John W. Armstrong

Potential for Areawide Integrated Management of Mediterranean Fruit Fly (Diptera: Tephritidae) with a Braconid Parasitoid and a Novel Bait Spray

Abstract The braconid wasp, Fopius arisanus (Sonan), a biological control agent for Mediterranean fruit fly, Ceratitis capitata (Wiedemann), was studied in coffee, Coffea arabica L. Fopius arisanus, comprised 79.3% of the total parasitoids (7,014) recovered from fruits collected at three small coffee farms. Data from seasonal host/parasitoid studies at a large coffee plantation also suggested that the most effective natural enemy of C. capitata in coffee may now reside in Hawaii. The original parasitoids introduced into Hawaii for C. capitata control (Diachasmimorpha tryoni (Cameron), Tetrastichus giffardianus Silvestri, and Dirhinus giffardii Silvestri) are now rare. Abundance of F. arisanus with respect to other parasitoids collected was influenced by elevation (274, 457, 610 m). Fopius arisanus was the dominant parasitoid at all three elevations, Diachasmimorpha longicaudata (Ashmead) occurred consistently, and T. giffardianus was abundant only at low elevation. The impacts on C. capitata and F. arisanus populations of bait sprays containing malathion, spinosad, or phloxine B applied to coffee were also evaluated. All three bait sprays suppressed C. capitata populations. Spinosad and phloxine B bait sprays appeared less harmful to the wasp than malathion. Fopius arisanus offers the potential for areawide management of C. capitata that includes biological control and integration with more environmentally safe chemical controls such as spinosad and phloxine B bait sprays.

TEMPERATURE-DEPENDENT DIELECTRIC PROPERTIES OF SELECTED SUBTROPICAL AND TROPICAL FRUITS AND ASSOCIATED INSECT PESTS

Knowledge of the dielectric properties of commodities and insect pests is important in developing thermal treatments for postharvest insect control based on radio frequency (RF) and microwave energy. The dielectric properties of six subtropical and tropical fruits along with four associated insect pests were measured between 1 and 1800 MHz using an open-ended coaxial-line probe technique and at temperatures between 20°C and 60°C. The dielectric loss factor of the fruits and the insects decreased with increasing frequency at constant temperatures. Especially over 10 to 300 MHz, the log of the dielectric loss factor decreased linearly with the log of increasing frequency. The loss factor of the fruits and the insects increased almost linearly with increasing temperature at 27.12 MHz radio frequency, but remained in a small range at 915 MHz microwave frequency. Both the dielectric constant and the loss factor were the highest in avocado fruit. The dielectric loss factors of insects were generally larger than that of the host fruit at all tested frequencies. But those values were within the same order of magnitude, suggesting that differential heating of insects in fresh fruits was unlikely to occur in RF and microwave systems. Direct measurement of electrical conductivity of fruit pulps can also provide a good estimation of the dielectric loss factor at 27.12 MHz. Matching the electrical conductivity of saline solution can be an effective and simple means to improve heating uniformity of the fruit when subjected to RF systems.

Thermal Death Kinetics of Mediterranean, Malaysian, Melon, and Oriental Fruit Fly (Diptera: Tephritidae) Eggs and Third Instars

ABSTRACT The late-aged egg and third-instar life stages of laboratory-reared Malaysian fruit fly, Bactrocera latifrons (Hendel); Mediterranean fruit fly, Ceratitis capitata (Wiedemann); melon fly, B. cucurbitae Coquillett; and oriental fruit fly, B. dorsalis (Hendel), (Diptera: Tephritidae); and the third instars of wild Mediterranean fruit fly were exposed to thermal treatments. A heating block system was used to determine the thermal death kinetics of the four fruit fly species. Treatments consisted of heating the fruit fly life stages to 44, 46, 48, and 50°C and holding for different times ranging from 0 to 120 min depending on the thermal mortality response and time required to obtain 100% mortality for each species and life stage. The 0.5-order kinetic model had the best fit to the survival ratio for all the treatment temperatures and was used to predict lethal times. The thermal death time (TDT) curves showed a tolerance order of Mediterranean fruit fly eggs ≤ third instars at 44, 46, and 50°C, third instars ≤ eggs at 48°C, and wild third instars < the laboratory-reared third instars. Comparison between Mediterranean fruit fly third instar thermotolerance from Hawaii and Israel showed that Israel Mediterranean fruit fly was more thermotolerant. A comparison of minimum treatment times at a given temperature required to obtain 100% mortality of laboratory-reared Malaysian, Mediterranean (Hawaii and Israel strains), melon, Mexican, and oriental fruit fly eggs or third instars and wild Mediterranean fruit fly (Hawaii strain) eggs or third instars showed that oriental fruit fly was the most thermotolerant among the third instars, and the difference in heat tolerance between third instars and eggs was negligible at 50°C.

