Control of Peronophythora fruit downy blight of lychee by neutralized phosphorous acid

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(1)Plant Pathology Bulletin 20: 90-97, 2011. Control of Peronophythora fruit downy blight of lychee by neutralized phosphorous acid Pao-Jen Ann1,3, Jyh-Nong Tsai1, and Hong-Ren Yang2 1. Plant Pathology Division, Taiwan Agricultural Research Institute (TARI), Council of Agriculture (COA), Wufeng,. Taichung, Taiwan Chia-yi Agricultural Experiment Station, TARI, COA, Chiayi, Taiwan. 3 Corresponding author: E-mail: pjann@tari.gov.tw; Fax: 886-4-2330-2803 2. Accepted for publication: July 23, 2012. ABSTRACT Ann, P. J., Tsai. J. N., and Yang, H. R. 2011. Control of Peronophythora fruit downy blight of lychee by neutralized phosphorous acid. Plant Pathol. Bull. 20: 90-97. Field studies were conducted to evaluate the effect of neutralized phosphorous acid solution (NPA) on the control of fruit downy blight of lychee (Litchi chinensis) caused by Peronophythora litchii during 1999-2003. Trees of lychee, variety ‘Black Leaf’, were sprayed with NPA at 1000 mg/L, 2 or 3 times at 7-day intervals, at the fruit maturing stage and then inoculated with sporangial suspension of P. litchii at 200-500 spores/mL. Matured fruits were harvested and percentage of downy blight fruit was recorded. Results of the 3-year field trials showed that lychee trees sprayed with NPA significantly (P<0.01) reduced the incidence of fruit downy blight (0.5-11.8%), compared to untreated controls (26.1-46.6%). The treatment of NPA also was as effective as the treatment of mancozeb 80WP (dilution 500 times), a commercial synthetic chemical registered for the control of lychee fruit downy blight in Taiwan. Meanwhile, three applications of NPA in the fields not only significantly (P<0.01) reduced the incidence of postharvest Peronophythora fruit rot of lychee (0-16%), compared to the untreated control (12.2-96.6%), but also delayed the development of postharvest fruit downy blight by 2-4 days. However, treatment of freshly harvested lychee fruits with NPA in the laboratory did not significantly (P>0.05) reduce the incidence of Peronophythora downy blight of lychee fruits during postharvest stage. These results of field and laboratory experiments indicate that NPA must be applied to lychee plants at fruit development or maturing stage in the fields to induce resistance of lychee fruits against P. litchii and, thereby, reduce downy blight of lychee fruits in the field and at postharvest stage.. Keywords: Lychee, Litchi chinensis, Lychee fruit downy blight, Peronophythora litchii, Disease control, Phosphorous acid, Induced resistance. was developed and used for the control of Phytophthora diseases in the fields (2,3,4). The NPA solution was prepared by. INTRODUCTION. dissolving phosphorous acid in water and then adding an Phosphorous. acid. (H3PO3). and. Phosphonate. equal weight of potassium hydroxide to the solution.. compounds have been used since 1980s for the control of. Previous studies showed that the NPA solution was easy to. diseases of field crops caused by Oomycetes (8). In Taiwan, a. prepare and was effective in the control of late blight of. neutralized phosphorous acid solution (NPA) at pH 6.2-6.7. potato and tomato caused by Phytophthora infestans.

