Hatching of the winter eggs of the fruit‐tree red spider mite (Panonychus ulmi (Koch))

Abstract

SUMMARY Observations on the hatching of winter eggs of Panonychus ulmi (Koch) from apple orchards in England over the 5 years 1962‐6 are described. Differences of 2–3 weeks between orchards in the date at which 50% hatch was reached were quite common and this was out of step with petal fall in the majority of orchards. There was a continuous range between early and late hatching populations and a tendency for the populations to hatch in the same order every year. In 1966 populations on Cox's Orange Pippin hatched earlier than those on Worcester Pearmain but the difference was unlikely to be of practical importance. Neither recording accumulated day degrees for populations hatched out‐of‐doors nor hatching in an incubator after chilling was considered to give a sufficiently reliable forecast of 50% hatch but observations in 1966 suggested that this might be predicted from the total eggs hatched in an incubator expressed as a percentage of total healthy eggs.

Variation in the intensity of diapause in winter eggs of fruit tree red spider mite, Panonychus ultni

“…The continuous distribution of the mean hatching date observed by Light et al (1968) is in line with the evidence of the present study that field populations are mixtures of low Kd and high Kd types.…”

“…The stability of relative differences in time of hatch from year to year, which was observed by Light et al (1968) and Dicker (1962) suggests inheritance of the character. The stability of relative differences in time of hatch from year to year, which was observed by Light et al (1968) and Dicker (1962) suggests inheritance of the character.…”

The Effects of Fruit Tree Red Spider Mite (Panonychus ulmi) on Yield of Apple Trees in Kent

“…No other pomological effects were noted in any of the five years and there was no hint at Wye in 1966 of yield depression resulting from infestations in the previous year (Coghill, 1969). The relatively greater importance of early infestations would suggest that damage is more likely where early hatching populations are involved (Dicker, 1961;Light et al, 1968). Indeed the Sittingbourne experiment was situated in the same orchard in which a late hatching population had been found in 1966.…”

Ecology of tetranychid mites and their natural enemies: A review: III. Biology, ecology, and pest status, and host-plant relations of tetranychids

“…During a five-year study, Light et at. (1968) observed variations of two to three weeks in the date at which 50 per cent hatch was reached, while all grada tions, from early to late hatching, were represented in the orchards studied.…”