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Garden Guy: Help your Indian hawthorn flourish


Could you please advise as to the best way to control a white mold that has appeared on my Indian hawthorn? Also, should I fertilize, and if so, what should I use? Thank you for your help. — P.M.

What you describe sounds like a fungus known as powdery mildew. Indian hawthorn is susceptible to this pest, though it seldom occurs. In fact, Indian hawthorn is fairly resistant to most insect and disease pests.

The one disorder most often identified on the plant is called Entomosporium leaf spot. It is a fungal disease that causes dark reddish brown spots, sometimes surrounded by a yellow halo appearing on the leaves. The spots darken and enlarge as the leaves mature.

Infected plants may prematurely drop many leaves.

The powdery mildew on Indian hawthorn, as well as on other plants, can be controlled with sprays of horticultural oils, neem oil, potassium bicarbonate (Kaligreen), Immunox and the biological fungicide Serenade. More than one application will be needed.

As for fertilizers, although Indian hawthorn plants do well in soils low in nutrients, nitrogen applied one to two times per year will help. As for a need to add potassium or phosphate, that would be determined by taking a soil analysis.

The College of Tropical Agriculture and Human Resources office in Hilo will process the order. Call 981-5199.

To simplify matters though, any well-balanced fertilizer applied once or twice a year would suffice. The plant’s vigor and color (yellow leaves versus green leaves) are an indication for a need to fertilize. In addition, applying organic mulch is advisable.

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With the increase of online shopping, empty cardboard boxes can pile up around the home. What to do with them all?

A simple solution incorporates recycling and soil nutrition as well as weed, slug and snail management all at the same time!

Many gardeners know that mollusks (slugs and snails) are a major pest. They are able to completely destroy newly set out seedlings as well as devouring many established plants. They feed on a variety of living plants as well as decaying plant matter. They can adapt to a wide range of host plants.

Several control measures are available including chemical baits, sanitation, chickens and ducks, together with trap boards. A trap board is any board, about 12 inches by 12 inches, or any manageable size, placed on the ground near slug and snail activity. Place one end of the board on a small rock, or another object in order to give it enough lift for the slugs to crawl under, about an inch. This board then becomes a good hiding place for the slugs.

Under the category of trap boards, we can also place cardboard boxes. Simply break down all the used boxes and place them in the garden in an area where slug damage is frequent; preferably in the shade, although not necessary. To escape the heat of the day, the snails and slugs will seek shelter and hide under the cardboard. Periodically, turn over the boxes, collected the pests and disposed of them.

Over time, the cardboard will breakdown and return to the soil. You may also notice some white fuzzy growth on the cardboard. These are various species of fungi which help break it down. They will not harm the plants and are a benefit to the soil.

The one drawback to this method is that the boxes will not add much to the beauty of the landscape; perhaps some nontoxic biodegradable paint will help color them up.

For more details on controlling slugs and snails see www.gardenguyhawaii.com and search slugs and snails.

Hilo resident Nick Sakovich is a professor emeritus of the University of California. He has worked in the field of agriculture for 30 years. Email your questions to Sakovich at askthegardenguy@earthlink.net. You also can visit his website at www.gardenguyhawaii.com.

 

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