(2) Control of lychee fruit rot by phosphorous acid. (Montagne) de Bary. (14). , leaf and blossom blight of lily. caused by P. nicotianae Breda de Haan (= P. parasitica Dastur ). (3). Leonian. (3). 91. Pathogen and of inoculum preparation Peronophythora litchii used in this study was a. , basal stem rot of pepper caused by P. capsici. single-zoospore, homothallic strain PL5-1 (TARI98125). and seedling root rot of avocado caused by P.. isolated by the first author from a diseased lychee fruit. cinnamomi Rands, fruit rot of and leaf blight of kumquat. collected at Caotun, Nantow county in 1998. Stock cultures. caused by P. citrophthora Leonien and basal stem rot and. were prepared using the modified method of Boesewinkel (5). root rot of loquat caused by P. nicotianae (4).. by adding 5% V-8 juice agar blocks containing mycelial mats. In Taiwan, lychee (Litchi chinensis) (also called litchi). into sterile distilled water in test tubes and storing the. is an economically important fruit-tree crop. One of the. cultures at 20-24°C. The 5% vegetable juice agar (VA). major factors limiting production of lychee fruits is the. contained 5% V-8 juice (Campbell Co. USA), 0.02% CaCO3. disease of fruit downy blight (also called Peronophythora. and 1.5% agar (Hwei Shen Co., Taiwan). fruit rot or Peronophythora downy blight) caused by (7,12). To prepare working cultures, P. litchii in stock cultures. . The pathogen. was transferred to fresh 5% VA and incubated at 24°C for 3-5. could ruin almost all of ripening fruits in lychee orchards,. days. An agar disc (av. 0.5 cm × 0.5 cm × 0.3 cm) containing. especially under high humidity caused by continuing. mycelial mats was removed from the periphery of. rainfalls. Since P. litchii is a member of Oomycetes and there. 3-5-day-old colony and placed at the center of a Petri dish (9. were no previous reports on the control of fruit downy blight. cm diam.) containing fresh 10% VA. Numerous sporangia. of lychee by phosphorous acid, the objective of this study. were formed after the cultures were incubated at 24°C under. was to determine effectiveness and practicality of using NPA. continuous fluorescent light at 3000 Lux for 5 to 7 days. The. for the control of fruit downy blight in lychee orchards.. culture in each dish was sprayed with 20 mL sterile distilled. Peronophythora litchii Chen ex Ko et al.. water to wash off sporangia and the solution was filtered. MATERIALS AND METHODS. through double-layer sterile cheesecloth with the aid of an automizer to collect sporangia suspension. The sporangia suspension was adjusted to about 200-500 spores/mL and. Preparation of phosphorous solution Neutralized phosphorous acid (NPA) solutions were prepared by the method of Ann et al.. used for inoculation of lychee fruits.. (3). , using high purity. phosphorous acid (H3PO3, 99% white crystal, Aldrich Co.,. Control of Peronophythora fruit rot of lychee by NPA. USA) and experimental grade potassium hydroxide (>85%. and synthetic fungicides in the fields. KOH pellet GR, Merck Co., USA). The procedure was. Field experiments were conducted in two lychee. dissolving phosphorous acid into distilled water first and. orchards, one located at Fenyuan, Changhwa in 2000 and. then adding an equal weight (1:1 ratio, w/w) of potassium. another located at Caotun, Nantow in 2001 and 2002. Ten to. (3). fifteen-year-old lychee trees, var. ‘Black-leaf‘, were used for. reported that pH values of NPA solutions at 500-5000 mg/L. the experiments. Treatments were NPA applications (2 and/or. were 6.26-6.45. The prepared NPA solution was applied to. 3 times) and untreated control, one or two plants per. test plants (lychee trees and fruits) immediately. In the. treatment; and there were 3 replicates per treatment arranged. preliminary tests, the NPA exceeding 1000 mg/L was. by randomized complete block design (RCBD). During fruit. phytotoxic, causing skin browning of lychee fruits. Therefore,. maturing stage, each lychee tree was sprayed with 20 L of. the concentration of NPA at 1000 mg/L was used for. NPA at 1000 mg/L, 2-3 times at 7-day intervals. Seven days. spraying on lychee trees at fruit maturing stage in this study.. after last chemical spray, lychee fruits turning green-red. hydroxide to the phosphorous acid solution. Ann et al.. color were selected for inoculation with P. litchii by spraying 10 mL sporangial suspension on each fruit bunch, 20.

