UNIVERSITY OF CALIFORNIA 
 
 COLLEGE OF AGRICULTURE 
 
 BERKELEY 
 
 AGRICULTURAL EXPERIMENT STATION 
 8ENJ. IDC WHEELER, President 
 THOMAS FORSYTH HUNT, DEAN AND DlWECTOd 
 H. E. VAN NORMAN, VlCE-DlR ECTOR AND DEAN 
 University Farw School 
 
 CIRCULAR No. 157 
 
 (November, 1916) 
 
 CONTROL OF PEAR SCAB 
 
 By RALPH E. SMITH 
 
 This circular is published on account of the unusual prevalence of 
 pear scab in California in 1916 and the fact that our bulletin 163 has 
 
 Fig. 1. — Pear scab. 
 
long been out of print. Growers who have observed the following 
 directions explicitly year after year have had little or no trouble from 
 scab. 
 
 1. Plow under dead leaves as thoroughly as possible. 
 
 2. Spray with Bordeaux mixture twice while the buds are unfold- 
 ing, first when the leaf buds are just opening, as in Figure 3 ; second, 
 a week or ten days later, just before the individual blossoms open, as 
 
 Fig. 2. — First stage in opening of pear tree buds. A little early for spraying. 
 
 in Figures 4 to 5. The first spraying is the more important, but both 
 should be given. 
 
 3. In large orchards begin spraying when the buds are about like 
 those which are open the least in Figure 3, so that if delays occur the 
 trees will get at least one good spraying before it is too late. Spraying 
 before the first stage, Figure 2, or after the last, Figure 5, will do little 
 or no good in scab control, especially with Bartletts. 
 
 4. As an extra precaution, make a third scab spraying by mixing 
 the first lead arsenate codling moth spray with Bordeaux mixture in- 
 stead of plain water. 
 
 5. Spray with good equipment and high pressure, and cover the 
 trees thoroughly, especially the twigs and buds. 
 
Fig. 3. — Further development of buds. 
 COMMENCE FIRST SPRAYING 
 
 Fig. 4. — Blossom buds appearing. 
 COMMENCE SECOND SPRAYING 
 
Fig. 5. — Blossom buds well out. Second spraying should be finished. 
 
 Directions for Making Bordeaux Mixture 
 
 Bluestone 20 lbs. 
 
 Quicklime 25 lbs. 
 
 Water 200 gals. 
 
 Dissolve the bluestone and slake the lime in separate vessels. 
 Strain the bluestone into the spray tank and fill it half full or more 
 with water. Strain in the lime mixed with the rest of the water. 
 Always have the materials well diluted before mixing them together. 
 
 (Note. — If a third spraying, of lead arsenate combined with Bor- 
 deaux mixture, be made, the amounts of bluestone and lime may be 
 reduced to 15 and 20 pounds, respectively.)