Effect of cultural measures on the population density of the fruit tree red spider mite,Metatetranychus ulmi Koch (Acari, Tetranychidae)

Phytopathological consequences of changing agricultural methods

“…MOORE (1936) demonstrated that apple trees suffering from nitrogen deficiency are less susceptible to scab than apple trees with an adequate nitrogen supply. The observations of POST (1962) that in different years the damage done by apple powdery mildew and by the fruit tree red spider mite (Panonychus uIrni) in apple orchards in which no nitrogen dressing was applied was of minor importance whereas both parasites caused severe damage in plots given a norreal nitrogen dressing (80-120 kg pure nitrogen per hectare per year), is in corn-plete agreement with MOORE'S results for apple scab. BREUKEL & POST (1959) showed that nitrogen dressing led to a higher total nitrogen content of the leaves and that the fruit tree red spider mite on these leaves produced more eggs.…”

The influence of the predaceous miteTyphlodromus (A.) potentillae (Garman) on the development ofPanonychus ulmi (Koch) on apple grown under various nitrogen conditions

“…It was shown that P. ulmi reacted to an increased N content of the host plant by an increased rate of reproduction; T. potentillae responded numerically to,the increased density of its prey and prevented P. ulrni from reaching damaging levels. Similar results were obtained with the same or other spider mite species by RODRIGUEZ (1958), HUKUSIMA (1958), BREUKEL & POST (1959), KUENEN • POST (1958), CHABOUSSOU (1960), POST (1962), STOR~IS (1967, 1969 and KOLBE (1968). It has been shown by various authors that the nitrogen content of leaves of the host plant may influence the reproductive capacity of the fruit tree red spider mite, Panonychus ,dmi (KocH).…”

Influence of variety on the within-plant distribution of cassava green spider mite (Acari: Tetranychidae), and leaf anatomical characteristics and chemical components in relation to varietal resistance

“…Since leaf 3 data pooled over the six sampling months, showed E. N. Nukenine et al 184 *P < 0.05; **P < 0.01; ***P < 0.001. no significant differences in the thickness of the spongy and palisade mesophyll of the lamina, scelerenchyma and phloem, the density of the spongy mesophyll of the lamina, sclerenchyma and midrib parenchyma, among the resistant, moderately resistant and susceptible genotypes, these anatomical characteristics are not likely to be involved in the varietal resistance of cassava to M. tanajoa. Contradictory results were reported by Blair (1951) and Post (1962), who demonstrated an association between visible damage in different apple genotypes and the number of layers of mesophyll, and suggested that injury occurred earlier in genotypes with only one layer of mesophyll than in those with several layers. Blair (1951) observed that in genotypes with large leaves and thick layers of palisade parenchyma, the nutrients in the lower layers were exhausted less rapidly and that the leaf therefore was slower to show discoloration.…”