Quarantine Disinfestation of Papaya Mealybug, Paracoccus marginatus (Hemiptera: Pseudococcidae) Using Gamma and X-rays Irradiation.

Paracoccus marginatus is a highly polyphagous invasive pest that poses a significant quarantine threat to tropical and subtropical countries. Infested commodities in international trade should undergo phytosanitary treatment, and irradiation is recommended as a viable alternative to replace methyl bromide fumigation. Dose-response tests were conducted on the 2-, 4-, and 6-day-old eggs and gravid females of P. marginatus using the X-ray radiation doses of 15-105 Gy with an interval of 15 Gy. Radiotolerance was compared using ANOVA, fiducial overlapping and lethal dose ratio (LDR) test, resulting in no significant difference among treatments, except for the overall mortality and LDR at LD90 (a dose causing 90% mortality at 95% confidence level). The estimated dose for LD99.9968 was 176.5-185.2 Gy, which was validated in the confirmatory tests. No nymphs emerged from a total of 60,386 gravid females exposed to a gamma radiation dose range of 146.8-185.0 Gy in the confirmatory tests. The largest dose in confirmatory tests should be the minimum threshold for phytosanitary treatment, consequently, a minimum dose of 185 Gy is recommended for the phytosanitary irradiation treatment of papaya mealybug-infested commodities, ensuring a treatment efficacy of ≥99.9950% at 95% confidence level.

Phytosanitary irradiation treatment of the aerial root mealybug, Pseudococcus baliteus (Hemiptera: Pseudococcidae).

The aerial root mealybug, Pseudococcus baliteus Lit (Hemiptera: Pseudococcidae), is an important invasive and quarantine pest that poses a potential threat to fruits, vegetables, and ornamental plants. As a result, phytosanitary treatments are necessary to ensure the commodities of international trade are free from these pests. To determine the minimum absorbed dose required for phytosanitary irradiation (PI) application, irradiation dose-response and large-scale confirmatory tests were conducted. Eggs that were 2, 4, and 6 days old and late gravid females (containing 0-day-old eggs) of P. baliteus were X-ray irradiated with doses of 10, 20, 40, 60, 80, 100, and 120 Gray (Gy). The efficacy of preventing egg-hatching (mortality) was compared using two-way ANOVA, 95% confidence interval overlapping and lethal dose ratio test in probit analysis. The radiotolerance sequence of mealybugs egg was found to be 0 < 2 ≈ 4 < 6-day-old eggs, and their estimated LD99.9968 values with 95% confidence interval were 132.0 (118.9-149.5), 137.6 (125.2-153.7), 145.5 (134.5-159.1), and 157.4 (144.6-173.6) Gy, respectively. Subsequently, target doses of 135 and 145 Gy were used in the confirmatory gamma radiation treatments. No F1 generation neonates developed from a total of 47,316 late females irradiated at the measured dose of 107.7-182.5 Gy, resulting in the treatment efficiency of 99.9937% at the 95% confidence level. Therefore, the highest dose of 183 Gy measured in the confirmatory tests is recommended as the minimum absorbed dose in PI treatment of P. baliteus for establishing national and international standards.

Vapor heat treatment against Planococcus lilacinus Cockerell (Hemiptera:Pseudococcidae) on dragon fruit.

BACKGROUND: The coffee mealybug Planococcus lilacinus Cockerell, is an invasive pest that infests dragon fruit [Selenicereus undatus (Haworth) D.R. Hunt], that may require a phytosanitary treatment to meet quarantine requirements. In this study, vapor heat treatment was conducted to disinfest P. lilacinus on dragon fruit and the quality of dragon fruit was evaluated thereafter. RESULTS: Adult female P. lilacinus was the most heat-tolerant stage at 47, 48 and 49 °C. The death kinetic model and probit model were used to predict LT99.9968 at the three temperatures. The treatment times predicted by the kinetic model that could effectively disinfest adult female P. lilacinus females were 120.84, 78.06 and 67.96 min at 47, 48 and 49 °C, respectively. In a confirmatory test of vapor heat treatment at 49 °C for 70 min, complete mortality was recorded for 33 195 adult females infesting 148 dragon fruits; thus, the efficacy level of disinfestation was 99.9910% at 95% confidence level. The quality of dragon fruit generally was not affected by heat treatment, fruit firmness was increased remarkably and respiration rate was significantly decreased. CONCLUSION: Our result indicates that vapor heat treatment at 49 °C for a duration of 70 min is an effective phytosanitary treatment for control of P. lilacinus on dragon fruit that minimally impacts fruit quality. © 2021 Society of Chemical Industry.

[Study on endpoint determination method of tablet coating based on 3σ criteria and logic regression].

