Guy J. Hallman

Ionizing Irradiation Quarantine Treatment Against Oriental Fruit Moth (Lepidoptera: Tortricidae) in Ambient and Hypoxic Atmospheres

Abstract Oriental fruit moth, Grapholita molesta (Busck), is a pest of many rosaceous temperate fruits, including pomes, Malus spp., and stone fruits, Prunus spp., in much of the world. However, some areas are free of the pest, and shipments of fruit hosts from infested to noninfested areas may be regulated. Current quarantine treatments for oriental fruit moth include methyl bromide fumigation and cold storage for several weeks. Methyl bromide use is being restricted because it is a stratospheric ozone-depleting substance, and alternatives are sought. Cold is not tolerated by many hosts of oriental fruit moth. The objective of this research was to develop irradiation quarantine treatments against the pest under ambient and hypoxic storage conditions because some hosts of oriental fruit moth are stored in hypoxic atmospheres, and hypoxia is known to lessen the effects of irradiation. In ambient atmospheres, no adults emerged from 58,779 fifth instars (the most radiotolerant stage present in fruit) irradiated with a target dose of 200 Gy (195–232 Gy measured). In atmospheres flushed with nitrogen, 5.3% of adults emerged from 44,050 fifth instars irradiated with a target dose of 200 Gy (194–230 Gy measured), but they died at a faster rate than control adults and without laying eggs. A dose of 232 Gy (the maximum recorded when 200 Gy was targeted) is recommended to disinfest any fruit of oriental fruit moth under ambient and hypoxic atmospheres.

Ionizing radiation quarantine treatments

A irradiacao e um tratamento de desinfestacao em quarentena viavel que tem sido estudado nos ultimos 40 anos, embora tenha tido pouco uso comercial. Ha dois obstaculos principais a aplicacao comercial da irradiacao: 1) o fato que os insetos nao sao mortos imediatamente; e 2) a oposicao de consumidores a irradiacao, a qual tem sido aceita de certa forma, mas permanecendo o impedimento ao uso comercial em grande escala em funcao de protocolos de aprovacao por agencias regulamentadoras de paises importadores. O Departamento de Agricultura dos Estados Unidos tem tomado os primeiros passos em permitir o movimento de frutas do Havai ao resto do pais que passaram por tratamento de irradiacao. As medidas da eficacia dos tratamentos de desinfestacao por irradiacao devem incluir prevencao da emergencia de adultos, quando apenas ovos e larvas estao presentes, ou esterilidade quando as pupas ou adultos estao presentes. Isto pode ser conseguido pelo uso de doses baixas as quais sao toleradas por muitas frutas para pragas como moscas tefritideas, besouros curculionideos, e alguns Homoptera. Lepidoptera necessitam de doses moderadamente altas. O estagio mais tolerante a radiacao e usualmente o mais avancado em seu desenvolvimento. As femeas de insetos sao mais suscetiveis a radiacao que induz esterilidade; alguns acaros femeas (Tetranychidae) sao mais tolerantes que os machos. Pesquisas futuras devem se concentrar em confirmar as doses dos tratamentos quarentenarios para outras especies de insetos (isto so tem sido feito para varios tefritideos); determinar doses para alguns grupos importantes de organismos para os quais pesquisas insuficientes foram conduzidas (Mollusca, Coccoidea, Thysanoptera, Eriophyidae), e identificar e quantificar fatores de radiacao modificantes.

Ionizing Radiation as a Phytosanitary Treatment Against Fruit Flies (Diptera: Tephritidae): Efficacy in Naturally Versus Artificially Infested Fruit

ABSTRACT Some phytosanitary irradiation treatment research against tephritid fruit flies (Diptera: Tephritidae) has used artificially infested fruit with the unstated and untested assumption that the method adequately simulated a natural situation. We compare grapefruit, Citrus paradisi Macfayden, naturally infested by Mexican fruit fly, Anastrepha ludens (Loew), via oviposition until larvae reached the late third instar versus insertion of diet-reared third instars into holes made in grapefruits 24 h before irradiation; the latter technique has been used in other studies. Both infestation techniques resulted in statistically indistinguishable results, indicating that insertion of diet-reared third instar Mexican fruit fly into holes bored into grapefruit and subsequently sealed 24 h before irradiation would adequately represent natural infestation and could be used to develop a radiation phytosanitary treatment of the insect in grapefruit when prevention of adult emergence is used as the measure of efficacy. Nevertheless, it may not be advisable to extend this conclusion to other fruit fly/fruit combinations without doing appropriate comparison studies. Dissection of puparia from nonirradiated control insects that failed to emerge as adults showed a relatively even distribution of mortality among the developmental stages within the puparium. In contrast, dissection of puparia from irradiated third instars that did not emerge as adults revealed a sharp attenuation in development from cryptocephalic to phanerocephalic pupae demonstrating this transition to be the developmental step most affected by radiation.