Quarantine Security of Bananas at Harvest Maturity Against Mediterranean and Oriental Fruit Flies (Diptera: Tephritidae) in Hawaii

Abstract Culled bananas (dwarf ‘Brazilian’, ‘Grand Nain’, ‘Valery’, and ‘Williams’) sampled from packing houses on the islands of Hawaii, Kauai, Maui, Molokai, and Oahu identified specific “faults” that were at risk from oriental fruit fly, Bactrocera dorsalis (Hendel), infestation. Faults at risk included bunches with precociously ripened bananas, or bananas with tip rot, fused fingers, or damage that compromised skin integrity to permit fruit fly oviposition into fruit flesh. No Mediterranean fruit fly, Ceratitis capitata (Wiedemann), or melon fly, B. cucurbitae (Coquillett), infestations were found in culled banana samples. Field infestation tests indicated that mature green bananas were not susceptible to fruit fly infestation for up to 1 wk past the scheduled harvest date when attached to the plant or within 24 h after harvest. Recommendations for exporting mature green bananas from Hawaii without risk of fruit fly infestation are provided. The research reported herein resulted in a USDA-APHIS protocol for exporting mature green bananas from Hawaii.

Hot-Water Immersion Quarantine Treatment Against Mediterranean Fruit Fly and Oriental Fruit Fly (Diptera: Tephritidae) Eggs and Larvae in Litchi and Longan Fruit Exported from Hawaii

Abstract Immersion of litchi fruit in 49°C water for 20 min followed by hydrocooling in ambient (24 ± 4°C) temperature water for 20 min was tested as a quarantine treatment against potential infestations of Mediterranean fruit fly, Ceratitis capitata (Wiedemann); and oriental fruit fly, Bactrocera dorsalis Hendel, eggs or larvae in Hawaiian litchi, Litchi chinensis Sonnerat. The 49°C hot-water immersion of litchi provided probit 9 (99.9968% mortality with >95% confidence) quarantine security against eggs and first instars. There were no survivors from 15,000 each feeding and nonfeeding Mediterranean fruit fly or oriental fruit fly third instars immersed in a computer-controlled water bath that simulated the litchi seed-surface temperature profile during the 49°C hot-water immersion treatment. Litchi served as the model for longan, Dimocarpus longan Lour., a closely related fruit that is smaller and also has commercial potential for Hawaii. Modified fruit infestation and holding techniques used to obtain adequate estimated treated populations from poor host fruit, such as litchi and longan, are described. Data from these experiments were used to obtain approval of a hot-water immersion quarantine treatment against fruit flies for litchi and longan exported from Hawaii to the U.S. mainland.

Scouting Methods for Detection of Thrips (Thysanoptera: Thripidae) on Dendrobium Orchids in Hawaii

Abstract Thrips are important pests of dendrobium orchid flowers in Hawaii primarily because of the risk that exported flowers found to be infested will be rejected by quarantine inspectors. Using nondestructive sampling, the population dynamics of thrips infesting dendrobium orchids was monitored at two farms on the Island of Hawaii over a period of 1 yr. Average thrips populations varied between 0 and 1.0 thrips per spray (flower spike). At both sites, adult thrips almost always outnumbered nymphs. The western flower thrips, Frankliniella occidentalis (Pergande), was the predominant species found. Using randomization tests, adult thrips were found to be randomly distributed on orchid sprays. The binomial probability distribution was used to graphically describe the accuracy of scouting results as a function of sample size and the proportion of thrips-infested flowers. Efficient methods for counting adult thrips included nondestructive field counts (direct observation), flower shakes, and extractions via Berlese funnels.

Generic Phytosanitary Radiation Treatment for Tephritid Fruit Flies Provides Quarantine Security for Bactrocera latifrons (Diptera: Tephritidae)

