Monday, December 30, 2013

GMO Corn

Is most of our corn GMO? It is true that most corn bought in the supermarket is genetically modified (GM) or engineered (GE). Over 80% of the corn grown in the US today is GM corn. Similar statistics hold for sugar beets at 95%, cotton at 88% and soybeans at 91%.

Not only is the corn, along with all its products genetically modified, but so are a host of other ingredients. In fact, it has been estimated by the Center for Food Safety that upwards of 70 percent of processed foods in supermarkets contain ingredients from genetically engineered foods. (
On the other hand, when eating foods such as tomatoes, radicchio, wheat, flax and potatoes, the probabilities are small that they will be genetically engineered.

For those who may be wondering about edamame (specially prepared soybeans), there are no genetically-engineered edamame. There has been some concern that an edamame field might become cross-pollinated from neighboring fields of genetically engineered soybeans. Soybeans, however, are self-pollinating. Even if the edamame were grown in an area where GM soybeans were planted, there would only be a slight chance (less than 1%) of cross-pollination.

In addition, there are two papaya varieties grown in Hawaii that are genetically engineered, UH Rainbow and UH SunUp. The publication “UH Rainbow Papaya” is available for viewing at the UH CTAHR website:  This bulletin describes the characteristics of the new varieties, the process of genetically engineered fruit, and answers and questions on safety. CTAHR is an abbreviation for College of Tropical Agriculture and Human Resources at University of Hawaii-Manoa.

The frequent question asked, “Is genetically modified food safe to eat?” Some people see no threat eating GM foods, while others vehemently oppose it. The best advice is to get the facts. One place to start is an informative CTAHR website created by Dr. Ania Wieczorek, Department of Tropical Plant and Soil Science.  Topics on the site include Hawaii Biotech, Benefits/Risks, Labeling, Regulations and FAQ. 

Monday, December 16, 2013

Onion Thrips

As a common problem in the vegetable, onion thrips is a major insect pest not only of onions and leeks but also attacks broccoli, cabbage, carrots, cucumbers, garlic, melons, papaya, pineapple, squash and tomato. (Note - thrips refers to one or many.) 

The damage from the feeding results in whitish or silvery streaking on the leaves. Black droppings from the insect may also be seen. Thrips populations are often greater in the warmer months of the year.

There are predators and parasites that attack the thrips but often are not effective for proper control. Sometimes washing with a stream of water will help. Plants, of course, will tolerate a certain level of infestation causing only cosmetic damage. If injury threatens crops loss, then treatment is called for. Synthectic pyrethroid insecticides such as Warrior (lambdacyhalothrin) and Ammo (cypermethrin) are effective in controlling onion thrips.

Bulb Onion Production in Hawaii by R.Hamasaki and H. Valenzuela is a publication available on the CTAHR website.

Monday, December 9, 2013

Planting Hyacinths

Hyacinths, hyacinthus orientalis and its hybrids, are in the lily family, planted as bulbs and known for their beautiful, fragrant flowers. The Roman or French hyacinth is native to Southern France and can remain in the ground year after year in areas of little or no winter chill but not Hawaii or other tropical regions.

They do well in cold climates; they are not a tropical plant. Even garden books note that they can be grown in all zones except Hawaii.  In areas of the country with distinct cold winters, bulbs can be left in the ground and with proper chilling, will bloom the next year.

For gardeners in tropical regions: as mentioned the bulbs need cold weather to stimulate bloom. Here are some instructions when purchasing a potted hyacinth: after the bloom has died, put the bulb with its leaves in the ground. The leaves should eventually yellow and die back. At this point, dig up the bulb, set it in a small pot with potting soil, cover to keep dark, also keep the soil moist. Place in the refrigerator, it must be below 45 degrees Fahrenheit and remain there for at least 10 weeks. Roots will grow and eventually a shoot tip will emerge. At this point, it can be removed from the refrigerator. This is considerable effort and no guarantee it will work; hyacinths may be one of those plants that has to be purchased each year.

Monday, December 2, 2013


The jaboticaba tree is a relatively small tree, growing to a height of 25 feet but spreading up to 50 feet. The unique characteristic about this tree is the fact that the flowers, and thus the fruit, are borne on the trunk and branches. In the Hawaiian Islands, the trees grow well from near sea level up to 4000 feet. Several different cultivars exist. 

Jaboticaba trees are susceptible to a fungal rust disease. The yellow powder on the leaves is the spores of this fungus. Severity of the rust depends upon the amount of rain; drier years may see no rust, but with an abundance of rainfall, the disease will be quite common. A copper fungicide would help to protect the fruit but multiple applications will be needed in rainy weather. Though not mentioned, a larger problem is the birds eating the fruit.

Depending on the abundance of rain, trees can produce up to 6 crops each year.  Jaboticaba is mostly propagated by seeds which run true to type. Air layering, grafting, and cuttings are possible but with limited success. Yields can be well over 1000 pounds per tree.   

And what to do with all that fruit? Jaboticaba jelly is a favorite in the Hawaiian Islands. Jars of  the bright purple fruit appear in local cupboards and are sold at craft fairs. 

Photos by Emily  Needham

Monday, November 18, 2013

Moths Attack Palms

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 weedwacker! 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. For new readers CTAHR is College of Tropical Agriculture and Human Resources - University of Hawaii - Manoa. 

Monday, November 11, 2013

Controlling Insects with Neem

 The neem tree (Azadirachta indica) is a fast growing shade tree native to Southeast Asia and India. Compounds (Azadirachtin) extracted from the seed have been found to possess pesticidal qualities; the greatest concentrations of these substances are found in the seed.

