Effect of Water on Survival and Development of Diapausing Eggs of Apolygus lucorum (Hemiptera: Miridae)

Abstract

The green mirid bug Apolygus lucorum is a regional pest of multiple crops in northern China, and the survival and development of diapausing eggs during winter plays an important role in the population dynamics of this species. The effect of water on the survival and development of A. lucorum eggs was investigated using laboratory-induced diapause. Diapausing eggs were exposed to various humidity regimes under three conditions: (1) termination of diapause with exposure to warm long-day (WLD) conditions (i.e., 26 ± 1°C and 75 ± 5% relative humidity (RH) under a photoperiod of 16 hours light and 8 hours dark), (2) termination of diapause by chilling at 4°C, or (3) during the post-diapause stage, i.e., from transfer to WLD conditions after chilling, until the hatching of nymphs. The results indicate that water availability is crucial for the post-diapause resumption of development of A. lucorum. However, exposure to excessive moisture was detrimental, as indicated by a decrease in diapause termination rate and a prolonged pre-hatching period of diapausing eggs, compared to limited moisture conditions. This implies that both too dry and too humid environmental conditions would suppress survival and postpone hatching of overwintered A. lucorum eggs, and might explain why this pest has not caused severe damage in either southern or western China where the respective climates are very humid or dry.

Embryonic stage of obligatory diapause and effects of abiotic conditions on egg hatching in the balsam twig aphid, Mindarus abietinus

“…In temperate climates where cold hardiness may depend on dehydration, water intake or absorption may be necessary to allow proper diapause development (Danks, ). When moisture is reported as a crucial factor in postdiapause resumption of development (e.g., Apolygus lucorum Meyer‐Dür in northern China; Jin et al., ), an unbalance between water and temperature may ultimately decrease hatching rates, as observed here for M. abietinus in the low‐temperature regime. As with M. abietinus , egg size increase under high‐moisture treatment was necessary for successful hatching in Trirhabda geminata Horn, a species of southwestern USA (Bethke & Redak, ).…”

When natural enemies go to sleep: diapause induction and termination in the pear psyllid predator Pilophorus gallicus (Hemiptera: Miridae)

“…Photoperiodic induction of winter diapause is common in multivoltine insects from temperate zones, with just a few species known to exhibit other kinds of responses. 3,[43][44][45] The long-day photoperiodic response (sensu Beck 15 ) observed in P. gallicus has been widely reported amongst the Hemipterans that overwinter as eggs, [46][47][48] but has also been found for those that overwinter as nymphs 28,49,50 or adults. 38,[51][52][53][54][55][56] This generalized response reveals the importance of this mechanism for the survival of a great number of species.…”

Effects of photoperiod and relative humidity on diapause termination and post-winter development ofRhagoletis cerasipupae

“…Nonetheless, moisture is rarely expected to serve as a cue for diapause induction because of spatial and temporal variability in its occurrence (Tauber et al ., 1998). However, moisture remains an important factor that triggers resumption of development at the end of dormancy stimulating adult emergence in many insects (Hodek, 2003; Jin et al ., 2016; Socías et al ., 2016). For example, the larvae of the wheat blossom midges, Contarinia tritici and Sitodiplosis mosellana (Diptera: Cecidomyiidae), need high soil moisture or rainy conditions for pupation after the temperature-regulated diapause development (Cheng et al ., 2017).…”

“…Recently, inadequate soil moisture was found to promote prolonged diapause in already diapausing individuals of S. mosellana (Cheng et al ., 2017). On the other hand, exposure to excessive moisture can be detrimental for the resumption of post-diapause development as well (Jin et al ., 2016). Regardless of the amount of precipitation, the timing of rainfall and the persistence of moist soil may regulate diapause processes of insects, given that diapausing stages may only be sensitive to soil moisture for a short period and different soil textures have various water-retention capacities (Ma et al ., 2017).…”

“…Regardless of the amount of precipitation, the timing of rainfall and the persistence of moist soil may regulate diapause processes of insects, given that diapausing stages may only be sensitive to soil moisture for a short period and different soil textures have various water-retention capacities (Ma et al ., 2017). A combined effect of moisture with temperature on post-diapause development rates has also been reported for Apolygus lucorum (Hemiptera: Miridae) (Jin et al ., 2016), S. mosellana (Cheng et al ., 2017) and Leptinotarsa decemlineata (Coleoptera: Chrysomelidae) (Tauber et al ., 1994).…”