) and fresh growth can only be forced under greenhouse conditions and with low light levels this leads to straggly growth.
The other significant challenge winter brings is Downey Mildew in Brassica vegetables. I have written about mildew previously, and offered Dangerous Don's Milk remedy to control the fungus. So here's a quick refresher:
1. the Downey Mildew fungus spores are endemic and they are a particular problem with young seedlings, in the right conditions older plants can grow out of the problem.
2. Position is everything. This is where we grow our Brassica vegies.
This area running down our main driveway is too exposed for almost anything else but the high light levels and exposure to free moving air have 2 benefits: first because we don't use any Plant Growth Regulators on our seedlings we have to "harden" the plants almost from the moment the shoots emerge from the soil and second Downey Mildew and many other fungi thrive where light levels are low and humidity is high, that won't happen out here.
3.Timing is everything else. Watering in a period between 11.00am & 1.00pm is ideal. Watering before 11.00 provides moisture for spore germination which happens predominantly around mid-morning, watering after 1.00pm can leave foliage wet over night which encourages the bacteria Pseudomonas.
4. Hygiene. Sitting up on these benches on concrete ensures we can easily remove any plant debris that may carry fungal spores.
5. Nutrition. Fertilizer programs must be "balanced", avoiding too much Nitrogen and Phosphorus which soften cells, allowing fungal infection.
6. Treatment. Dangerous Don recommends a milk solution to control various mildews. Australian research recommends regular chemical treatment with a combination of Phosphorus acid (Yates, Anti-Rot) and Zineb (not available in consumer packs but Yates, Mancozeb Plus Garden Fungicide and Miticide should make a suitable alternative). By the way treatment is the last item of 6 for a good reason, it is the least effective.
Hope this helps.