777, | CONTROL OF POSTHARVEST BROWN ROT OF SWEET CHERRIES AND PEACHES WITH CHEMICAL AND HEAT TREATMENTS =< << 7"¥ shh No QV : AKT sat Cw VL? * e % Nae NS z —~ LORY wafls e\ cs ia A “ PRY Sew > GUND Marketing Research Report No. 979 Agricultural Research Service UNITED STATES DEPARTMENT OF AGRICULTURE ent = LS eG ae te) oe - <3 - i “se rey i Daf) ee agen Brey Bie ay r *. eae - we 1! re bear? : — rn , 7 : oe har ee 7 qs . bf 7 Wht i? a ; > fa i tT or on ee ms. a Sai 7 > 1 Historic, archived document Do not assume content reflects current scientific knowledge, policies, or practices. CONTENTS Page SUMMARY is e8 facies og oS See se ee ee eee ere it Introductione. ..3. 35%. 2.) os 255. 3 See ee eee See iE Materials and:methods -32.4:3>...... (an eens os eee ee 2, Results ks oh a 2 oe S os ee ee 4 Decay of cherries duesto Monilinia 4... 7. 245 4 Injury to cherries 2.0.23 52253 «0 oe a a ee eee 4 Decay..of péaches. 5. 2-0. Bi ee eee 6 Fruit temperature in 105 je) air 4 i ee 8 Appearance and ripening of peaches .... 2... 322 ..4.. 5. 8 Discussion) 2.9.5... 6 ss eee ae eee 9 Literature: cited” < i150... ac ee oe ee eee 11 This publication reports research involving pesticides. It does not contain recommendations for their use, nor does it imply that the uses discussed here have been registered. All uses of pesticides must be registered by appropriate State and/or Federal agencies before they can be recommended. CAUTION: Pesticides can be injurious to humans, domestic animals, desirable plants, and fish or other wildlife -- if they are not handled or applied properly. Use all pesticides selectively and carefully. Follow recommended practices for the disposal of surplus pesticides and pesticide containers. US. DEPARTRIET OF AGEL T EOE Washington, D.C. Issued December 1972 For sale by the Superintendent of Documents, U.S. Government Printing Office Washington, D.C. 20402 - Price 15 cents CONTROL OF POSTHARVEST BROWN ROT OF SWEET CHERRIES AND PEACHES WITH CHEMICAL AND HEAT TREATMENTS By W.L. Smith, Jr., research plant pathologist, R. W. Penny, research mechanical engineer, and R. Grossman, student aid, Northeastern Region, Agricultural Research Service, United States Department of Agriculture, Beltsville, Md. SUMMARY Hot-water and hot-air treatments effectively controlled decay in sweet cherries and peaches. Treating in 125° F. water for 2.5 minutes or 115° water for 5 minutes decreased the percentage of decayed fruit with almost equal effectiveness. Treatment in 115° water for 2.5 minutes was somewhat less effective. The addition of 100 p.p.m. methyl 1-(butylcarbamoyl)- 2-benzimidazolecarbamate (benomyl) to 115° water was more effective in controlling decay of cherries than treatment in 115° water only for a 2.5-minute exposure. Injury sometimes occurred on fruit exposed to air near 100 percent relative humidity at 125° F. for 30 minutes and to fruit dipped in suspensions of benomy] in 125° water. Exposing fruit to 105° air of high relative humidity for 24 hours controlled decay about as effectively as the best of the brief hot-water treatments. When the relative humidity during the 105° exposure was high (85 to 95 percent), decay was less prevalent than when it was low (37 percent). Peaches exposed 24 hours to 105° air of high relative humidity ripened normally at 65°; those exposed to 105° air of low relative humidity were badly shriveled. INTRODUCTION Brown rot, caused by Monilina fructicola (Wint.) Honey, is a serious postharvest disease of sweet cherries and peaches. Fruits may be infected in the orchard before harvest or in contaminated containers or packing houses after harvest. Control of this disease, 1 2 therefore, cannot depend on proper orchard practices alone. After harvest, low-temperature refrigeration, chemical treatments, and heat treatments are the principal methods for controlling decay of most produce. Both postharvest chemical and heat treatments and a combination of the two have been extensively tested to control postharvest decay of peaches (2, 3, 4, 5, 6, 10, 11, 13, 15, 16, 17, 19, 20, 21).' With sweet cherries, decay is controlled mainly by low-temperature refrigeration or high concentrations of carbon dioxide (1, 7, 8). Postharvest chemical treatments of cherries have been tried only to a limited extent (12, 14). To date, no publications on heat treatments to control postharvest decays of this fruit are known. ; In the United States, heat treatments to control postharvest decays of peaches and other fruits have been limited mostly to hot-water treatments or heated chemical suspensions (15, 17, 20, 21). In Australia, on the other hand, exposing peaches to 105° F. air for 24 hours is the major heat treatment tested (9, 18) and used commercially. This study compares the effectiveness of unheated and heated suspensions of chemicals with hot-water or hot-air treatments to control decay in sweet cherries and of hot-water or hot-air treatments to control decay in peaches. MATERIALS AND METHODS ‘Royal Anne’, ‘Cumberland’, and ‘Windsor’ sweet cherries, grown commercially in Maryland, were used in most of these tests. At harvest many of these fruits had numerous splits or cracks and some of them had been injured by hail. Since such fruit could not be evaluated accurately for injury due to treatment, ‘Bing’ cherries from Washington and Oregon, free of injury, were used for these tests. Duplicate lots of 25 cherries each were used for each treatment in all tests. ‘Sunhaven’, ‘Redhaven’, ‘Blake’, . ‘Sunhigh’, and ‘Loring’ peaches, obtained from commercial orchards in Maryland and Virginia, were used in these tests. All fruit were sorted before the tests for uniformity of size and freedom from diseases or other -blemishes. Twenty fruit were used per treatment in all except one test in which 15 fruit were used. Both cherries and peaches were inoculated 24 hours before treatment by dipping the fruit into a _ beef-peptone broth suspension containing about 9 x 10* Monilinia spores per milliliter. Peaches were also inoculated with Rhizopus stolon- ‘Italic numbers in parentheses refer to Literature Cited, p. 11. 