Quick knockdown results in high mortality: is this theory correct? A case study with phosphine and the red flour beetle

BACKGROUND

The fumigant phosphine is used all over the world for disinfestation of stored grains and commodities. Adults of 23 different populations of Tribolium castaneum from 10 different countries were evaluated for phosphine resistance using a modification of the Detia Degesch Phosphine Tolerance Test Kit (DDPTTK). Adults were exposed to 3000 ppm and recorded for 5–270 min for their mobility.

RESULTS

Among the tested populations, high levels of phosphine resistance were recorded in populations from Brazil, Serbia, and Spain. No survivals were recorded after 7 days post exposure for eight of 23 in a tested population.

CONCLUSIONS

Our work revealed four scenarios: 1, quick knockdown–low (or no) recovery; 2, Slow knockdown–high recovery; 3, Quick knockdown–high recovery; and 4, Slow knockdown–low recovery. Our data indicate that post exposure period is critical for the evaluation and characterization of phosphine resistance. © 2023 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.     

Review A Review of the Mechanisms Involved in the Action of Phosphine as an Insecticide and Phosphine Resistance in Stored-Product Insects

Phosphine gas has been used world-wide for more than four decades as an ideal fumigant for disinfestation of stored grains and other commodities. Its use as a safe fumigant of stored products has become even more important with recent restrictions on the production of the only alternative, methyl bromide. Widespread resistance to phosphine has emerged in several species of stored-product insects in many countries, which in some instances may have caused control failures. Chemically, phosphine is a strong reducing agent and biological redox systems, especially the components of the mitochondrial electron transport chain, are probably the site of its action in insects. The oxidation of phosphine could produce reactive phosphorylating species and interactions of phosphine with biological redox systems have been reported to cause generation of highly reactive oxyradicals. This appears to be the basis of phosphine toxicity to insects, which differs from that of respiratory inhibitors such as hydrogen cyanide. Phosphine-resistant strains of several species of stored-product insects have been reported to absorb very small amounts of the compound compared to their susceptible counterparts. This reduced uptake in resistant insects appears to result from respiratory exclusion of phosphine. The overall mechanism of resistance also involves a detoxification process. Despite the likely involvement of oxyradicals in the insecticidal action of phosphine, the level of anti-oxidant enzymes in resistant insects is apparently not higher than that in their susceptible counterparts. The reduced uptake of the compound might be due either to the presence of a phosphine insensitive target site or to a membrane-based efflux system that excludes phosphine gas in resistant insects. Studies have indicated the oxygen uptake in mitochondrial preparations from susceptible and resistant insects to be equally sensitive to inhibition by phosphine in vitro. The nature of the phosphine-exclusion system in resistant insects has not been fully elucidated. The possibilities of controlling resistant insects with phosphine and prospects for developing new alternative fumigants are also discussed. © 1997 SCI.     

无色书虱不同虫态对PH3抗药性的研究

在25℃±1℃,75%±2%RH条件下,用FAO推荐的测定储粮害虫磷化氢(PH3)抗性的方法,对无色书虱敏感品系YNQJLd1、弱抗品系QLD-8和强抗品系GXHZLd1的成虫、若虫和卵进行了毒力测定,分别得出相应的磷化氢致死中浓度(LC50).YNQJLd1、QLD-8和GXHZLd1的成虫LC50值分别为0.0079、0.7127和1.7586mg/L,抗性品系的抗性系数(Rf)分别为90和222倍;YNQJLd1、QLD-8和GXHZLd1的若虫LC50值分别为0.00974、081053和1.63821mg/L,抗性品系的Rf分别为83和168倍;YNQJLd1、QLD-8和GXHZLd1的卵LC50值分别为0.4317、2.1495和5.22146mg/L,抗性品系的Rf分别为5和12倍.结果表明,无色书虱同一品系成虫和若虫对PH3抗性差异不明显,卵对PH3的抗性相比成虫和若虫是最强的,也是最难防治的虫态.本研究的测定为今后的书虱磷化氢抗性研究工作提供了基础数据,为实仓的磷化氢熏蒸试验提供了可靠的参考依据.     

A kinetic model of fumigant sorption by grain using batch experimental data

BACKGROUND: Most fumigants are adsorbed by grain at differing rates depending on the fumigant or grain type. Sorption can reduce the concentrations of fumigation doses to sublethal levels before grain has been disinfested. A model to predict fumigant losses due to sorption in industrial scenarios is needed. RESULTS: This work reviews the kinetics of grain fumigant sorption and develops a new alternative model based upon key factors established from the literature and batch experimental results. The novel model accounts for linear mass transfer within the grain, irreversible 'binding' and linear partitioning of the fumigant to the grain. Model coefficients were estimated by minimizing the sum of squared residuals between model predictions and experimental data. The model was compared with other options including diffusion into spheres, and results for methyl bromide and phosphine are provided. CONCLUSION: The model describes the transient changes of fumigant concentrations in both the intergranular air and grain. It provides the capacity to predict fumigant concentrations throughout grain stacks for a wide range of scenarios of industrial importance.     

