Phytosanitary irradiation of Liriomyza trifolii (Diptera: Agromyzidae)

Agromyzid leafminers are economic and quarantine pests of a variety of vegetables, flowers, and ornamental foliage. Methyl bromide fumigation is often used as a phytosanitary treatment when quarantined agromyzids are found in shipped commodities; alternative treatments are sought. Ionizing radiation is a viable alternative that is increasing in use worldwide. A dose of 400 Gy is accepted by USDA-APHIS for all insects (except Lepidoptera pupae and adults) on all commodities. Efforts to lower this dose and make it acceptable to other countries involve determining radiotolerance of families of major quarantine pests. Agromyzidae is one such family for which no useful information on radiotolerance exists. This research sought to determine the dose required to control a major agromyzid pest, Liriomyza trifolii (Burgess) and was performed on L. trifolii collected in Weslaco, TX, reared on Phaseolus vulgaris L. and Capsicum annuum L. and irradiated in the late puparial stage. The measure of efficacy was prevention of F1 mine formation. Puparia collected from Gossypium hirsutum L. and reared on P. vulgaris were more radiotolerant than those collected and reared on C. annuum. A dose of 214 Gy may prevent F1 mine formation of L. trifolii. This research used a variation of probit analysis where the direct response of the treated individual is not measured, but the response of the F1 generation is. This type of analysis is useful in phytosanitary irradiation research where the measure of efficacy often involves a response of the F1 generation.     

Ionizing irradiation of adults of Angoumois grain moth (Lepidoptera: Gelechiidae) and Indianmeal moth (Lepidoptera: Pyralidae) to prevent reproduction, and implications for a generic irradiation treatment for insects

Ionizing irradiation is used as a phytosanitary treatment against quarantine pests. A generic treatment of 400 Gy has been approved for commodities entering the United States against all insects except pupae and adults of Lepidoptera because some literature citations indicate that a few insects, namely, the Angoumois grain moth, Sitotroga cerealella (Olivier) (Lepidoptera: Gelechiidae), and the Indianmeal moth, Plodia interpunctella (Hübner) (Lepidoptera: Pyralidae), are not completely controlled at that dose. Radiotolerance in insects increases as the insects develop, so the minimum absorbed dose to prevent F1 egg hatch for these two species when irradiated as adults was examined. Also, because hypoxia is known to increase radiotolerance in insects, Angoumois grain moth radiotolerance was tested in a hypoxic atmosphere. A dose range of 336-388 Gy prevented F1 egg hatch from a total of 22,083 adult Indianmeal moths. Dose ranges of 443-505 and 590-674 Gy, respectively, prevented F1 egg hatch from a total of 15,264 and 13,677 adult Angoumois grain moths irradiated in ambient and hypoxic atmospheres. A generic dose of 600 Gy for all insects in ambient atmospheres might be efficacious, although many fresh commodities may not tolerate it when applied on a commercial scale.     

Development of a model system for rapid assessment of insect mortality in heated controlled atmosphere quarantine treatments

The development of postharvest quarantine treatments can be both expensive and time-consuming. It is necessary to determine the species and stage of the pest most tolerant to the treatment, if more than one species is the target of the treatment. Initial laboratory studies often include infesting the commodity with various egg and larval stages of the pest and performing treatments and evaluations of the fruit. In collaboration with others, I have previously developed combination high temperature under controlled atmosphere treatments against two quarantine pests in apples (Malus spp.) and peaches and nectarines (both Prunus spp.). I decided to develop an artificial system that can be used for these initial tests without the need for infesting large quantities of the fruit. I tested the system on the immature stages of the pests under regular air and controlled atmospheres by using the controlled atmosphere water bath system. This system can be used for rapid assessment of the most tolerant stage and species of a pest to a combination heat and controlled atmosphere treatment without the expense of infesting, treating, and evaluating the commodity.     

