Tropical Gardening: Dangerous diseases and pests pose potential hazards to travelers

  • Photo courtesy of Voltaire Moise Feral pigs are the carriers of several diseases that can infect humans. Mosquitoes breed where pigs create mudholes.

Due to the COVID-19 pandemic, folks worldwide, and Hawaii as well, have fantasized about travel to all kinds of exotic places. It is forecast that the travel industry will soon be booming. However, some caution should be considered. Hawaii is a great choice for most mainlanders, but what about residents of Hawaii that have dreams of Machu Pichu, Tahiti or Southeast Asia?

We still have to be wary of COVID-19, but there are many other diseases to consider when traveling.


Dengue fever is just one of many mosquito transmitted diseases with which we should be concerned. There has been a serious epidemic of chikungunya in the South Pacific. West Nile virus is another that may be transmitted to humans from infected birds.

We are all getting better educated about the potential hazards of bringing plants and animals into Hawaii without following the proper procedures. Of course it is common sense that flu and similar diseases can come with travelers. We experience this each flu season, but dengue fever, yellow fever and perhaps even malaria could become a problem if we are not careful.

Unfortunately we do have the specific mosquito carriers or vectors present. They also require a reservoir where the disease organisms can reside unnoticed. Some research shows that dengue may be harbored by animals other than humans like monkeys, pigs or rats, although this seems to be rare. I learned this several years ago through a conversation with a Hawaii Department of Health worker.

The reason I was concerned is that I became very sick with dengue on a Peace Corps trip to Nicaragua. I was so sick that I had to delay coming home for two weeks. If I had felt better I would have returned to Hawaii immediately, thus inadvertently being potentially infectious. Travelers should be aware that if running a fever on return to the islands, it would be a good idea to check in with their local physician or urgent care clinic.

Folks returning to Hawaii after a trip sometimes comment with pride about the plant or seeds they got past the inspector. Bringing unchecked plants is foolish and dangerous. For example, the banana skipper became established here in the mid 1970s. No doubt, this butterfly-caterpillar was brought in by someone’s carelessness. The insect is a problem because it feeds on banana leaves. This requires more spraying by the farmer or homeowner. The pest also feeds on cannas, heliconias, and bird of paradise. The banana bunchy top virus that threatened the Big Island banana industry is another that was probably introduced through illegal importation of banana plants.

The thought of accidently transporting pests into a non-infested area may not excite the average gardener, but beware. Plant pests tend to multiply at an amazing rate. One new female insect brought to our islands can lay hundreds to thousands of eggs. Without natural enemies, these insects could possibly ravage much of our tropical vegetation.

Another example of pest introduction is that of several species of fruit flies. These insects brought into Hawaii years ago have spread throughout the islands and caused untold millions of dollars damage to tropical fruit and vegetables. It will cost millions to rid our selves of these pests.

And again, there is lethal yellowing. This is a disease that killed most Florida coconut palms. Luckily we have not found one case of this disease in Hawaii. Unfortunately, it has reached Mexico and is spreading along the Caribbean coast. Replanting with the resistant Dwarf Coconut Palm and its hybrids have allowed the areas to flourish with palms again.


Who would want to be the cause of bringing some pest to Hawaii? You are probably thinking, “Oh, no, not me, I know if a plant is healthy or not.” Most growers do recognize the telltale signs of insect activity—wilting, chewed leaves, or blasted flowers. But plant pests do not always leave signs of their presence. Plants may be contaminated by bacteria, virus, larvae, or insect eggs even if we don’t see them.

With the world soon being open to travel again, we must be even more cautious about spreading unwanted pests and diseases of plants, animals and humans.

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