Eat The Yard

When I wrote a few weeks ago about the preponderance of male flowers in my winter squash as the culprit behind the failure my cucurbits to fruit, I had also spent some time researching another symptom that had been plaguing those plants.  The fruitlessness is the result of insufficient pollination, as I previously indicated.  The now certain failure and death of this out-of-season crop will be at the hand of this other problem.

R.I.P. Waltham Butternut, Pink Banana, and Table Queen Acorn Squash.

Powdery Mildew infects a variety of plants, but the cucurbits — the family of edibles that includes squash — are particularly susceptible.  The infection reduces yields, deforms fruit that does manage to ripen, affects flavor, and predisposes the host plant to other diseases.  Powdery Mildew is caused by any number of fungi in the order Erysiphales, but the most common for the cucurbits are S. fuliginea and E. cichoracearum.

The fungus is an aggressive sexual and a-sexual reproducer that is wind dispersed, hopping from leaf to leaf and plant to plant in the breeze.  Dry weather, as we have here in San Diego in abundance, helps the mildew get established.  It starts with the oldest plants first, working down from the crown leaves until the plant, stem and all, is dusted snow white with spores.  Infected leaves die, and the plant senesces prematurely.

Wetting plant leaves when watering can make them prime breeding grounds for this type of fungus — something that was nearly impossible to avoid with the raised beds I built.  Crowded plants make the transmission easier, and that is another quality of my garden: I packed the plants in and didn’t thin nearly enough for the space available, partially because I was so keyed up on producing something in the aftermath of my summer losses.  Also, raising my beds put my squash at the perfect height to catch the hot, dry winds that race off the canyon behind our property — the likely vehicle of the original spores.

Apparently the fungus can be wiped off, but this seems a dubious suggestion since the reproductive structures of this fungus are smaller than the eye can see, and my eyes don’t see that well anyway.  Most recommendations for treatment quickly turn to chemicals — at the same time that they note chemical treatment breeds resistant strains of fungus, in addition to secondary pollution of groundwater and humans.  When I originally researched Powdery Mildew, my plants had a mild infection and my reading led me to believe that established plants might not be adversely affected.  Further reading and my own experience has proven this to be … wishful thinking, at best.

My winter squash hang languidly from the planters, their leaves largely withered, browned and yellowed by a parasitic relationship with this fungus that is not mutually beneficial, as some pairings in nature tend to be.  The four butternut fruits stopped growing sometime ago, and the promising pink bananas have begun to wrinkle and wilt into themselves.

I think it’s quits for the winter squash I was so cocky about at the start of the fall planting.  This weekend I’ll cut them out and make room for the true cold season crops — the broccoli and the beets and the carrots — to get fat in roomier digs.

Tags: container gardening, fungus, pesticides, pests, powdery mildew, raised beds, squash, winter crop