Potential increase in fruit fly (Diptera: Tephritidae) interceptions using ionizing irradiation phytosanitary treatments

Irradiation postharvest phytosanitary treatments are used increasingly and show further promise because of advantages compared with other treatments. Its chief disadvantage is that, unlike all other commercially used treatments, it does not provide acute mortality, although it prevents insects from completing development or reproducing. The objective of this research was to determine to what extent irradiated egg and early instars of tephritids would develop to later instars that could be found by phytosanitary inspectors or consumers. Mexican fruit fly, Anastrepha ludens (Loew), eggs and first instars in grapefruit, Citrus paradisi Macfayden, were irradiated with 70-250 Gy and held at approximately equal to 27 degrees C until third instars completed development. The accepted minimum absorbed phytosanitary dose for this pest is 70 Gy, although higher doses may be applied under commercial conditions. The more developed a fruit fly before it was irradiated, the greater the proportion that survived to the third instar. Also, dose was inversely related to developmental success, e.g., a mean of approximately 65 and 35%, respectively, of late first instars reached the third instar when irradiated with 70 and 250 Gy. Of those, 65.1 and 23.4%, respectively, pupariated, although no adults emerged. Irradiation may result in a greater frequency of live (albeit incapable of resulting in an infestation) larvae being found than would be expected compared with other treatments that provide acute mortality. The regulatory community should be aware of this and the fact that it does not increase the risk of irradiation phytosanitary treatments resulting in an infestation of quarantine pests.     

我国进境植物检疫性有害生物检疫鉴定标准浅析

进境检疫性有害生物的检疫鉴定标准是检疫鉴定工作的重要参考依据,目前我国进境植物检疫性有害生物共计446种(属),并发布了479项相关检疫鉴定标准,覆盖了我国进境植物检疫性有害生物名录中的423种(属)有害生物。为了解我国检疫鉴定标准的制定发展现状、发现其中问题并及时改进,本文对现有检疫鉴定标准进行统计分析,并对其进行特点总结和问题剖析。目前我国检疫鉴定标准制定与修订工作快速发展,呈现不断更新、多方合作、方法多样化、综合化等特点,但我国检疫鉴定标准在完整性、现势性、规范性、创新性、体系规划性等方面仍存在一定的问题。因此,系统完善检疫鉴定标准,综合发展先进鉴定技术,加快建设标准化体系,有助于植物检疫工作的长足发展,对维护我国经济贸易及生物安全具有重要意义。     

Irradiation as a phytosanitary treatment for white peach scale (Homoptera: Diaspididae)

Irradiation was examined as a potential phytosanitary treatment to control white peach scale, Pseudaulacaspis pentagona (Targioni-Tozzetti) (Homoptera: Diaspididae), a serious quarantine pest of papaya, Carica papaya L., in Hawaii. Dose-response tests were conducted with second-stage nymphs, adult females without eggs, and adult females with eggs at a series of irradiation doses between 60 and 150 Gy to determine the most tolerant stage. The adult female with eggs was the most tolerant stage. In large-scale validation tests 35,424 adult female scales with and without eggs irradiated at a dose of 150 Gy produced no F1 generation adults with eggs. Irradiation treatment with a minimum absorbed dose of 150 Gy should provide quarantine security for white peach scale on exported papaya and other commodities.     

Irradiation as a phytosanitary treatment for Aspidiotus destructor (Homoptera: Diaspididae)

Coconut scale, Aspidiotus destructor Signoret (Homoptera: Diaspididae), is a quarantine pest of banana (Musa spp.) and many tropical crops. Irradiation was examined as a potential phytosanitary treatment to control coconut scale. Dose-response tests were conducted with second-stage nymphs, adult females without eggs, and adult females with eggs at a series of irradiation doses between 60 and 200 Gy to determine the most tolerant stage. The adult female with eggs was the most tolerant stage. In large-scale validation tests and dose-response tests, a total of 32,716 adult female scales with eggs irradiated with doses between 100 and 150 Gy produced no F1 adults with eggs. Irradiation treatment with a minimum absorbed dose of 150 Gy should provide quarantine security for coconut scale on exported commodities.     