(3) 92. 植物病理學會刊第 20 卷第 3-4 期 2011. bunches per treatment. Each fruit bunch was covered with a. Control of Peronophythora fruit rot of lychee by. plastic bag (60 cm × 60 cm, L x W) and tied with a string.. postharvest treatment with NPA. Each fruit bunch of lychee in the plastic bag was harvested 7. The effect of postharvest treatment of lychee fruits with. days after inoculation and the number of fruits infected by P.. NPA on the control of fruit downy blight was also evaluated.. litchi were recorded for calculation of incidence (%) of. Fruits without pre-treatment with NPA in the fields were. downy fruit rot. Each treatment consisted of 20 bunches of. harvested from an orchard at Caotun, Nantow in 2002. They. lychee fruits from one or two trees and had 3 replicates. The. were washed, air-dried, dipped in NPA solution at 1000 mg/L. experiment was repeated for 3 years. Fruits on lychee trees. for 5 min, air-dried for 30 min, inoculated with sporangial. without chemical application but inoculated with P. litchii. suspension of P. litchii (200-500 spores/mL) for 5 min and. were covered with plastic bags and used as controls.. then incubated in moist containers at 24°C for 7 days. Fruits. To compare the effects of NPA with other fungicides in. without treatment of NPA but inoculated with P. litchii were. the control of lychee fruit downy blight, lychee plants. used as controls. Disease incidence was recorded daily for 7. sprayed with 80 Mancozeb WP (Rohm and Haas Co., Ltd.. days. Each treatment consisted of 50-100 fruits with 3. in Taiwan) diluted 500 times (conc. ai 1600 mg/L) or 50. replicates. The study was repeated once.. Prochlorate manganese WP (Aige Fu Co., Ltd. in Taiwan) diluted 4000 times (a.i. 500 mg/L) in 2001 were inoculated. Statistical analysis. with sporangial suspension of P. litchii and fruits were. Data collected from each experiment were analyzed by. harvested and examined for the incidence of fruit rot by the. analysis of variance (ANOVA), and means were compared. same method described in the NPA treatment.. by least significant difference (LSD) test at P=0.05 or P=0.01.. Control of postharvest fruit rot of lychee by NPA in the fields. RESULTS. To understand the effect of field application of NPA on the control of lychee fruit downy blight at postharvest stage,. Control of Peronophythora downy blight of lychee. NPA was sprayed on lychee trees at fruit maturing stage in. fruits with NPA in the fields. the fields in 1999 at Fenyuan, Changhwa, and in 2001, 2002. Results of the three-year field experiment in lychee. and 2003 at Caotun, Nantow. The lychee variety and NPA. orchards in 2000-2002 showed that application of NPA. application methods and schedules were the same as those. solution (1000 mg/L) on lychee trees, two to three times at. described previously. When lychee fruits turned red and. 7-day intervals, significantly (P<0.01) reduced the incidence. matured, they were harvested from the trees in the fields,. of Peronophythora fruit downy blight of lychee (Table 1).. washed with tap water, air-dried for 30 min, dipped in the. For example, the incidence of fruit downy blight of lychee in. sporangial suspension of P. litchii at concentration of. 2000, 2001 and 2002, in the treatment of three applications. 200-500 sporangia/mL for 5 min, placed on moist paper in. of NPA was 7.3, 6.7 and 0.5%, respectively, compared to. plastic containers (35 cm × 25 cm × 10 cm), and incubated at. 26.1, 36.4 and 46.6% in the untreated controls. Application. 24°C. Disease incidence was recorded by daily examination. of NPA two times in the field was also effective and the. of downy fruits rot for 7 days, based on the tests of 50-100. incidence of fruit rot in 2000 was 11.8% in the treatment of. fruits. For the control treatment, lychee fruits from trees. NPA, compared to 26.1% in the untreated control. Although. without treatment of NPA in the field were harvested,. 3 applications of NPA was more effective than 2 applications,. inoculated with P. litchi in the laboratory and examined for. the difference in fruit rot incidence was insignificant (P>0.05). the incidence of fruit rot. Each treatment consisted of 50 to. between two and three applications.. 100 fruits with 3 replicates. The study was repeated 7 times..