Also extracted from the seed kernel is the oil. Neem oil, like other horticultural oils, works by suffocating the insect, coating its body and blocking the breathing openings. Products are available which contain neem oil alone or with azadirachtin.  In tests involving the control of aphids, products containing both had a greater efficacy than either ingredient alone.  Neem oil can also prevent the germination of some fungal spores such as powdery mildew. 

Azadirachin, the active ingredient in many neem products, actually consists of more than 25 closely related compounds.  They work in several ways. 1.  as a feeding deterrent against a number of insect pests. 2. to disrupt the molting process so the immature larvae do not develop into adults.  3. some insect larvae are killed by direct contact with the spray,  4.  adult insects are normally not killed but mating may be disrupted and 5. Azadirachtin also has a repellent effect on certain insects and mites.         

Insect pests affected by azadirachtin include aphids, beetles, caterpillars, lace bugs, leafhoppers, leafminers, mealybugs, psyllids, thrips and whiteflies.  Generally, neem will have less of a detrimental effect on beneficial insects (parasites/predators) compared to the broad spectrum pesticides.

Multiple applications of neem are generally recommended. Frequent spraying is more effective because neem does not persist on plant surfaces. Like other botanical insecticides, it is quickly broken down by sunlight and washed away by rain. For smaller plants, neem seems to work well as a soil drench; the product is absorbed by the roots and translocated systemically throughout the plant.

Another product sold as a fertilizer is neem cakes. They are the residual seed meal remaining after extraction of oil from seeds. 

Monday, November 4, 2013

Bolting in Vegetables

Bolting is the process of premature flower formation in response to high temperatures, as well as drought and starvation.  This unwelcome occurrence in leafy plants such as broccoli, cabbage, lettuce, and spinach,  takes the plant out of its leaf producing mode and switches over to flower and seed production.

Many vegetables are divided into two groups: cool season and warm season vegetables. Although in Hawaii seasons may vary little in temperature and many vegetables can be grown year around, some will do better when planted within the given time frame. 

Broccoli and lettuce are cool season vegetables. As long as the temperatures remain cool, the lettuce will continue to produce tender leaves, and the broccoli flower buds will remain closed. Generally lettuce and broccoli are planted from September through March/April.  During the hot summer months plants can bolt.  At higher elevations, cool season vegetables such as lettuce, beets, broccoli, cauliflower, chard, kale, peas, turnips and mustard, may be successful planted in late spring and summer.   

Warm season vegetables include tomatoes, cucumbers, melons, squash, peppers, corn and eggplant.

Monday, October 28, 2013

Propagation of Blueberries

Blueberries are propagated from either softwood or hardwood cuttings. 

Hardwood cuttings  are collected in late January or February, after sufficient chilling has occurred.  1. Select healthy material. 2. Avoid propagating from plants that have odd-looking or stunted foliage. 3. Collect shoots from the previous summer, 12 to 36 inches in length.  4. Divide these shoots into pieces 5 to 6 inches long, removing any flower buds. 5. Place cuttings in a propagation bed at a depth of one-half to two-thirds of their length. Keep moist.

Softwood cuttings are taken in late spring from the current season's growth, 4 to 5 inches long.  Collect these cuttings when the stems have developed woody tissue but are still somewhat flexible. Remove all leaves with the exception of two or three terminal leaves.  Place cuttings in the propagation bed, under mist at a depth of one-half to two-thirds of their length.

Rooted cuttings are eventually transplanted into pots and held for about one year.   During the time of rooting, keep beds moist while being aware not to over water.
A greenhouse is not necessary, but some type of propagation bed/chamber, under 40 to 70 percent shade with a mist system is recommended; an area as small as 3x3x3 can be used.

The mist system should keep the media uniformly moist but not soggy.  An intermittent-mist system with frequent, short misting intervals is recommended in order to keep the humidity near 100 percent.  However, keeping the cuttings at this constant moisture also creates an ideal environment for pathogenic fungi to grow. Thus cleanliness is very important; use new or sterilized planting mix and pots, keeping them raised off the ground.

Potting media containing various mixtures of coarse sand, ground pine bark, perlite, sawdust, and peat moss have proven satisfactory.  One such recipe is a mixtures of coarse sand, ground pine bark, and peat moss (1:1:1) and perlite and peat moss (1:1)

Monday, October 21, 2013

VOG Equals Hawaiian SMOG

People living in the Los Angeles, California Basin have known for years that smog affects plants.  There exists a similar situation on the Big Island of Hawaii. It’s called VOG, emissions that spew from the Kilauea Volcano at Halemaumau. The discharges include sulfur dioxide, sulfites, ash and hydrochloric acid.

 Many gardeners, especially those living near the Volcano area, have experienced the distressing effects of vog on their plants.   Sulfur dioxide  enters the leaf through the stomata.  The degree of injury will depend upon its concentration and duration, and upon the sensitivity of the specific plant. The symptoms of low concentrations of sulfur dioxide are general chlorosis (yellowing) of the plant foliage. Higher concentrations cause a bleaching or browning of tissues between the leaf veins.

Volcanic ash appears as a dust and is composed of fine rock particles from the volcano. The ash does not damage plants directly but can block sunlight on foliage as well as detract from the appearance of the plant. Harvested fruits and vegetables should be thoroughly washed prior to their consumption.