ABSTRACT Bactrocera latifrons (Hendel) (Diptera: Tephritidae) is a quarantine pest of several solanaceous crops and tropical fruits that are treated using irradiation before export from Hawaii to the U.S. mainland. A dose of 150 Gy is approved as a generic irradiation treatment for tephritid fruit flies, but no confirmation of efficacy has been reported for B. latifrons. Dose response of B. latifrons was used to determine the most tolerant life stage and identify a dose that prevents adult emergence. Data indicated doses (plus 95% confidence limits) required to prevent adult emergence of 13.4 (10.0–29.6), 17.5 (14.4–24.8), and 88.1 (68.0–133.8) Gy for eggs, first instars and third instars, respectively. In large-scale confirmatory tests of the most radiotolerant life stage, a radiation dose of 150 Gy applied to B. latifrons late third instars in bell peppers (Capsicum annuum L.) resulted in no survival to the adult stage of 157,112 individuals, a treatment efficacy consistent with Probit 9-level mortality. The relative radiotolerance of melon fly Bactrocera Cucurbitae Coquillet, and B. latifrons also was tested using a diagnostic radiation dose of 30 Gy. In diet, a mean of 6.9% of irradiated B. cucurbitae third instars developed to the adult stage, whereas no B. latifrons third instars developed to adults. In papaya, Carica papaya L., fruit, a mean of 3.3% of irradiated B. cucurbitae third instars developed to the adult stage, whereas 0.5% B. latifrons third instars developed to adults. This report supports the use of a generic radiation dose of 150 Gy in quarantine scenarios to control tephritid fruit flies on fresh commodities.

Effects of Methyl Bromide Concentration, Fumigation Time, and Fumigation Temperature on Mediterranean and Oriental Fruit Fly (Diptera: Tephritidae) Egg and Larval Survival

Abstract The effects of methyl bromide (MB) concentration (16, 32, 48, or 64 g/m3), fumigation temperature (15, 20, 25, or 30°C), and fumigation time interactions on the survival of Mediterranean fruit fly, Ceratitis capitata (Wiedemann), and oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), eggs and first and third instars were recorded. Increasing the fumigation temperature from 15 to 20°C or from 20 to 25°C resulted in a significant reduction in fumigation time required for equivalent egg and larval mortalities at all studied MB concentrations; no further reductions in fumigation time resulted from increasing the temperature from 25 to 30°C. Conversely, increasing temperature and time allowed for a reduction in MB concentration to obtain equivalent mortality. Thus, the optimum fumigation temperature for Mediterranean and oriental fruit fly eggs and larvae was 25°C. Reducing MB concentrations required for phytosanitary fumigations would save time and expense, and reduce the amount of MB released into the atmosphere during aeration. Mediterranean fruit fly was as or more tolerant to MB than oriental fruit fly in MB tolerance for eggs and first instars. The egg stage was generally more tolerant to MB regardless of concentration. However, Mediterranean fruit fly eggs showed similar tolerance to first instars at 25°C for the three highest concentrations and to third instars at 25 and 30°C for the highest concentration, with no significant difference between them. Therefore, eggs alone can be used to obtain MB fumigation efficacy and quarantine security data at fumigation temperatures between 15 and 30°C for Mediterranean and oriental fruit fly.

Host status of blueberry to invasive tephritid fruit flies in Hawaii.

ABSTRACT Forced infestation studies were conducted to determine whether northern or southern highbush blueberries, Vaccinium corymbosum L., are hosts for the invasive tephritid fruit flies in Hawaii. Fruit were exposed to gravid female flies of Bactrocera dorsalis Hendel (oriental fruit fly), Ceratitis capitata (Wiedemann) (Mediterranean fruit fly), or Bactrocera cucurbitae Coquilet (melon fly) in screen cages outdoors for 6 h and then held on sand in the laboratory for 2 wk for pupal and adult emergence. The number of puparia, number of puparia per gram, and percentage of adult emergence on ‘Bluecrop’ blueberry were significantly higher for B. dorsalis and C. capitata than B. cucurbitae; B. dorsalis, C. capitata, and B. cucurbitae produced an average of 1.06, 0.60, and 0.09 pupae per g fruit and had 50.8, 54.1, and 12.7% adult emergence, respectively. ‘Berkeley’ blueberries produced an average of only 0.06, 0.02, and 0.0 pupae per g fruit for B. dorsalis, C. capitata, and B. cucurbitae, respectively. Similarly, six blueberry cultivars were harvested weekly for 10 wk, exposed to Bactrocera latifrons (Hendel) in cages, and held for pupal and adult emergence on either sand or artificial diet. In total, 2,677 blueberries were exposed to 2,681 B. latifrons and held on sand, and no pupariation or adult emergence was observed. Small numbers of B. latifrons puparia and adults emerged from the artificial diet treatment in all cultivars. Results from rearing on sand and diet indicate that blueberry is an acceptable oviposition host for B. latifrons but not an adequate developmental host. These data suggest blueberry is potentially a good host for B. dorsalis and C. capitata, and an adequate host for Bactrocera cucurbitae, but that there may be significant variation in resistance among cultivars. Blueberry seems to be a nonhost for B. latifrons.