Bug Off!: Part 3

March 2, 2020, 3:27 PM HST (Updated March 2, 2020, 3:27 PM)
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This spaghetti squash in the author’s garden developed a bad case of powdery mildew and rust. The plant has since been treated and is happily producing plenty of food. Photo: J.M. Buck

Right now, I am kicking myself for all those times I bemoaned the weather with “Rain, rain, go away.” During normal weather conditions, there is usually some evening rain on the windward side, making watering with a sprinkler minimal. Lately, I have had to resort to using a sprinkler every morning and to my surprise, a perfectly healthy spaghetti squash vine developed a bad case of powdery mildew and rust. I’m not sure if the cause was the water switch (from natural rainfall to the slightly chlorinated water in my catchment tank), but I’m taking a wild guess that it may have been. So, this brings us to how this problem, and others like it, can be handled — the plant problem, not the water problem).

One thing about the Islands — it’s fairly humid. And garden fungi and diseases love humid conditions. Since we can’t do anything about the humidity, the best cure is prevention. When purchasing seeds or plants, read the package or ask a nursery attendant if the variety is disease resistant. Be aware that some seed companies base resistances and growing tips on mainland climate conditions. Hawai‘i has a very unique and diverse climate, so not all seeds will be suited to your particular area.

When planting, be sure plants are not crowded and have adequate air circulation. Overcrowding and poor air movement are major causes of plant ailments. Watering from above in the evening may also cause problems — moisture sitting on leaves overnight creates a prime breeding ground for fungi and bacteria. Drip irrigation is the best, otherwise, water in the morning. Also, adding neem seed meal to your soil helps strengthen plant immunities. Neem seed meal is produced from the oily extract of the Indian Neem tree (Azadiracta indica) and is a potent, organic mildewcide/fungicide.

Let’s say you have an outbreak of something on your plants. You’re not sure what it is, you just have this feeling that it’s “something bad.” You can:

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1. Look it up online and find out how to remedy it.

2. Cut off a leaf and bring it over to ‘Ohana Greenhouse and Garden in Kona or Garden Exchange in Hilo. I have found the staff at both places to be extremely knowledgeable and both have an impressive stock of organic seeds, fertilizers, and insect and disease treatment products.

3. Watch with a kinda sick fascination as the plant withers away. I don’t recommend the third option.

A caveat on the use of any pest/disease treatment — it usually takes care of the symptom, but not the cause. At the first sign of trouble, I recommend removing the affected area then applying a foliar spray of an organic seaweed product with a guaranteed cytokinin content. Cytokinin is a hormone produced by plant roots that has an important function in protein synthesis. When plants are under stress, cytokinin production is reduced or ceases altogether. Subsequently, protein synthesis is inhibited and the plant weakens, resulting in insects and diseases.

If you recognize the ailment, here are some solutions: First, cut off all diseased parts, tie them in a plastic bag and dispose of it. Do not put diseased plant material into your compost pile! For mildews, molds, rust, blights, bacterial soft rot and a host of leaf spot diseases, a spraying regimen of liquid copper organic fungicide is the ticket. This, combined with the addition of neem seed meal in your soil, should take care of most common garden ailments. Spraying of neem oil is also effective for powdery mildew and many other problems.

Happy gardening!

J.M. Buck
J.M. Buck has been a Hawai‘i news writer and columnist since 2003. She has extensive writing experience and has served the media industry in a variety of capacities, including news editor, investigative reporter, online publisher, columnist, web content writer, graphic designer and photographer. She has lived in the Hawaiian Islands for most of her life and is a graduate of University of Hawai‘i.
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