Oct 212014

Professor Tsang and collaborative UH research team received the Governor’s Award in 2010 as State Team of the Year for developing hot water systems for disinfesting exports. 


Professor Tsang and collaborative University of Hawai‘i research team developed a hot water shower system using a Matson container as the treatment chamber to rid potted plants of coqui frogs. The team was recognized for the impact the invention made on the state’s export business with the Governor’s Award in 2010 as State Team of the Year.

Marcel Tsang

Marcel Tsang

Marcel Tsang is a professor of agricultural engineering and mechanization at the College of Agriculture, Forestry and Natural Resource Management, University of Hawai‘i at Hilo. His research interests include drying and processing of agricultural crops; post harvest treatments of tropical fruits, vegetables and floricultural crops; system design for heat treatments of agricultural commodities and potting media; non-chemical methods for disinfesting potting media; enhancing greenhouse environment for crop production and developing sustainable technologies for greenhouse food crop production.

“Since joining UH Hilo (in 1985), I have worked on a variety of agricultural products in Hawai‘i,” Tsang says. “These include macadamia nuts, coffee, ginger root, papaya, cut flowers and foliage, potted plants, sweet potatoes and vegetables among others.”

For the last twenty years, Tsang has concentrated his research on heat treatments using hot water or heated air to disinfest agricultural commodities and potting media of insect pests and other pathogens. A large part of the research was devoted to nursery products.

“This work was crucial to find reliable alternative non-chemical disinfestation treatments for our floriculture products due to the phasing out by the EPA of ozone-depleting fumigants commonly used for disinfesting agricultural commodities of quarantine pests,” he explains. “As a result, the industry was in danger of losing access to their export markets.”

Most of this work has been done in collaboration with Arnold Hara, an entomologist at the Department of Plant and Environmental Protection Sciences at UH Mānoa College of Tropical Agriculture and Human Resources. The team developed a hot water dip system for disinfesting cut flowers and foliage of quarantine pests. Later, they also developed a hot water shower system using a Matson container as the treatment chamber to rid potted plants of coqui frogs.

“We were able to develop heat treatments that are lethal to targeted pests with no detrimental effects on the plants,” says Tsang. “Our effective and innovative treatments have been adopted by the local producers and exporters so that Hawai‘i’s growers are able to continue to ship their nursery products inter-island as well as export to markets on the mainland.

For these efforts, the research team received the Governor’s Award in 2010 as State Team of the Year.

Researchers from UH Manoa and UH Hilo recognized for their dedication to the agriculture community


Professor Tsang stands with Arnold Hara (front center with lei), the research team, then-Governor Lingle (at right) and others as the team received the Governor’s Award in 2010 as State Team of the Year. Click to enlarge.

The team was selected as the State Team of the Year honoree in the 2010 Governor’s Awards from among 52 exceptional group and individual nominees from the state’s executive branch departments who exemplify the highest caliber of public service and dedication to serving the people of Hawai‘i.

The Quarantine First Responders is led by Dr. Arnold Hara, a CTAHR entomologist, and is comprised of CTAHR’s Kris Aoki, Susan Cabral and Ruth Niino-DuPonte of the Komohana Research Extension Center in Hilo; Jon Katada of the Waiakea Research Station in Hilo; Charles Nelson of CTAHR’s Department of Molecular Biosciences and Bioengineering; and Dr. Marcel Tsang of UH Hilo’s College of Agriculture.

The team has been recognized for their extensive work on the coqui frog. When other agencies were uncertain about how to deal with an amphibian pest, the team organized the Coqui Frog Working Group and prompted each agency to contribute in their respective areas of expertise. The team knew initial control efforts using chemical sprays would only be a temporary solution so they conducted extensive literature searches, documented the frog’s life cycle in Hawai‘i, screened promising chemicals and delivery methods, and studied the frogs in their native habitat while continuing to look for a long term solution. They also developed frog traps and barriers to prevent the spread and establishment of the coqui in Hawai‘i’s certified nurseries.

To meet quarantine security requirements for floriculture crops, the team generated copious amounts of data to determine the thermal tolerance of various quarantine pests. They successfully designed and constructed a hot-water dip treatment that eliminated pests without killing the plant itself. They also discovered that the treatment extended the shelf life of certain flowers and foliages and had the added benefit of preventing geotrophism, which is a bending of flower stems in response to gravity and is problematic for shippers.

The Quarantine First Responders have visited elementary schools to educate children in recognizing the dangers of touching pests such as the stinging nettle caterpillar, little fire ant, and the dangers in handling slugs. They also educate frustrated homeowners who want to rid their property of the coqui, conduct workshops for commercial growers, make scientific presentations to academic colleagues, and have provided information to thousands of Hawai‘i residents through their publications and websites.

Hot water treatment continues to be one of the main weapons against invasive pests into Hawai‘i. Last year, the State Department of Agriculture used the hot water shower system to clean imported Christmas trees from hitchhiking pests.

Currently, Tsang is interested to develop a low cost, modular solar pasteurization system to disinfest potting media of detrimental pests and also to allow growers to recycle their used potting media and waste organic products.

“My hope is that this system can be incorporated into a sustainable greenhouse system for container grown vegetable crops where a zero-waste practice can be implemented,” he says.

He also would like to refine a hot water system to manage insect pests on the growing vegetable plants in lieu of using chemical spray.

