Life cycle traits of the parthenogenetic earthworm Octolasion cyaneum (Savigny, 1826)

This laboratory-based study provides baseline life cycle data for the obligatory parthenogenetic earthworm Octolasion cyaneum. Singleton and twin hatchlings were cultured individually with biomass, survival and reproductive condition recorded at 4-weekly intervals during a complete year. After maturation, cocoon production, masses and incubation time were also recorded along with viability and number of hatchlings per cocoon. Individual mean mass of singletons was significantly (P < 0.05) greater than twins at the outset (0.042 and 0.025 g respectively) and remained so until week 52 (2.22 and 1.96 g respectively). Singletons matured more rapidly than twins (24 vs. 32 weeks respectively) and produced more cocoons than twins (3.2 and 2.2 coc worm⁻¹ (4 weeks)⁻¹ respectively). Approximately 20% of all viable cocoons produced twins. Singleton hatchlings weighed significantly (P < 0.05) more than twin hatchlings (0.032 and 0.018 g respectively) but there was no significant difference (P > 0.05) between mean masses of singleton (mean masses 0.033 and 0.032 g) or twin (0.017 and 0.018 g) hatchlings produced by singleton and twin parents. The likelihood that a cocoon contained twins or a singleton was not influenced by the singleton/twin status of the parent. There was no significant difference (P > 0.05) in the incubation times of cocoons produced by singletons and twins (129 and 128 days respectively).     

Inoculation of earthworms into reclaimed soils: the UK experience

Earthworms have positive effects on soil structure, therefore their incorporation during the process of soil reclamation is a sensible route towards the final restoration of a site. Over the past 20 years, 16 documented field trials have been conducted in the United Kingdom. These trials took place at locations with a number of previous uses, for example, landfill sites, steelworks and opencast mines. The species of earthworm used varied, as did the techniques used for introducing them into the soil. This paper assessed the suitability of the earthworms chosen for each trial and, more importantly, trial outcomes. The most appropriate species were not always selected (possibly due to availability) and the introduction technique was not always the most appropriate for the site. Monitoring of trials generally occurred over relatively short periods of time (possibly due to limited funding). It is evident that more recent trials were not always informed by previous events. It is suggested that work of this nature may only be viable if brought about through site-related legal obligations. Copyright © 1999 John Wiley & Sons, Ltd.     

Differential susceptibility of Hyalomma excavatum adults and nymphs to the entomopathogens Metarhizium anisopliae ARSEF 4556 and Steinernema carpocapsae

This study investigated the virulence of the entomopathogenic fungus, Metarhizium anisopliae strain ARSEF 4556, and the entomopathogenic nematode Steinernema carpocapsae against adult and nymphal stages of the tick Hyalomma anatolicum excavatum. The fungus was tested at three different concentrations, 10⁶, 10⁷, and 10⁸ conidia ml^?1. Ticks were exposed to 4000 IJs of S. carpocapsae in 0.5 ml distilled water in Petri dishes lined with 2 layers of moist filter paper. Adult ticks were not susceptible to M. anisopliae, whereas the nymphs were highly susceptible. Nymph mortality was dose dependent with all ticks being killed at the highest dose 96 hours post-inoculation. In contrast, S. carpocapsae was much more effective against engorged adults than unfed adults or nymphs. Tick susceptibility was not influenced by gender. The mean mortalities of the unfed adult males, females, and nymphs were 30% ± 9.2%, 40% ± 7.5%, and 36% ± 4.7%, respectively. Nymphal mortality was 36% and there was a significant difference between nematode treatment and control group (P < 0.05).     

