Arnold H. Hara

Population Densities of the Coquí, Eleutherodactylus coqui (Anura: Leptodactylidae) in Newly Invaded Hawaii and in Native Puerto Rico

Abstract Eleutherodactylus coqui was accidentally introduced to east Hawaii Island in the late 1980s and has since become established as scattered populations across the island. Mark-recapture study plots indicate that population size remains small for the first year after initial colonization. Plots in heavily forested areas where the Coquí has become well-established yield population estimates of frog density three times the estimates reported from native populations in Puerto Rico. Surveys of the Hilo area using sound pressure level meters found many loud chorusing populations producing sound pressure levels up to 73 dB suggesting that this frog will achieve high densities through broad areas of Hawaiian forest and towns. We suggest that the apparent lack of native or exotic predators in Hawaii and abundance of suitable retreat sites contribute to achievement of unusually high population densities of E. coqui in Hawaii compared with Puerto Rico.

Differential susceptibility of lepidopterous pupae to infection by the nematode Neoaplectana carpocapsae.

Prepupae of Galleria mellonella, Spodoptera exigua, and Pseudaletia unipuncta were highly susceptible to infection by the nematode Neoaplectana carpocapsae and its associated bacterium, Xenorhabdus nematophilus. On the other hand, pupae of the three species were significantly different in their susceptibility to the nematode. G. mellonella pupae were highly susceptible (100% mortality), S. exigua pupae were moderately susceptible (ca. 75% mortality), and P. unipuncta pupae were least susceptible (ca. 54% mortality). In the latter two species, many pupae died without any nematode development, but the typical signs associated with a nematode infection were evident. Age of the pupae and increasing the dosage of the nematode did not significantly affect mortality of S. exigua or P. unipuncta.

Parasite loss and introduced species: a comparison of the parasites of the Puerto Rican tree frog, (Eleutherodactylus coqui), in its native and introduced ranges

The Puerto Rican frog, Eleutherodactylus coqui has invaded Hawaii and reached densities far exceeding those in their native range. One possible explanation for the success of E. coqui in its introduced range is that it lost its co-evolved parasites in the process of the invasion. We compared the parasites of E. coqui in its native versus introduced range. We collected parasite data on 160 individual coqui frogs collected during January-April 2006 from eight populations in Puerto Rico and Hawaii. Puerto Rican coqui frogs had higher species richness of parasites than Hawaiian coqui frogs. Parasite prevalence and intensity were significantly higher in Hawaii, however this was likely a product of the life history of the dominant parasite and its minimal harm to the host. This suggests that the scarcity of parasites may be a factor contributing to the success of Eleutherodactylus coqui in Hawaii.

Molluscicides and mechanical barriers against slugs, Vaginula plebeia Fischer and Veronicella cubensis (Pfeiffer) (Stylommatophora: Veronicellidae).

Thirteen molluscicides containing metaldehyde, three molluscicides containing metaldehyde plus carbaryl, one molluscicide containing metaldehyde plus methiocarb and one molluscicide containing methiocarb alone were tested for efficacy against the brown slug, Vaginula plebeia Fischer, and the two-striped slug, Veronicella cubensis (Pfeiffer). With the exception of Corrys Liquid Slug, Snail and Insect Killer against V. plebeia, all tested molluscicides caused significant mortalities against both species. Selected molluscicides were further evaluated for persistence under simulated rainfall; Deadline One Last Meal for Slugs and Snails, Deadline 40, Deadline Bullets and Slug and Snail AG Pelleted Bait, all of which contain metaldehyde as the active ingredient, consistently produced high mean percentage mortalities against both species. Efficacy of certain molluscicides decreased steadily with time, whereas efficacy of other molluscicides increased initially before declining. Mold grew on the majority of molluscicides after application. Liquid paste and liquid formulations were more resistant to mold development than pelleted, granule or coated granule formulations. In a separate study, physical barriers composed of copper or fiberglass screens repelled both slug species.

Hot-air induced thermotolerance of red ginger flowers and mealybugs to postharvest hot-water immersion.

Abstract Vase life of red ginger flowers, Alpinia purpurata (Vieill.) K. Schume, subjected to postharvest hot-air conditioning (40°C, 64% r.h.) for 2 h prior to hot-water immersion (49°C for 12 min) equaled or exceeded the vase life of red ginger treated in hot-water immersion only and control flowers in 96% of the trials conducted during a one year period. Reduced flower quality (marketability) (13% of trials) and reduced vase life (4% of trials) from hot-air and hot water treatments occurred in months with high rainfall (≥58 cm month−1) or drought (≤5 cm month−1). Flowers conditioned in hot air before hot-water immersion tolerated 49°C water for up to 13 min, exceeding a proposed 12 min treatment time with no significant loss in vase life or marketability. No apparent benefits were observed for conditioning flowers longer than 2 h in hot air. Hot-air conditioning prior to hot-water immersion increased mealybug survival by 0.4–40%.