There is not much that can be done about the harmful chemicals the volcano churns out. As far as the plant is concerned however,  leaves should be rinsed with adequate water after exposure. Susceptible plants can be grown under cover such as greenhouses, and during periods of intense vog, valuable plants can be temporarily covered with fabric or plastic.

Different plants have varying degrees of susceptibility to vog.  Here is a list of plants documented to be susceptible to vog:
Ornamentals - African lily, Oriental lily, cypress, Dutch iris, eucalyptus, ginger, hydrangea, heavenly bamboo, pine, podocarpus, rose and tuberose.
Native plants -  koa, naio, pilo, uki, akala.
Vegetables - broccoli, cauliflower, Chinese cabbage, daikon, lettuce, Swiss chard, tomato and watercress.

Some of the more resistant plants are asparagus, celery, coffee, corn, and ohia.

For a more in depth look at the volcano’s effects on plants, with some excellent photographs, read, “Volcanic Emissions Injury to Plant Foliage”, by Scot Nelson and Kelvin Sewake, UH Department of Plant and Environmental Protection Sciences. The publication can be found on the CTAHR website -

Monday, October 14, 2013

Little Fire Ants

The sting of the little fire ant (LFA) is very painful and produces red welts. With some people, welts last as long as three days with aching pain, and later intense itching. 

LFA are tiny (about 1/16 inch long), pale orange and move rather slowly.  They are highly adaptive. They live in the open or under shade, in areas of 10 inches of rainfall to over 100 inches, they are found from sea level to 1700 feet and can nest on the ground or in trees.  They eat just about anything. They can remain up in the tree, or they may move up and down. They will also infest homes under carpets and along baseboards.

Control Measures
 For controlling LFA, researchers recommend a three pronged attack and a whole property approach; spot treating is inadequate. 
1.  Place ant baits in infested areas.  In general, this is done to control ground nests.  The ants will take the bait back to their nest and share it with others. Baits are the front-line tool for ant control.  This approach should be tried first. Wait a couple weeks before applying barrier treatments. 
2.  Barrier treatments – the application of insecticides (liquid or granular) around areas where ants need to be excluded.  As ants crawl over the treated areas they are killed. The more ground you treat, the better. However, if you want to limit your use of chemicals, treat those areas where you want the most protection, areas most used by people and pets.  
3.  Ants nesting in trees may not be controlled by bait applications. Therefore a foliar insecticidal spray, applied to infested trees and vegetation, is needed.

  •  Suitable baits for Little Fire Ants -For step 1  Amdro, Probait, Maxforce Complete, Extinguish Plus (reported as moderately attractive) and Tango, a new product recently registered in Hawaii. Even though the products Extinguish Pro and Esteem Fire Ant Bait are registered for use on many food crops, they are not highly effective; see website below. Tango, on the other hand, is registered for use on food crops and is very effective and safe.
  • Suitable barrier treatments For step 2  Products with the active ingredient bifenthrin (examples, Ortho Home Defence Max granules, Ortho Home Defence spray and others)
  • Suitable chemicals for foliar spraying and drenching potted plants –  For step 3   Look for the active ingredient carbaryl (examples, Eliminator            Bug Killer Sevin Concentrate, Gardentech Sevin Concentrate Bug Killer  and others)

If you suspect that you may have the LFA, coat a chopstick, or any small stick, with peanut butter and stick several in the ground around your property.  If any ants are caught on this bait, take them to the Hawaii State Department of Agriculture at 16 E. Lanikaula St. in Hilo for positive identification.

In addition to the information presented here and for more detailed information, I refer you to an excellent LFA website It was put together by Cas Vanderwoude, a researcher with the Hawaii State Department of Agriculture.   Furthermore, check out the latest research on Tango. Although this product is expensive, it is thought that applications of Tango may control ants well enough that steps 2 and 3 can be eliminated.  Tango is an insect growth regulator (IGR). This type of product works by preventing the insect larvae from completing their pupation process. It also slows down egg production by the queen. Information and directions for making the new gel bait (Tango) are on the website.

Monday, October 7, 2013

Breadfruit Food for a Famine

 It is thought that breadfruit trees spread throughout the Pacific Region by migrating Polynesians and were brought from the Samoan Island of Upalu to Oahu in the 12th Century. Its common name in Hawaiian is ulu, as it is also in Samoa, Rotuma and Tuvalu. The fruit is a staple food in many Pacific Island cultures.

The Movie
Some will remember the movies, Mutiny on the Bounty, and The Bounty. Did you know it was all about breadfruit? Due to several famines in Jamaica between 1780 and 1786, plantation owners in the British West Indies petitioned King George III to import breadfruit trees in order to provide a food source for the slaves. Captain Bligh sailed to Tahiti in 1787 to obtain breadfruit plants to transport them to the British West Indies. On that calamitous voyage, he lost 1,015 potted breadfruit plants. Was the true reason for the mutiny the fact that he rationed water to his crew in order to give ample water the plants? Was Captain Blight a true gardener at heart? For more details, see the movie or read the book.  After being forced overboard in a nineteen foot cutter, Bligh miraculously navigated himself and some of his faithful crew to safety, crossing almost 4,000 miles.

 After returning to England, Bligh set sail again, in 1791, for Tahiti, and this time he was able to successfully deliver 5 different varieties of breadfruit trees, totaling 2,126 plants, to Jamaica in 1793.  The trees flourished and were subsequently planted in other islands of the West Indies as well as Central America and northern South America. Ironically, it is reported that the slaves rejected the fruit. But today, Bligh is revered as a hero in Jamaica.