Acute exposure to low-dose radiation disrupts reproduction and shortens survival of Wasmannia auropunctata (Hymenoptera: Formicidae) queens

Irradiation is a postharvest quarantine treatment option to control ants and other hitchhiker pests on fresh horticultural products exported from Hawaii. The radiotolerance of the invasive little fire ant, Wasmannia auropunctata (Roger) (Hymenoptera: Formicidae: Myrmicinae), was studied to determine a dose sufficient for its control. Queens from each of five laboratory microcolonies started from five geographic locations in Argentina were irradiated at 20, 50, 70, or 100 Gy or left untreated as controls and then followed for 13 wk to observe colony growth. In general, queen survivorship, and the number of eggs, larvae, and pupae observed in the microcolonies decreased with increasing irradiation dose. In the 50-, 70-, and 100-Gy treatments, the number of eggs observed was reduced by 68, 66, and 76%, respectively, compared with untreated control microcolonies. The number of larvae in the 50-, 70-, and, 100-Gy treatments was reduced by 99.6%, and only one pupa was observed in the 50-Gy treatment and none in the 70- and 100-Gy treatments during the 13-wk experiment. Queens in the 100-Gy treatment had significantly reduced longevity compared with queens in the other treatments. Radiation doses > or = 70 Gy stopped reproduction in W. auropunctata queens and should be sufficient as a phytosanitary treatment. Information from additional invasive ants in Myrmicinae and other subfamilies is needed before recommending a generic irradiation treatment for ants.     

Comparison of in vitro heat and cold tolerances of the new invasive species Bactrocera invadens (Diptera: Tephritidae) with three known tephritids

Bactrocera invadens Drew, Tsuruta & White (Diptera: Tephritidae) is spreading throughout central Africa attacking a variety of fruit; quarantines are placed on fruit from this region that are considered hosts. The only phytosanitary treatment that is commercially available is an ionizing irradiation treatment for all Tephritidae at 150 Gy. The development of other treatments, such as heat, cold, or fumigation, usually requires testing tens of thousands of insects at a dose that provides efficacy and may take several years. It may be possible to shorten the time required to develop treatments by comparing tolerance of a new quarantine pest to tolerances of pests with similar behaviors and modes of infestation for which treatment schedules are available. Cold and heat tolerance ofB. invadens was compared with tolerance of Anastrepha ludens (Loew), Bactrocera dorsalis (Hendel), and Ceratitis capitata (Wiedemann) in vitro. Third-instar B. invadens was no more cold tolerant than the other species when treated in diet at 0.94 +/- 0.65 degrees C and no more heat tolerant than C. capitata when immersed in vials in water at 44.7 +/- 0.1 degrees C. The data at 0.94 +/- 0.65 degrees C was used to include B. invadens in a USDA cold treatment schedule for citrus fruit from Africa so that trade would not be interrupted while protecting U.S. agriculture from this invasive pest.     

Factors affecting ionizing radiation phytosanitary treatments, and implications for research and generic treatments

Phytosanitary irradiation (PI) treatments are promising measures to overcome quarantine barriers to trade and are currently used in several countries. Although PI has advantages compared with other treatments one disadvantage bedevils research, approval, and application: organisms may remain alive after importation. Although this does not preclude their use as a phytosanitary treatment, it does leave the treatment without an independent verification of efficacy and places a greater burden for assuring quarantine security on the research supporting the treatment. This article analyses several factors that have been hypothesized to affect PI efficacy: low oxygen, pest stage, host, dose rate, and temperature. Of these factors, the first is known to affect efficacy, whereas host and dose rate probably need more research. The International Plant Protection Convention considered several PI treatments for its international standard on phytosanitary treatments and did not approve some at first because of perceived problems with the research or the presence of live adults after irradiation. Based on these concerns recommendations for research and dealing with the issue of live adults postirradiation are given. Generic PI treatments are suggested.     