Postharvest heat treatment of red ginger flowers as a possible alternative to chemical insecticidal dip

Abstract A postharvest treatment in hot water at 49 °C for 12 to 15 min eliminated > 95% of ants, banana aphids and mealybugs infesting red ginger flowers, Alpinia purpurata (Vieill.) K. Schum. In a ‘systems-approach’ to quarantine security, preharvest chlorpyrifos applications combined with either a postharvest hot-water immersion at 49 °C for 12 min or 5-min insecticidal dip in a combination of fluvalinate 2.0 flowable (F) and insecticidal soap eliminated all pests, including aphids, mealybugs, thrips, soft scales, and ants. Phytotoxicity resulting from hot-water treatment was characterized by bract necrosis and shortened vase life. Flowers were more susceptible to heat injury if harvested during periods of high rainfall. Conditioning flowers in hot air at 39 °C for 2 h before hot-water treatment eliminated phytotoxicity.

A review of postharvest disinfestation of cut flowers and foliage with special reference to tropicals

Abstract The commerce of floricultural commodities is very important to the economy of the producing locations. To protect the agriculture of consumer countries, import regulations require that the product be free of insects. Successful disinfestation eliminates the pest without damage to the commodity. Current postharvest approaches to disinfestation are hand removal, irradiation, fumigation, insecticidal dips, temperature treatments, and the use of biological control agents. In this review, the advantages, disadvantages and status of each method are discussed with examples provided.

Irradiation as a possible quarantine treatment for green scale Coccus viridis (Green) (Homoptera: Coccidae)

Abstract The green scale, Coccus viridis (Green), can be controlled effectively by irradiation at a minimum absorbed dose of 250 Gy. Reproductive capacity of irradiated gravid adults was reduced greatly and any resulting offspring were not able to develop beyond the crawler stage. Development of nymphs to the adult stage was not arrested completely nor was development of immature stages eliminated, but all survivors were sterile. Generally, higher doses of irradiation (≥400 Gy) caused faster kill of all life stages than lower doses (250 Gy). At 250 Gy, there was prolonged survival of green scale, with 8.8–11.4% of nymphs and up to 8.8% of crawlers alive 3 months after irradiation; 100% mortality of the most resistant adult stage took longer than 20 weeks post-treatment. An absorbed dose of 500, 750 or 1000 Gy caused 100% mortality in all stages of the green scale by 7, 6, and 3 weeks post-treatment, respectively. Adults appeared to be more resistant to treatments ≥500 Gy. Irradiation doses ≥500 Gy killed crawlers by 3–5 weeks post-treatment and rendered nymphs and adult green scale sterile until their eventual death. When irradiated at 250 Gy, survival of non-infested gardenia plants and green scale-infested gardenia and coffee plants were reduced by 69, 56, and 18%, respectively, as compared with non-irradiated plants. Nonreversible, sublethal phytotoxicity included tip browning of young leaves, absence of new leaf growth in gardenia plants, failure to form new leaves in coffee plants, and eventual plant death. While irradiation at 250 Gy is sufficient to provide quarantine security for crops that are hosts of green scale, product quality will need to be evaluated on a case-by-case basis since certain commodities, such as gardenia seedlings, have sustained phytotoxic effects.

Hot water as a potential disinfestation treatment for an invasive anuran amphibian, the coqui frog, Eleutherodactylus coqui Thomas (Leptodactylidae), on potted plants

The Puerto Rican tree frog, or coqui frog, Eleutherodactylus coqui Thomas (Anura: Leptodactylidae), accidentally introduced in Hawai‘i in 1988, has negatively affected Hawai‘is

Insecticidal dips for disinfesting commercial tropical cut flowers and foliage

105 million floriculture industry as it acquired quarantine status in Hawai‘i, California and Guam. An effective, non-phytotoxic quarantine treatment for E. coqui on potted plants is urgently required. Chemicals available against E. coqui in Hawai‘i, citric acid and hydrated lime (calcium hydroxide), can affect plant appearance, are corrosive, and can be hazardous to human health. The potential of hot water, effective against many arthropods, to disinfest potted plants of E. coqui, was examined. In in vitro trials, no eggs hatched after 2 and 5 min at 43 and 45°C, respectively; 100% mortality of adults was achieved by 5 and 1 min at 39 and 45°C, respectively. Most potted plants tested tolerated 45–49°C water for 5-, 10-, or 15-min durations, with a few exceptions where new leaves and flowers were less heat-tolerant. Hot water is an effective disinfestation treatment for E. coqui on most commercially important potted plants.