Rotifers and especially the Brachionus calyciflorus species have already shown advantages (e.g. good sensitivity, simplicity, ecological relevance, short generation time) for the chronic toxicity assessment of water pollutants. In this study, the B. calyciflorus three-day test was evaluated on ethinylestradiol, nonylphenol and testosterone for the determination of endocrine disrupting (reproductive) effects. Reproduction (intrinsic rate of population increase) and sex ratio (males/females and mictic females/amictic females) were explored and discussed as suitable endpoints. B. calyciflorus has shown a fair sensitivity to detect reproductive disrupting effects after exposure to ethinylestradiol, nonylphenol and testosterone. Population growth (intrinsic rate of population increase, r) and the ratio ovigerous females/ non-ovigerous females are both suitable endpoints, whereas the occurrence of males was not frequent enough to be used as endpoint.

The performances of four chronic toxicity tests, comprising the Daphnia magna 21-day (d) (crustacean), Brachionus calyciflorus 2-d (rotifer), Pseudokirchneriella subcapitata 72-h (green algae), and the Microtox chronic 22-h (bacteria) tests, were compared. Sixteen chemicals with toxicity covering 6 orders of magnitude were studied. Very high correlations were found between the NOEC/EC(10) Pseudokirchneriella 72-h, NOEC/EC(10) Brachionus 2-d, and the NOEC Daphnia 21-d tests. The toxicological response of rotifers and microalgae were within the same order of magnitude as the response of Daphnia in 80% of cases (13/16 chemicals). The Microtox chronic test also anticipated the overall results of the Daphnia 21-d test, but the prediction was rather imprecise, compared with microalgae and rotifers. The test measuring the algal growth inhibition of P. subcapitata after 72h was the most sensitive bioassay. Toxicity on microalgae after 72h could be estimated after 5h by measuring either the direct fluorescence of either photosynthetic pigments or fluorescein diacetate in 56 and 43% of cases, respectively. The median value of the ratio between EC(10) and EC(50) was 3.75, 2, and 1.5 with the algae, the rotifers, and the bacteria, respectively.

The Daphnia magna 21‐d test may be required by European authorities as a criterion for the assessment of aquatic chronic toxicity for the notification of new substances. However, this test has several drawbacks. It is labor—intensive, relatively expensive, and requires the breeding of test organisms. The Brachionous calyciflorus 2‐d test and Microtoxr̀ chronic 22‐h test do not suffer from these disadvantages and could be used as substitutes for the Daphnia 21‐d test for screening assays. During this study, the toxicity of 25 chemicals was measured using both the Microtox chronic toxicity and B . calyciflorus 2‐d tests, and the no—observed‐effect concentrations (NOECs) were compared to the D . magna 21‐d test. The Brachionus test was slightly less sensitive than the Daphnia test, but the correlation between the two tests was relatively good ( r 2 = 0.88). On average, the Microtox chronic test presented the same sensitivity as the Daphnia test, but the results did not correlate as well ( r 2 = 0.54). The B. calyciflorus 2‐d test, and to a lesser extent the Microtox chronic 22‐h test, were able to predict the chronic toxicity values of the Daphnia 21‐d test. They constitute promising cost—effective tools for chronic toxicity screening.

Walnut blight is the major disease in the walnut orchards of Dauphine (France). The causal bacterium Xanthomonas campestris pv. juglandis can infect leaves, catkins, buds and nuts and can induce important crop losses. Field observations have shown that the nature of the soil seems to play a prominent role in crop losses. The hypothesis that soil may modify the amount of polyphenols in walnut tissues and modify the natural resistance of fruits to necrosis has been assumed. We have shown that the nature of the soil, especially its permeability, induces variations in polyphenols in walnut tissues. Differences of susceptibility to walnut blight between the two cultivars studied, Franquette and Parisienne, may also be explained by different behaviours in relation to polyphenols. Moreover, the massive use of copper treatments against walnut blight may induce an imbalance in polyphenol contents and could explain crop losses despite repeated copper sprays. ((C) Inra/Elsevier, Paris.)

Walnut is one of the major regional crops produced in Dauphiné (SE France). Unfortunately, walnut blight has been recorded as the main disease for years. Crop losses due to this disease may reach high levels in spite of repeated copper sprays. In order to monitor the bacterial contamination of the fruits, two orchards differing in soil, irrigation and treatment were selected. Fruit sampling was performed once a week for 11 weeks. Results showed that the percentage of contaminated fruits was more important at the beginning of a maturation, that bacterial populations rapidly reached a maximum level and that there was no obvious relation between the number of bacteria infecting a fruit and the occurrence of necrosis. These results did not indicate any significant difference between the two orchards, in these respects.

Walnut is one of the major regional crops produced in Dauphine (SE of France). Unfortunately, walnut blight has been mentioned as the main disease for years. Until now, the only way to control this disease has been the use of copper sprays, therefore copper accumulation into the soils is alarming and tends to turn the soils sterile for subsequent crops. We have dosed copper in the soils of twelve different orchards and showed that copper accumulation may disturb the metabolism of the trees.

Following a dispute between walnut producers and an anglers association, the toxicity of walnut washings has been determined and followed in a sewer and in a stream in a walnut production area near Grenoble (France) and compared with juglone toxicity. Toxicity of the washings has also been determined after storage at two different temperatures, with and without light. Juglone was found only to be responsible for a small part of this toxicity.