(4) Control of lychee fruit rot by phosphorous acid. Results of the field experiments in 2001 and 2002 also. 93. 2-4 days, compared to the untreated controls (data not. showed that all the chemicals, NPA (1000 mg/L), 80%. shown).. mancozeb WP (1600 mg/L) and 50% Prochlorate manganes. Control of Peronophythora fruit rot of lychee by. WP (500 mg/L), applied 3 times on lychee trees in the. postharvest treatment with NPA. orchards at 7-day intervals were effective in the control of. Results of the laboratory experiments in 2002 showed. fruit downy blight of lychee (Table 2). The efficiency in. that postharvest treatment of lychee fruits with NPA was. reducing fruit downy blight by NPA (1000 mg/L) was the. ineffective in the control of Peronophythora fruit downy. same as the synthetic chemical 80% mancozeb WP (1600. blight (Table 4). All harvested lychee fruits treated with NPA. mg/L). In 2001, the incidences of fruit downy blight of. and inoculated with P. litchii or the control (inoculated with. lychee in the treatments of NPA, mancozeb and Prochlorate. the pathogen without pre-treatment of NPA) developed. manganes was 6.7, 10.6 and 19.8%, respectively, compared. symptoms of downy fruit rot in 2-3 days after inoculation of. to 36.4% in the untreated control. Results of the field. the pathogen.. experiment in 2002 were similar to those in 2001 (Table 2).. DISCUSSION Effect of treatment of lychee plants with NPA in the fields on control of Peronophythora fruit rot of lychee. Fruit downy blight caused by P. litchii is an important disease of lychee in Taiwan. fruits at postharvest stage. (7,12). . This disease has existed in. Lychee fruits were harvested from trees sprayed with. Taiwan for more than 70 years and it is particularly severe in. NPA at 1000 mg/L, 2-3 times at 7-day intervals in the. rainy season because humid climates are favorable for. orchards and tested for control of Peronophythora fruit rot at. propagation, dissemination and infection of the pathogen (P.. postharvest stage, 7 times during the 4-year period in 1999,. J. Ann, unpublished data). Under continuing rainfalls which. 2001, 2002 and 2003. Results showed that compared to the. occurred frequently in May-July, P. litchii could ruin almost. untreated controls, lychee plants treated with NPA at fruit. all of the maturing and matured fruits in the lychee orchards. maturing stage in the fields significantly (P<0.01) reduced. with heavy infestation of the pathogen.. the incidence of downy fruit rot of lychee after harvest. Several synthetic fungicides have been registered for. (Table 3). Meanwhile, NPA applied to lychee fruits in the. commercial use in the control of fruit downy blight of lychee. fields also delayed the development of fruit downy blight by. in the fields in Taiwan (9), including mancozeb, oxine-copper,. Table 1. Control of Peronophythora fruit downy blight of lychee by neutralized phosphorous acid solution (NPA)a in the fields Incidence of infected fruitsc (%) Treatmentb NPA , 2 sprays NPA , 3 sprays Control. 2000 11.8 ad (54.8)e 7.3 a. (72.0). 26.1 b. 2001. 2002. NTf. NT. 6.7 a (81.6) 36.4 b. 0.5 a (99.1) 46.6 b. a. 1000 mg/L of H3PO3 solution was neutralized with equal weights of KOH. Both chemicals are experimental grade.. b. Trees of lychee var. ‘black leaf’ were sprayed with NPA at 7-day intervals during fruit maturing stage.. c. Seven days after the last H3PO3 application, fruits covered with plastic bags, were inoculated with sporangial suspension (200-500 spores/mL) of Peronophythora litchii in the fields, and disease was assessed 7 days after inoculation.. d. Means followed by the same letters in the same year were not significantly different at 1% level according to LST test.. e. Data in parenthesis refer to disease reducing rates (%).. f. NT=not tested..

