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