Thursday, December 26, 2019

All Toads Are Frogs, But Not All Frogs Are Toads


How to control toads and frogs in the garden?

Having found no control manual for toads and frogs, the common sense approach is to change the habitat to make it unfriendly for them. This will include eliminating water sources for their reproduction and moist areas for them to hide – almost an impossibility in areas of heavy rain! But eliminating piles of yard rubbish and trimming back thick ground cover will help. Various types of barrier-fences can be erected either around the property or just around certain desired areas. Since toads and frogs eat insects, controlling the bugs would also be a way of discouraging their presence, again not practical for backyards in Hawaii. But eliminating any outdoor lighting, which attracts many insects, should help. 


For clarity, all toads are members of the family Bufonidae, which falls under the order of Anura, commonly called frogs. Therefore, all toads are frogs but not all frogs are toads.

Toads tend to have a thicker skin allowing them to live away from water longer than most frogs. A toad’s skin is often covered with bumps and glands. The similarities are that frogs and toads both reproduce and develop in water, both ‘sing’ and are both carnivorous.

Of note, when the bufo toad is attacked, its defense is to exude a milky fluid known as ‘bufotoxin’. This poison protects it from some predators but not all. Most snakes and birds seem to be unaffected. Humans need to be careful since the toxin may cause skin irritation and possibly worse, but there are no reports of human fatalities. Unfortunately the toxin can be fatal to small animals such as cats and dogs.  Thus ridding the yard of bufo toads is a protection for your pet.

Pictures from Forest and Kim Starr: Bufo marinus, The Cane Toad

Wednesday, December 4, 2019

Citrus Scab Disease


                                                       
What causes the scabby bumps on citrus fruit? This disorder, common in high rainfall areas, is called citrus scab. The disease occurs in Hawaii, as well as in Florida, but not in California due to the dry climate. It is caused by a fungus, Elsinoe fawcetti, and affects a wide range of citrus.

                                                       
The light brown, raised, warty scabs appear on young stems, leaves and fruit.  Leaves develop some resistance to citrus scab with age. The scabs consist of the body of the fungus plus the swollen tissue of the host plant.

Spores are produced within these scabs and will spread to other tissues by the splashing rain or irrigation water. Infection occurs when the spores germinate on a susceptible plant surface that remains wet for approximately 3 to 4 hours.
                                                 
                                                         

Control 
·        Select a resistant species or variety. 
·        Plant in a sunny and dry location as is available.
·        Intercrop citrus with non-citrus plants or resistant citrus trees.

Citrus scab can reduce yield and will certainly reduce the quality of the fruit. For home production, as bad as it looks, the fruit can still be sweet and juicy. For those caring about the external appearance of the fruit, trees can be sprayed with a copper fungicide. Yet even numerous applications may not be effective in high rainfall areas.

Highly susceptible citrus types: Fremont, Clementine, Murcott and Frost Satsuma mandarins; Orland Tangelo; Tahitian lime and Rangpur lime, often referred to as the common lemon in Hawaii.

Not susceptible or immune citrus types: Sweet orange, navel orange, pummelo and grapefruit.

Monday, November 4, 2019

Citrus - Remove First Year Fruit or Not?




This question comes up often in regards to young citrus trees. The answer is applicable to many fruit trees: trees spend energy in order to develop their fruit. For an older tree, there is usually enough energy to both grow the tree and develop the fruit. When a young tree produces its first bloom, there is a limited amount of energy. Will all the energy be used to grow leaves and branches or will some of it be applied to develop fruit? Many citrus growers will choose to sacrifice the first year’s crop - remove the young developing fruit - so their trees will grow quickly and eventually produce more fruit. 

On the other hand, if the first fruit is left until maturity, that fruit is using energy at the expense of the growth of leaves and branches.  For the homeowner, since the resulting differences in yields are generally small, my advice is to enjoy the first season and let the fruit set!

Monday, September 30, 2019

Problems with Acidic Soils: Lime Can Work Wonders




Note: pH is the measurement of the soils acidity/alkalinity. The pH scale is from 0 to 14 with 7 as the neutral point; below 7 is acidic, above 7 is alkaline. Here are a few common pH examples:

  • Extremely acid:  lemon-2.5; vinegar-3.0; stomach acid-2.0; soda pop-2–4

  • Strongly acid:  carrots-5.0; asparagus-5.5; cabbage-5.3

  • Slightly acid:  cow's milk-6.5

  •  Neutral:  saliva-6.6–7.3; blood-7.3

  • Slightly alkaline: eggs-7.6–7.8

  • Moderately alkaline: sea water-8.2; sodium bicarbonate-8.4

  • Very strongly alkaline: soapy water-12; household bleach-12.5


Concerning the pH of soils, there is a preferred range in which plants will grow best. Most soils in Hawaii, as in other parts of the country, are acidic. Extremely acid soils can have a toxic effect on many plants. One common problem is excessive aluminum and manganese becoming soluble in the soil adversely effecting plants.  Acidic conditions can also change the type of microorganisms living in the soil. This will affect the amounts of nitrogen, sulfur and phosphorus available to the plants since the microorganisms breakdown these nutrients into plant-available forms.