Evaluation of the Efficacy of the Methyl Bromide Fumigation Schedule Against Mexican Fruit Fly (Diptera: Tephritidae) in Citrus Fruit

ABSTRACT Methyl bromide fumigation is widely used as a phytosanitary treatment. Mexican fruit fly, Anastrepha ludens (Loew) (Diptera: Tephritidae), is a quarantine pest of several fruit, including citrus (Citrus spp.), exported from Texas, Mexico, and Central America. Recently, live larvae have been found with supposedly correctly fumigated citrus fruit. This research investigates the efficacy of the previously approved U.S. Department of Agriculture—Animal and Plant Health Inspection Service treatment schedule: 40 g/m3 methyl bromide at 21–29.4°C for 2 h. Tolerance of A. ludens to methyl bromide in descending order when fumigated in grapefruit (Citrus × paradisi Macfad.) is third instar > second instar > first instar > egg. Two infestation techniques were compared: insertion into fruit of third instars reared in diet and oviposition by adult A. ludens into fruit and development to the third instar. Inserted larvae were statistically more likely to survive fumigation than oviposited larvae. When fruit were held at ambient temperature, 0.23 ± 0.12% of larvae were still observed to be moving 4 d postfumigation. Temperatures between 21.9 and 27.2°C were positively related to efficacy measured as larvae moving 24 h after fumigation, pupariation, and adult emergence. Coating grapefruit with Pearl Lustr 2–3 h before fumigation did not significantly affect the proportion of third instars moving 24 h after fumigation, pupariating, or emerging as adults. In conclusion, fumigation with 40 g/m3 methyl bromide for 2 h at fruit temperatures >26.7°C is not found to be inefficacious for A. ludens. Although a few larvae may be found moving >24 h postfumigation, they do not pupariate.

Radiation-Induced Pathology in the Metamorphosis of the Mexican Fruit Fly (Diptera: Tephritidae)

Late third instars of the Mexican fruit fly, Anastrepha ludens (Loew), exposed to ≥20 Gy of gamma radiation are able to pupariate normally but do not emerge as adults. Contrary to expectations, the...

Phytosanitary Cold Treatment for Oranges Infested With Bactrocera zonata (Diptera: Tephritidae)

ABSTRACT The peach fruit fly, Bactrocera zonata (Saunders), attacks a wide range of tree fruits in countries from Egypt to Vietnam and is occasionally trapped in the United States. Phytosanitary treatments may be required to export fruit hosts of this insect from countries where it is endemic to countries where it is absent but could become established. This research describes comparative studies to determine if B. zonata could be phytosanitarily controlled by cold treatment schedules existing for Ceratitis capitata (Wiedemann) and Anastrepha ludens (Loew), and the development of a cold treatment of 18 d at 1.7°C for B. zonata infesting oranges. Fruit were infested by puncturing holes in oranges and allowing tephritids to oviposit in the holes. The treatments were initiated when the larvae reached late third instar because previous research had shown that stage to be the most cold-tolerant. B. zonata was not found to be confidently as or less cold tolerant than C. capitata; therefore, treatment schedules for the latter are not supported by this research for the former. B. zonata was found to be more susceptible to 1.7°C than A. ludens; therefore, the use of treatment schedules for A. ludens is supported by this research for B. zonata. However, the treatment for A. ludens requires 22 d. A shorter treatment was verified for B. zonata when 36,820 third instars reared from the eggs in oranges were stored at 1.7°C for 18 d with no larvae moving on examination 24 h after removal from the cold treatment chamber.

Physical Control of Insect Pests

Publisher Summary Physical control is one of the main approaches to crop protection against insects, the others being chemical, biological, and cultural. This chapter focuses on the physical control. Physical control methods in crop protection comprise techniques that limit pest access to the crop/commodity, induce behavioral changes, or cause direct pest damage/death. The primary action may have a direct impact, for example, when insects are killed immediately by mechanical shock. In other instances, the desired effect is attained through stress responses.The different methods of physical control used against crop pests have some common characteristics. Passive physical control measures have long-lasting effects, although they may require periodic renewal such as trap replacement or maintenance, i.e., physical barriers, mulching. Present methods of physical control are more labor-intensive and often time-consuming. This drawback is one of the main reasons physical control techniques have had little success in penetrating the field-crop market. Given these circumstances, crops with a high profit margin per hectare represent an obvious market for physical control methods. From the viewpoint of implementation, physical methods compare favorably with biological methods, which often entail labor-intensive field observations and may be difficult to apply in a field-crop setting.

