Monday, September 19, 2016

Poinsettia Scab Disease


Poinsettia scab is a disease caused by the fungus  Sphaceloma poinsettiae. It is a problem for greenhouse poinsettia growers in Florida and Central America and is quickly spreading to other regions. Some Euphorbia weed species are also hosts of the disease. It has been in Hawaii for many years.




The disease affects both the leaves and stems; small, round lesions form on the leaves. These spots develop whitish to brown centers, have a dark red to purple rim, and often show a yellow halo. Occasionally, an infected stem will grow six inches or more above the rest of the plants. This is due to the production of growth regulating chemicals called gibberellins, produced by the fungus.



The disease thrives in high humidity and wet growing conditions.  Splashing water will easily spread the spores from leaf to leaf and plant to plant. The key in controlling this disease is to stop the spread of the spores. When frequent rains occur, a cover over the plant or plants is one solution. Another approach would be to apply a protective copper fungicide that would prevent the splashed spores from starting new infections.  

Infected plants will usually continue to live. However, the severity of the disease is dependent upon the amount of rainfall. Remove infected leaves, and if appropriate, prune out infected stems.  Then apply either a copper fungicide or one with the active ingredient chlorothalonil (Bravo, Daconil). As new leaves emerge, reapply the fungicide. In the future, if the disease is not severe, removing infected leaves may keep the disease under control.

Sunday, September 11, 2016

Bamboo Spider Mite




The bamboo spider mite is a common pest of bamboo and will occasionally attack rice and sugar cane.  Mite damage can potentially lower the bamboo's aesthetic and economic value. The mites have a flattened body, which is straw-colored to greenish yellow with small blackish green spots.

Mite feeding will result in chlorotic (pale yellow) areas on the upper leaf surface. On the underside of the leaf, mite colonies will be found under tightly woven webbing. Generally the mites remain under the web to feed and lay eggs.

A couple of miticides, Avid and Floramite, are registered in Hawaii and are quite effective. Silicon-based surfactants such as Silwet and Silgard are recommended for use with Floramite.
 
Before buying any of the above products, however, try spraying with a soap solution or a commercial product like Safer Soap. They usually do a good job.  Make sure to spray the undersides of the leaves, good coverage is important. Come back in seven to ten days for one or more repeat applications. 

Photos: Oregon State University

Wednesday, August 24, 2016

Pineapples - Easily Propagated





Can the top of the pineapple fruit be cut off and planted in order to produce a new plant? The answer is YES! There are many variations on how to propagate pineapple. The drier the environment, the more precise the instructions need to be followed. In Hawaii, especially in high rainfall areas, propagating pineapple is relatively easy. 
  


The simplest method is to cut off the top of the pineapple, called the crown, as you normally would do when cutting the fruit. Let the top sit in a shaded, dry area for 2-7 days. Before planting, remove the dried fruity portion and some of the lower leaves exposing  ½ -1 inch of the stem. Letting the crown sit for several days will seal the wound and make it less susceptible to rot. When planting, keep in mind that the mature plant can grow to 3-4 feet in diameter and height. Mature plants also have a tendency to fall over, thus planting several together, they will give each other support.

Alternatively, the stem can be placed in a shallow glass of water. Be careful to place only the stem and not the leaves in the water.  After a short time, roots will form; it is then ready to be planted outside.