These acidic soils will benefit when lime is applied. As an amendment, lime in its various forms can raise the pH of the soil and eliminate a number of problems.
Ground limestone is almost pure calcium carbonate and comprises the largest percent of lime used in the United States. It is usually the cheapest form of lime. Limestone with significant amounts of magnesium carbonate is called dolomitic limestone (dolomite), containing approximately equal parts of magnesium and calcium carbonate. Dolomite works well especially if the soil has a magnesium deficiency.

Hydrated lime, another form, is one and a half times more effective at raising the soil pH but is also more caustic, and therefore,  hazardous to handle. Protection for the skin and lungs is recommended. Excessive amounts of hydrated lime can cause a pH shift towards a highly alkaline condition. Conversely, when using dolomitic lime, it is difficult to apply too much as long as it is thoroughly mixed into the soil.

When purchasing lime, a fine powdered lime, about 60-100 mesh, is the fastest acting grade available.  However, being a fine powder, it is a potential eye irritant under windy conditions. It will also cake rather easily, and when improperly mixed, it will stratify forming a layer that can burn roots and repel water.

A coarser limestone (similar to salt grains) is also available and is easier to handle, but its disadvantage is that it is slower acting.  In summary, incorporating lime as an amendment in any of its forms can make a big difference in acidic soils.

Friday, July 5, 2019

Passionfruit - Hawaii’s Favorite Flavor




The yellow passionfruit, Passiflora edulis f. flavicarpa, and the purple passionfruit, Passiflora edulis, are grown in most tropical and subtropical parts of the world. The yellow passionfruit is a tropical plant while the purple is considered subtropical, being able to survive some freezing temperatures.


Of the hundreds of species in the genus Passiflora, these two, P. edulis, and P. edulis f. flavicarpa, are solely designated as passionfruit.  In Hawaiian, the fruit is called lilikoi and in Portuguese, maracuja peroba.  When the seeds of purple passionfruit first came to Hawai`i from Australia in 1880, they were planted in East Maui in the District of Lilikoi and that name stayed with the fruit. The seeds of the yellow passionfruit were brought to Hawai`i from Australia in 1923. 


In 1951, there were only a few acres of passionfruit plantings. It was then that the University of Hawai`i chose passionfruit as the most promising crop for development. And by 1958, there were 1,200 acres of primarily yellow passionfruit, and the industry was firmly established.

The lilikoi vine is a shallow rooted perennial, displaying beautiful, fragrant flowers, 2-3 inches wide. The fruit is nearly round approximately 1 ½ - 3 inches wide.  Inside, the fruit is filled with an aromatic mass of juicy pulp and within are as many as 250 small, edible seeds.  These vines, especially the yellow, are fast-growing and will begin to bear in 1 to 3 years. In fact, some vines can flower and fruit within a year after being started from seed. In Hawai`i, passionfruit matures from June through January; the ripe fruit will fall to the ground.

Carpenter bees are efficient pollinators for the yellow passionfruit. Honey bees and the hover fly also help in pollinating but are much less efficient. Wind is ineffective as a pollinator because of the heaviness and stickiness of the pollen.

The yellow lilikoi vine tends to be more vigorous and the fruit generally larger than the purple. While the purple appears to grow better at higher elevations, 400 to 3,000 feet, the yellow fruit is best adapted to lower elevations, from sea level to 1,500 feet. Furthermore, the yellow will yield 3 to 4 times that of the purple, yet the purple fruit is considered to have better flavor and aroma with the pulp being less acid with a higher proportion of juice.

Passionfruit vines are usually grown from seeds.  If the seeds are planted soon after being removed from mature fruit, most will germinate in 2 to 3 weeks. Fortunately, seeds do not require cleaning, drying or storage. They can be planted immediately after being removed from the fruit, even separation from the pulp is not necessary. In fact, allowing the pulp to ferment for a few days may hasten germination. In contrast, seeds that have been cleaned and stored actually have a lower and slower rate of germination. 

Propagation of passionfruit can also be accomplished through air layering and cuttings. Good soil drainage is essential for successful plantings.

Commercially, vines are trained on wire trellises. For backyard production, however, the yellow passionfruit is more productive and less subject to pests and diseases if allowed to climb a tall tree.

In Hawai`i, Oriental and melon fruitflies will deposit eggs in young fruit. This may cause fruit to shrivel and fall from the vine. If older fruit is pierced, the only ill effects will be an external scar. Other pests include aphids, scale, thrips and mites. In spite of all these, passionfruit or lillikoi vines flourish on fences and in trees, in backyards and vacant lots around the Islands.

The juice with its distinct flavor and aromatic bouquet is a key ingredient in making sauce, candy, ice cream, sherbet,  iced tea, or in cocktails.  In the Hawaiian Islands lillikoi is a favorite flavor enjoyed by young and old alike. 

Photos  by Forest and Kim Starr