Beiträge zur Lebensweise des Ampferblattkäfers (Gastrophysa viridula Deg.)

Abstract

The habits, injuriousness and control of G. viridula Deg. on Rheum palmatum var. tangutium Rhl. were studied during an outbreak. The beetles and their developmental stages are described and their development recorded. The dock leaf beetle has three generations per year, two in upland areas (1300 m. or above). The female lays from 100 to 600 eggs. The adventitious parthenogenesis known for G. viridula was not observed either outdoors or in the laboratory. The larvae moult twice and are mainly destroyed by Coccinellids, Syrphid larvae and the like. In the main zone of attack, every rhubarb plant had about 6,000 eggs from the females of a single generation. The larvae from these can show losses of up to 50% a few days after hatching. In a given population, the egg mortality is about 1%, larval mortality 80–98% and pupal mortality 1–10%. The total mortality from egg to adult was calculated as 98% for the first generation and 99,9% for the second. The dock leaf beetle was present outdoors from the end of April to the middle of November. The eggs, larvae and pupae still to be found in November, perish. In 1953, the development from egg to adult took 50 days, of which the egg stage needed 7–10 days, the larval stage 21–30 days and the pupal stage 6–9 days. The beetle and its larvae feed mainly on various species of Polygonaceae and prefer Rumex spp. Complete development of G. viridula on Chinese rhubarb, Rheum palmatum var. tangutium Rhl. could be proved, but nowhere was the edible rhubarb observed to be attacked. The larvae are able to feed on several species of other plant families if food is short. In 1953, each generation of the dock leaf beetle destroyed one-sixth of the total leaf area of the Chinese rhubarb. The loss of leaves caused by three generations was tolerated by the rhubarb without measurable decrease in yield. Beetles and larvae can be destroyed by phosphoric acid ester preparations such as E605 dust in one hour and by DDT-lindane or lindane dust preparations in 21/2 hours. G. viridula is liable to mass increases which can be of phytopathological importance because of the polyphytophagy of the larvae for Rumex and rhubarb cultures.