Insect Thermotolerance Comparing Host Infestation Methods: Anastrepha ludens (Diptera: Tephritidae) Reared in Grapefruit or Diet

ABSTRACT Research on insect control should be conducted in a manner that mimics as closely as is feasible its commercial application in all of its practicably conceivable forms. When significant deviations from commercial application are used in research, the effect of the deviations on efficacy should be evaluated. Pest control techniques are sometimes based on research that used untested assumptions about variables that might affect efficacy. For example, some phytosanitary treatments are based on research done with diet-reared larvae inserted into holes bored in fruits, although the effect of this manipulation has not been evaluated. This research compares this type of infestation of grapefruit with Mexican fruit fly, Anastrepha ludens (Loew), third instars with a more natural infestation technique whereby females were allowed to oviposit on picked grapefruit in laboratory cages and third instars were reared inside the fruit. Although the results did not show statistically significant differences between infestation techniques, tendencies in the data caution against researchers making assumptions about efficacy without testing them when experimental techniques stray from more natural situations for which the research is designed.

Potential for Hypobaric Storage as a Phytosanitary Treatment: Mortality of Rhagoletis pomonella (Diptera: Tephritidae) in Apples and Effects on Fruit Quality

ABSTRACT The efficacy of low-oxygen atmospheres using low pressure, referred to as hypobaric conditions, to kill egg and third-instar Rhagoletis pomonella (Walsh) in apples was investigated. Infested apples were exposed to 3.33 and 6.67 kPa in glass jars at 25 and 30°C for times ranging from 3 to 120 h. Probit analyses and lethal dose ratio tests were performed to determine differences in lethal time values. Eggs were more tolerant of low pressure compared with third-instar R. pomonella. Mortality of eggs and larvae increased with increase in time of exposure to low pressure and temperature. Lower pressures increased percent mortality of eggs, but these values were not significantly different at the pressures tested in this investigation. The LT99 for R. pomonella eggs at 3.33 kPa was 105.98 and 51.46 h, respectively, at 25 and 30°C, which was a significant effect of the higher temperature on egg mortality. Investigation into consumer acceptance of low-pressure-treated apples was done with ‘Red Delicious’ and ‘Golden Delicious’. Apples exposed to 3.33 kPa at 25 and 30°C for 3 and 5 d were stored at 1°C for 2 wk and presented to a sensory panel for evaluation. The panelists rated treated apples with untreated controls for external and internal appearance and taste. Golden Delicious apples were unaffected for all three sensory factors across both temperatures and exposure times. Although taste was unaffected for Red Delicious, the internal and external appearances deteriorated. Use of low pressure for disinfestation and preservation of apples is a potential nonchemical alternative to chemical fumigants such as methyl bromide and phosphine.

Efficacy of Delayed Atmospheric Modification in a Heat/Modified Atmosphere Phytosanitary Treatment

ABSTRACT The combination of heat and low levels of oxygen increases mortality to insects infesting fruit compared with either heat or low oxygen alone. This combination treatment shows promise to disinfest commodities of quarantine pests. Heated air/modified atmosphere treatments employ the modified atmosphere (e.g., low oxygen) during the entire treatment interval. There is a positive relationship between temperature and efficacy of heat/modified atmosphere treatments. Efficacy of delaying atmospheric modification in a heat/modified atmosphere treatment was studied with the Mexican fruit fly, Anastrepha ludens (Loew) (Diptera: Tephritidae), a quarantine pest of citrus and other fruit in Mexico, Central America, and southern Texas. Larvae were subjected to heat/low oxygen treatments in vitro as well as in grapefruit, Citrus paradisi Macfayden. The relationship between time delay of the modified atmosphere and estimated time required to kill 99% of Mexican fruit fly third instars was not linear, which would indicate an additive relationship, but followed a sigmoid relationship. When infested grapefruit were heated with 47°C air in three atmospheric regimes: 1) air; 2) N2 at 99 kPa plus O2 at 1 kPa; or 3) air for 55 min then N2 at 99 kPa plus O2 at 1 kPa for the remainder of the treatment, estimated 99% prevention of pupariation was 157, 127, and 141 min, respectively.