Judging by the record warm temperatures we are experiencing already this year, we likely will have a summer ideal for plant disease problems.
The best disease prevention measure you can take is to start with healthy or disease-resistant plants.
According to University of Hawaii plant pathologists, once a plant becomes badly diseased, it is difficult to nurse it back to health. For this reason, every effort should be made to prevent introduction of disease-causing organisms on plant material or in soil.
Many common diseases are caused by fungus organisms.
Plants with poor or weak growth are usually more susceptible to these diseases. Good cultural and sanitation practices will help prevent trouble, such as removing diseased parts, including leaves or branches, as soon as they appear. Treat pruning wounds with a specially prepared material to stop entrance of wood-decaying organisms and wood-feeding insects.
For treatment of fungus diseased plants, fungicide applications should begin when disease development first appears and continue as recommended by the manufacturer.
Other organisms that cause problems on plants, people and even buildings might not be disease-related but are bothersome.
Two types that are found throughout the tropical world including Hawaii are house mildew and green algae.
Mildew flourishes in damp places. Hawaii’s high humidity often creates conditions favorable to the growth of this unsightly problem.
Where mildew is already established on walls, remove as much as possible by scrubbing the discolored surfaces with a strong detergent in warm water. The remaining mold spores should then be killed with a treatment of household bleach, applied at the rate of 1 pint per gallon of water.
If the infected surfaces need repainting, then the use of a mildew-resistant paint is recommended. Paints that provide a hard surface also will discourage the lodging of mold spores.
Algae commonly grow on the surface of soil that is moist for periods of time. This is very common during the rainy season.
These minute green plants often develop in such profusion that they forms a rather thick, greenish to blackish mat. Growth of such magnitude in a turf planting is detrimental to the grass because the algae competes with the grass for space and nutrients. In addition, if the algae mat dries, it forms a crust that retards or prevents the movement of water into the soil.
If this occurs, the grass is subjected to a moisture stress directly because of the presence of the algae.
The same conditions that favor the growth of algae also favor the growth of fungi that bring on turf grass diseases. In fact, a close association was noted between frequent disease outbreaks and the presence of algae.
Therefore it’s desirable to control both of these pests with one practice.
Reducing the moisture level would be the ideal method; however, in many situations this is not possible, and other control measures must be used. The use of fungicides that are effective against turf diseases and algae is an efficient method of control.
Bacteria, fungus and algae are not all bad guys. Limu is an algae, yogurt is the result of certain types of bacteria and those delicious mushrooms we enjoy incorporated in gourmet cooking are a fungus.
However, prevention of disease organisms is vital and also includes keeping them from being introduced into Hawaii.
Some folks get unhappy when they learn they can’t bring certain plants or seeds here, or if they can they have to go through all kinds of red tape, fumigation or extended quarantines to get the plants through.
A few of these folks figure it is a bother to get permits and go through the proper procedure to bring plants to Hawaii. They smuggle a few plants, thinking it won’t make any difference.
This attitude couldn’t be further from the truth or more dangerous.
One disease that might have been accidentally introduced to Hawaii is rapid ohia death, which is thought to be caused by a Ceratocystus fungus. It is presently killing large stands of ohia in places on the Big Island, including Puna.
No cure is known at this time, but sanitation is the key. Moving plant materials, or even wood and soil, from infected areas to healthy forests could decimate our forests
This, again, shows why we should support our state and federal agricultural quarantines. Importing plants illegally could bring devastating diseases like that to Hawaii.
There are ways to bring in new plants legally. The state Department of Agriculture and USDA Plant Quarantine Office can give you the details.
By following the law, hundreds of new plant introductions are being made each year. These can enrich our lives without bringing with them unwanted insects and diseases that could bring disaster to our economy.