The Influence of the Manurial Treatment of Orchards on the Population Density of Metatetranychus Ulmi (Koch) (Acari, Tetranychidae)

Abstract

The influence of the nitrogen‐content of apple leaves on the development of the fruit tree red spider mite (Metatetranychus ulmi (Koch)) was studied under laboratory and semi‐field conditions. The experiments in the laboratory showed that a higher egg production per female in 24 hours, a lower mortality rate of the eggs, larvae and nymphs, and a shorter period of development of the male as well as the female mites was obtained on the leaves with a high nitrogen‐content. However, these differences were statistically significant only in the case of egg production and mortality rate. From the experiments under semi‐field conditions it became evident that the egg‐female ratio on leaves with high nitrogen content originating from manured rootstocks was also significantly higher than this ratio on leaves with a low nitrogen content. In both series of experiments the differences gave a factor of 1.6. The experiments confirm the results, we obtained earlier from perennial field trials where an effect of manuring of the apple trees on the development of M. ulmi was found. It is concluded that the mortality of predators of M. ulmi, caused by chemical treatment, is not the only reason why the red spider mite populations are stimulated in well kept orchards. The higher level of nitrogen content of the leaves, brought about by cultural practice, in particular manuring, may be of considerable importance also. ZUSAMMENFASSUNG Der Einfluß der Düngung in Obstgarten auf die Populationsdichte von Metatetranychus ulmi (Koch). Der Einfluß des Stickstoffgehaltes der Blätter auf die Entwicklung der Roten Obstbaum‐Spinnmilbe, Metatetranychus ulmi (Koch), wurde unter Laboratoriums‐ und halbfeldmäßigen Bedingungen geprüft. Steigender Stickstoffgehalt ergibt eine höhere Eiprodukten pro Weibchen und je 24 Stunden, eine geringere Absterberate der Eier, Larven und Nymphen und eine höhere Entwicklungsgeschwindigkeit sowohl der Männchen wie der Weibchen. Im Falle der Eiproduktion und der Mortalitätsraten waren die Unterschiede gesichert. Unter den Halb‐Freilaudbedingungen wurde es deutlich, daß das Ei‐Weibchen‐Verhältnis bei hohem Stickstoffgehalt der Blätter gedüngter Wurzelstöcke ebenfalls signifikant höher war als auf Blättern mit niedrigem N‐Gehalt. Sowohl im Labor wie im Freien betrug der Faktor 1,6. Diese Feststellungen bestätigen die Ergebnisse langfristiger Feldversuche Post's über die Wirkung der Düngung von Apfelbäumen auf die Entwicklung von Metatetranychus ulmi. Aus diesen Befunden ergibt sich ganz deutlich, daß die Abtötung der Feinde von M, ulmi nicht der einzige kausale Faktor für die Zunahme dieser Milbe ist. Der Anstieg des Stickstoffgehaltes der Blätter, der durch die Kulturmaßnahmen, besonders die Düngung, hervorgerufen wird, kann ebenfalls von beträchtlicher Beteutung sein.

OBSERVATIONS ON THE RELATIONSHIP BETWEEN MINERAL NUTRITION OF APPLE ROOTSTOCKS IN GRAVEL CULTURE AND THE REPRODUCTION RATE OF TETRANYCHUS URTICAE (ACARINA: TETRANYCHIDAE)

“…There are many conflicting results of investigations on the physiological condition of the plants and the effect of changes in these conditions on the development of their pests. For example Breukel & Post (1959) found a correlation between the development of P. ulmi on apple leaves and the N-content of the leaves at a difference in N-content of only 0.35% while Putman (1964), on the contrary, found no difference in the development of P. ulmi on peach leaves differing in N-content by at least 1.250/0. The following explanation may be offered to explain these contradictions.…”

“…Bondarenko (1949), Rodriguez & Neiswander (1949) and Garman & Kennedy (1949) found a positive correlation between high rates of mineral fertilizer and population increase of T. urticae on cucumbers, tomatoes and beans. Further work on the effect of plant nutrients on mite development has been published by Hamstead & Gould (1957) and Rodriguez (1958) for T. urticae on apple trees, Le Roux (1954) for T. urticae on cucumbers, Henneberry (1963) and Watson (1964) for T. urticae on beans, Kuenen & Post (1958) and Breukel & Post (1959) for Panonychus ulmi on apple trees, and Chaboussou (1960) for P. ulmi on peach.…”

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

“…Since some of the laboratory and other detailed experiments have already been published (BREUKEL & POST, 1959), only a summary of the results will be given here together with a few additional data. In Chapter 5.1 significance at the 5 % level was determined with Wilcoxon's test (see WABEKE & VAN EEDEN, 1955).…”

Host plant species and carbohydrate supplements affecting rate of multiplication of redlegged earth mite

“…The host plant species influences fecundity, egg viability, mortality and rate of development of immature stages, through chemical composition, structural features, and the physical characteristics of the leaf surface (van de Vrie et al, 1972;Gerson and Aronowitz, 1980;Rodriguez and Rodriguez, 1987). The fecundity of tetranychid mites is positively correlated with levels of soluble carbohydrates in different plant species (Henneberry, 1962;van de Vrie et al, 1972;Rodriguez and Rodriguez, 1987), and tends to be greater in leaves of different plants with higher levels of nitrogen (Breukel and Post, 1959;Morris, 1961;Henneberry, 1962;van de Vile et al, 1972). Positive correlations occur between spider mite fecundity and total nitrogen, total amino acids and glucose levels in leaves (Dabrowski and Bielak, 1978).…”