(5) 植物病理學會刊第 20 卷第 3-4 期 2011. 94. Table 2. Control of Peronophythora fruit downy blight of lychee in the fields by neutralized phosphorous acid solution (NPA)a and other synthetic chemicals Chemical. Incidence of infected fruits (%)c. Concentration. b. (mg/L). 2001. 2002. 6.7 ad (81.6)e. NPA. 1000. 80% Mancozeb WP. 2000. 10.6 a (70.8). 30.0 a (62.8). 50% Prochlorate manganese WP. 500. 19.8 b (45.6). 62.0 b (23.1). 36.4 c. 80.7 c. Control (water). 33.0 a (59.1). a. 1000 mg/L of H3PO3 solution was neutralized with equal weights of KOH. Both chemicals are experimental grade.. b. For each chemical treatment, trees of lychee var. ‘black leaf’ were sprayed with chemical, 3 times at 7-day intervals, during fruit maturing stage.. c. Seven days after the last chemical application, fruits in the fields were inoculated with sporangial suspension (200-500 spores/mL) of Peronophythora litchii, covered with plastic bags for 7 days, and examined for disease incidence.. d. Means followed by the same letters in the same year were not significantly different at 1% level according to LST test.. e.. Data in parenthesis refer to disease reduction rates (%). Table 3. Effect of application of neutralized phosphorous acid solution (NPA)a in the field on control of Peronophythora downy blight of harvested lychee fruits. Incidence of infected fruitsc (%). b. Treatment. 1999-1. 1999-2. 2001. 2002-1. 2002-2. 2003-1. 2003-2. NPA, 2 sprays. 8.1 a d. 16 a. NT d. NT. NT. NT. NT. NPA, 3 sprays. NT. NT. 0a. 7.1 a. 0a. 0a. 0. 12.2 b. 55 b. 25 b. 96.6 b. 42 b. 12.2 b. Control. a. 59.0 b. a. 1000 mg/L of H3PO3 solution was neutralized with equal weights of KOH. Both chemicals are experimental grade.. b. Trees of lychee var. ‘Black-leaf’ were sprayed with NPA at 7-day intervals during fruit maturing stage.. c. The harvest lychee fruits were inoculated with Peronophythora litchii by dipping fruits in a suspension of sporangial (200-500 spores/mL) for 5 min, placed on moist paper in plastic containers, incubated at 24°C for 3 days and examined for disease incidence.. d. Means followed by the same letters in the same year were not significantly different at 1% level according to LST test.. e.. NT=not tested.. Table 4. Effect of postharvest treatment with NPAa on control of Peronophythora fruit downy blight of lychee Treatment. Incidence of infected fruits (%)2 at the day after inoculation 1st. 2nd. NPA. 0. 7.5 a c. Control. 0. 10.5 a. 3rd. 4th. 5th. 6th. 73.0 a. 100. 100. 100. 69.3 a. 100. 100. 100. a. 1000 mg/L of H3PO3 solution was neutralized with equal weights of KOH. Both chemicals are experimental grade.. b. Mature fruits of lychee var. ‘Black-leaf’ were harvested, dipped in NPA solution for 5 min, air-dried for 30 min, and then dipped in a suspension of sporangia (200-500 spores/mL) of Peronophythora litchii for 5 min. The inoculated fruits were placed on moist paper in plastic containers, incubated at 24°C for 7 days and examined for disease incidence.. c. Means followed by the same letters on the same tests were not significantly different at 5% level according to LST test..

(6) Control of lychee fruit rot by phosphorous acid. 95. (2). mancozeb + cymoxanil, dithanon + copper hydroxide,. equal weight of potassium hydroxide in water (NPA). . The. kasugamycin + carbendazin and fosetyl-aluminium +. NPA solution is cheap and easy to prepare. The NPA in this. oxine-copper. However, control of fruit diseases with. study may be a viable alternative for practical control of fruit. synthetic fungicides at fruit maturing stage prior to harvest is. downy blight of lychee as it is effective, easy to use and. prohibited for safety reason. Therefore, searching alternative. affordable.. materials that are effective, safe, cheap and easy to use for. In our previous reports, NPA was effective in the control. the control of Peronophythora downy blight of lychee fruits. of Phytophthora diseases of vegetable, flower and fruit. have become a major task for researchers in Taiwan. Results. seedling crops, including late blight of potato and tomato. of this study reveal that NPA sprayed on lychee trees at fruit. caused by P. infestans (14), basal stem rot of pepper caused by. maturing stage is effective in the control of