This paper explores the statistical distribution characteristics of coating film thickness, so as to present a new method for determining coating endpoint based on 3σ criterion and logic regression. Firstly, the spectrum and thickness of 4 batch samples were collected. Secondly, the spectral range of normal products was obtained by 3σ criterion, with the spectral feature NI as the number of test spectrum in the above range. Then, the model based on 3σ criterion and logic regression was built according to the best condition in K-fold cross-validation and the determined threshold of qualified rate in the coating endpoint. Finally, the qualified rate of test set samples at different time points was calculated by the above model, and the above change trend and the threshold value were combined to determine the coating endpoint. The results of KS analysis showed the distribution of thickness of the qualified products followed the normal distribution(P=0.081>0.05). The accuracy of the coating endpoint determination was as high as 100% by the model based on 3σ criterion and logic regression when the determined threshold of qualified rate was 90%. Therefore, the 3σ criterion was feasible to the research of coating eligibility. This paper reveals certain random phenomena in the coating process, and the method features a high accuracy, quick analysis and a good interpretability, which provides a reference for online detection and qualify evaluation in future.

Combination of Modified Atmosphere and Irradiation for the Phytosanitary Disinfestation of Trogoderma granarium Everts (Coleoptera: Dermestidae).

The khapra beetle, Trogoderma granarium Everts, is defined as one of the most important quarantine pests globally, and fumigation with methyl bromide, an ozone-depleting substance, is a common phytosanitary measure currently used. The modified atmosphere (MA), irradiation, and their combination treatments of T. granarium larvae and adults were performed at room temperature (24-26 ℃) to develop an ecofriendly phytosanitary disinfestation measure and to shorten the exposure time and overcome treatment disadvantages of irradiation. Late-stage larvae are determined as the most tolerant stage resulted in large LT99.9968 values of 32.6 (29.2-37.5) and 38.0 (35.1-41.7) days treated under 1% and 2% O2 (with N2 balance) atmosphere, respectively. Ionizing radiation was used to enhance the effect of MA and the mortality was highly significantly affected by all the interaction effects, indicating that the synergistic effects present in all the combined treatments. The synergistic ratios, which is defined as the estimated lethal time for MA treatment (LD90, LD99, and LD99.9968), divided by that of combined treatment, were between 1.47 and 2.47. In the confirmatory tests, no individuals recovered from a sum of 111,366 late-stage larvae treated under 1% O2 atmosphere for 14- or 15-d after 200 Gy irradiation, which resulted in validating the probit estimations and achieving an efficacy of 99.9973% mortality at 95% confidence level. Therefore, these treatment schedules are recommended to disinfest T. granarium infecting commodities for phytosanitary purposes under the warehouse, MA packaging, or in combination with international transportation by train or sea container.

Radioprotective Effects on Late Third-Instar Bactrocera dorsalis (Diptera: Tephritidae) Larvae in Low-Oxygen Atmospheres.

Ionizing radiation creates free radicals, the effect of which is enhanced by the presence of oxygen; a low oxygen level produces radioprotective effects for insects compared with irradiation in ambient air. Modified (controlled) atmosphere packaging is used for maintaining quality and shelf-life extension; therefore, treatment efficacy may be affected, and there is a need to determine the critical O2 levels that may cause radioprotective effects. Late third-instar Bactrocera dorsalis (Hendel) larvae were irradiated in bags filled with ambient or low-oxygen air (0%, 2%, 4%, 6%, 8% O2) and were exposed to radiation doses of 8 to 64 Gy with intervals of 8 Gy. Efficacy was measured by the prevention of adult emergence. Dose-response data on mortality (failure of adult emergence) were analyzed via two-way ANOVA (analysis of variance), ANCOVA (analysis of covariance), and probit regression. The difference in radiotolerance was only significant in 0% O2 atmospheres through two-way ANOVA; therefore, the 95% confidence limits (CLs) of lethal dose ratios at LD99 were used to determine significant differences between treatments at different O2 levels. The differences in radiotolerance were significant in 0% and 2% O2 but insignificant in 4%, 6%, and 8% O2 environments when compared with radiation in ambient air. The critical threshold of radioprotective effects for late third-instar B. dorsalis larvae is an O2 level of ≥4% and <6%, but a maximum radiation dose of 14 Gy can compensate for this effect during phytosanitary irradiation treatment.

Cold Disinfestation for 'Red Globe' Grape (Rhamnales: Vitaceae) Infested With Drosophila suzukii (Diptera: Drosophilidae).

