By Debra Knapke

Late summer: the time of year when I look at the abundance of my garden and start taking away what is too much: pruning, thinning and removing diseased plants. I call this simplifying the garden and opening up space for ideas gleaned from seminars, trade shows and garden tours.

But first, I have to deal with nature’s effects on the edibles.

We can all agree that this has been another challenging growing year. Mother Nature has muddled the spring and summer seasons with excessive rain and unseasonable lower temperatures. By the last week in June, my tomato plants were gorgeous; loaded with blossoms and fruit… all green. We had lots of rain and little sun in May and June. The temperatures – while delightful for humans – were not hot enough to develop colorful and tasty fruit. By the second week of July early blight plus Septoria leaf spot showed up on tomato leaves – see above.

We finally had some hot, sunny days in July, but this generated severe sunscald on the tomatoes. They were not accustomed to sunny days. Low temperatures caused most of my tomatoes to ripen unevenly resulting in irregular coloration, white spotting, mealy texture and little true tomato flavor. To add insult to injury, anthracnose lesions developed on the tomatoes that were ripening well.

Left to right: Black Krim tomato with sunscald, middle Black Krim and Gold Medal tomatoes show mottled coloration that indicates low temperature conditions and lastly, an undersized Brandywine tomato with anthracnose.

Are these tomatoes safe to eat? Yes, but after you remove all the diseased sections, there isn’t much left. What does one do with tomatoes such as these? Make tomato sauce.

Now, I have plants that are covered with disease. This calls for an experiment. I removed all diseased portions of each plant, rinsing my pruners and fingers in 91% alcohol as I moved from plant to plant. I cleaned up the area under the plants and then watered in a low nitrogen organic fertilizer. These are my Charley Brown tomato plants, and I wonder if they will be able to rebound from all of the above.

Next sad story concerns basil. I started my own plants this year in an effort to bypass the downy mildew disease that has plagued my favorite pesto herb. My 32 plants started off great. I kept them evenly moist and healthy with compost tea. Just as I was thinking to plant them out – late May – I noticed my plants had downy mildew.

Here, it is important to explain what downy mildew is. First, it is not a fungus. Therefore, a fungicide will not be effective on this pathogen. It is a water “mold” in the Kingdom Protista. TMI? Maybe, but if you are going to try to defeat it, you have to understand its nature. This is not a post about downy mildew, but it is important to understand that it is a difficult disease to control. We do not have a cure, instead we have to prevent it with cultural and mechanical practices:

• Clean up all plant debris and remove infected leaves
• Sterilize your tools and fingers frequently with alcohol when removing diseased parts from plants
• Keep the plants healthy by side-dressing with compost
• Do not allow the soil to dry out – avoid water stress.

Below are three infected leaves. On the left is the top of the leaf. Notice the blotchy yellowing. The other two leaves show the “gray” infected areas under the leaf.

Take a closer look and you can see the spores; the carriers of downy mildew to the next leaf or plant.

The below plant was doing well, but I was at a conference for a week and this is what I found when I returned.

Downy mildew has returned. I missed my pesto-making window. This plant has been moved to the “bad” compost pile.

I have since destroyed my most affected plants – the triage – and then removed affected leaves from the healthier plants. I am trying a product: BioSafe Disease Control. It is based on hydrogen peroxide which has been shown to have a preventative effect on water molds. I will let you know.

There are other tales of woe, like swamped lavenders, and tales of joy: having the best summer phlox bloom ever. But that is for the next post.

Wishing you excellent pesto and tomatoes…