Breadfruit trees are medium sized, growing to about 50 tall at maturity. There are hundreds of different varieties of breadfruit, both seeded and seedless types. It is truly a tropical plant, more susceptible to cold than the mango. The breadfruit tree is best grown in deep, fertile, well-drained soil. The optimal growing range temperature is 60° to 100°F.  Due to the large number of different varieties of breadfruit, however, trees do exhibit a wide range of adaptability to ecological conditions.

Seeded breadfruit varieties can be grown from seeds. But it has been noted that they do not run true to type. Seedless breadfruit is often propagated by transplanting suckers which spring up naturally from the roots. Pruning the tree will increase the number of suckers produced, as will exposing and injuring a root. New branches and shoots can also be air layered.

Breadfruits are abundant in Hawaii from July to February.  Fruit is picked when mature, which is indicated by the appearance of small drops of white latex on the surface. Breadfruit can be eaten before it is ripe, as a vegetable, or eaten as a fruit when it ripens.  For the former, it is picked while still starchy and is boiled or roasted. Fully ripe fruit are sweeter and often baked whole. The seeds are boiled, steamed, roasted and eaten with salt. The leaves are eaten by domestic livestock.

Breadfruit is high in carbohydrates and a good source of fiber, vitamins and minerals. The trees are relatively free of pests and insects; fruit flies will infest ripe fruit. The following websites contain an abundance of information for an in-depth study of breadfruit trees.  

Photos by Forest and Kim Starr

Monday, September 30, 2013

Organic Weed Control

Cinnamon, clove and thyme oils, acetic acid (vinegar), citric acid, d-limonene (a component of the oil extracted from citrus rind) and lemongrass have all been used as an organic approach in controlling weeds. They are strictly contact herbicides with no residual activity; good coverage is essential. These products are most effective on small annual seedlings; weeds in the first true leaf stage are easier to control. They are also more effective on broadleaf weeds than grasses.  These compounds will burn the tops of perennial weeds, but they will quickly recover.  Repeat applications are needed for perennial weeds.

This type of herbicide will damage any green vegetation they contact but are safe against woody stems and trunks.  In general, the organics listed above do a moderately good job. In trying to control weeds in large areas like acres, however, the economics of using these products is poor. It is expensive.

Many of the organic herbicides work better when temperatures are above 75 Fahrenheit; sunlight may also improve the effectiveness of some.
Adding a spray adjuvant, a product added to the herbicide mix to enhance the effectiveness of the herbicide, will result in improved control. 

As stated, the age of the weed is important, the younger the better. A group of organic herbicides were tested and found to control broadleaf weeds between 80 to 100 percent when the weeds were 12 days old. But after 26 days of age, control was between 17 and 38 percent. For grasses, control was between 25 – 42 percent for 12 day old seedlings; for 26 day old seedlings control dropped to 0-8 percent control.

In addition to the chemical sprays, other approaches in controlling weeds include mechanical, physical and biological.  Mechanical weed control involves hoeing, hand pulling, and mowing. Burning is another mechanical method – the use of a propane tank with attached hose and nozzle. This application is best when weeds are less than three inches tall.

Physical weed control consists of placing a layer of opaque material over the soil surface.  This may include inorganic (synthetic) material like plastic sheeting, or organic material like bark, wood chips, straw and compost. Place 4-6 inches of an organic mulch for best results.  Biological weed control is where sheep, goats and geese are used to chew down the weeds.

The main point to stress is: do not allow weeds to go to seed!  Get rid of existing weeds before they flower and produce seed. The average number of weed seeds in soil is 30,000 – 350,000 seeds/square meter, or 120 million to 1.4 billion per acre.  

Monday, September 23, 2013

Citrus Fruit Drop

In most cases, less than 5% of citrus blossoms will actually develop into mature fruit.  An overwhelming number of the blooms naturally drop from the tree during bloom and shortly thereafter. This is a natural thinning process.  Once the tiny fruit has reached about 1 inch in diameter they tend to stay on the tree.  After this point, if fruit continue to drop, it is due to some type of environmental stress. Here are several possibilities: nitrogen deficiency or excess, sudden high temperatures, a lack of water or too much, a heavy insect/mite infestation, hot dry winds, air pollution and severe pruning. Constant rain during the bloom period can also stress the tree. Any one of these factors that occurs around the time of bloom can cause the flowers and young fruit to drop.

The question may arise, “Why does one citrus variety drop its fruit, but other varieties in the same garden do not?”  Here are some of the more common answers.

 1. Different citrus varieties obviously have a different genetic composition.  Consequently, the various varieties will react differently to the numerous stresses. 

 2.  In the same manner, citrus trees are normally budded or grafted onto different rootstocks. These various rootstocks will react differently to the many diverse environmental conditions.  

3. And lastly, although difficult to observe, some locations in the garden may be more conducive to plant growth: better soil drainage, greater soil fertility or more protected from dry wind and high temperatures. 

