March, igso 



BETTER FRUIT 



Page 5 



because of their fertilizing value it is 

 not desirable, but early plowing should 

 be practiced and the leaves all turned 

 under before the buds break and ex- 

 pose the flower parts. Such sanitary 

 measures are valuable in connection 

 with subsequent spraying during the 

 summer season, but in themselves are 

 incapable of controlling the disease. 



In spraying for pear scab as well as 

 for other fungous diseases the funda- 

 mental point to be considered is that 

 spraying is preventive and not curative 

 in nature; that is, after infection has 

 taken place and the fungus has estab- 

 lished its growth in the host, it can not 

 usually be eliminated by spraying. To 

 be most effective the fungicides must 

 be applied before infection takes place; 

 the spray coating must be present be- 

 fore the spores reach the parts that may 

 be infected. The action of such sprays 

 is to inhibit the germination of the 

 spores or to destroy the fungus before 

 it can penetrate the cuticle. 



To combat pear scab successfully re- 

 quires, first of all, cflicienl fungicides as 

 spray materials; second, thorough 

 spraying, so as to cover all growing 

 parts; and, third, properly timed appli- 

 cations to cover the requirements of the 

 locality and the season. Bearing in 

 mind the fact that scab infection must 

 be anticipated and that the period of 

 greatest infection is from the time the 

 buds appear until about four weeks af- 

 ter blossoming, it is apparent that dur- 

 ing this period the trees should be cov- 

 ered at all times with a protective spray 

 coating. But since scab development 



Figure 5 — A BartlrtI pear twig showiiiR the 



condition of the Inicis at the time wiuri the 



second scab spray or the "pink" spray sliould 



be applied. 



is dependent upon moisture conditions 

 it is evident that the number of spray- 

 ings must vary with the season. 



Among the most efhcient fungicides 

 against pear scab are two materials 

 quite universally used, lime-sulphur so- 

 lution and bordeaux mixture. Both may 

 be purchased in convenient form on the 

 market, but often may be more econ- 

 omically prepared at home. The former 

 sometimes causes foliage injury, but at 

 a dilution of 1 to 40 it is quite safe to 

 use on pears. Bordeaux mixture is 

 a somewhat stronger fungicide, but it 

 frequently causes an objectionable rus- 

 seting when applied to tender young 

 fruits and is in less favor on this ac- 

 count. It is, however, very efTicient in 

 controlling pear scab. Sulphur, very 

 finely divided, in the form of an im- 

 palpable powder and applied with a 

 dusting machine (Figine 3), is also an 

 efticient fungicide against pear scab, be- 

 ing much more satisfactory in this re- 

 spect than the commercial bordeaux 

 dusts that are now on the market. 



These general statements concerning 

 spray materials, as well as those which . 

 follow in regard to their application, 

 are based upon a series of experimental 

 tests carried out by the Office of Fruit 

 Disease Investigations of the Bureau of 

 Plant Industry during the seasons of 

 1915 to 1918, inclusive, at Vancouver, 

 Clarke County, Washington, and at 

 Salem, Marion County, Oregon. The 

 results agree, however, rather closely 

 with those previously obtained, and 

 with well-established usage, in the 

 humid Northeastern United States, 

 especially in the Great Lakes region, 

 where pear scab is very severe. 



When to Spray for Pear Scab — Make 

 the first application for pear scab be- 

 fore the cluster buds begin to separate 

 (Figure 4), and about the time that the 

 first white is seen in the flower buds, 

 using a strong bordeaux mixture (4-4- 

 50 is satisfactory) or lime-sulphur so- 

 lution (testing ^2° Baume) diluted 1 to 

 20. This application is important in 

 those orchards whose immediate past 

 history reveals serious scab infection, 

 especially if early plowing has not been 

 resorted to to dispose of infected leaves 

 on the ground or if twig cankers re- 

 main plentiful on the trees. This appli- 

 cation is frequently very valuable when 

 the weather continues rainy and when 

 the fungus may obtain a foothold on 

 the exposed leaves before the time for 

 the next spraying. As the disease is 

 brought under control and the orchard 

 is maintained free from infection, it 

 lirobably will be found that this appli- 

 cation may be eliminated. A practice 

 that has met with favor with some or- 

 chardists is to delay the application of 

 dormant strength lime-sulphur solution 

 (1 to 8) until this time, making what is 

 known as a "delayed dormant" appli- 

 cation. However, this procedure in- 

 volves considerable danger of injury 

 to advanced fruit buds, and can not be 

 considered a safe practice, especially 

 if the buds are pushing out rapidly. If 

 the blister mite is present the "delayed 

 dormant" spray is too late for the best 

 results against this pest, and the strong 

 lime-sulphur should be applied at the 



Figure 6 — Bartlett pears, showing the condi- 

 tion of the fruit at the time when the third 

 spray or calyx spray should be applied. 



time it will be most beneficial against 

 the blister mite, a separate fungicidal 

 application being made for scab. 



The second application (correspond- 

 ing to the "pink" spray in the case of 

 apples) should be made as soon as the 

 buds are separated and showing white, 

 which will be just before blossoming 

 (Figure 5). Either bordeaux mixture 

 (4-4-50) or lime-sulphur solution dilut- 

 ed 1% to 50 should be used. At this 

 time all of the outer flower parts are 

 exposed and may be protected by spray- 

 ing. The period for most effective 

 spraying does not usually exceed three 

 or four days. This is probably the most 

 important single application, especially 

 in a wet season, and should not under 

 any circumstances be neglected, since 

 infection of the flower stalks at this 

 time is almost certain to cause the fruit 

 to drop. 



The third application, known as the 

 "calyx spray," is also highly important 

 and should be made as soon as the pet- 

 als fall (Figure 6), using lime-sulphur 

 diluted 1 to 40 instead of Wi to 50. In 

 practice it is best to begin spraying be- 

 fore the petals are all ofl", if a large 

 acreage is to be covered, since the pe- 

 riod for most efficient spraying some- 

 times does not exceed two or three days 

 after the blossoms fall, depending on 

 the weather conditions. By this time 

 the young pears are fully exposed and 

 must be protected. Infection at this 

 time causes a serious stunting and dis- 

 lo.lion in the growth of tlie fruit. For 

 the control of the syncia leaf beetle lead 

 arsenate should be added to the fungi- 



