The cottony scale attacking the peach in Ontario is apparently the European species Pulvinaria vitis (L.) and may have been introduced to North America prior to 1897. It is thelytokous and has only one generation per year. The partly grown, adult female overwinters on the bark of its host. The eggs, laid about mid-May, are enclosed in a white, felt-like ovisac that is secreted by submarginal glands in the ventral region of the scale's body. The eggs, which on peach averaged about 4,000 per female, were laid over a relatively short period when the temperature was 14°C. or higher. Eggs began to hatch after about 200 day degrees above 10°C. Increasing the temperature increased the rate of hatching, but no close correlation was found between the rate of hatching and the average daily temperature during the hatching period.Tlie newly emerged nymphs were both phototactic and photokinetic, and their estat)lishment on the host plant was affected by several factors including light, humidity, and air movement. For a given set of conditions there appeared to be a maximum number of nymphs that could become established per unit area of host. P. vitis was dispersed hy wind at any stage when it was ,active, but especially at the early crawler stage.Growth of the scales was discontinuous with varying periods when no growth took place. There were three moults: the first 12 t o 18 days after hatching; the second 28 to 36 days; and the third St3 to 93 days. At ecdysis only the cuticle of rhe ventral surface and the appendages was shed. Movement of the scales on the host plant was particularly frequent till the first moult, but some movement took place throughout the summer and early fall except for a period in late August and early September. Only a small percentage of the scales reached the barlc from the leaves, probably due to random movement.Feeding appeared to he discontinuous with periods of days when no feeding took place. The scales fed on the phloem, but on twigs the stylets penetrated as far as the xylem and destroyed the cambium in the feeding area.Though parasites and predators exist in the area and appeared to be capable of exercising a large measure of control, the spray programs used in the orchards held them to relatively small numbers. A t least one species of parasite was almost absent from sprayed orchards.
Laboratory tests, at constant temperatures, were conducted to evaluate quantitatively the influence of temperature on development of the Oriental fruit moth, Grapholitha molesta (Busck). The results showed that at the highest temperature (30°C) some larvae had four instars and some had five, indicating a mixed population. Fifth instar larvae developed only at the highest temperature (30°C) where larval development was also most rapid. It can, therefore, be assumed that the Oriental fruit moth has four distinct larval instars when reared in the laboratory at 15°–24 °C.
Unsprayed apple trees measurably increased the numbers of the Oriental fruit moth, Grapholitha molesta (Busck), in adjacent peach trees in only 1 of 4 years, though the apples were rather heavily infested. The moth became evenly dispersed throughout a previously uninfected peach orchard within three generations. Caged orchard trees were unsatisfactory for studying behaviour because the environment within the cages differed from that in the orchard. Experimental studies indicated that fecundity of the females was variable between years and generations and a varying proportion laid no eggs. Intraspecific competition between newly hatched larvae occurred at low egg densities; egg mortality was small but mortality of newly hatched larvae was large.
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