Saturday, August 19, 2017

Trouble with Palms

"The bottom fronds of our triangle palm started to die, and then suddenly the whole palm fell over," a friend complained.
A significant pest of Pritchardia palms is the banana moth, Opogona sacchari. The triangle palm is also attacked by this moth. It seems that the female moth targets wounded or stressed palm tissue to lay her eggs. Stresses can include drought, flooding, mechanical wounding, poor nutrition, and herbicide injury. The larvae generally feed on decaying and dead plant tissue but will feed on living tissue, too, causing extensive damage. In affected palms, larval tunneling, along with the characteristic frass (insect droppings), can often be seen. Fully developed caterpillars measure just over an inch. The adults have greyish brown wings are 3/8 to 5/8 inches long.

The main treatment is prevention: keep palms growing well; give them adequate fertilizer, and supplemental water during a drought. Gardeners also need to be careful with the weed wacker! Female moths are looking for wounds to lay their eggs. Bt (Bacillus thuringiensis), an organic insecticide, can be applied to these wounds, as well as those caused during pruning.

For more information about this pest see the CTAHR Cooperative Extension Service publication, “Banana Moth – A Potentially Fatal Pest of Pritchardia and Other Palms”, by Scot Nelson and Mark Wright.  CTAHR stands for the College of Tropical Agriculture and Human Resources at the University of Hawaii. 

Thursday, July 20, 2017

Ohia Trees (Metrosideros sp)

There are four distinct species of ohia tree that are endemic to Hawaii. In addition to genetic differences, environmental factors will cause physical variations in the trees. Elevation, rain, and temperature all have an effect upon these trees. 
In general, the shapes of leaves from trees growing in hot, dry deserts are often small in order to conserve water loss through the leaf. Contrast this to the large-leafed plants of the tropics. Ohias occur in a wide range of habitats, from just above sea level to 8,200 feet: from dry forests with less than 16 in annual rainfall to wet forests with more than 33 feet of annual rainfall. This along with its genetic propensity for variation will produce trees of diverse appearance. The species name, polymorpha which actually means many forms has eight varieties. Thus tree height and form, leaf shape and flower color are highly variable.
Concerning the care, ohia trees can be damaged and even killed from a lack of water. During periods of drought especially, supplemental watering will be needed. Trees growing in the pahoehoe lava (exhibiting a smooth, billowy, ropy surface) may do well when young and water requirements are low. Nevertheless, as trees increase in size, if adequate water is not supplied, they can dry out and even die.  Mulch will help, but of course, not piled against the trunk.

Since ohias are adapted to grow in low nutrient soils, beware of over-fertilizing. Slow-release fertilizers or natural compost is best. 

Tuesday, July 4, 2017

Start a Garden

Here are some fundamental points to help along the way: 

·      Plant only as large a garden as you can easily maintain. Don’t over plant and become overwhelmed with the many garden chores: weeding, planting, pest control, soil preparation. 

·      Choose recommended varieties for your region. Midwest and Eastern US seed catalogs, with pictures of giant tomatoes are fine, but those varieties are not necessarily adapted for a tropical climate. University of Hawaii CTAHR seed program develops and sells vegetable seeds suitable for the Hawaiian Islands.

·      Consider locating the garden within easy walking distance to your house in order to carry tools there and eventually return with baskets of produce. 

·      Select a site that receives at least 8 hours of full sun each day.  Plant vegetables where they are not shaded by trees, walls or fences. Nearby trees and shrubs with roots reaching into the garden will compete with the vegetables for water and nutrients.

·      For those with minimal space, grow crops that produce the maximum amount of food for the area available.  You can harvest a lot of radishes, onions, lettuce, bok choy and tomatoes in a small plot.  Plants like pineapple, watermelon and pumpkin squash take up lots of space for what is harvested.  In addition, consider planting vegetables that can be grown vertically instead of horizontally. Vining crops such as tomatoes, squash, cucumbers and pole beans can be trellised or staked to minimize ground space and increase garden productivity.

·      Plant perennial vegetables such as rhubarb and asparagus to one side of the garden so they are not disturbed as you prepare the ground for subsequent annual crops.

