Introduction. Bacterial canker, caused by Pseudomonas syringae pv. syringae, is a destructive disease where stone fruit trees are cultivated. The efficacy of nitrogen and calcium fertilization on bacterial canker susceptibility was evaluated in stone fruits. Materials and methods. Field experiments were conducted to study the efficacy of foliar applications of calcium nitrate, and ground fertilization with CAN-17 plus low-biuret urea foliar spray on bacterial susceptibility in ‘Riegel’ peach, ‘French’ prune and ‘Nonpareil’ almond growing in ring nematode-infested and nematicide-fumigated soils. Host susceptibility was evaluated by measuring the length of lesions developed following inoculation with P. syringae pv. syringae. Results and discussion. Foliar applications of Ca(NO3)2 significantly increased leaf nitrogen and bark calcium concentrations in peach trees growing in both fumigated and nonfumigated areas. Peach trees growing in nonfumigated areas developed significantly longer lesions than trees growing in fumigated areas. However, Ca(NO3)2 foliar applications had no effect in decreasing peach susceptibility to bacterial infection in both nonfumigated and fumigated areas. After inoculation, diseased prune trees developed significantly longer lesions than healthy trees. Leaf and bark calcium concentrations of diseased prune were significantly increased after Ca(NO3)2 foliar sprays, but again the treatments did not significantly affect prune susceptibility to bacterial infection. However, nitrogen fertilization with CAN-17 and urea significantly increased the bark nitrogen concentration of almond trees, and these trees had significantly smaller lesions than those not receiving nitrogen fertilization. Foliar application of calcium (Nutri-Cal) did not affect almond susceptibility to bacterial canker. Collectively, these data support the previous hypothesis that increased susceptibility of stone fruits to P. syringae pv. syringae under nematode infestation conditions is mediated by both nitrogen effects and nitrogen-independent effects, and application of ammonium nitrogen may have some beneficial effects in reducing stone fruit susceptibility to bacterial canker where ring nematode infestation prevails.

The influence of various agents on the adhesion of endospores of Pasteuria penetrans to the nematode Meloidogyne javanica was studied. Similarly, but to a lesser degree, we have also studied the adhesion of conidia of the fungus Dilophospora alopecuri and the coryneform bacterium Clavibacter sp. (syn. Corynebacterium rathayi) to the nematode Anguina agrostis (syn. A. funesta). Reduction in the degree of both spore and conidial attachment following their pre-treatment with periodate and the presence of PAS staining material on spores, conidia and bacteria implicated carbohydrate in these interactions. Tests involving both unbound and FITC-bound lectins demonstrated that wheat germ agglutinin (WGA) can inhibit the degree of attachment of P. penetrans to M. javanica and that this inhibition can be overcome by pre-treatment of the lectin with N, N′-diacetyl chitobiose. Endospores of P. penetrans, amphid and buccal secretions of 2nd-stage larvae of M. javanica and the cuticle and excretory pore secretions of 2nd-stage dauer larvae of A. agrostis bound WGA, indicating that accessible N-acetyl-D-glucosamine residues are present on these structures. Endospores of P. penetrans also bound Con A, indicating the presence of accessible α-D-glucose/α-D-mannose residues on their surface.

Introduction. This rearing technique is applicable to migratory nematodes (e.g., Pratylenchus spp. and Radopholus similis) for mass production of nematodes for experimental purposes, conservation of nematodes, and direct studies of nematodes’ multiplication or reproduction mechanisms. The principle of the method applied, key advantages, starting plant material and time required are presented. Materials and methods. Necessary laboratory materials, and details of the nine steps required for the preparation of carrot discs, preparation of nematodes, inoculation of nematodes and collection of nematodes out of petri dishes are described. Possible troubleshooting is explained. Results. Several thousands of nematodes can be extracted out of one carrot disc after 6–8 weeks of culture, depending on nematode species and geographical population.

Introduction. The centrifugal-flotation technique allows all nematode species and life stages to be separated from root debris and residual soil particles to facilitate their observation. The principle of the method applied, key advantages, starting plant material and time required are presented. Materials and methods. Necessary laboratory materials, and details of the 19 steps required for extracting nematodes from plant tissue for counting are described. Possible troubleshooting is explained.

Introduction. Nematodes are significant pests of bananas and plantains worldwide. Different levels of susceptibility to these pests have been reported. Studies were carried out to investigate differences in root systems and development of Musa clones with different levels of susceptibility and their possible role in the host-parasite relationship. Materials and methods. Five Musa clones, of which four were susceptible and one resistant to the nematode Radopholus similis, were grown in a plot naturally infested by this nematode. Root samples were collected 6 months after planting and measurements were made on the significance of tissue areas in root cross-sections, and the significance of root mass, root development and nematode populations with depth. Results. No significant difference was observed between cultivars in their general structural organisation or the relative significance of the tissue component of the root cross-section. A significantly lower number of air lacunae was found in the resistant accession in comparison with the susceptible ones. All the accessions except Christine (ABB) were comparable in their root development in the soil profile with more than 70% of the total root mass produced above 40 cm. The greatest nematode population and damage on roots were found at depths between (20 and 40) cm. Conclusions. This is the first report on differences in air spaces between Musa cultivars, and their role in the Musa-nematode relationship needs further investigation.

Introduction. In Cameroon, most subsistence farmers apply a mixed cropping system, resulting in a range of possible nematode host plants. Bananas and plantains (Musa spp.) are an important component of these cropping systems, both as a source of cash income and as a staple food. In order to program future extension projects, our study analyzed the cropping associations and their constraints in the West and Northwest provinces of Cameroon highlands. As nematodes have been identified as a major constraint to Musa production worldwide, we tried to assess the nematode presence. Materials and methods. A survey of over 200 households was done throughout the Cameroon highlands to identify the types of crop associations and preferences, management practices and pest awareness of small-scale farmers. In addition, samples were taken to examine the prevalence of Pratylenchus goodeyi on bananas and plantains in the home garden and one field of each household visited. Results and discussion. Cropping systems were highly variable between households, in so far as they could not easily be typified. Thirty-eight crops were identified planted in association with Musa spp. Bananas and plantains ranked as the most important crop for 43% of the farmers, followed by the staple crop maize (19%) and the traditional cash crop coffee (12%). Pest awareness (% awareness) was relatively high with respect to weevils (72%). The major constraints as perceived by the farmers related to leaf necrosis, weevils and nematode damage. Nevertheless, only 15% of them had heard of a nematode before. All root samples revealed nematode presence (over 40% showed more than 104 individuals·100 g–1 root fresh weight). P. goodeyi was the dominant species found.