On understanding and manipulating the hatching patterns of Diabrotica virgifera virgifera eggs to improve the design of experiments

Abstract

Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae) is a well-studied pest of maize (Zea mays L., Poaceae) in North America and Europe. Many studies on its biology, behaviour, or management rely on individuals reared from either field-collected insects or laboratory colonies. Naturally, D. v. virgifera eggs require an obligate 8-10-month diapause, which can cause technical challenges such as a deceleration of research activities. To allow better planning of experimentation, we have investigated the survival and temporal hatching patterns of the pest's eggs depending on diapause length as well as post-diapause incubation temperature. Laboratory assays revealed that the highest hatching rates and most synchronized hatching times in a wild diapausing population occurred when eggs were overwintered at the natural diapause length (8-10 months) or shorter (5-7 months) and then incubated at 20-24 °C. Eggs diapaused for only 2 months showed comparably good hatching rates, but hatching patterns appeared more variable. Diapause of <2 or >10 months reduced hatching success, as did low (16 °C) incubation temperatures. For comparison, a wellstudied non-diapausing laboratory colony was assessed as well. Data matrices on egg overwintering survival, the start, peak, duration, and end of egg hatching, as well as hatching rates are provided for various diapause lengths and three incubation temperatures for both populations. This information will support scientists in choosing a D. v. virgifera colony that fits best their experimental set-up and study conditions, as well as in optimally planning such studies.

Limited Influence of Abiotic and Biotic Factors on the Efficacy of Soil Insecticides and Entomopathogenic Nematodes when Managing the Maize Pest Diabrotica v. virgifera (Coleoptera: Chrysomelidae)

“…Parallel with the artificial infestation in the field, some eggs were transferred onto moistened filter paper to check their overwintering survival and hatching success. The average hatching ratio was always between 50 and 80%, with a relatively high variability, and hatching patterns were comparable to reports from the literature [55].…”

“…Eggs were obtained from laboratory-reared beetles that had been collected from fields in southern Hungary the previous year. For rearing and overwintering procedures, see [54,55]. In April, the eggs were transferred to a 24-degree-Celsius environment to stop diapause.…”

“…The formulated nematodes were then diluted in water and injected into the seeding row behind seed placement (200 up to 550 L of water per hectare). Different applicators were used as described in [55].…”