Plumeria Rust Disease

Rusts are a group of fungi that cause disease on many plants including grasses, ohia, eucalyptus, guava, lemongrass and blueberries. It has long been a dreaded disease of wheat. In fact, rust disease on wheat is thought to be one contributing factor to the fall of the Roman Empire.

Plumeria rust first appeared in Hawai`I in 1994.  It attacks the leaves and produces bright orange blisters on the underside of the leaf.  These blisters rupture and release masses of orange colored spores. Heavily infected leaves can drop prematurely.  The disease is rarely severe enough to cause serious damage to the tree and fungicidal applications are unnecessary. The problem is worse, however, in wet areas and during rainy periods.  In dry areas where irrigation is necessary, the foliage should not be watered.  Picking up dropped leaves and disposing of them will help to control the disease. 

Citrus Leafminer

What is happening to my citrus leaves? They look like something is tunneling through them?  

The tunneling damage is caused by the citrus leafminer, Phyllocnistis citrella.   It is not the same one that attacks tomatoes, cabbage and ornamentals like chrysanthemums. It is relatively new to the Hawaiian Islands. It was first noticed on Oahu in 2000 and now infests all the islands. 

The citrus leafminer is a tiny ½ inch silvery moth with a black spot at the tip of each wing.  It is the larval stage which lives inside young terminal leaves, feeding as they meander throughout the leaf. The moths are attracted to the new growth and once the leaves harden, the larvae will not be able to travel within the leaves. At the same time this pest came to Hawai`i, a tiny parasitic wasp came along with it.  Because of the presence of this wasp, citrus leafminer damage has been minimized. 

 What to do when the leafminer is present: avoid excessive pruning which will stimulate new flushes of growth. Even if the new flush of mature trees is heavily damaged and looks unsightly, the yields of most citrus varieties will be unaffected.   

Stinging Nettle Caterpillar

                                                        Caterpillar and pupa 

The stinging nettle caterpillar (Darna pallivitta)has a voracious appetite for many plants in the garden including palms, dracaena, ti, coffee, gardenia, banana, perennial peanut, California grass, mondo grass, guava, macadamia, monstera and red and shampoo gingers. What is even more alarming is the burning and itching caused by the spiny hairs on the caterpillars.    

                                                             Adult Moth

The stinging nettle caterpillar is new to the Big Island, coming here in 2001.  It has spread throughout the East side of the Island and is currently closing in on the Kona area.  The larvae are up to 1 inch long and covered with many rows of stinging spines.  The caterpillar varies from white to light gray with a dark stripe down it‘s back. The adult moth is about ½ inch long, with a rust to light brown coloration.

Control – Since the moths are nocturnal and attracted to light, putting up a bug-zapper with an ultraviolet bulb should reduce the pest’s population. Place a bucket of soapy water underneath the trap to catch fallen moths.  This is done in case the zapper doesn’t kill them and to give an idea of how bad the situation is. The Hawai`i Department of Agriculture is working on releasing parasites for natural biological control.   

There are a number of insecticides that are effective against the larval stage.  One of the safer materials is Bacillus thuringiensis (Bt), also known as Dipel. It is a bacterium which is harmless to humans but deadly to caterpillars.

If you are stung by this caterpillar:

·        Wash the area immediately with soap and water.

·        An oral antihistamine may stop itching and swelling

·        Hydrocortisone creams may stop itching and swelling.

·        Get medical attention immediately if you experience difficulty breathing or are stung in the eye. Skin reactions vary from a red welt to severe swelling lasting a couple of days.

Check out CTAHR’s website at  www.ctahr.hawaii.edu  for pictures and a more detailed informational brochure.  

Photos by Brian Bushe

Organic Insecticides

                                                                                                                                  Here is a list of materials most commonly used and often accepted as organic insecticides:  

·        Bacillus thuringiensis (Bt) -  for the control of many lepidopteran larvae (butterfly/moth), mosquito and beetle larvae. Some trade names include, dipel, gnatrol, biobit and javelin.

·        Diatomaceous earth –An abrasive and absorptive powder made from the shells of diatoms - fossilized remains of microscopic, marine organisms.  This white powder causes dehydration in pests such as ants, cockroaches, snails and slugs.

·        Insecticidal oils – controls aphids, scale insects, mites, as well as aphid and mite eggs.

·        Neem – a plant derivative; controls a broad range of insects.  Low human toxicity.

·        Pheromones – these are chemical attractants used mainly for monitoring insect populations.  They can also be used to confuse insects in order to disrupt mating. Occasionally they are used to catch large numbers of specific insects like fruit flies to reduce future generations.

