Toxicity of dimethoate and fenoxycarb to honey bee brood (Apis mellifera), using a new in vitro standardized feeding method

A new in vitro method was devised to assess the effects of pesticides on honey bee brood. The method allowed the quantification of doses ingested by larvae and the assessment of larval and pupal mortality. Larval mortality in control samples was lower than 10%. Two active substances were tested: dimethoate and fenoxycarb. The LD(50) of dimethoate was 1.9 microg larva(-1) 48 h after oral exposure of larvae at day 4. Additional dose-related effects on pupal mortality were noted. After a chronic intoxication, the NOAEC (No Observed Adverse Effect Concentration) for larval mortality at day 7 was 2.5 mg kg(-1), whereas a NOAEC of 5 mg kg(-1) was found at day 22 for delayed effects on the reduction of adult emergence. Fenoxycarb applied at day 4 showed no effect on larvae, whereas emergence of adults was affected at doses higher than 6 ng larva(-1).     

Experimental study on the toxicity of imidacloprid given in syrup to honey bee (Apis mellifera) colonies

Two groups of eight honey bee colonies were fed with two different concentrations of imidacloprid in saccharose syrup during summer (each colony was given 1 litre of saccharose syrup containing 0.5 microg litre(-1) or 5 microg litre(-1) of imidacloprid on 13 occasions). Their development and survival were followed in parallel with control hives (unfed or fed with saccharose syrup) until the end of the following winter. The parameters followed were: adult bee activity (number of bee entering the hive and pollen carrying activity), adult bee population level, capped brood area, frequency of parasitic and other diseases, mortality, number of frames with brood after wintering and a global score of colonies after wintering. The only parameters linked to feeding with imidacloprid-supplemented saccharose syrup when compared with feeding with non-supplemented syrup were: a statistically non-significant higher activity index of adult bees, a significantly higher frequency of pollen carrying during the feeding period and a larger number of capped brood cells. When imidacloprid was no longer applied, activity and pollen carrying were re-established at a similar level for all groups. Repeated feeding with syrup supplemented with imidacloprid did not provoke any immediate or any delayed mortality before, during or following the next winter, whereas such severe effects are described by several French bee keepers as a consequence of imidacloprid use for seed dressing in neighbouring cultures. In any case, during the whole study, mortality was very low in all groups, with no difference between imidacloprid-fed and control colonies. Further research should now address several hypotheses: the troubles described by bee keepers have causes other than imidacloprid; if such troubles are really due to this insecticide, they may only be observed either when bees consume contaminated pollen, when no other sources of food are available, in the presence of synergic factors (that still need to be identified), with some particular races of bees or when colonies are not strong and healthy.     

A monitoring study to assess the acute mortality effects of indoxacarb on honey bees (Apis mellifera L.) in flowering apple orchards

To evaluate the effect of the indoxacarb 300 g kg(-1) WG, Steward 30WDG, on the honey bee (Apis mellifera L.) in apple orchards, a monitoring study was conducted in Dutch apple orchards in April/May 2004. Before apple flowering began, two honey bee colonies were placed in each orchard to investigate honey bee mortality. Each hive was provided with a Münster dead bee trap to collect dead honey bees. The numbers of dead bees found in these Münster dead traps were counted every 3-4 days for about 2 weeks before and after the period of the insecticide treatment. In nine flowering orchards no indoxacarb was applied during the flowering period, which served as control sites. In 30 flowering orchards indoxacarb was sprayed by the fruit growers according to local practice at 170-260 g formulated product ha(-1) (51-78 g AI ha(-1)). In the control orchards the average mortality was 8 honey bees colony(-1) day(-1). The average daily honey bee mortality before and after indoxacarb application was 8 and 10 honey bees colony(-1) day(-1) respectively. At one test site, indoxacarb was mixed with other plant protection products plus plant nutrients, and in this orchard a slight but biologically non-significant increase in acute honey bee mortality was recorded. It was concluded that the application of indoxacarb caused no effects on honey bee mortality, and that the number of dead honey bees counted in the Münster traps in the orchard treated with indoxacarb was comparable with those determined in control orchards.     

小麦不同生育期施用丙硫菌唑及施用次数对小麦赤霉病及籽粒DON毒素的控制效果

为探明在小麦不同生育期施用新型杀菌剂丙硫菌唑及施用次数对小麦赤霉病及籽粒DON毒素总量[包括脱氧雪腐镰刀菌烯醇(DON)?3-乙酰脱氧雪腐镰刀菌烯醇(3-ADON)?15-乙酰脱氧雪腐镰刀菌烯醇(15-ADON)]的控制效果, 2020年-2021年通过田间自然发病和人工接种发病试验的方法, 研究了小麦不同生育期施用丙硫菌唑及施用次数对小麦赤霉病的防效, 并通过液相色谱-串联质谱法测定了不同处理小麦籽粒中对DON毒素总含量?结果表明, 30%丙硫菌唑可分散油悬浮剂(OD)防治2次对小麦赤霉病的防效和对DON毒素的控制效果均显著高于防治1次; 防治2次时, 其首次最佳防治时期为小麦齐穗期至扬花20%, 防效为90.25%~95.13%, 毒素控制效果为77.35%~79.97%?30%丙硫菌唑OD作为防控小麦赤霉病的新型药剂具有良好的应用前景, 本研究为该药剂推广应用于小麦赤霉病及籽粒DON毒素的防控提供了科学依据?     

氯虫•噻虫嗪不同剂型对水稻二化螟、稻纵卷叶螟的防治效果及施用技术

2007-2008年,应用氯虫•噻虫嗪不同剂型防治水稻二化螟、稻纵卷叶螟的田间试验结果表明：0.6%氯虫•噻虫嗪颗粒剂对二化螟的效果较好,但难以控制稻纵卷叶螟危害;40%氯虫•噻虫嗪水分散粒剂可有效防控以上2种虫害且持效期长达30 d。同一时期同等剂量下,各施用1次0.6%氯虫•噻虫嗪颗粒剂、40%氯虫•噻虫嗪水分散粒剂,前者撒施处理对其药效均显著低于后者茎叶喷雾处理。     

模拟加工对菠菜中农药残留量及膳食暴露评估的影响

采用田间喷药、室内模拟加工和气相色谱检测方法,研究了水洗、漂烫和烘干处理对菠菜中毒死蜱、氯氰菊酯和氰戊菊酯残留量的影响。结果表明:在田间推荐剂量下,当毒死蜱、氯氰菊酯和氰戊菊酯的有效成分用量分别为0.038 8、0.001和0.01 g/m2时,经水洗和漂烫处理,菠菜中上述3种农药的残留量分别降低22.6%、53.8%和50.8%;而加倍剂量处理时,则分别降低8.5%、61.4%和40.2%;烘干处理对毒死蜱的去除作用大于50%,但对氯氰菊酯和氰戊菊酯的去除作用仅为10%左右。对新鲜菠菜和干制菠菜的农药残留量进行膳食暴露评估的结果表明,合理的加工方式可以降低农药膳食摄入估计量的62.1%~76.7%。研究结果表明:毒死蜱的残留受水洗和漂烫影响较小,受烘干影响较大;而氯氰菊酯和氰戊菊酯的残留受水洗与漂烫影响较大,受烘干影响较小;引入加工因子后膳食暴露评估结果更接近真实值。