It seems just when we think we have dealt with one epidemic another pops up. The avocado lace bug caused widespread defoliation of avocado trees in 2021, and now we have a new pest attacking our native koa, wiliwili and uhiuhi.
The acacia whitefly (Tetra-leuodes acacaciae) has become widespread on Oahu and will soon be found on the Big Island, if it is not already here. Not only does it attack our native acacia koa, other hosts include shower tree (cassia species) and related legume trees like the bauhinias are vulnerable as well. Acacia whitefly infestations may cause leaf yellowing, wilting and even defoliation.
Other landscape plants may be affected as well. Luckily, we have several predators that feed on whitefly, like ladybeetles and a parasitoid wasp, so this should help bring down the populations. Before nature does its job to balance things, whitefly numbers may make affected trees unsightly, since the honeydew secretions from these insects may lead to sooty mold.
If you notice acacia whitefly attacking your shower trees, acacia or others, call the state Department of Agriculture’s Plant Quarantine Division at (808) 643-PEST or visit 643PEST.org. You may also contact Janelle Saneishi at (808) 973-9560 ors hdoa.info@hawaii.gov.
In the meantime, enjoy spring flowering trees that are beginning to make a show. The royal poinciana, Delonix regia, usually has flowers of crimson red to burnt orange. A rare form with yellow flowers is also available at some nurseries.
The many types of cassia or shower trees areon display as well. The golden shower or Cassia fistula and the pink and white shower, Cassia javanica are spectacular but do have one draw back in that they have seedpods like the royal poinciana. However the hybrids created by the two species are sterile and flower more prolifically over a longer period with no seedpods. These are referred to as Rainbow Showers and are usually propagated by air layers or grafted on to golden shower rootstocks.
Our native wili wili, Erythrina sandwichensis is in bloom now and may be spotted with a sharp eye along the Mamalahoa Highway driving from Kailua-Kona to Waimea. You might even catch the last of Waimea’s cherry blossoms completing their bloom.
There was a time when forests covered much of the lands that are now grass, savannah and desert. Early Polynesians brought with them pigs, rats and jungle fowl that are the ancestors of modern-day chickens. The impact on our endemic loulu palm forests was devastating, but with the introduction of grazing animals in the late 18th century, our forests really began to shrink. The vast koa forests once common are now mere remnants of their past glory. Now the threat of rapid ohia death fungus may further decimate our forests.
Well planned areas, like the resorts of West Hawaii, are literally being transformed from lava flows into tropical oases thus urban forestation. These are examples we can follow.
You don’t have to be a big landowner to add to the forests of our island. Even folks with small lots can help. By planting trees in our little pieces of paradise, we can actually change the microclimate and make our communities several degrees cooler in the summer. If you place your trees just right, you can even create a garden climate that is milder during cool, windy periods. It’s really interesting when you expand these basic principles. What happens when everyone in your neighborhood or community plants shade trees? You can actually change the climate over fairly large areas. Foresters have research data that show reforestation may increase local rainfall and modify temperature extremes.
Now let’s look at the tree planting from another angle. Visitors bring millions of dollars to Hawaii each year. Our sunny winter skies are a big attraction. It used to be that our beaches and tropical woodlands were part of that appeal. Now with urban sprawl and rising ocean levels on some of our best beaches, our main salvation from endless asphalt alleys is abundant landscaping and protection of green open spaces.
Planting trees to give shade and beautify our communities isn’t the complete answer, but it can help. Shopping is miserable when streets are barren and parking lots are hot and uncomfortable. Hotels, restaurants and gas stations that are attractively landscaped with shade trees, shrubs and grass attract customers. Even grocery and department stores are finding that landscaping pays off.
In tree planting activities, remember, proper planting is important, as well as a knowledge of the tree’s requirements. Be sure to choose trees that fit the space in which they must grow. The rapid development of West Hawaii must include more efforts to landscape. Just imagine our new roads and highways shaded by spectacular trees like the royal poinciana or flamboyant. This tree from Madagascar was almost extinct in its native habitat, but thanks to its beauty, it has been spread to tropical regions around the world. Our state tree, the kukui brought to Hawaii by the first Polynesians should also be used more. Lets not forget the many endemic species of pritchardia or loulu. We need to use them in the landscape to assure their survival.
In some new developments, underground utilities are installed. This allows freedom from wires and poles. In such well planned tracts, street side shade trees may be planted to minimize the negative impact of asphalt and concrete. There are many good books to help in choosing the right trees to plant. Sunset’s New Western Garden Book covers all the climate zones we have here even if one lives at sea level or at 6,000 feet elevation.
In Hawaii, we have a wide variety of plants for beauty and as a food source for both humans and our wildlife. By keeping abundant vegetation as an integral part of our human communities, we actually find a constant healthy connection with our natural world.
For further assistance in tree selection and maintenance call the Master Gardener Helpline in Kona at (808) 322-4893 or (808) 981-5199 in Hilo.