·      And finally, try succession planting. A crop like indeterminate tomatoes can be harvested over a long period of time; one planting will last for many months. With other crops like corn, beets and lettuce, the entire crop will mature at approximately the same time. Unless you want to eat all your corn in a short period of time, stagger the plantings at 2-3 week intervals, or more. Read more about growing vegetables by clicking on the column on the right.

Friday, June 16, 2017

When Are Pineapples Ripe?

The following information is applicable to pineapple varieties presently available in the marketplace, yellow or white.

Select a pineapple that is plump and fresh-looking. The leaves in the crown should be crisp and green with the body of the pineapple firm. A larger fruit won’t necessarily be better tasting or riper than a smaller one.

According to Maui Land and Pineapple Company, pineapples, unlike bananas, do not ripen after harvest. They may advance in shell color, but they do not get any sweeter; they actually begin to degrade. A pineapple on a shelf in the market is as ripe as it’s going to be.  In terms of sweetness, color is not an indication.  Often times, depending upon the weather, green fruit will be sweeter than yellow fruit.  The only true indication is the size and flatness of the 'eyes' of the fruit. Typically, the bigger the eyes and the flatter the eyes, the sweeter the pineapple will be.

The color of the outer shell of the pineapple is not necessarily a sign of maturity or ripeness: a pineapple’s flesh can be ripe, sweet, and ready to eat when the shell is still quite green. A University of Florida publication states, “For optimum fruit sweetness, pineapple fruit should be harvested when 1/3 to 2/3 or more of the peel color has turned from green to yellow.”  

Other indicators are as follows: a good, ripe fruit has a dull, solid sound; immaturity and poor quality are indicated by a hollow thud. If the pineapple is at its peak freshness, it will have a sweet and fragrant odor. If the odor coming from the pineapple smells too sweet and almost alcoholic, it is past its peak. If you don't plan to use your fresh pineapple right away, store it in the refrigerator, where it will keep longer. Generally, once it is ripe, fruit may be held in the refrigerator for up to a week. In addition, the ease of pulling leaves from the crown is not a sign of ripeness.

 Many years ago scientists classified fruits into two categories: climacteric and non-climacteric.  Climacteric fruit usually undergo dramatic changes during ripening. These changes have often been associated with a surge in respiration and ethylene production. Ethylene is a natural plant hormone.
The avocado, apple, melon and banana are classified as climacteric fruits whereas the pineapple is classified as a non-climacteric fruit.

 Non-climacteric fruit (oranges, pineapple, grape, watermelon) do not exhibit the increase in respiration or the rise in ethylene production. In addition, they normally do not undergo dramatic changes such as softening after harvest.

Wednesday, May 10, 2017

Growing Roses in the Tropics

Roses indeed are associated with cool climates like San Francisco, Portland and even London. They will, however, flourish in a variety of climates in Hawaii. The early missionaries brought the older type of roses, not hybrids, to the Islands.  

In Hawaii, roses can flower throughout the year in the warmer, sea level climates. They can also be in continuous bloom in the cooler mauka (mountain) communities.

In order to reap the benefit of these beautiful flowers, some care must be taken when growing and maintaining the plants. Here are a few essential points to consider:
  • Roses require at least six hours of sun each day,
  •  a well-drained soil  and
  • adequate protection from strong continuous winds                                             
Rose bushes grown with less sunlight than six hours will tend to be tall and leggy with fewer blossoms.

Roses will benefit from mulch 4-6 inches. This reduces the temperature of the root environment, helps to control weeds, supplies nutrients to the ground and improves the physical characteristics of the soil. 

A fertilization program should be guided by a soil analysis. For further information on nutrition, and other rose topics, including specific cultivar recommendations, the UH CTAHR (College of Tropical Ag & Human Resources) website has an old, but good publication entitled, Rose Growing in Hawaii.

Roses are seldom free of pest. This is especially true in the tropics. Chinese Rose beetles are frequent and serious pests which come out after sunset and chew on the leaves. Tiny spider mites, aphids, thrips and grasshoppers will also attack the plants. Diseases like powdery mildew, black spot and rust are common. The rust appears on the underside of the leave as powdery pustules of bright orange spores. Diseases are particularly difficult to control when rainfall is high.

