Hanging or lifting irrigation lines where possible, and using covers over the spaghetti tubes, are effective methods to reduce rabbit damage to irrigation. In addition, nurseries may consider encouraging irrigation tubing manufacturers to develop spaghetti tubing more resistant to rabbit gnawing. Nurseries may want to consider an ongoing program to reduce rabbit harborages by using habitat modification where possible. It may be appropriate to target areas that unintentionally provide habitat to reduce suitability. Some measures to reduce influx and suitability may include fencing between natural areas/groves and the nursery; decreasing cover for the rabbits in runways; thinning border vegetation that provides cover, such as the hedges, to reduce hiding places; regularly moving debris piles, recycled wood piles, and storage pallets to reduce breeding and cover within the nursery; and rotating pallets of stock. In the circumstances when trapping is desirable to remove rabbits from an area, the use of traps in runways created by drift fence will be the most effective method. Two species of tree frogs native to the Caribbean have recently become established in the Hawaiian Islands . Since their introduction via the import horticultural trade, the frogs have rapidly expanded their range on the islands of Hawaii, Maui, Oahu, and Kauai. There are two modes of spread for tree frogs. The first is the accidental transport via horticultural products or material from infected nurseries or gardens to uninfected areas. The second mode is the intentional introduction of frogs by citizens into sites that aren’t infested. Theoretically both activities are illegal under Hawaii state law , though enforcement is difficult.

There is a concern on the part of federal, state,vertical farming technology and private agencies/entities managing natural and agricultural resources in Hawaii that introduced Eleutherodactylus frogs pose a serious threat to these resources. E. coqui can reach densities of greater than 24,000/ha and is capable of consuming approximately 114,000 arthropod prey items per hectare in a single night in its native range in Puerto Rico . It is believed that these frogs, once established in native habitats, could prey on endemic arthropods as well as compete indirectly and directly with native birds for limited food resources . Tree frogs may be a vector for plant nematode eggs, and the recent discoveries of frogs in certified nurseries make the frogs a potential quarantine issue that could greatly impact the exportation of disease and pest-free nursery products from the state. Surveys indicate that frog populations have become firmly established in nurseries, parks, residential gardens, resort areas, and lowland forest habitats on the islands of Hawaii and Maui . The number of reported locations has significantly increased on these islands in the last 3 – 4 years . Frog populations have been documented on the islands of Oahu and Kauai , and there is grave concern that these populations will continue to spread. In one horticultural site on the island of Hawaii, one species of tree frog has been documented to obtain densities comparable to the native range . Localized loud vocalization of male frogs throughout the nighttime hours has also been a source of numerous angry complaints from sleepless residents and tourists alike. Restricting the transfer of infected plant materials via the horticultural trade or by the casual public has the potential of stemming further spread of frogs to uninfected areas. However, enforcement of laws dealing with the transportation of alien species within the State of Hawaii has been limited at best. Currently, an enforceable legal mechanism that specifically restricts the movement of plant hosts harboring E. coqui within the state has been proposed by Hawaii Department of Agriculture staff but has not been enacted.

Though the status of an enforceable quarantine on the movement of frogs is currently in question, there is an immediate need to: 1) reduce or eradicate localized frog populations that serve as reservoirs for new infestations and 2) treat infested plant material to insure this situation does not get any worse. Since 1998, research has been conducted with the goal of developing control techniques for these frogs. Current trapping techniques proved in field trials to be inefficient . Cultural practices or hand capture may be effective on a small scale; however, chemicals appear to be the only broad-range and cost-effective immediate method of controlling frog populations. A laboratory study was conducted to screen 35 selected 1) pesticides registered for invertebrate control in ornamental nurseries and floriculture in Hawaii, 2) human pharmaceutical and food products, and 3) surfactants as potential chemicals for E. coqui and E. planirostris frog control . During initial screening, one of two commercially available pesticides containing resmethrin , a synthetic pyrethroid, was found to cause mortality to slightly greater than 50% of tree frogs tested at registered or recommended dosage rates . No surfactants tested were found to cause frog mortality rates greater than 50%. Of the human pharmaceuticals and food products tested, food grade caffeine , applied as a topical spray, proved effective against both E. coqui and E. planirostris. The lowest concentration solution of caffeine and water that resulted in 100% tree frog mortality was a 12.5 mg/ml solution applied to tree frogs topically with a spray bottle. Following the completion of laboratory screening of potential chemicals for Eleutherodactylus control, field trials were conducted on the directed spray application of three different caffeine solutions for controlling introduced Eleutherodactylus frogs in floriculture and nursery crops in Hawaii . The directed spray application of 0.5%, 1.0% and 2.0% caffeine solutions reduced Eleutherodactylus coqui abundance in test situations on or bordering infested ornamental plant nurseries in East Hawaii. Treatment of plots with a single spray application of a 2.0% concentration caffeine solution caused a 100% decline in the relative abundance of Eleutherodactylus frogs and in the relative abundance of frogs adjusted for nightly variation in frog activity before and after treatment on control and treatment plots.

