Asiimwe Peter, Naranjo Steven E, Ellsworth Peter C
Department of Entomology, University of Arizona, Maricopa Agricultural Center, 37860 West Smith-Enke Rd., Maricopa, AZ 85138, USA.
Environ Entomol. 2014 Apr;43(2):263-73. doi: 10.1603/EN12328. Epub 2014 Feb 17.
Variation in plant quality and natural enemy abundance plays an important role in insect population dynamics. In manipulative field studies, we evaluated the impact of varying irrigation levels and insecticide type on densities of Lygus hesperus Knight and the arthropod predator community in cotton. Three watering levels were established via irrigations timed according to three levels of percent soil water depletion (SWD): 20, 40, or 60, where 40% SWD is considered standard grower practice, 60% represents a deficit condition likely to impose plant productivity losses, and 20% represents surplus conditions with likely consequences on excessive vegetative plant production. The two key L. hesperus insecticides used were the broad-spectrum insecticide acephate and the selective insecticide flonicamid, along with an untreated check. We hypothesized that densities of L. hesperus and its associated predators would be elevated at higher irrigation levels and that insecticides would differentially impact L. hesperus and predator dynamics depending on their selectivity. L. hesperus were more abundant at the higher irrigation level (20% SWD) but the predator densities were unaffected by irrigation levels. Both L. hesperus and its predators were affected by the selectivity of the insecticide with highest L. hesperus densities and lowest predator abundance where the broad spectrum insecticide (acephate) was used. There were no direct interactions between irrigation level and insecticides, indicating that insecticide effects on L. hesperus and its predators were not influenced by the irrigation levels used here. The implications of these findings on the overall ecology of insect-plant dynamics and yield in cotton are discussed.
植物质量和天敌数量的变化在昆虫种群动态中起着重要作用。在人工控制的田间研究中，我们评估了不同灌溉水平和杀虫剂类型对棉田牧草盲蝽（Lygus hesperus Knight）密度以及节肢动物捕食者群落的影响。根据土壤水分消耗百分比（SWD）的三个水平，通过定时灌溉建立了三个浇水水平：20%、40%或60%，其中40% SWD被视为种植者的标准做法，60%代表可能导致植物生产力损失的亏缺状况，20%代表可能导致植物营养生长过剩的过剩状况。使用的两种关键的牧草盲蝽杀虫剂是广谱杀虫剂乙酰甲胺磷和选择性杀虫剂氟啶虫酰胺，以及一个未处理的对照。我们假设，在较高灌溉水平下，牧草盲蝽及其相关捕食者的密度会升高，并且杀虫剂会根据其选择性对牧草盲蝽和捕食者动态产生不同影响。在较高灌溉水平（20% SWD）下，牧草盲蝽更为丰富，但捕食者密度不受灌溉水平影响。使用广谱杀虫剂（乙酰甲胺磷）时，牧草盲蝽密度最高，捕食者数量最低，牧草盲蝽及其捕食者均受到杀虫剂选择性的影响。灌溉水平和杀虫剂之间没有直接相互作用，这表明杀虫剂对牧草盲蝽及其捕食者的影响不受此处使用的灌溉水平的影响。本文讨论了这些发现对棉花昆虫-植物动态和产量的整体生态学的影响。
