Najar-Rodríguez Adriana J, Walter Gimme H, Mensah Robert K
School of Integrative Biology, The University of Queensland, Brisbane QLD 4072, Australia.
Pest Manag Sci. 2007 Jun;63(6):596-607. doi: 10.1002/ps.1384.
The primary mode of action of petroleum spray oils (PSOs) on pest insects is through direct contact. Indirect effects are, however, also possible, and deposits of the oils may influence pest populations by killing insects and/or by influencing their behaviour. The indirect effects of deposits of a new nC24 oil against the cotton aphid, Aphis gossypii Glover, were therefore determined. The effects of oil deposits on the acceptance of cotton as host plant by the aphids were assessed, as well as aphid mortality rates and their success in the establishment of colonies. The efficacy of deposits of a heavier oil (nC27) was also evaluated. Deposits of PSO were toxic to A. gossypii and remained effective until 8 days after spraying. Mortality decreased with time, so that, the older the deposit, the lower was the mortality. Significantly higher aphid mortalities were achieved on younger leaves than on mature ones. Thus, leaf age proved a significant factor in the efficacy of the deposits. Consecutive prophylactic applications (at 9 day intervals) did not have a cumulative effect, and their killing power proved to be independent of one another. Thus, applying the oil prior to aphid infestations would confer only minimal protection. The mortality inflicted by the deposits was not improved by increasing the molecular mass of the oil used (nC27 oil), but the toxic life of the oil deposit was increased. Oil deposits did not deter alates from landing on oil-sprayed plants. Oil deposits did, however, affect subsequent alate and nymphal survival, and thus the establishment of aphid colonies. The impact that the oils could have on the longer-term development of aphid populations in the field was thus demonstrated. First- and second-instar nymphs were the most susceptible life stages, with > 50% mortality compared with < 10% for the other stages. These nymphs did not show the typical signs of oil-induced mortality observed in aphids killed by direct oil applications, which suggests an alternative mode of action to that of the directly applied oil. Anoxia does not seem to be involved in either process, and alternative modes of action of the oil deposits are discussed. The implications of these findings for cotton aphid control are also considered, primarily in relation to the timing and frequency of oil application.
石油喷雾油（PSOs）对害虫的主要作用方式是直接接触。然而，间接影响也有可能存在，油的沉积物可能通过杀死昆虫和/或影响其行为来影响害虫种群。因此，确定了一种新型nC24油的沉积物对棉蚜（Aphis gossypii Glover）的间接影响。评估了油沉积物对棉蚜将棉花作为寄主植物的接受程度的影响，以及棉蚜死亡率及其建立虫群的成功率。还评估了一种较重的油（nC27）的沉积物的功效。PSO的沉积物对棉蚜有毒，并且在喷洒后8天内仍然有效。死亡率随时间下降，因此，沉积物越陈旧，死亡率越低。嫩叶上的棉蚜死亡率明显高于成熟叶。因此，叶龄被证明是沉积物功效的一个重要因素。连续预防性施用（每隔9天）没有累积效应，并且它们的杀伤力被证明是相互独立的。因此，在棉蚜侵染之前施用这种油只能提供最小程度的保护。使用的油分子质量增加（nC27油）并没有提高沉积物造成的死亡率，但油沉积物的毒性持续时间增加了。油沉积物并没有阻止有翅蚜降落在喷洒了油的植物上。然而，油沉积物确实影响了随后有翅蚜和若蚜的存活，从而影响了棉蚜虫群的建立。由此证明了这些油对田间棉蚜种群长期发展可能产生的影响。一龄和二龄若蚜是最易感的生命阶段，死亡率>50%，而其他阶段<10%。这些若蚜没有表现出在直接施用油杀死的棉蚜中观察到的典型的油诱导死亡迹象，这表明其作用方式与直接施用的油不同。缺氧似乎在这两个过程中都不涉及，并讨论了油沉积物的其他作用方式。还考虑了这些发现对棉蚜防治的影响，主要涉及油施用的时间和频率。