Confirmation and efficacy tests against codling moth and oriental fruit moth in peaches and nectarines using combination heat and controlled atmosphere treatments

Two high-temperature, forced air treatments under controlled atmosphere conditions, called CATTS for controlled atmosphere/temperature treatment system, were developed for control of all life stages of codling moth, Cydia pomonella (L.), and oriental fruit moth, Grapholita molesta (Busck), infesting peaches and nectarines (both Prunus spp.). These treatments were used in efficacy and confirmation tests to kill > 5,000 fourth instar oriental fruit moths and > 30,000 fourth instar codling moths with zero survivors. The treatments consist of linear heating rates of either 12 or 24 degrees C/h to a final chamber temperature under a 1% O2, 15% CO2, and > 90% RH atmosphere with air speed between 1.2 and 2.0 m/s. At a 12 degrees C linear chamber heating rate, treatment takes approximately 3 h to reach a final chamber temperature of 46 degrees C. The average lowest core temperatures of the fruit reached 43.8 degrees C within the last 30 min of the treatment. At a 24 degrees C linear chamber heating rate, it takes approximately 2.5 h to reach a final chamber temperature of 46 degrees C. The average lowest core temperatures of the fruit reached 44.6 degrees C for the last 15 min of the treatment. It also was determined that both treatments did not significantly alter the quality parameters that were evaluated to a degree that would have negatively influenced the marketability of the fruit. Positive benefits of treatment included a slower ripening of treated fruit and an inhibition of the loss of juiciness during storage in some cultivars. These treatments may be used to replacement to methyl bromide fumigation for conventional fruit or as a new treatment for organic fruit contingent upon importing country approval.     

Confirmation and efficacy tests against codling moth and oriental fruit moth in apples using combination heat and controlled atmosphere treatments

Codling moth, Cydia pomonella (L.), and oriental fruit moth, Grapholita molesta (Busck), are serious pests of apples (Malus spp.) grown in the United States and other countries. In countries where these species are not found, there are strict quarantine restrictions in place to prevent their accidental introduction. The treatment used in this study consisted of hot, forced, moist air with a linear heating rate of 12 degrees C/h to a final chamber temperature of 46 degrees C under a 1% oxygen and 15% carbon dioxide environment. We found that the fourth instar of both species was the most tolerant to the treatment, with equal tolerance between the species. Efficacy tests against the fourth instar of both oriental fruit moth and codling moth by using a commercial controlled atmosphere temperature treatment system chamber resulted in > 5,000 individuals of each species being controlled using the combination treatment. Confirmation tests against codling moth resulted in mortality of > 30,000 fourth instars. These treatments may be used to meet quarantine restrictions for organic apples where fumigation with methyl bromide is not desirable.     

Fecundity and longevity of Argentine ant (Hymenoptera: Formicidae) queens in response to irradiation

Irradiation is a post‐harvest quarantine treatment option to control ants and other hitchhiker pests on fresh horticultural products traded between countries. As little is known about irradiation effects on ants, radiotolerance of the Argentine ant, Linepithema humile (Mayr) (Hymenoptera: Formicidae: Dolichoderinae), was studied to determine a dose sufficient for its control. Queens collected from Buenos Aires, Argentina, were irradiated with 30, 60, 90 Gy or left untreated as controls, and then followed for 8 weeks to evaluate their survival and fecundity. Overall queen survival and brood viability decreased with increasing irradiation dose. The number of eggs was reduced by 50%, 69% and 56% in the 30, 60 and 90 Gy doses, respectively, compared with untreated control queens. The percentage of eggs that developed into larvae decreased from 41.1% in the control to 22.5%, 1.4%, and 0% in the 30, 60, and 90 Gy treatments, respectively. Thus, the number of larvae was reduced by 69% in the 30 Gy treatment compared with the control, only one larva was observed in the 60 Gy treatment, and none in the 90 Gy treatment. Only one pupa was observed in the 30 Gy treatment and none in the 60 and 90 Gy treatments during the 8‐week experiment. Queens irradiated with 60 and 90 Gy had significantly reduced longevity compared with queens treated with lower doses or untreated queens. Radiation dose ≥90 Gy stopped brood development in Argentine ant queens and should be sufficient as a phytosanitary treatment. The radiotolerance of Argentine ant appears to be similar to that of two other important invasive ants.     