Influence of concentration, temperature and humidity on the toxicity of phosphine to the strongly phosphine-resistant psocid Liposcelis bostrychophila Badonnel (Psocoptera: Liposcelididae)

BACKGROUND: The psocid Liposcelis bostrychophila Badonnel, is a widespread, significant pest of stored commodities, has developed strong resistance to phosphine, the major grain disinfestant. The aim was to develop effective fumigation protocols to control this resistant pest. RESULTS: Time to population extinction of all life stages (TPE) in days was evaluated at a series of phosphine concentrations and temperatures at two relative humidities. Regression analysis showed that temperature, concentration and relative humidity all contributed significantly to describing TPE (P<0.001, R(2)=0.95), with temperature being the dominant variable, accounting for 74.4% of the variation. Irrespective of phosphine concentration, TPE was longer at lower temperatures and high humidity (70% RH) and shorter at higher temperatures and low humidity (55% RH). At any concentration of phosphine, a combination of higher temperature and lower humidity provides the shortest fumigation period to control resistant L. bostrychophila. For example, 19 and 11 days of fumigation are required at 15 degrees C and 70% RH at 0.1 and 1.0 mg L(-1) of phosphine respectively, whereas only 4 and 2 days are required at 35 degrees C and 55% RH for the same respective concentrations. CONCLUSIONS: The developed fumigation protocols will provide industry with flexibility in application of phosphine.     

我国主要储粮害虫抗性调查研究

通过对全国范围内23个省、市和自治区的55个地区粮库中的主要储粮害虫进行取样，用FAO抗性测定方法对92个虫样进行磷化氢抗性测定，得出无抗性虫样占调查虫样总数的54．3％、低抗性虫样占9．8％、中等抗性虫样占7．6％、高抗性虫样占13．0％、极高抗性虫样占15．2％。在调查的几种主要储粮害虫中，高抗性虫样主要为锈赤扁谷盗、谷蠹和米象，其中锈赤扁谷盗的抗性普遍比较严重，谷蠹和米象通过与1995年抗性调查所取的样品进行比较，在最近的8年内米象的抗性倍数增加了10．7％、谷蠹增加了71．2％。磷化氢抗性较高的区域主要是我国西南、华中和华南地区。     

谷蠹和米象的PH_3抗性品系对3种粮食保护剂的交互抗性研究

本文报道了两种主要储粮害虫谷蠹和米象的抗磷化氢品系对马拉硫磷、虫螨磷和溴氰菊酯 3种储粮保护剂的毒力测定。其结果表明 ,抗磷化氢的谷蠹和米象品系对上述 3种储粮保护剂都不产生交互抗性     

磷化氢熏蒸尾气净化试验

为减少和避免磷化氢熏蒸尾气较高浓度散气风险,我库引进一种新技术——臭氧紫外线净化磷化氢尾气,探索仓内环流结合直排方式净化磷化氢尾气的效果。通过实仓试验并适时检测记录数据,结果表明:臭氧紫外线技术可以实现磷化氢熏蒸尾气净化处理,达到磷化氢尾气无毒化排放要求。     

模拟环境条件下湖泊沉积物中磷化氢的行为

采用实验室模拟方法,考察了水泥比、搅动、铁盐(Ⅱ、Ⅲ)和锰盐(Ⅱ)等理化因素对湖泊沉积物中吸附态磷化氢生成和释放的影响。结果表明,当水泥比为3∶1时,吸附态磷化氢和顶空磷化氢气体均取得最大值,分别为7517ng·kg-1和40ng·m-3。扰动对沉积物中吸附态磷化氢的生成和释放均有影响。50r·min-1的低扰动强度下,吸附态磷化氢的变化不显著;100r·min-1的中扰动强度下,吸附态磷化氢的量先增加后下降,其净含量是磷化氢生成和释放相互平衡后的结果;扰动强度增加到150r·min-1后,磷化氢释放加剧,吸附态磷化氢的量急剧下降。铁盐(Ⅲ)可加速沉积物中磷化氢的消失,铁盐(Ⅱ)和锰盐(Ⅱ)对吸附态磷化氢的影响不显著。     

磷化铝动态潮解膜下环流熏蒸法研究与应用

利用动态潮解膜下环流熏蒸法在高大平房仓一次性投入磷化铝，进行实仓熏蒸试验。结果表明：仓内磷化氢浓度分布均匀，保持有效浓度时间长，杀虫效果良好；且具有省工省时、操作简便、经济实用和对环境污染小的特点。