. Bulletin of the Department of Agriculture. Agriculture; Agriculture -- United States. 14 BULLETIN 173, U. S. DEPARTMENT OP AGRICULTURE. not entirely destroyed. Plate III, figure 1, shows a mature Bartlett pear the one-sided appearance of which was caused partly by adults and partly by larvse. When thrips are more numerous a greater amount of the bud surface is injured, consequently there is a greater loss of sap. If this loss is sufficient to cause the cluster buds to "bleed" (sap to drop from the end), fermentation quickly sets in and the entire cluster is soon destroyed. (Se
. Bulletin of the Department of Agriculture. Agriculture; Agriculture -- United States. 14 BULLETIN 173, U. S. DEPARTMENT OP AGRICULTURE. not entirely destroyed. Plate III, figure 1, shows a mature Bartlett pear the one-sided appearance of which was caused partly by adults and partly by larvse. When thrips are more numerous a greater amount of the bud surface is injured, consequently there is a greater loss of sap. If this loss is sufficient to cause the cluster buds to "bleed" (sap to drop from the end), fermentation quickly sets in and the entire cluster is soon destroyed. (See fig. 3, in comparison with fig. 2, which shows the cluster buds developing normally.) In many cases blue molds gain a foothold in this fermenting sap and greatly accelerate the injury, causing complete destruction of all fruit buds. The dead clusters later dry up without opening. (See PI. Ill, fig. 1, and compare it with PI. Ill, fig. 2, which is from a photo- graph of the sprayed portion of the same orchard, taken on the same day.) These dead buds may remain on the trees for months unless washed off by rain or blown by winds. The writers have seen many orchards so severely injured that it was difficult to find a single healthy blossom, and the entire orchard from a dis- tance presented at blossoming time a brownish color and dead appearance, due to these blasted buds. Weather conditions influ- ence to a great extent the de- struction following the injury caused by the thrips. For instance, the weather of 1909 in the mterior valleys during late February and the first 20 days of March was open and comparatively dry, with more or less wind blowing, giving quick evaporation throughout the day. Many clusters of buds that were kept under observation throughout the season, with from 10 to 20 thrips in the cluster, developed many of their buds and produced fruit, a large percentage of which was first class. During this period for 1910 there was considerable rain and the atmosphere w
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