His future research plans are to see an enhanced production during the winter period by extending the daily growing period through a solar assisted grow light system in the greenhouse.


Tsang received his master of science in agricultural engineering and his doctor of philosophy in engineering science from Louisiana State University.


Apr 242014
Research into sustainable food and fuel production is high on the priority list at UH Hilo. This photo shows cattle grazing in Pololu Valley, where soil scientists are working with a wetlands grant to study soil nutrient bioavailability. Photo courtesy of Bruce Mathews, professor of soil science who is conducting the research.

Research into sustainable food and fuel production is high on the priority list at UH Hilo. This photo shows cattle grazing in Pololu Valley, where soil scientist Bruce Mathews is working with a wetlands grant to study soil nutrient bioavailability.

Bruce Mathews

Bruce Mathews

Bruce Mathews is a professor of soil science and agronomy at the University of Hawai‘i at Hilo. He currently serves as interim dean of the College of Agriculture, Forestry and Natural Resource Management. His areas of research are plant nutrient cycling and soil fertility as affected by environmental conditions and crop management; assessment of the impact of agricultural and forestry production practices on soil, coastal wetlands, and surface waters; and development of environmentally sound and economically viable nutrient management practices for pastures, forests, and field crops in the tropics.

Mathews is best known for his research on nutrient cycling in tropical pastures and potentially environmentally sensitive release of phosphorus from pasture soils to surface waters.

He says he has had quite a few surprising findings in his research, one of which is discovering that the behavior of cattle in pastures located in the humid tropics – huddling under shade trees during the day – affects the redistribution of soil nutrients differently than the behavior of cattle in cooler climates.

“In the humid tropics, structural features of pastures, particularly the position of shade and to a lesser extent water sources have a greater effect on animal redistribution of soil nutrients than stocking method and associated stocking density-mediated effects on competition for forage,” he says. “This is in contrast to findings in cooler temperate climates where rotational stocking methods with short grazing periods and high stocking densities tend to promote more homogenous distribution of animal excreta on pasture than other stocking methods. In the humid tropics, cattle tend to congregate under shade during the warmer parts of the day, regardless of stocking density.”

In other research, Mathews discovered hilograss is a sulfur hyperaccumulator to the point that the high sulfur concentrations can have adverse effects on grazing cattle performance. Another of his research projects showed soil exchangeable calcium protects some minerals in soils from dissolution by complexing certain organic acids.

Other of his studies show the apparent influence of hydrologic conditions on the relative importance of amorphous iron in retaining phosphorus in Hawaii’s iron rich soils. He discovered phosphorus availability in Hawaii’s kikuyugrass pastures was great enough that the phosphorus concentration in mineral supplement premixes for grazing livestock could be reduced by 25 to 50 percent, while calcium supplementation needed to be increased due to lower bioavailability of organically complexed calcium for horses relative to ruminant livestock.

Mathews also discovered the benefit that annual nitrogen fertilization of pastures can have on increasing earthworm populations and thereby nutrient recycling efficiency.

One study with favorable results actually ended up being a disappointment. The study showed outstanding daily weight gains of 2.0 to 2.4 pounds per day for cattle that could be obtained when perennial forage peanut is established in pastures.

“The high costs of imported forage peanut seed and the labor associated with vegetative propagation alternatives prohibited adoption of this forage in Hawai‘i,” he says. “Nevertheless over 200,000 acres of this forage have been planted in pastures elsewhere in the tropics.”

The main benefits of Mathews’s research have been improved management recommendations that benefit farmers and the environment.

“For example, little environmentally sensitive phosphorus release to surface waters was predicted until the phosphorus saturation index of Hawai‘i’s upland soils exceeded six percent and that for wetland — alluvial valley soils — exceeded 10 percent,” he says. “This means that phosphorus in fertilizers and manures should not be applied to such soils when the threshold saturation index has been attained.”

Mathews has traveled to the Philippines on several projects related to his work and did a sabbatical leave there during 2001-2002.

Currently, Mathews is examining the effects of hydraulic gradients in Hawai‘i’s wetland valleys on soil biogeochemistry and redox mediated transformations of iron and phosphorus. He is also doing comparisons of soil properties along hydraulic gradients of former Hilo Coast sugarcane lands presently in pasture and planted forest with those of native forests on the same soil types. In another project, he is examining a five-fold range in hilograss sulfur concentrations on in vitro digestibility and production of toxic hydrogen sulfide.

Mathews also has a grazing trial underway at the UH Hilo Farm Laboratory in Pana‘ewa to compare the performance of Angus and locally developed dual purpose Zebu-crossbred cattle on mixed mulatograss-guineagrass-glycine pastures. Mulatograss is a new Brachiaria hybrid grass that was developed from two Brachiaria species already existing in Hawaii.

In the future, Mathews hopes to spend more time on Big Island community outreach and summarizing local and international tropical agricultural research that is relevant to the island.


Mathews received his bachelor of science in agriculture, with high honors, in 1986 from UH Hilo. He received his master of science in agronomy from Louisiana State University and his doctor of philosophy in agronomy, with a minor in animal science, from the University of Florida.





Professor Mathews talks at forum on campus entitled, “Building Momentum Toward a Resilient and Sustainable Local Farming Culture.” The panel was held on May 22, 2014, and hosted by the college and the County of Hawai‘i.