Peronophythora. P. capsici. (3). , foliar and blossom blight of lily caused by P.. (3). downy blight of lychee fruits in the fields and at postharvest. nicotianae. , and seedling foot and root rot of avocado,. stage. Since the use of mancozeb 80WP (dilution 500 times). kumquat and loquat caused by P. cinnamomi, P. citrophthora,. for control of downy blight of lychee fruits is prohibited at. and P. nicotianae (4) . This study shows the effectiveness and. fruit harvest stage due to potential risks of chemical residues. usefulness of NPA for the control of Peronophythora downy. on fruits, this study reveals that NPA is an ideal alternative to. blight of lychee fruits caused by P. litchii in the fields and at. mancozeb 80WP for practical control of P. litchii because it. postharvest. This study also indicates that NPA must be. is effective, safe, cheap and easy to use.. applied on lychee trees in the fields at fruit development. Phosphorous acid and its salt-base compounds have. stage for effective prevention of downy blight of lychee. been reported as effective chemicals for control of crop. fruits. Besides lychee, this study can be a model of using. diseases caused by Phytophthora species and other. NPA for control of fruit rot of other crops caused by. (13). Phytophthora species and other Peronospoaceae, in both. indicated that phosphorous acid ion could induce host. conventional and organic fruit production because of no. resistance. residue problems on harvested fruits.. Oomycetes in many countries. against. (8,11). pathogen. . Saindrenan and Guest. infection. as. the. major. mechanism for control of diseases by these chemicals. In this. ACKNOWLEDGMENTS. study, NPA is effective in the control of downy blight of lychee fruits in the fields and in storage only when the chemical is applied in the fields, but is ineffective by the. This study is partially funded in 1999 and 2000 by the. treatment of lychee fruits with NPA after harvest. These. Council of Agriculture, Executive Yuan, R.O.C. The authors. results indicate that induced resistance to P. litchii is also the. thank Dr. Hung-Chang Huang, Principal Scientist Emeritus,. mechanism for effective control of downy blight of lychee by. Agriculture and Agri-Food Canada, for critical review of this. NPA.. manuscript. Many reports indicated that Phosphorous acid and its. LITERATURE CITED. salt-base compounds could reduce severity and incidence of some fungal diseases such as melanose of citrus and bacterial diseases such as brown spot of citrus. (1). . Currently, several. 1.. Agostini, J. P., Bushong, P. M., Timmer, L. W. 2003.. products of phosphorous compounds have been developed. Greenhouse evaluation of products that induce host. and used commercially for control of Oomycete diseases. resistance for control of scab, melanose, and Alternaria. (6,10,15). brown spot of citrus. Plant Dis. 87: 69-74.. . However, none of these products are commonly used. in Taiwan due to high price and easy oxidation in air. An. 2.. Ann, P. J., Hsieh, T. F., and Hsieh, M. L. 1997. Control. alternative method for the direct use of phosphorous acid was. of Phytophthora diseases of horticultural crops with. developed in TARI by neutralizing phosphorous acid with an. phosphorous acid. Plant Prot. Bull. 39: 403-404..

(7) 96. 3.. 植物病理學會刊第 20 卷第 3-4 期 2011. (Abstract in Chinese). Stanghellini, M. E. 1998. Effect of phosphite on tomato. Ann, P. J., Tsai, J. N., Wong, I. T., Hsieh, T. F., and Lin,. and pepper plants and on susceptibility of pepper to. C. Y. 2009. A simple technique, concentration and. Phytophthora root and crown rot in hydroponic culture.. application schedule for using neutralized phosphorous. Plant Dis. 82:1165-1170.. acid to control Phytophthora diseases. Plant Pathol. Bull. 18: 185-195. 4.. 6.. 12. Ko, W. H., Chang, H. S., Su, H. J., Chen, C.C. and Leu,. Phytophthora disease of fruit tree seedlings by. L. S. 1978. Peronophythoraceae, a new family of. neutralized phosphorous acid. J. Taiwan. Agric. Res. 60:. Peronosporales. Mycologia 70: 380-384.. 8.. phytoalexins in the response of phosphonate-treated. water. Trans. Br. Mycol. Soc. 66: 183-185.. plants to infection by Phytophthora species. Pages. Chaluvaraju, G., Basavaraju, P., Shetty, N. P., