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The energy turnover of weevil populations ofRhynchaenus fagi L.,Strophosomus (Schönherr) andOtiorrhynchus singularis L. (Curculionidae) was investigated in the following stages: a) Observation of habits and life-cycle; b) investigation of abundance-dynamics; c) establishing the energy budget of average individuals; d) calculation of the energy turnover of the populations. In the case ofRhynchaenus fagi the investigations were carried out with all developmental and maturity stages, in the cases ofStrophosomus sp. andO. singularis only with the imagimes. 1. The larva ofR. fagi mines the beechleaf. The development takes 5\2-6 weeks from oviposition (beginning of May) to the emergence of the beetle. The imago lives for about 12 months. There is a first eating period lasting until the end of July, followed by about 9 months of almost no food consumption; after hibernation there is the second eating period (May to June) and reproduction (beginning of May). Strophosomus sp. emerges on the ground in September and eats in the top shoots of the trees till the leaves fall; it feeds on fallen foliage on the ground during the winter and high in the trees again from May to July.Strophosomus sp. reproduces mainly parthenogenetically and dies no later than the end of August. O. singularis emerges mainly in May and June. After an intensive feeding period these females also deposit mostly unfertilized eggs. The beetles live for several years, imagines from different years living side by side. 2. Beginning in JulyR. fagi migrates increasingly to nearby spruce forests which are its favourite winter quarters in the Solling. Microclimate and thigmotaxis between the needles protectR. fagi from higher mortality. 3. Abundance and mortality of eggs, larvae, pupae and young beetles ofR. fagi were determined by counting the larvae and pupae on a large number of leaves and by marking leaves with a numbered label. For the beetles a linear progression of mortality was assumed from emergence to reproduction. In the case ofStrophosomus sp. the numbers of beetles emerging and the winter mortality were determined by means of eclector catches. Shaking samples yielded data concerning the mortality after hibernation. WithO. singularis the numbers of beetles emerging was established by means of eclectors. 4. In the case ofR. fagi the production of an average individual is 2.654 cal till the end of the pupal stage, 6.353 cal until death. 1.103 cal are taken up for cocoon and exuviae, 0.809 cal for egg production. From emergence to the end of July of the following yearStrophosomus sp. produces body substance of a calorific value of 28.630 cal, of which 9.690 cal are taken up for eggs. 5. A new calorimetric method was applied for the first time in determining the respiration ofR. fagi during its leaf-mining stages. The results agreed with the calculation of energy losses based on manometric measurement of O-consumption. With all weevil imagines manometric measurement of O-consumption was carried out under near-natural conditions. The imagines showed seas...

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Experiments to control crown gall, caused by Agrobacterium tumefaciens, were carried out in an apple‐rootstock nursery. One‐year‐old apple rootstocks (M 9) were dipped in different concentrations of several copper compounds before planting. The compounds were used alone or in mixtures with clay or glue. Good control of crown gall was obtained with Copac E cuprammonium (ammoniacal cupric sulphate) and with copper oxychloride in clay slurries or mixed with glue. Although treatment with 2‐methoxyethylmercury chloride prevented the development of crown gall, phytotoxicity was severe.