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

Abstract

Tetranychus urticae was reared on the leaves of one year old apple rootstocks grown on eight different nutrient solutions in gravel culture. The N‐content of the apple leaves derived from plants growing on the different nutrient solutions showed a strong variation during the experimental period which was independent of the NO3− level of the nutrient solutions. The ranges in N‐content at each moment were small in comparison with the range during the whole experiment. An increase in the total nitrogen content in the leaves resulted in an increase in the egg production of the mites. Differences in the K+/Mg+ + ratio in the nutrient solutions were not correlated with mite reproduction on the plants grown on these solutions. No significant difference was found in the water content of the leaves of apple plants on the eight nutrient solutions. The shootlength of the plants grown in a nutrient solution with a high NO3− concentration and a high Mg+ +/K+ ratio was much greater than the shootlength of the plants grown in a solution with a low NO3− concentration and a low Mg+ +/K+ ratio. There was a slight tendency towards higher egg‐production on the younger expanded leaves than on older leaves. The mean number of production days per female was significantly higher on young and full‐grown leaves than on old leaves. The longevity of the mites reared on leaves with a high N‐content was greater than on leaves with a low N‐content. RÉSUMÉ OBSERVATIONS SUR LE RAPPORT ENTRE LA NUTRITION MINÉRALE DE POMMIERS CULTIVÉS SUR UN SUBSTRAT DE GRAVIER ET LA FÉCONDITÉ DE TETRANYCHUS URTICAE (ACARINA: TETRANYCHIDAE) L'araignée rouge (Tetranychus urticae) a été élevée sur pommiers âgés d'un an, alimentés avec des solutions nutritives ioniquement équilibrées. Les plantes sont cultivées sur un substrat de gravier. Les résultats obtenus au cours de ces expériences sont les suivants: La teneur en N des feuilles provenant des plantes cultivées sur les huit solutions nutritives présente une variation très grande pendant la durée de l'expérience, variation qui est indépendante de la teneur en NO3− des solutions nutritives. La variation des teneurs en N des feuilles des échantillonnages individuelles était plus petite que celle observée pour l'ensemble de l'expérience. Un excès de N dans les feuilles augmente la fécondité des acariens. Le rapport de K+/Mg+ + dans les solutions nutritives n'avait pas d'influence sur la fécondité des acariens. Les feuilles des plantes cultivées sur les huit solutions nutritives différentes ne montraient pas une différence significative quant à la teneur en eau. La longueur des pousses des plantes augmente lorsque l'azote et le magnésium sont fournis en excès à la plante‐hôte. La fécondité des acariens augmente, bien que non significativement, lorsqu'ils sont élevés sur des feuilles jeunes. Le nombre de jours productifs, par femelle, était plus élevé sur des feuilles jeunes que sur des feuilles vieillies. La durée de vie des acariens augmente lorsqu'ils sont élevés sur des feuilles à teneur élevée en azote.

Potential of predation byMetaseiulus occidentalis in compensating for increased, nutritionally induced, power of increase ofTetranychus urticae

“…The females in the low nitrogen system spent an average of 25.28 days of egg laying in contrast to 22.75 days for females in the high nitrogen system. This result is in opposition to the findings of STORMS (1969), who found a 25 ~ greater longevity of egg production of females grown on high nitrogen apple leaves versus ones with low nitrogen and of WATSON (1964) who found similar results using lima beans. GASSER (1951), working with T. urticae in Europe, found the average number of eggs/~ on bean to be 67.7 eggs.…”

“…Chemically defined diets are being developed for the two-spotted mite (RoDRIGUEZ, 1969;EKKA et al, 1971;STORMS ~;NOORDINK, 1972).…”

“…Some workers (POST, 1962;STORMS, 1969;CHANT, 1966) have felt that improved nutritional status of the host plant releases the population of spider mites from their natural enemies while other workers (COLLYER, 1964;PUTNAM t~ HERNE, 1958;HUFFAKER FLAHERTY, 1966;HUFFAKER et al, 1970; VAN DE VRIE and BOERSMA, 1970), feel that a good predator may keep a spider mite under control in spite of improved nutritional status of the host plants.…”

Population dynamics of two-spotted spider mites in multiple year strawberry crops in Canterbury

“…However, Henneberry (1962Henneberry ( , 1963 found a positive correlation between TSSM populations on lima beans and leaf carbohydrate which in tum was negatively correlated with N absorption. Connor & Connell (1965) and Storms (1969) also positively correlated TSSM populations with N levels.…”

Resistance in Cucumis sativus L. to Tetranychus urticae Koch. 2. Designing a reliable laboratory test for resistance based on aspects of the host-parasite relationship

“…The behaviour and reproduction of insects and mites on excised plant parts, like detached leaves and leaf disks, may differ from the normal pattern on an intact plant (BECK, 1956 ;MULLER, 1958 ;LE BERRE, 1967 ;STORMS, 1969 ;MOREAU, 1971 and VAN EMDEN & BASHFORD, 1976) . Nevertheless, leaf disks have been used on a large scale to determine differences in reproduction of the twospotted spider mite (RODRI-GUEZ, 1953 ;DABROWSKI et al ., 1971 ;MACDONALD et al ., 1971 ;DABROWSKI .…”