·        Pyrethrum –  a natural insecticide made from the dried flowers of certain species of chrysanthemum. During the Napoleonic Wars (1804-1815) this “insect powder” was used to control flea and body lice infestations by French soldiers. A disadvantage to this natural insecticide is its sensitivity to sunlight.  It can break down in as little as 12 hours.

A group of synthetically produced, similar compounds called pyrethroids are more stable in sunlight, therefore more environmentally persistent and, in general, are more toxic. Examples of synthetic pyrethroids are, allethrin, bifenthrin, cyfluthrin, permethrin and resmethrin.  These names will be  listed under active ingredient.

·        Soaps – controls mites, aphids and other plant-sucking arthropods.  May cause some plant burn under certain conditions. 

·        Vegetable oils – used as a contact spray to control scale insects, aphids and mites.

What’s So Hot About Manure ?

In general, organic fertilizers contain a lower percentage of nutrients than their inorganic counterparts. Some exceptions are 13% nitrogen in dried blood meal and 23% phosphorus in bone meal. Furthermore, manures are low in nitrogen, phosphorus and potassium (N-P-K).  The analysis for chicken mature (dry) is nitrogen 2-4.5%, phosphorus 4.6-6% and potassium 1.2-2.4%.

Even at 4% nitrogen, 25 lbs. of manure are needed to supply one pound of nitrogen, whereas only 6 lbs. of 16-16-16 fertilizer would be needed to supply the same one pound of nitrogen.

Manures, however, offer a lot more than just N-P-K:

·        They add organic matter to the soil.

·         They help improve soil structure.

·         In addition to N-P-K, they also add zinc, manganese, magnesium, calcium and sulfur.

·        Manures improve water infiltration and the nutrient-holding capacity of soils.

·        Manures can act as a food source for many beneficial microorganisms living in the soil.

In general, 3 – 10 tons of manure, per acre, can be applied. For smaller backyard gardens, applying 15 – 50 pounds of manure per 100 square feet of soil is suggested. Chicken manure contains salts which can burn plants; all manures of course contain some salts. Rainfall safely leaches these salts beyond the root zone of plants. In areas of low rainfall, caution must be exercised with repeated applications of large dosages of manure, especially chicken mature.

Propagating Surinam Cherry

 Surinam cherry, (Eugenia uniflora), is also known as Brazilian cherry, cayenne cherry and pitanga.  It is propagated almost entirely by seed which usually germinates in less than a month. Plants generally come true to seed, i.e., they carry the same characteristics as the mother plant. In countries where the fruit is commercially grown, like Brazil and India, grafted plants are sometimes used; the graft wood comes from trees producing superior fruit. Successful air layering is also reported.  The seeds do not withstand low temperatures and remain viable for about one month.

 The Surinam cherry is eaten fresh and also made into jam, jelly, relish or pickles. The people of Brazil ferment the juice into vinegar, wine and distilled liquor.  

Mushrooms in the Lawn

 

Mushrooms, sometimes called toadstools, are the reproductive structures of certain types of fungi. They contain thousands of spores carried by the wind.  Most fungi that live in lawns are beneficial because they decompose organic matter, thereby releasing nutrients that are available to the plant.  Because of this, areas of lawn where mushrooms are growing may be darker green in color.

Mushroom fungi don’t attack lawns directly.  The fungus grows underground and consists of a network of filaments, tiny threads that resemble cotton.  But at some point this mass of fungal cotton will die and due to its hydrophobic or water repelling characteristic, will form a dense mat that repels water. This will cause the soil beneath it to be dry. Even though the lawn receives ample water, brown areas will appear due to the repelling effects of the mushroom mat. 

The underground fungal structures can grow in the soil for years.  But when conditions are right, after periods of prolonged wet weather, mushrooms will appear. Picking mushrooms soon after they appear may prevent their spores from further infecting the lawn, but new spores will blow in, and the underground fungal growth still remains. The primary reasons for removing mushrooms from lawns are to keep them away from children and pets and to improve the lawn's appearance.

If significant dying or dead areas occur in the grass, lawn renovation may be required. If the grass is not dead, it can reestablish itself if water penetration is improved by breaking up the dense fungal mat. This can be done by removing cores of soil that are at least 1/4 to 1 inch in diameter and slightly deeper than the fungal mat. The use of a lawn aerator a few times a year may be sufficient to improve water penetration.

Predisposing factors for mushrooms developing in a lawn are 

• Buried wood in the landscape (tree logs, limbs, dead roots, construction lumber)
• Stressed or under-nourished turf
• Excessive irrigation
• Heavy or unmanaged thatch
• Poor soil aeration

Do not eat these mushrooms or other fungal fruiting bodies unless you are well acquainted with the different species. Many species are poisonous, and only an expert can distinguish between edible and poisonous. There are no simple tests that can be used to identify poisonous mushrooms.