Effects of acetamiprid on Lipaphis pseudobrassicae (Hemiptera: Aphididae) resistant and susceptible to the parasitoid Diaeretiella rapae (Hymenoptera: Braconidae, Aphidiinae)

INTRODUCTION The aphid Lipaphis pseudobrassicae (Davis) (Hemiptera: Aphididae) is a cosmopolitan pest of Brassica, directly damaging crops by feeding on the leaves, causing deformation and yellowing, and indirectly damaging plants by transmitting more than ten types of plant pathogenic viruses, among them, collard green black ring and the mosaics of cauliflower, turnip and radish (Peña-Martinez, 1992; Blackman & Eastop, 2007). Because it is widely distributed, control of this aphid is extremely important throughout Brassica producing regions in such crops as canola, collard greens, broccoli, and cauliflower (Blackman & Eastop, 2000). The dose required to eliminate 50% of the population (LD50) of resistant insects is greater than that required for control of susceptible populations, and LD50 values are used to monitor the level of resistance in a population or pest (Szendrei et al., 2011; Paramasivam & Selvi, 2017). [...]it is not only the lethal effect of an insecticide that determines its effect on an insect's population, but also any sub-lethal effects it may cause, such as decreased fertility and longevity and changes in the development period (Stark & Rangus, 1994; Storch et al, 2007; Miao et al., 2016). [...]it is not known if the resistance of L. pseudobrassicae to D. rapae changes the effects of the insecticide on aphids. [...]this study determined the LD50 of the insecticide acetamiprid and its sub-lethal effect on fertility of resistant or susceptible clones of L. pseudobrassicae to see if there is such a relationship between resistance of the aphid to the parasitoid and the lethal and sub-lethal effects of the insecticide on L. pseudobrassicae. First instar nymphs were obtained from adults that were placed in Petri plates containing leaf disks of collard greens for 24 hours, after which the adult aphids were removed and the first instar nymphs left in the dish.