The effect of photoperiod and light quality on Macrolophus pygmaeus Rambur (Hemiptera: Miridae) nymphal development, fecundity and longevity

Abstract

Development time of immatures, fecundity, longevity and egg hatching of the predatory bug Macrolophus pygmaeus were studied over three years under artificial lighting in growth chambers to assess if light quality and photoperiod could explain its poor establishment in winter tomato crops at northern latitudes. In the first year, the effect of photoperiod was assessed using fluorescent lamps (FLs) at 16L:8D, 13L:11D, 11L:13D and 8L:16D. In the second year, the effect of light quality was assessed by producing the 16L:8D photoperiod with FLs, high pressure sodium lamps (HPSLs) and HPSLs complemented with red (R) light emitting diodes (LEDs) (11+5h, HPSLs+R). In the third year, 16L:8D, 11L:13D, 8L:16D photoperiods were produced by HPSLs and 16L:8D with FLs. In all the treatments, females from the first, second and third generation oviposited, and their eggs hatched pointing that M. pygmaeus does not undergo reproductive diapause. In general, shorter photoperiods prolonged the development time of immatures regardless the light source, whereas fecundity increased with decreasing photoperiod irrespectively of light quality. In FLs, fecundity was significantly lower than in HPSLs alone or in HPSLs+R in one experiment, whereas light quality (FLs and HPSLs) did not affect fecundity in the other experiment. The results suggest that HPSLs as such do not adversely affect reproductive biology of the bug except for the pre-adult development time, and that part of the long photoperiod could be replaced with red LEDs without negatively affecting the bug’s biology. The 16-h light period produced by artificial lighting in year-round tomato production, however, is not optimal for the fecundity of M. pygmaeus, and fertility may also decrease. Further research is needed from greenhouse winter conditions where the bugs perceive and may respond also to the natural short photoperiod.