Chemical strategies to manage pest populations that have evolved pesticide resistance can involve killing resistant individuals by using higher rates of the same pesticide or applying alternative pesticides for which resistance does not exist. However, the dilemma is that alternative pesticides available for many pest species are limited, while higher pesticide rates may lead to the evolution of higher resistance levels. Here, both strategies are tested in a resistant population of the redlegged earth mite, Halotydeus destructor, which contained resistance against two groups of chemicals: synthetic pyrethroids and organophosphates. Resistant mites were introduced into exclusion field plots, which were then treated with pyrethroid, organophosphate or alternative chemicals for 2 years at a low pressure (one spray at the registered field rate per year) or a high pressure (two sprays at the registered field rate per year). A single pyrethroid application suppressed mite numbers, but pyrethroid-resistant allele (kdr) frequencies quickly rose from ∼50% to nearly 100%. Thereafter, pyrethroid chemicals lost effectiveness. However, kdr frequencies declined across mite generations when pyrethroids were not used, regardless of other treatments. Organophosphates continued to suppress mite populations under both high and low pressures, irrespective of kdr allele frequencies, and laboratory bioassays showed no increase in organophosphate resistance levels. One of the alternative chemicals, diafenthiuron, applied once per year over two years, successfully suppressed mite numbers, whereas other treatments did not control mites. These findings demonstrate that different strategies are required to manage H. destructor with pyrethroid resistance and organophosphate resistance.

管理已进化出农药抗性的害虫种群的化学策略可能涉及通过使用更高比例的相同农药或使用不存在抗性的替代农药来杀死具有抗药性的个体。然而，困境在于可用于许多害虫物种的替代杀虫剂是有限的，而更高的杀虫剂率可能导致更高的抗性水平的演变。在这里，这两种策略都在红脚土螨Halotydeus destructor的抗性种群中进行了测试，其中包含对两组化学物质的抵抗力：合成拟除虫菊酯和有机磷酸盐。将抗性螨引入排除田地，然后用拟除虫菊酯、有机磷或替代化学品在低压（每年以登记的田地率喷洒一次）或高压（以登记的田地率喷洒两次）下处理 2 年每年）。单一的拟除虫菊酯应用抑制了螨虫数量，但抗拟除虫菊酯等位基因 ( kdr ) 频率迅速从约 50% 上升到接近 100%。此后，拟除虫菊酯化学品失去效力。然而，kdr当不使用拟除虫菊酯时，无论其他处理如何，螨虫世代的频率都会下降。不管kdr等位基因频率如何，有机磷在高压和低压下继续抑制螨类种群，实验室生物测定显示有机磷抗性水平没有增加。其中一种替代化学品丁醚脲在两年内每年施用一次，成功地抑制了螨虫数量，而其他处理方法不能控制螨虫。这些发现表明需要不同的策略来管理具有拟除虫菊酯抗性和有机磷抗性的H. destructor。