Generic ionizing radiation quarantine treatments against fruit flies (Diptera: Tephritidae) proposed

Tephritid fruit flies comprise the most important group of quarantined pests of fresh produce. Most quarantine treatments of fresh agricultural commodities are directed against these pests, and considerable effort in detection, trapping, and population control is expended worldwide to prevent these pests from invading new territories. Ionizing radiation has been studied for 70 yr for its possible use as a quarantine treatment against fruit flies, but has only been applied commercially on a limited basis since 1995. The treatment has great potential and will probably be used extensively in the future as it is tolerated by more species of fruits than any other major treatment. The U.S. Department Agriculture, Animal and Plant Health Inspection Service only recently proposed allowing irradiation for fresh agricultural imports from other countries, and other countries are studying proposals to do likewise. In 1991, the International Consultative Group on Food Irradiation recommended a generic dose against all tephritid fruit flies of 150 Gy. This article examines the literature dealing with irradiation quarantine treatments against fruit flies and recommends minimum absorbed doses of 70 Gy for Anastrepha spp., 101 Gy for Bactrocera jarvisi and B. tryoni, and 150 Gy for all Tephritidae except when fruits have been stored in hypoxic atmospheres.     

Effects of gamma irradiation on the life stages of yellow flower thrips, Frankliniella schultzei (Trybom) (Thysanoptera: Thripidae)

Irradiation at a minimum absorbed dose of 250 Grays (Gy) has been approved by the USDA as a quarantine treatment for certain fruits in Hawaii to control four species of tephritid fruit flies. Subsequent research must determine whether this dose is sufficient to control other quarantine pests, such as mealybugs, thrips, mites, beetles, moths, and scale insects, on other commodities with export potential that are approved for irradiation treatment for fruit flies. This study demonstrated that irradiation at 250 Gy caused non‐emergence of eggs and pupae, failure of larval development, and sterility of adults of yellow flower thrips, Frankliniella schultzei (Trybom). Adults were the most resistant stage tested, with 100% mortality at 57, 36 and 30 days post‐treatment for the 250, 350 and 400 Gy treatments, respectively. Untreated adults survived up to 66 days. After receiving an irradiation dose of 250 Gy, no one‐ to two‐day old eggs hatched successfully, while 3–4‐day old eggs hatched but did not develop beyond the larval stage. Of the controls, 96.0% of 1–2‐day old eggs and 75.9% of the 3–4‐day old eggs hatched and survived through pupation. No first or second instar larvae treated with a target dose of 250 Gy were able to pupate. When pupae were irradiated at 250 Gy, 37% emerged as adults and all were sterile compared to 88.3% emergence of controls.     

Reaction orders for thermal mortality of third instars of Mexican fruit fly (Diptera: Tephritidae)

Mexican fruit fly, Anastrepha ludens (Loew), is a quarantine pest of several fruit, including citrus, avocados, and mangoes, from extreme southern Texas to Costa Rica. To provide information for modeling heat phytosanitary treatments, third instars were heated with an aluminum heating block between 44 and 50 degrees C for time intervals up to those causing 100% mortality. At 44 and 50 degrees C, 100% mortality was achieved at 100 and 2 min, respectively. Each 2 degrees C increase in temperature resulted in a three-fourths reduction in the amount of time required to achieve 100% mortality. Mortality was modeled using thermal death kinetics, and the most suitable reaction order was the 0.5th. The thermal death activation energy was 560.7 kJ/mol, which is very similar to the value found for Mediterranean fruit fly, Ceratitis capitata (Wiedemann), in a previous study, indicating similar modes of action for heat mortality. However, the Mexican fruit fly had a lower threshold for heat-induced mortality, resulting in less time at all temperatures studied to achieve 100% mortality compared with the Mediterranean fruit fly. This type of information being gathered for fruit flies could lead to the development of generic phytosanitary heat treatments, which are available for other major phytosanitary treatments, such as cold storage, methyl bromide fumigation, and ionizing irradiation.     

