HAWAI'I GARDENS
Devastating cycad scale needs powerful insecticide
By Heidi Bornhorst
Q. I live near to the ocean in West Maui and have noticed that not only are our sago palms and cycads covered in scale, but that many of our neighbors are experiencing the same blight. What do you recommend? I've been told that we should inject a systemic into the soil. Is this going to be an ongoing affair and/or how many treatments will be necessary? Will the plants survive without the systemic?
A. This scale is devastating to cycads and will kill them if left untreated. This pest came into Hawai'i a few years ago, and many gardeners have been treating their cycads to rid them of the problem. I called Steve Oda at Garden House, who recommended systemic control. Get practical advice on chemicals from your local garden shop. The suggested treatment is:
- Cut off and dispose of any bad/yellowed/dead fronds.
- Spray with diazinon and Volck oil, or Volck oil with ortho systemic insect killer, or Volck oil and Bayer rose and flower with merit according to the directions and dilution rates on the label.
- Repeat in a few weeks. You can use alternate insecticides to knock out the pests.
Wear rubber gloves, rubber boots and eye protection at the minimum. Do not spray near food crops or where spray can blow toward them. Insecticides are the most toxic garden chemicals.
You also need to remove scales you have killed with a rag or toothbrush. Even the dead scales block light and reduce photosynthesis. They also look ugly on your plants. If the poison has killed them, they will flake right off. Rub them off, spray with clean water.
You can put mulch on the soil to improve fertility and make sure they are watered. Moisture stress, like the severe drought we've been experiencing in Hawai'i for more than five years, allows pests and diseases to more easily attack and infest our plants.
Make sure your neighbors treat their cycads, too. This scale attacks all kinds of cycads, especially Cycas circinalis and C. revoluta. The new whorl of leaves that emerges about once a year should be clean and uninfested if you follow this treatment. Monitor new growth.
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What's in bloom:
Golden plumeria
Rainbow shower trees are seeing the end of the blooming season. There are some flowers to be found, but our gusty trade winds and welcome showers are rapidly dispersing them. Royal poincianas also are winding down.
Plumeria are having a second blooming season, just like mangoes did a few months back. It's rare, but the kids and I managed to make a double yellow plumeria lei for Tutu Karlene on the Mainland from the prolific blooming tree of a generous neighbor in Foster Village. I didn't think we'd have enough blossoms, but with kokua from the nieces and grand-niece, and strong nephew Jimmy and Tutu Kane George holding the ladder, we managed to pluck enough precious blossoms. Ten-year-old Tianna turned out to be an expert and diligent lei maker. Now this was a true Hawai'i experience!
Mangoes in winter?
I've always wanted us to have mangoes to eat, year round. In some countries, notably Brazil, there are mango varieties that produce fruit throughout the year. Fruit experts Frank Sekiya and Lynn Tsuruda are working on bringing in new cultivars of mangoes and promising mango relatives. They also have some kinds of mangoes that do well in cooler, upland sites. (Our present mango varieties do best in hot, dry lowland areas like Kapahulu and Wai'anae).
This year, we had a second fruiting season of mangoes. Many readers and gardeners were amazed and overjoyed to see this late-season blossoming. The fruits were a bit different from our normal-season mangoes. They were slower to ripen and got less color, maybe because of shorter, cooler days. One grower said rats or birds ate more of this second crop.
I noticed a lot of seed weevils in the perfect-looking mangoes I was given, but that just made me eat them quicker!
Heidi Bornhorst is a sustainable landscape consultant. Submit questions to islandlife@honoluluadvertiser.com or Island Life, The Advertiser, P.O. Box 3110, Honolulu, HI 96802. Letters may be published or distributed in print, electronic or other forms.