Monday, September 16, 2013

Perils of Growing Zucchini

For some gardeners, growing zucchini  is an effortless task, the end result being zucchini bread, zucchini cake, zucchini pancakes, zucchini salad,  baked zucchini, broiled zucchini, fried zucchini, etc., etc. Having lived in California, I know this to be true.  Living in the tropics, on the other hand, is a different story. Here is mine:

My first attempt at growing zucchini squash failed because a bird or rat stole the seed. Then I planted the seeds in small containers and placed them in a netted area waiting to be transplanted. On my second attempt, the plants grew well but finally died, succumbing to the powdery mildew (PM) fungus. Next, I planted PM resistant varieties. This helped, but I still needed to use fungicidal sprays such as horticultural oil, Serenade and/or baking soda. See this website for more information on powdery mildew. This points out that the word ‘resistant’ means just that; it doesn't mean immune! It could also mean that in tests, the resistant variety simply did ‘better’ than nonresistant varieties.

Well, the bird or rat problem seemed resolved; the PM problem was addressed, more or less, and a new crop was growing well. The plants were blooming, and small fruit developing on the plant, but then they dropped off. This was an attack of the pickleworm! So I threw some ¾ inch bird netting over the plants. This will keep most of the pickleworm moths out but allowed bees to come in and pollinate.

When the zucchini was nearly ripe, I observed that the whole plant was dying with what appeared to be a virus, one of several that attack squash: squash mosaic virus SMV, cucumber mosaic virus CMV and watermelon mosaic virus WMV. These different viruses are transmitted by insects which feed on virus-infected squash plants or some nearby weeds. Once the plants are infected, there is nothing that can be done. The virus  will eventually kill the plant. Symptoms include distortion of the leaves, chlorotic (yellow) mottling and a dark green mosaic pattern. Infected fruit coming from such plants show a strong mottled pattern. The best preventive measures include insect control along with host weed management.

Note: Squash, along with melons and cucumbers (cucurbits) are unique vegetable plants that bear two kinds of flowers on the same plant, male and female.  In order to produce fruit, the pollen from the male flower must be transferred to the female flower.  Insects do the major pollination work.  Female flowers can easily be distinguished from the male by the presence of a miniature fruit at the base of the flower. 

Sometimes gardeners are concerned because none of the first blooms produce any fruit.  This is because the first flowers produced on the plants will be male and cannot give forth fruit. In time female flowers, and subsequent fruit, will be produced.

Unfortunately,  zucchini is one vegetable I will not be planting in the future. 

Monday, September 2, 2013

Too Much Rain & More about Corn

 Some areas of the world receive plenty of rainfall.  When there’s too much rain, the following ill-effects on plants may be observed.

1.  A general yellowing.   a.) This can be due to the soil remaining wet for a long period of time thus excluding soil oxygen. In this anaerobic condition, plants will yellow. b) Likewise, the profusion of rain is washing the soil nitrogen below the root zone, and plants become nitrogen deficient, causing yellowing.

2. More fungal leafspot diseases (most notably tomatoes ). Disease causing spores land on the surface of a leaf, germinate and infect the leaf. In a short time thousands of spores are produced. When a rain droplet or water from irrigation lands on the leaf, these newly produced spores will be splattered to other areas of the leaf and to nearby leaves. They in turn germinate and infect these new areas. Thus, more rain, more splashing, more spreading of the spores and more disease.

3. Problems with corn. 
 If the abundance of rain occurs during corn pollination, the ears of corn may lack a full complement of kernels. This is due to a lack of pollination because  the wind-born pollen is washed away. Low pollination is also caused by improper planting densities. Do not plant one or a few individual seedlings, or even a single row. Plant a minimum of 4 rows, 8ft long.  For more on growing corn:  search corn in the blog search

Tips for Picking Corn
·        Mark the calendar the day the corn was planted. In Hawaii, sweet corn is harvested 7O-85 days after planting.
·        Corn is ready when the silks begin drying and turning brown.
·        Record the date at which half of the plants show the silks emerging from the new ears. Under warm summer conditions, the corn will be ready about 18 days later.

·        Perhaps the easiest clue is to pull the green husk back from the cob and check the appearance of the corn kernels. If the corn looks ready, it’s time to pick.  

Monday, August 19, 2013

White Deposits on Avocado Trunks

What causes the white exudate on avocado trunk and branches?

When avocado trees are wounded, tree sap oozes out. The white residue seen on tree trunks is simply the sugars left behind as the water from the sap evaporates. The wounds can be made by just about anything including poking holes with a knife or nail and insects trying to bore into the tree. 

There are also a few avocado diseases, caused by fungi and bacteria, which will result in wounds that ooze leaving a white residue. In areas of heavy rainfall the sugars are not always visible as they may be washed away. 

Although not a major pest of avocados, one invader which will leave small amounts of white residue is the black twigborer.

Search black twigborer on this website for more information on this pest.

Photos from Topics in Subtropics,by  Dr. Ben Faber

Monday, August 12, 2013


Gladiolus is relatively easy to grow.  They, gladioli, require well-drained soils in a sunny location. While often classified as bulbs, gladiolus are actually corms, enlarged stems. Corms which have a plump shape with high centers are better than large, flat ones; the thicker the corm is, the higher the quality of bloom will be.  It is best to select corms 1 1/2 to 2 inches in diameter. They will produce full, attractive flower spikes. Small corms produce foliage but may not bloom.

Planting depth varies with the size of the corms. Large corms should be planted 4 to 6 inches deep and 6 inches apart. Small corms should be planted at a depth of 3 inches and about 2 inches apart.   A general rule of thumb is plant deeper in sandy soils and shallower in heavy soils.

Gladiolus may fall over because of the weight of the blossoms if the corm is not planted deep enough. The remedy, of course, is to plant deeper for better support.  If the soil is rocky, and it is difficult to dig a deep enough hole, the plants will require staking. 