Friday, April 21, 2017

Not All Bugs Are Bad

There are some gardeners who do not want to see bugs of any kind on their plants. Yet, this condition does not always spell disaster.  Consider the following situations:

1. Some bugs found on plants may not be feeding or causing damage to the plant. They are merely there for other reasons.                                                                                                     
2. Not only might they be benign, they may be a good guy, a parasite or predator looking for pests to consume. Two well-known good bugs are preying mantis and lady bird beetles; spiders are also good predators.
3. Some insects, of course are known pests, but cause little damage. 

4. On the other hand, some bugs do inflict damage, but it is only cosmetic. That is, the leaves or fruit may be scared or misshapen but there is no real loss of yield. Cosmetic damage should be tolerated. This type of damage on fruit does not affect the internal quality.    
  5. The last possibility is an infestation of an insect pest which will cause yields to be significantly lowered. In this case, you will have to decide whether to wait a  while and see if biological control will work (if parasite/predators can control the population) or to spray. If spraying is the choice, consider first a bio-rational pesticide, such as soap, oil, Bt or sulfur. These are less injurious to the environment including the predator/ parasite populations. 

Photos: University of California IPM Program

Wednesday, April 5, 2017


 Nematodes are microscopic roundworms. There are both good and bad nematodes. Many nematodes live in our soils and are beneficial.  But there are a number of harmful species that attack plants. These nematodes insert their stylet mouth-part, much like a  hypodermic needle, into the  tissue and suck out the plant juices.  

Plants which are infested with nematodes may exhibit symptoms of stunting, yellowing and wilting. Further symptoms may be smaller and fewer leaves, and smaller fruit.  Also, due to this feeding, the root knot nematode, in particular, will cause the plant cells to rapidly enlarge, thus developing characteristic bumps or knots on the roots. 

What to do?  If root knot nematodes are in your garden, take it seriously. Eradicating the garden of nematode pests is highly unlikely, but they can be managed with good sanitary procedures. Here are some measures:
·      Apply organic matter (OM) to the soil.  OM will encourage the growth of beneficial organisms, fungi, bacteria and good nematodes. They, in turn, will ‘attack’ the plant parasitic nematodes and deplete their numbers. A note of interest, there is one species of fungus that forms loops with its fungal threads. Nematodes will become stuck in these loops, which will actually tighten, and eventually the nematode dies. 

·      Crop rotation  Do not replant the same crop or any susceptible crop into infested soil.  For instance, if you discover root knot nematodes on your cucumbers, plant a resistant crop, like garlic or corn, in place of the cucumbers. For best results, do not plant with a susceptible crop for 3 years.

·      Keep the soil fallow. A more drastic form of crop rotation is simply keeping the infested area fallow. This starves the nematodes. Do not allow any crop, even weeds to grow there. But do add organic matter. Again, 3 years is best.

·      Soil sterilization  This involves covering the infested area with a piece of clear plastic for at least one month and preferably two. This should be done during the hottest part of the year.  In hot climates with clear skies, enough heat can be produced underneath this tarp to kill most of the nematodes. 

·      Plan resistant varieties. The best control against nematodes is to use resistant varieties. You may notice on a tomato seed package the letters VFN.  This means that the variety is resistant to the fungus, Verticillium and Fusarium and to the root knot nematode.  Such varieties include Celebrity and Better Boy. Asparagus, corn, garlic, onion, strawberry, zinnia, salvia and marigolds are also resistant to root knot nematode.  

Perhaps the most important aspect of controlling nematodes is to stop them from spreading throughout the garden.  If your tomato patch is newly infested with nematodes, keep those nematodes there. Nematodes will slowly spread in the soil by themselves. Don’t help them by carrying soil from the infested area to other areas, or by carrying around contaminated dirt clinging to garden tools and shoes. Work in an infested area last. Always clean tools and shoes.  Be cautious when receiving potted plants from other gardens or even from a nursery that has non-sterilized soil.    

Marigolds have been reported for many years as a way of reducing the nemotode populations. The French marigolds are most effective; varieties include Nemagold, Petite Blanc, Queen Sophia, and Tangerine. Unfortunately, planting a few marigolds next to each susceptible plant will NOT eliminate the problem. To be effective, the entire infested area needs to be planted in marigolds, each plant about 7 inches apart. The flowers must be planted for a minimum of two months and then turned under. The area also needs to be kept free of weeds. Then, root knot sensitive plants can be planted back into that area the following planting season. Replanting marigolds every other year will almost certainly be necessary.