Culture of commercially obtained Lumbricus terrestris L.: Implications for sub-lethal ecotoxicological testing

The use of commercially purchased or field-collected earthworms of unknown age, exposure or pre-treatment in sub-lethal ecotoxicological studies is questionable. In this study, adult (clitellate) Lumbricus terrestris, obtained from 5 commercial suppliers in the UK and also field collected, were kept under controlled environmental conditions (15 °C and 24 h darkness) in a sterilised loam soil and fed horse manure. Survival, biomass and cocoon production was monitored every 4 weeks over 1 y. Marked differences were recorded in survival rates (ranging from 40-100% after 40 weeks) and cocoon production (ranging from 15.1 to 32.2 worm⁻¹ y⁻¹) between treatments. Biomass in all treatments (mean mass 4.32-5.61 g at the outset) increased with time to week 20 (maximum 6.7 g) and then declined steadily (3.23-4.7 g at week 52). This pattern was also observed in cocoon production and was considered to be a function of an initial period of acclimation (0-12 weeks) followed by a period of high production (12-36 weeks) under optimal conditions and then fatigue (36-52 weeks) caused by reproductive exhaustion. Results suggest that earthworm origin may influence the validity and reproducibility of sub-lethal ecotoxicological studies and where applicable laboratory-reared earthworms of known age and history are recommended as test subjects.     

The hybridization of coffea canephora pierre- A technique using waxed cartons

Previous doubts about the allogamous nature of the stocks of robusta coffee in Uganda were removed after using improved pollination chambers made from waxed cartons. Their use facilitated the production of hybrids. The preparation of the cartons is described, and their advantages and adaptability to other studies are mentioned.     

Temporal patterns of airborne conidia of Podosphaera leucotricha, causal agent of apple powdery mildew

In each of the five years 1969 and 1971-1974 inclusive a volumetric spore trap was used in an apple orchard to monitor changes in the number of airborne conidia of Podosphaera leucotricha , the causal agent of apple powdery mildew. The number of trapped conidia varied greatly between years. Time-series analyses, using autoregressive integrated moving average (ARIMA) models, revealed that the temporal pattern of the number of airborne conidia was similar in all years, generally following a diurnal pattern with an afternoon peak. A strong correlation between consecutive hourly counts indicated that the number of trapped conidia depended on the strength of sporulating sources. Using the time-series transfer function (TF) method, it was shown that in each year the most important weather variables influencing the number of airborne conidia were vapour pressure deficit (VPD) and rainfall. Variation between years in the dynamic effects of these variables on conidium numbers was detected, and may reflect weather differences between years. Stepwise regression analysis was applied to the combined daily data for 1973 and 1974 using a subset of weather variables as independent variables, chosen on the basis of TF analysis. A resulting regression model accurately predicted the temporal pattern of conidium numbers (expressed as a percentage of the maximum daily number trapped in the same year) in both years. When this model was applied to the other three years there was good agreement between predicted and observed temporal patterns. Application of this regression model for practical disease control is discussed.     

Predatory potential of three hunting spiders inhabiting the rice ecosystems

Present study was designed to assess the prey preference behaviour of three most dominant hunting spiders [Lycosa terrestris Butt, Anwar and Tahir 2006 (Araneae: Lycosidae), Pardosa birmanica Siman 1884 (Araneae: Lycosidae) and Oxyopes javanus (Thorell 1887) (Araneae: Oxyopidae)] of rice ecosystems both in the laboratory and in the field. Two types of laboratory experiments, i.e., choice and no choice feeding, were performed using only adult male and female specimens of the spiders. No choice test showed that each of the three hunting spiders readily consumed larvae and nymphs of rice pests offered. Female hunting spiders consumed more prey compared to male hunting spiders. Results of choice feeding test indicated that L. terrestris and P. birmanica preferred nymphs of rice insect pests while O. javanus preferred larvae of rice insect pests. Results of direct observations showed that in August, dipterous insects were the most numerous rice pests consumed by L. terrestris, P. birmanica and O. javanus, comprising over 56.3, 38 and 48% of their respective diets. In contrast, in September, the proportion of dipterous insects decreased dramatically and hoppers become the most numerous pests, comprising over 50, 51 and 41% of all prey and spiders consumed by L. terrestris, P. birmanica and O. javanus, respectively. In October, aquatic Heteroptera were frequently observed in their diets. Predatory potential of these hunting spiders differed statistically in the laboratory as well as in the field. It is concluded from the results of present project that studied species of spiders could successfully be used to control insect pests of rice ecosystems.