The pest that primarily attacks gladioli are called thrips. They are tiny, slender black insects, about 1/25 of an inch long, obviously, difficult to see with the naked eye.  Thrips cause white specks or streaking on the leaves and blooms. Flowers can also be misshapen, discolored and occasionally will fail to open. 

Thrips feed by puncturing the plant tissue and sucking out the cell contents.  Preferring to feed on rapidly growing tissue, thrips often cause stunting.  These insects are the culprits which also cause silvery to brownish scarring on avocado and citrus fruit surface, but this cosmetic damage does not harm the internal fruit quality.

Horticultural oils, azadirachtin (Safer BioNeem), neem oil and insecticidal soaps can be somewhat effective for the temporary reduction of the number of thrips if applied when damage first appears. Sprays must be applied to thoroughly cover susceptible areas of the plant including new leaf growth and buds.  Note: these insecticides only kill newly hatched thrips and recently emerged adults, thus repeat applications are required, usually 5 to 10 days apart depending on the temperature. Moving the location of the gladiolus bed each year will discourage the spread of thrips.

Avoid the use of insecticides such as malathion and carbaryl: 1) they are highly toxic to natural enemies, 2) can cause dramatic increases in spider mite populations, and 3) are generally not effective against most thrips.


Monday, August 5, 2013

Fertilizers - Nourishing the Garden

Which is the best fertilizer? With the countless number of fertilizer products on the market, little research has been conducted to show whether there is significant differences among the various brands. If you have found a particular product that produces outstanding results, and you are willing to pay the price, then by all means, continue to use it.

Otherwise, let me give you some fertilizer basics. In the broadest sense, nitrogen is nitrogen (N), phosphorus is phosphorus (P), and potassium is potassium (K).  Plants only absorb nutrients that have been broken down into inorganic, water-soluble forms.  For example, whether nitrogen comes from brand A or B, whether it was derived from anhydrous ammonia (gas) or urea, or from manure or the compost pile, it makes no difference to the plant. Stick with a basic N-P-K fertilizer, buy on sale, and don’t fall for promotions.

The question now is what type of formulation to purchase?  Nitrogen only, potassium only, phosphorus only, or combinations?   Nitrogen is always needed in areas of heavy rainfall, because it is easily leeched out of the soil.  Fertilizers like ammonium sulfate, ammonium nitrate, urea and calcium nitrate are all good fertilizers for supplying nitrogen. Calcium nitrate will also give calcium but is more expensive. 

Like nitrogen, potassium can also move in the soil with water; phosphorus moves very slowly. The question of whether to apply potassium and phosphorus can be answered accurately by a soil analysis.  Without an analysis, statements about soil fertility are only guess work. Check with local university cooperative extension offices for information about soil analysis.

 If an analysis is not taken, then buying a fertilizer with all three ingredients (N-P-K) is a good idea. The only problem with that is if the soil has adequate phosphorus, and over the years more is added, a soil imbalance may occur, and the excess phosphorus will cause a deficiency in iron and zinc - seen as interveinal chlorosis, a yellowing between the veins.  Also, it is cheaper to supply nitrogen than all three nutrients. On the other hand, you can apply nitrogen alone and supply the potassium and/or phosphorus only when deficiency symptoms occur.

Sometimes micronutrients are added to an N-P-K formulation. But they are added at such low amounts that they are seldom beneficial to the plant, especially trees. If a micronutrient (zinc, manganese, magnesium) deficiency truly occurs, buy that specific nutrient and apply to the soil or as a foliar treatment, whichever is appropriate. Special formulations of ‘citrus food’ or ‘avocado food’ or ‘palm food’ are good fertilizers. But note that they are higher priced, and a basic all-purpose (N-P-K) fertilizer should work as well.

Organic vs. Inorganic
Inorganic fertilizers often contain rather high percentages of the major nutrients and are applied on a per pound per acre basis. Organic fertilizers, on the other hand, have relatively low amounts of nutrients and are applied on a per ton per acre basis.  Although organic fertilizers have many benefits - including improving soil structure and the water holding capacity of the soil, feeding beneficial microorganisms and  of course, acting as a reservoir of nutrients that can be released to the soil - they are rather expensive in some places like Hawaii.  Gardeners, however, are encouraged to take advantage of any free or inexpensive supply of organic fertilizers, i.e., manures, in their area.

Monday, July 29, 2013

Bananas vs Plantians

The starchy, cooking varieties of bananas are known as plantains and are not the same as the typical fresh eating variety of bananas. The distinction between the two is based purely on how the fruits are consumed: cooked or eaten fresh out of hand.  

The common banana is sweet, easily digested and ready to eat when the skin is yellow. Plantains, on the other hand, are thick skinned and must be boiled, steamed, roasted, baked or deep fried to make them soft and palatable. When the peel is green to yellow, the flesh has a starchy texture with a bland flavor.  As the peel changes to brown or black, the plantain losses some of its starch and becomes slightly sweet.  At this stage plantains have more of a banana aroma but are still unsuitable until cooked. The interior color of the fruit is creamy, yellowish or lightly pink.

Plantains are native to India and are popularly grown in tropical climates, especially in Western Africa and the Caribbean countries.  They are often used in soups and stews or simply mashed.

There are over 500 different types of bananas.

Monday, July 15, 2013

Control of Maile Pilau, a Weedy Vine

The weedy vine, Paederia foetida, or in Hawaiian maile piau, is able to grow 30 feet in length, climbing up into tree canopies or crawling along the ground. The vines can engulf and cover trees and shrubs. The weight of the vine climbing over vegetation can cause branches or entire trees to break or collapse. Crawling vines can form a dense layer of vegetation that smothers other plants. This leafy vine is pervasive in vacant lots and forests on the Hawaiian Islands.