The spotted wing drosophila, Drosophila suzukii Matsumura, which is widely spread in the main soft-skinned fruits production areas in China, presents a threat to importing countries. In order to develop a phytosanitary cold treatment measure for preventing the movement of this drosophila fly, cold tolerance of six immature life stages of D. suzukii was compared followed by time-mortality and large-scale confirmatory tests on the most tolerant stage in grape fruit. Egg was defined as the most cold-tolerant stage by comparing the mortality of all the immature stages (egg, first, second, and third instars, early and late pupa) treated at 0 and 2°C. The minimal lethal time (LT) for 99.9968% mortality (95% confidence level [CL]) estimated by the probit model was 10.47 d at 0°C and 11.92 d at 2°C, respectively. Hence, 11 d (at 0°C) and 12 d (at 2°C) were chosen as the target time to conduct the confirmatory tests. No survivors were found among the estimated 50,385 and 57,366 treated eggs, which resulted in the efficacy of 99.9941 and 99.9948% mortality (95% CL) at 0 and 2°C, respectively. Our study suggests a technical basis for cold disinfestation on D. suzukii in cage-infested Chinese 'Red Globe' (Vitis vinifera L.) grape, which could provide flexible phytosanitary treatment for control of D. suzukii in the international trade of grape.

The Effects of a Cold Disinfestation on Bactrocera dorsalis Survival and Navel Orange Quality.

Citrus sinensis (L.) Osbeck is an important economic product in South China, but the presence of quarantine pests in this product proposes the potential threat to international trade security. To find a proper phytosanitary cold treatment for Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), commonly called oriental fruit fly, one of the most serious quarantine insects in navel orange, eggs in petri dish and larvae in navel orange fruits were exposed to a 1.7 °C cold chamber for 0-11 days to compare the tolerance to cold treatment. The 2nd instar larva (4 days) is the most tolerant stage, and the estimated time for 99.9968% mortality at the 95% confidence level is 11.3 (9.5, 14.6) days. Then 15 days was selected as the target time for the confirmatory tests, resulting in no survivors from 37,792 treated larvae with the efficacy of 99.9921% mortality at the 95% confidence level. The quality assessments were conducted to compare the effect on the navel orange fruit between cold treatment and the conventional cold storage. Results indicated that the cold treatment did not negatively affect the fruit quality. Therefore, this cold treatment showed potential as a commercial quarantine treatment for navel orange in international trade.

Effects of X-Ray Irradiation on the Eggs and Females of Dysmicoccus lepelleyi (Hemiptera: Pseudococcidae).

The mealybug of Dysmicoccus lepelleyi Betrem (Hemiptera: Pseudococcidae) attacks a wide range of fruits, vegetables, and ornamental plants and is categorized as a quarantine pest in China. Utilization of phytosanitary irradiation (PI) as a potential treatment to disinfest agricultural commodities in trade (which has expanded rapidly in the recent years) and preventing the hatch of F1 generation eggs is used as a criterion for the PI treatment of mealybugs. A RS-2000 Pro X-ray irradiator (Rad Source Technologies, Inc.) was used to treat the gravid adult females and eggs of the mealybug. The primary tests were conducted to explore the minimum dose for preventing egg-hatch from the irradiated adult females, resulted in a 1.69% of eggs hatched from 100 Gy-irradiated adult females and no crawler developed as treated at the dose of 110 and 120 Gy. To estimate the minimum dose for preventing egg-hatching, the dose-response tests were conducted for 1-, 2-, and 3-d-old eggs at the dose of 20, 40, 60, 80, 100, and 120 Gy, respectively. The results showed that the radio-tolerance increased very slowly with developmental times of eggs, and the estimated dose for 99.9968% mortality at the 95% confidence level (Probit 9) by Probit analysis is 146.2, 155.7, and 156.1 Gy for 1-, 2-, and 3-d-old eggs, respectively. Therefore, dose range between 110 and 160 Gy could be efficient to prevent the reproduction of this mealybug.

Evaluation of Low-Temperature Phosphine Fumigation for Control of Oriental Fruit Fly in Loquat Fruit.

Oriental fruit fly, Bactrocera dorsalis (Hendel; Diptera: Tephritidae), is recognized as a quarantine pest and a threat to Chinese loquat (Eriobotrya japonica Lindl.) fruit exports. Since loquat fruit is very sensitive to methyl bromide (MB) fumigation and cold treatment, in this study, low-temperature phosphine (PH3) fumigation was investigated to develop an alternative phytosanitary treatment method. Tolerance tests showed that the third instar was the most tolerant of all life stages of B dorsalis to PH3 gas at 8°C. Toxicity assay with 500-3000 ppm PH3 and subsequent probit analysis showed that 2000 ppm PH3 was optimal for fumigation and 152.75 h of treatment duration were required to achieve 99.9968% mortality. In the verification test, 144 and 168 h of treatment duration with 2000 ppm PH3 completely killed 35,277 and 35,134 B. dorsalis third instars, respectively. However, 13 live larvae were found after 120 h of treatment. Furthermore, these treatments reduced fruit respiration rates while causing no adverse effects on other fruit quality parameters, including firmness, soluble solid content, and titratable acidity over 192 h storage at 8°C. The results strongly suggest that low-temperature PH3 fumigation could be used for the postharvest control of B. dorsalis in loquat fruit.