3 ifer (Ehr ex. Fr.) Vuill. by dipping them into a suspension containing about 21 x 10* spores per milliliter. Neither the cherries nor peaches were artificially injured before inoculation with Monilinia spores, but a shallow cut, resembling fingernail injury, was made on each cheek of peaches inoculated with Rhizopus spores. After inoculation all fruits were held at 65° F. For treatments, fruits were submerged into a _ constant temperature hot-water bath at 115° F. for 2.5 or 5 minutes or at 125° for 2.5 minutes. In addition, cherries were treated with suspensions of methyl 1-(butylcarbamoy])-2-benzimidazole- carbamate (benomyl) at 100 and 500 p.p.m. in 70° water and at 100 p.p.m. in 115° and 125° water. Fruits were also treated with hot air. Some were placed in a closed glass chamber and high-humidity air (95 to 100 percent) constantly circulated around them. Temperature within the glass chamber was maintained at 115° or 125° F. with 15- or 30-minute exposures. Others were held at 105° for 24 hours in metal drums sealed with glass lids. Relative humidity (RH) within a drum was controlled with a lithium chloride electric hygrometer in conjunction with a humidistat. Desired relative humidities within the different drums were 75, 85, and 95 percent. To obtain these relative humidities, a pump circulated air through heated water and into the respective drum when the relative humidity within that drum was below the setting of the humidistat. A second pump added dry air when the relative humidity was at, or above, the desired setting. The relative humidity level in each drum was monitored at intervals and at the end of each test by plugging the lithium chloride saturated element into a hygrometer indicator. In each test, on additional lot of peaches was placed at the ambient relative humidity of the 105° room. In the test chambers the pulp and subsurface temperatures of the fruit were measured at intervals by thermocouples embedded near the pit or just under the skin of the peaches. These thermocouples were connected to a 24-point temperature recorder. Temperatures of fruit in the ambient air were taken with thermocouples at the end of the tests. Both cherries and peaches were held at 65° F. and about 90 percent relative humidity after treatment. Six separate tests were conducted with cherries and eight with peaches. All data on decay were analyzed by the analysis of variance and the means were compared by using the Duncan Multiple-Range Test. The effect of the various treatments on softening of peaches was determined in five tests by using the Magness-Taylor pressure tester with a 5/16-inch plunger. RESULTS Decay of Cherries due to Monilinia After 3 days at 65° F., a very low percentage of decay developed on untreated cherries (dry or wet checks) and none on the treated fruit. After 6 and 9 days at 65° F., a high percentage of the untreated fruit developed brown rot (table 1). At each reading period decay of fruit given each of the treatments was significantly less than that of either check. Differences in decay developing on cherries treated with 100 or 500 p.p.m. benomyl were not significant. Cherries treated with heated suspensions of benomyl usually developed significantly less decay than those treated with unheated suspensions. When benomy] was added to 115° water and the fruit given 2.5-minute exposure, less decay developed on the cherries than on those treated with 115° water only. Fruit given the other hot-benomyl treatments and that treated with 115° water for 5 minutes or 125° water for 2.5 minutes developed about the same percentage of decay. Decay of cherries given the hot-air treatments did not differ significantly from those treated with hot water for 6 days after treatment. However, after 9 days at 65° most of the hot-water treated cherries developed less decay than the hot-air treated fruit. Injury to Cherries All cherries, treated and untreated, showed some degree of injury after 6 or 9 days at 65° F. The injury developed as small, round, slightly sunken areas giving the severely injured fruit a stippled appearance. Sometimes the skin was bleached. This injury was more severe on locally grown cherries that were injured before harvest than on the western grown Bing cherries. Locally grown fruit treated in 115° water for 5 minutes, and in 125° water with or without benomyl for 2.5 minutes, and in 125° air for 30 minutes had the most severe injury. All locally grown varieties had about the same degree of injury from the heat treatments. Bing cherries treated in 125° air were severely injured and unsalable. Somewhat less severe injury developed in Bing cherries treated in 115° water for 5 minutes, 125° water with benomyl, and 105° air and 80 percent relative humidity for 24 hours. Injury on the Bing Table 1.—Decay at 65° F. of sweet cherries inoculated with Monilinia _ fructicola spores 24 hours before treatment’ Decay during— Postharvest treatment 6 days 9 days Percent Percent Checks: Dry (no treatment) ............. 74.3a 83.0a Wet (iOneb water) 55500 as seas 71.0a 85.0a Benomy] treatment, 70° F. water— DOOM IPAM Gy rece ee cutie 15.5 bed 31.7 bede MOOR DSH ep erect soe core Ge 27.0 be 41.7 be Hot-water treatments 115° F. water for— 2.5 min.: Wiatermomlliys cy ise ccsa se dais ssn: foirs-taeces 29.7 b 51.7 b Plus benomy! 100 p.p.m........ tO