Since broken stems of maile pilau are able to root readily in soil, care must be taken when disposing of the plant. When crushed, the leaves release a foul odor. The species, foetida, is Latin for stinky.

Chemical control is one of the most effective means for controlling maile pilau.  Yet, because of resprouting, single applications usually do not provide complete control; follow-up applications are necessary.  The herbicide recommended is one with the active ingredient, triclopyr, sold as Crossbow, Garlon, Pathfinder; unfortunately, they are rather expensive. Along with the herbicide, a non-ionic surfactant at 2 teaspoons per gallon of spray solution is suggested.  A 2% to 3% solution of glyphosate (Roundup, etc.) may also be effective, although some report it is not.  If you have Roundup, you may want to try it first before purchasing triclopyr.  

Presently biological control agents are being collected in Japan and Nepal.  It is hoped that these  ‘good guys’ which include a leaf and root feeding chrysomelid beetle will be able to help control the spread of this weed pest.

Photos by Forest and Kim Starr 

Monday, July 1, 2013

Pomegranates In Hawaii

There are indeed pomegranate trees growing throughout the tropical Hawaiian Islands. Pomegranates are rather small trees growing 15 – 20 feet tall.  What they lack in height they make up in longevity; some are reported to be 200 years old.  

The trees seem to tolerate a wide range of conditions. They do well in hot and dry conditions with high alkaline soils, as well as growing in deep, acidic loam soils.  Pomegranate trees also tolerate wet, heavy (clay) soils but produce better in soils that are well-drained. Trees do not come true from seed, and therefore, good quality fruit trees are propagated from cuttings.  Air layering is possible; grafting is seldom successful.

Pomegranates have been around for eons.  Over the centuries, their depiction has appeared in artwork, literature, coinage, jewelry and coat of arms. Believed to have originated around Persia and the Himalayas in Northern India, the pomegranate has been used as a symbol for many civilizations and sometimes viewed as a symbol of fertility in Asia.

The Spanish missionaries brought pomegranates to California, Mexico and Texas.  And recently, from 2006 to 2009, pomegranate acreage in California doubled from 15,000 to about 30,000 acres.

Pomegranate juice is rich in three types of antioxidants which are recognized in neutralizing free radicals and other unstable molecules in the body.  Besides eating the fruit or making a delicious beverage, the fruits can also be dried and used in wreaths and other decorations.  Pomegranate juice is being added to such products as jelly, ice cream bars, truffles and chewing gum. Ink can be made by steeping the leaves in vinegar. In Japan, an insecticide is derived from the bark.

Monday, June 24, 2013

Transplants vs. Direct Seeding

Should gardeners plant vegetable seeds directly into the ground or plant them in small pots first, then transplant them into the garden?  
Some vegetables need to be direct seeded, while others are best transplanted. But most vegetable plants do well either way.

In general, transplants are easier to care for.  They are usually started in a more controlled environment - a greenhouse or some type of sheltered area.  Here, the seedlings are better protected from soil diseases, especially when a sterile potting mix and clean pots are used. A greenhouse offers protection from insects, animals digging up the ground and environmental stresses like hot winds and cold temperatures.  In cooler areas, seeds can start in a warm  environment and later be transplanted outdoors. 

Yet from time to time transplanted vegetables suffer from transplant shock. When the seedlings are set into the ground, the roots are damaged in the process. Plant growth is delayed until the roots recover. 

Certain plants can regenerate new roots quickly and as a result transplant easily; they include broccoli, brussel sprouts, cabbage, lettuce and tomatoes. On the other hand, cauliflower, celery, eggplant, onion and peppers are slower to regenerate, but they can still be successfully transplanted. The cucurbits (cucumbers, melons, squash, etc.), legumes (beans and peas) and corn have even slower root redevelopment, but if root disturbance is kept at a minimum, they will do fine. 

Vegetables that have a taproot like beets, carrots and turnips should be direct seeded.  Transplanting these vegetables will cause deformations and undesirable lateral root development. 

Monday, June 17, 2013

Control of Mealybugs

In general, mealybugs are under good biological control. That is, because of the presence of a number of predators and parasites, this pest population is kept low.  There are, however, a number of factors that upset this balance. Two important factors are: the application of broad spectrum insecticides (BSI) and ants.  The application of BSI will not only kill the target pest but “the good bugs” as well.  When this happens, the resurgence of the pest can be worse than before. In addition, other pests, such as mites, will become a threat because their enemies have been eliminated.  

Ants also interfere with biological control because they protect the pest from its enemies.   By controlling the ants, the mealybug population will eventually diminish as the predators and parasites return. Although it takes time to work, even a couple of months, baits can be effective in controlling the ants.

For a quick solution, mealybugs may be sprayed with a soap and/or oil solution.  In addition, a high pressure stream of water from a garden hose will dislodge many of the pests.

Added note: mealybugs have filaments, or hairs around their body which protect them by repelling the spray droplets of  insecticides. Consequently,  a ‘spreader/sticker’ should be added to the spray solution. This product acts like soap to break down the surface tension and allow the liquid spray to spread out.  Spreader/stickers are necessary with most insecticidal applications but not when using soap and/or oil sprays. 