Phosphine inhibits transcription of the catalase gene through the DRE/DREF system in Drosophila melanogaster.

Phosphine (PH3) is a toxin commonly used for pest control. Its toxicity is attributed primarily to its ability to induce oxidative damage. Our previous work showed that phosphine could disrupt the cell antioxidant defence system by inhibiting expression of the catalase gene in Drosophila melanogaster (DmCAT). However, the exact mechanism of this inhibition remains unclear. Here, we implemented a luciferase reporter assay driven by the DmCAT promoter in D. melanogaster S2 cells and showed that this reporter could be inhibited by phosphine treatment. A minimal fragment of the promoter (-94 to 0 bp), which contained a DNA replication-related element (DRE) consensus motif (-78 to -85 bp), was sufficient for phosphine-mediated reporter inhibition, suggesting the involvement of the transcription factor DREF. Furthermore, phosphine treatment led to a reduction in DREF expression and consequent repression of DmCAT transcription. Our results provide new insights on the molecular mechanism of phosphine-mediated catalase inhibition. Phosphine treatment leads to reduced levels of the transcription factor DREF, a positive regulator of the DmCAT gene, thereby resulting in the repression of DmCAT at transcriptional level.

Effect of Low-Temperature Phosphine Fumigation on the Survival of Bactrocera correcta (Diptera: Tephritidae).

This laboratory-based study examined the effects of low-temperature phosphine fumigation on the survival of the eggs and larvae of the guava fruit fly, Bactrocera correcta (Bezzi). Individual flies at different developmental stages, from 6-h-old eggs to third instars, were exposed to 0.92 mg/liter phosphine for 1-7 d at 5°C. We found that 12-h-old eggs and third instars were the most tolerant to phosphine. Increasing phosphine concentrations from 0.46 to 4.56 mg/liter increased mortality in these two stages. However, increased exposure times were required to achieve equal mortality rates in 12-h-old eggs and third instars when phosphine concentrations were ≥4.56 and ≥3.65 mg/liter, respectively. C(n)t = k expression was obtained at 50, 90, and 99% mortality levels, and the toxicity index (n) ranged from 0.43 to 0.77 for the two stages. The synergistic effects of a controlled atmosphere (CA) with elevated CO(2) levels were also investigated, and we found that a CO(2) concentration between 10% and 15% under CA conditions was optimal for low-temperature phosphine fumigation.

Theoretical evaluation of flotation performance of carboxyl hydroxamic acids with different number of polar groups on the surfaces of diaspore (010) and kaolinite (001).

The adsorption behaviors of three carboxyl hydroxamic acids on diaspore (010) and kaolinite (001) have been studied by density functional theory (DFT) and molecular dynamics (MD) method. The results indicated that carboxyl hydroxamic acids could adsorb on diaspore surface by ionic bonds and hydrogen bonds, and adsorb on kaolinite surface by hydrogen bonds. The models of carboxyl hydroxamic acids adsorbed on diaspore and kaolinite surfaces are proposed.

Differential expression profiles of Alternaria alternate genes in response to carbonyl sulfide fumigation.

Carbonyl sulfide (COS) is a new fumigant used in phytosanitary treatments. It was developed as a potential alternative to methyl bromide, which is being phased out because of its ozone-depletion properties. To understand the molecular and cellular mechanisms occurring in fungal pathogens in response to COS fumigation, we cloned 510 cDNA fragments of Alternaria alternata (Fr.) Keissler genes that are differentially expressed; these genes were cloned using suppression subtractive hybridization. Changes in the levels of transcripts of 79 fragments were confirmed by microarray analysis and qRT-PCR. Further homology search revealed that they are highly homologous to 41 genes of other fungi, which were related to general metabolism, growth and division, defense, cellular transport, and signal transduction. These results provide an overview of differential expression profiles of A. alternata genes following COS treatment and some new clues about the mechanism of COS fungitoxicity.

Proteomic analysis of Alternaria alternata (Fr.) Keissler responds to COS fumigation.

Carbonyl sulfide (COS) is a new fumigant which has been a potential alternative to methyl bromide and phosphine in many applications. In this study, we investigated the fungitoxicity of COS towards the pathogen of pear black spot disease Alternaria alternata (Fr.) Keissler (A. alternata). Moreover, proteomic analysis and RT-PCR was performed and our results showed that during the fumigation, the regulation of 21 proteins in protein expression and mRNA accumulation levels is involved, which respond to growth inhibition caused by COS. These results provide new clues for the mechanism of the fungitoxicity of COS.