Abstract. Development and survival of larvae of two predatory ladybird species, Harmonia axyridis (Pallas) and Coccinella septem punctata L. on hibiscus (Hibiscus syridis L.) trees was followed daily outdoors during four seasons. Data were analysed and stagespecific mortality in a stage-structured model was estimated using Manly's (1997) method. Subsequently, key factor analysis was used to determine the life stages in which the daily mortality was best correlated with the total mortality during larval life. Consis tently with the results from the first two years, the larvae suffered the greatest mortality during the first and fourth instars. The k-values for these two instars were also best correlated with those for the whole larval life, especially in H. axyridis.

Competition, predation, and disturbance are important in shaping communities (e.g. Menge and Sutherland, 1987;Begon et al., 1996). Intraguild predation is common among arthropods in agricultural (Rosenheim et al., 1993(Rosenheim et al., , 1995Cisneros and Rosenheim, 1997) and natural ecosystems (Moran and Hurd, 1994;Snyder and Hurd, 1995); therefore, intraguild predation is thought to be an important factor affecting population dynamics and community structure in several taxa of predatory arthropods (Polis et al., 1989;Spence and Carcamo, 1991;Polis and Holt, 1992;Fincke, 1994;Wagner and Wise, 1996; Holt and Polis, 1997;Mizell, 2007;Montserrat et al., 2008).Many species of predatory arthropods are attracted to sites where aphids are abundant (Sakuratani, 1977;Aalbersberg et al., 1988;Winder et al., 1994;Wyss, 1995;Nakashima and Akashi, 2005;Alhmedi et al., 2007). In these aphidophagous guilds, intraguild predation often occurs and its incidence depends on prey abundance and the developmental stages and species of the predator involved (Takahashi, 1989;Agarwala and Dixon, 1992; Rosenheim et al., 1993;Cisneros and Rosenheim, 1997;Dinter, 1998;Lucas et al., 1998;Obrycki et al., 1998;Phoofolo and Obrycki, 1998).Of these aphidophagous arthropods, ladybirds are important, and because of their voracity and size they affect the survival of other aphidophagous insects (Lucas et al., 1998;Obrycki et al., 1998); however, the nature and relative strengths of intraguild predation on larval survival have not been quantified. Knowledge of the effect of these interactions on their performance throughout their larval development, when they coexist in the same habitat, is needed for a better understanding of Effects of intra and interspecific interactions on the survival of two predatory ladybirds (Coleoptera: Coccinellidae) in relation to prey abundance AbstractThe relative effects of intra and interspecific interactions on the larval survival of two species of aphidophagous ladybirds, Coccinella septempunctata brucki and Harmonia axyridis, were assessed at two different prey abundances. In single species rearing, the number of larvae of both species decreased during the latter developmental stages, mainly due to cannibalism. When prey was abundant, the survival of both species improved; however, in mixed species rearing, the mortality of C. septempunctata brucki due to cannibalism or intraguild predation was higher than in single species rearing, whereas the mortality was lower in H. axyridis. Consequently, the survival of C. septempunctata brucki decreased while that of H. axyridis improved. In addition, in the 18 intraguild predation events observed, H. axyridis was always the intraguild predator and C. septempunctata brucki was its prey. Thus, when these two species co-exist in the field, H. axyridis is likely to be an important intraguild predator of C. septempunctata brucki. In addition, when prey is scarce, it is likely that cannibalism and intraguild predation become more important factors in the intra and interspecific...

To improve the yield of sweet cherries (Prunus avium L.) grown by hedge-row training, the following two methods were compared: increased numbers of spurs and bouquet spurs to improve the spur composition and narrowed row intervals to increase planting density. To develop spurs and bouquet spurs, 30 cm long branches were positioned at 30 cm intervals on lateral branches in addition to the conventional spur development from 5 cm current shoots. Although this measure decreased the number of bouquet spurs, it increased the total number of spurs including the conventional short spurs to improve the yield to 1,024 kg・10 a −1 from 557 kg・10 a −1 using conventional hedge-row training. However, this method decreased solar radiation in the tree crowns thereby lowering fruit quality. In contrast, increasing planting density from 3-m intervals to 2-or 1.5-m intervals did not affect fruit quality. Moreover, in contrast to a yield of 588 kg・10 a −1 when row intervals were 3 m, the row intervals narrowed to 2 m and 1.5 m improved the yield to 881 kg・10 a −1 and 1,101 kg・10 a −1 , respectively. The above results show that decreasing row intervals is an effective method for increasing the yield of sweet cherries grown by hedge-row training without lowering fruit quality.

The purpose of this study was to examine the effects of summer pruning on the improvement and uniformity of the quality of fruit hedgerow-trained sweet cherry trees. The photosynthetic activity and translocation and distribution of photosynthates before summer pruning were compared with those after summer pruning to identify changes. Photosynthetic activity was measured in the basal part of current shoots 30 days after summer pruning. Photosynthetic activity did not change in response to weak sunlight, but it responded to changes in the photoenvironment to a 32% increase of strong sunlight from the level before summer pruning. The amount of 13 C translocation to fruit from various parts of the current shoots was in the following descending order: basal part > middle part > tip. The basal part provided the largest amount of 13 C translocation to fruit.Summer pruning further increased the rate of translocation to fruit from leaves in the basal part of current shoots. These data clearly show that current shoot management by summer pruning is an effective method to produce mass in sweet cherry.Key Words：assimilation, current shoot, matter production, palmette training

To improve the fruit set of sweet cherries, we investigated the effects of an acclimation method of pollen storage on the fruit bearing rate and pollen activity. Pollen stored at a low temperature, -30°C, led to a 14.0% germination rate immediately after being transferred from the freezer. When acclimated for 2 hours at relative humidity 90%, the germination rate rose significantly to 42.4%. By increasing the acclimation period to 4 hours, the germination rate did not change significantly at 45.9%. Under dry conditions of relative humidity 30% and an acclimation period within 4 hours, there was no significant difference in the pollen germination rate. Examination of the effect of the acclimation temperature on the pollen germination rate under relative humidity 90% for 2 hours showed little difference in the germination rates (43.0% at 4°C, 45.4% at 20°C). However, when pollen was acclimated for 12 hours at 25°C, the germination rate was significantly reduced to 7.9%. Artificial pollination using stored pollen that had been acclimated with the conventional method led to a fruit bearing rate of 2.5%. The fruit bearing rate was 17.2% with artificial pollination when stored pollen was acclimated for 2 hours at a high humidity (90%RH). Further more, the fruit bearing rate on artificial pollination with pollen acclimated under high humidity conditions was higher than when using pollen acclimated under dry conditions or using conventional methods.