The Hawaii Department of Agriculture’s Pesticide Branch prepared and submitted to the United States Environmental Protection Agency an application for an Emergency Registration for the spray application of caffeine for localized frog control in the State of Hawaii. The U.S. EPA granted the requested registration for a one-year period beginning on 27 September 2001 with the stipulation that data were collected on potential non-target impacts and monitoring of soil and ground water contamination concerns. There has been limited use of caffeine for frog control since the granting of the EPA registration, and the Hawaii Department of Agriculture’s Pesticides Branch has had to be revise and simplify data collection requirements considered cumbersome to potential users. Reporting requirements,vertical tower planter relatively high cost in comparison to other commercially available compounds for the control of pest insects and weeds, and limited data on non-target effects have been concerns raised by potential users of caffeine for frog control. Efforts have been made by other researchers and managers to identify additional compounds for frog control. Anecdotal laboratory observations and field applications suggest that the spray application of a concentrated hydrated lime and water solution may be an additional tool for frog control. As hydrated lime and water solutions are being sprayed on vegetation versus being applied to the ground as a soil supplement, this specific use pattern may need to be registered with the U.S. Environmental Protection Agency. Standardized data collected with some level of scientific rigor showing efficacy is needed to support the legal application of this solution for frog control. Other research is being conducted to determine if natural or synthetic pyrethroid compounds could be used for frog control . In late 2000, several species of potted plants were successfully treated for frogs in test situations using short term drenching with hot water . Since the first documentation of the presence of Eleutherodactylus frogs in Hawaii, populations have spread quickly and local abundance of frogs has grown dramatically, particularly in sites with higher levels of rainfall . Though this issue has garnered significant attention in the local and national media, efforts to control the spread of the frog have been limited. Frogs have, and will continue to, affect the quality of life of citizens who live in infested sites. Citizen frustration with a lack of progress dealing with this situation in infested residential and commercial sites has been building and will continue to build. There is a realistic concern that Eleutherodactylus frogs will be accidentally transported from Hawaii to mainland states within the United States and to other countries in infested cargo. Eleutherodactylus frogs are frequently found in Hawaii at retail nurseries associated with large department and hardware store chains. Eleutherodactylus frogs have been reported in California and Connecticut and these individual frog captures have been attributed to shipments of infested Hawaiian plant products . Though Eleutherodactylus frogs may not become established in many mainland sites within the United States, Eleutherodactylus infesting shipments within Hawaii or infesting shipments going to other Pacific Islands, tropical, and sub-tropical destinations internationally is a realistic quarantine concern. There is a clear need to establish if Eleutherodactylus frogs within certified nurseries are a potential vector for plant nematode eggs , as particular species of plant nematodes are a significant quarantine issue for plant products being shipped from Hawaii to the State of California. It is worth asking the question “why hasn’t there been a significant coordinated effort mounted to deal with introduced Eleutherodactylus frogs in Hawaii?” A primary reason is the lack of techniques to control the spread of frogs; hot water drenching was not tested as a quarantine technique until late 2000, and U.S. EPA emergency registration of the spray application caffeine and water solution for local control was not obtained until late 2001. It would be very hard to enact a quarantine on a pest that impacts a major industry without the ability to control the pest in a simple, cost effective manner. Lack of funding, unclear legal jurisdiction, and bureaucratic inertia are other reasons why the spread of the frogs has continued until it is unrealistic, given current progress dealing with this issue, to believe that frogs will be eradicated from the island of Hawaii . There have been significant efforts by individual staff members of various state, county, federal and non-governmental entities and private citizens to try to stem the spread of invasive frogs and eliminate local populations. USDA APHIS Wildlife Services staff and Hawaii Department of Agriculture staff have written a plan to control and/or eradicate frogs in the State of Hawaii . Funding for this plan is the most realistic means to deal with this situation. It is clear that decisive action to eradicate an introduced pest when it has a limited distribution is far less expensive than eradicating or controlling the pest when it is broadly established. Unfortunately, the window of opportunity for effective action against the Eleutherodactylus frogs in Hawaii is becoming shorter while the problems associated with these pests will become greater as more sites become infested and local frog abundance increases in previously infested sites. Exposure of susceptible plant tissues to non-freezing temperatures below 10–12 ◦C induces a physiological disorder called Chilling Injury . There appears to be two phases in the development of CI. The first phase is initiated in the cold and could involve a change in membrane fluidity or enzyme activity .These secondary symptoms are predicated by primordial events initiated in the cold, and include a host of metabolic and physiological changes that include increased membrane permeability , increased respiration and ethylene production , uneven ripening, disease susceptibility, water soaking and surface pitting . A technique that could detect the earliest physiological changes associated with CI would foster a better understanding of the initial events leading to this disorder, and point to more effective ameliorative action. Magnetic resonance imaging is a nondestructive imaging technique, which is increasingly used to visualize and quantify fruit physiological response to endogenous or exogenous stimuli . MRI uses the magnetic properties of nuclei and their interactions with radio frequency and applied magnetic fields to produce an image . Variations in the chemical composition and integrity of cellular structures can change the movement of water within and among tissues. These changes can be detected as modifications in the relaxation times of the protons in water, which in turn alters the signals used to construct MR images .