Effects of X‐ray irradiation on development and reproduction of the oriental tobacco budworm,Helicoverpa assulta (Lepidoptera: Noctuidae)

All stages of the life cycle of Helicoverpa assulta were irradiated with X‐rays to determine the inhibitory dose for development and reproduction to serve as a quarantine treatment. The 100‐Gy dose was effective for irradiation of eggs and larvae, and the 200‐Gy dose was effective for pupae and mixed‐sex adults. When either adult males or females were irradiated, however, 500 Gy was required to prevent the F1 eggs from hatching, and thus single‐sex adults required much higher doses of X‐ray irradiation. To gather confirmatory data applicable to phytosanitary quarantine regulations, pupae—the immature stage most resistant to X‐ray irradiation—were placed inside paprika in boxes for exportation and were irradiated with 300 Gy as a small‐scale confirmatory test. The dose given to 1,007 individual pupae resulted in 12.62 % survival, and 1.79 % of pupae emerged as normal adults; however, these adults produced only a few eggs that did not hatch, suggesting that a minimum dose of 300 Gy of X‐ray irradiation will provide quarantine security for immature H. assulta in paprika exports.     

Irradiation as a methyl bromide alternative for postharvest control of Omphisa anastomosalis (Lepidoptera: Pyralidae) and Euscepes postfasciatus and Cylas formicarius elegantulus (Coleoptera: Curculionidae) in sweet potatoes

Irradiation studies were conducted with three sweet potato, Ipomoea batatas (L.) Lam., pests to determine an effective dose for quarantine control. Dose-response tests indicated that the most radiotolerant stage occurring in roots was the pupa of sweetpotato vine borer, Omphisa anastomosalis (Guenee), and the adult of West Indian sweetpotato weevil, Euscepes postfasciatus (Fairmaire), and sweetpotato weevil, Cylas formicarius elegantulus (Summers). In large-scale confirmatory tests, irradiation of 60,000 C. formicarius elegantulus adults, 62,323 E. postfasciatus adults, and 30,282 O. anastomosalis pupae at a dose of 150 Gy resulted in no production of F1 adults, demonstrating that this dose is sufficient to provide quarantine security.     

Combined heat and controlled atmosphere quarantine treatments for control of western cherry fruit fly in sweet cherries

Nonchemical quarantine treatments, using a combination of short duration high temperatures under low oxygen, elevated carbon dioxide atmospheric environment were developed to control western cherry fruit fly, Rhagoletis indifferens Curran, in sweet cherries, Prunus avium (L.). The two treatments developed use a chamber temperature of 45 degrees C for 45 min and a chamber temperature of 47 degreesd C for 25 min, both under a 1% oxygen, 15% carbon dioxide, -2 degrees C dew point environment. Both these treatments have been shown to provide control of all life stages of western cherry fruit fly while preserving commodity market quality. There was no definitive egg or larval stage, which was demonstrated to be the most tolerant to either controlled atmosphere temperature treatment system treatment. Efficacy tests for both treatments resulted in 100% mortality of >5000 western cherry fruit flies in each treatment. These treatments may provide, with further study, quarantine security in exported sweet cherries where western cherry fruit fly is a quarantine concern and fumigation with methyl bromide is not desired.     

DNA diagnostics to identify internal feeders (Lepidoptera: Tortricidae) of pome fruits of quarantine importance

A diagnostic polymerase chain reaction (PCR) method is presented for differentiating among the North American internal apple-feeding pests codling moth, Cydia pomonella (L.); oriental fruit moth, Grapholita molesta (Busck); lesser appleworm, Grapholita prunivora (Walsh); and cherry fruitworm, Grapholita packardi Zeller. An approximately 470-bp fragment of mitochondrial cytochrome oxidase subunit I (COI) was sequenced in three to six specimens of each species. Consistent and diagnostic differences were observed among the species in two regions of COI from which forward and reverse primers were designed to amplify a 112-116-bp segment of the gene. The primer sets were used to selectively amplify DNA from specimens of diverse geographic origin for each corresponding target species. Protocols were adapted for conventional and quantitative PCR, the latter being substantially faster. The method was validated as a decision-making tool for quarantine identifications for Mexico by representatives of their phytosanitary agency (Sanidad Vegetal). The method can facilitate identification of intercepted internal feeding Lepidoptera in apple and pear for many other importing nations.