Photos by J.K.Clark, UCIPM

Monday, June 10, 2013

The Difficulties of Growing Spinach

For many gardeners, it’s a matter of throwing the spinach seed on the ground and later harvesting a plentiful crop. Yet others struggle; here are a few reasons why:

1. When growing spinach, knowing the soil pH is important. Spinach is sensitive to highly acid soils. The soil pH (acidity/alkalinity) should range from 6.4 to 6.8.  When the pH drops too low, the following symptoms can occur:  low germination, yellowing, slow growth, browning of the margins and tips of seedling leaves and even death of the plant. If the pH is too high, leaves may have a general yellowing (chlorosis).

 A pH of 7 is neutral, above is alkaline and below 7 is acidic. A soil analysis will reveal the pH.  If needed, adding lime will slowly raise the pH of the soil.  If a soil is alkaline, sulfur is added to lower the pH.

2. Most spinach varieties are susceptible to cucumber mosaic virus (CMV).  Symptoms include a slight chlorosis of younger leaves along with narrow or "puckered" young leaves. Leaves also can have an inward rolling of margins. In advanced stages of the disease, the plants often appear stunted. Melody F1 and Savoy hybrid 612F are reported to be resistant to CMV.

3. Spinach is a cool-season vegetable and belongs to the goosefoot family (Chenopodiaceae) along with beets and Swiss chard.  They thrive best during the cool, moist seasons of the year. During periods of warm weather and long days, the spinach plant will bolt - stop its leafy growth in favor of flower and seed production. The Tyee variety is one variety that is slow to bolt.

4. And lastly, it is important to use new, fresh seed each year. Spinach seed that is more than a year old, rarely germinates over 80%; the germination rate diminishes with each year. Beet seed will germinate in temperatures as low as 380F, but good germination for spinach is between 50 and 60 0F. High soil temperatures result in reduced germination. Spinach is a cold-hardy crop and can withstand temperatures as low as
20 0F.

Spinach can be grown successfully on a variety of soils, but a fertile sandy loam high in organic matter is preferred.

Ask the Garden Guy Science Based Answers to Garden Questions, is an excellent resource book for the gardener. Some popular topics include Slugs and Snails, Organic Pesticides, Reasons, Why Vegetable Seeds Do Not Germinate, What’s So Hot about Manure? and Mushrooms in the Lawn.  Purchase by clicking on the image of the book above.

Monday, May 27, 2013

What is Calamondin?


For many years the calamondin, or calamansi was grouped in the Citrus genus. It is now thought to be a hybrid, a cross between a tangerine (genus Citrus) and a kumquat (genus Fortunella) and has its own genus, Citrofortunella.  This fruit originated from China and has been described in Chinese literature as early as 1178. 

The Calamondin is a small tree, 7 to 25 ft. in height. The orange colored fruit are round to oblate and up to 1 ¾ inches wide. The peel of the fruit is sweet and edible while the juice is quite acidic.

Calamondins can be used to flavor anything where lemons and limes would be used and are often served with iced tea and seafood.  They were common in Florida before limes became plentiful.  Calamondins can also be preserved whole in sugar syrup, or made into sweet pickles or marmalade; a favorite is a calamondin-papaya marmalade.

 Calamondins haves been reported to promote hair growth when the juice is applied to the scalp after shampooing. Rubbing calamondin juice on insect bites removes the itching and irritation. 

In regards to horticultural care, calamondins should be treated as other citrus.

Monday, May 20, 2013

The Fungus Gnat - A Nuisance Pest

Adult fungus gnats are primarily a nuisance pest, although some damage can be done to plants due to larval feeding on root hairs.   This type of damage can be serious in greenhouses and nurseries.

Fungus gnats thrive under moist conditions, particularly where there is an abundance of decaying vegetation, algae, and fungi. They infest the soil and container media, specifically those rich in organic matter. Fungus gnats do not bite people or animals and are not known to carry human pathogens. They do have a beneficial role as decomposers helping to convert dead vegetation into nutrients for plant growth.

The adults are dark in color and similar in appearance to mosquitoes. They are about 1/16 to 1/8-inch long, although they can be larger. The gnats are relatively weak fliers and are usually not found flying around indoors.

Females lay tiny eggs in moist organic debris or potting soil.  The immature, legless larvae have a white to clear body with a shiny-black head and when fully grown are about 1/4 inch long. The larvae live in the soil and feed on organic mulch, leaf mold, grass clippings, compost, root hairs, and fungi.

Cultural and physical control includes reducing moisture as much as possible, eliminating any plumbing or irrigation system leaks and providing good drainage. Moist grass clippings, other organic mulches and composts are favorite breeding spots. The use of partially composted matter in potting mix will encourage the infestation of gnats.

Insecticides are used in commercial plant production but are seldom warranted to control fungus gnats around the home.  Bacillus thuringiensis subspecies israelensis (Bti) applied to the soil or potting media is a safe product for the control of fungus gnats. Repeated applications are needed for long-term control. Note: This particular Bt product is different from the one used to control caterpillars. Bt labeled for caterpillars is not effective against fly larvae. Insect growth regulators (kinoprene, cyromazine) applied to the potting mix can also be effective.

Pyrethrins or a pyrethroid (bifenthrin, permethrin) are an option to provide temporary, fast-acting control. Pyrethrins have low toxicity to people and pets. When spraying houseplants, it is best to move the plants outdoors for treatment and wait a day or so before bringing them back inside.

Biological Control - Predators, such as some beetles, mites and nematodes will help to control fly larvae outdoors.