Het vaststellen van de door de erwteknopmade (Contarinia pisi) veroorzaakte schade en de bestrijding van dit insekt

Summary The preceding paper deals with the damage caused byContarinia pisi. The technique used to determine the losses of yield is discussed. Heuver (1960) is of the opinion, that the cutting of flowerbuds (in fact flowers and young pods) of the pea plant is comparable to an infestation byContarinia pisi. However, according to the present authors' investigations these injuries are not comparable. It is also impossible to investigate the exact damage by treating small plots in larger untreated pea fields because reinfestation of the treated plots will occur.The most feasible method to determine crop losses is by comparing average yields in a well treated area with the yields obtained in untreated fields in the same area.The accuracy of this method is greatest in years when damage is heavy.The damage to both canning peas and harvesting peas may be serious.     

The role of quantitative electromyography (EMG) in horses suspected of acute and chronic grass sickness

REASONS FOR PERFORMING THE STUDY: Clinical evidence of motor neuron involvement in equine grass sickness (EGS) has not been reported. HYPOTHESIS: Quantitative electromyography (EMG) analysis can elucidate subtle changes of the lower motor neuron system present in horses with EGS, performed ante mortem. METHODS: Fourteen horses diagnosed clinically with acute, subacute or chronic EGS were examined and quantitative EMG performed. Previously published data on healthy horses and horses with proven lower motor neuron disease (LMND) were used as controls. In 8 horses post mortem examination was performed, and in 7 muscle biopsies of the lateral vastus muscle underwent histopathology and morphometry. RESULTS: Clinical electrophysiological evidence of neuropathy was present in 12 horses. Analysis of data from the first 4 horses resulted in 95% confidence intervals (CI) of nontransformed data for motor unit action potential (MUP) duration in subclavian, triceps and lateral vastus muscle of 11.0-13.7, 14.8-20.3 and 12.2-17.2 msecs, respectively, and for MUP amplitude 291-453, 1026-1892 and 957-1736 microV, respectively. For number of phases the 95% CI was 3.6-4.4, 2.9-3.6 and 2.9-3.4, respectively, and for number of turns 5.0-6.5, 4.3-5.3 and 3.7-4.6, respectively. No changes in duration of insertional activity were measured. Pathological spontaneous activity was observed in all horses. EGS as evidenced by degenerative changes in the autonomic ganglia in combination with minor degenerative changes of the spinal lower motor neurons was observed on post mortem examination in all 8 available autopsies. In muscle biopsies of 4 out of 7 horses changes consistent with slight neurogenic atrophy were found. CONCLUSIONS AND POTENTIAL RELEVANCE: EMG results demonstrated the presence of a neuropathy of skeletal muscles in all horses suspected to have EGS. The combination of clinical and electrophysiological evidence may aid differential diagnosis of neurogenic disease in cases of weight loss and colic.     

Artificial infection of Rhipicephalus appendiculatus with Theileria parva by percutaneous injection

Rhipicephalus appendiculatus nymphs were inoculated with fresh or cryopreserved blood containing Theileria parva piroplasms, or with cell culture grown stages of T parva. The use of fresh blood was successful. Cryopreserved blood containing dimethylsulphoxide (DMSO), killed most nymphs after inoculation: DMSO could be removed by slow dialysis, without destroying the infectivity of the blood. Attempts to infect ticks by inoculating cell culture grown stages of T parva failed, even when large numbers of merozoites were present in the inoculum.     

Invasion of stream fishes into low trophic positions

Abstract –  In the absence of other life-history constraints, fishes that can feed at low trophic levels (i.e., omnivores/detritivores) are predicted to be successful invaders because their food resources during the colonization and integration phases of the invasion are rarely limiting. Accordingly, we hypothesized that trophic position of non-native fishes in five mid-western and south-western U.S. river systems would be lower than native fishes. By standardizing δ ¹⁵N values with a common invertebrate (chironomids) across sites, we were able to evaluate differences in trophic position between natives and non-natives across sample locations and years. Our data tend to support this hypothesis, but there was notable spatial and temporal variation in this pattern. Moreover, three of four species generally fed at lower trophic positions in their introduced ranges than their native ranges. Although many factors influence the success of introduced species, our data suggest that the ability to forage on low-quality resources is a favourable trait for invasive fishes in lotic systems. Because these fishes feed at low trophic positions, it is important to consider how they will influence invaded systems, in contrast to invaders that feed at higher trophic positions. Future studies that evaluate the resistance of communities to invaders from different trophic positions would help understand the mechanisms that control the establishment and spread of species with different life-history traits.     

Diastereomer-selective resistance in Cladosporium cucumerinum to triazole-type fungicides

Diastereomers of triazole-type fungicides behaved differently with respect to their fungitoxicity towards wild-type strains of Cladosporium cucumerinum and strains resistant to ergosterol biosynthesis inhibitors. With increasing resistance to the fungicide ‘as a whole’, the difference in resistance to the two diastereomers of triadimenol became progressively smaller, whereas for the other triazole derivatives, this difference became progressively larger. The possible consequences of such phenomena for the practical use of diastereomeric fungicides are discussed.     

Uptake,distribution and metabolic fate of 3H-triforine in plants .I. Short-term experiments

Most of the label, present in the roots of bean, tomato and barley seedlings after short-term root-treatment with ³H-triforine, appeared only weakly adsorbed on to the root tissue and was desorbed after transplanting in fungicide-free soil. Label taken up accumulated almost exclusively in the leaves present at the time of treatment; all leaves expanding after termination of the treatment remained virtually devoid of radioactivity. In “adult” plants label was usually present in a concentration gradient from roots to youngest leaves; in tomato plants, however, distribution of label was rather irregular. Time-course studies with bean and barley plants revealed that the aerial parts were gradually supplied with label, from old to youngest leaves, the maximum relative accumulation of radioactivity slowly moving acropetally. Under the experimental conditions chosen, triforine was converted nearly quantitatively to one metabolite, which almost certainly is different from any known non-enzymic breakdown product of the fungicide.     

Cultivation of Theileria. I. Attempts to complete the cycle of Theileria parva in vitro

Microschizonts and free merozoites developed in bovine lymphoblastoid cell cultures containing macroschizonts of 6 different strains of Theileria parva. Clean bovine red cells were added to the cultures, which were incubated in various ways. No penetration of red cells by merozoites was observed, not even when cultures in diffusion chambers were introduced into the peritoneal cavity of non-infected cattle.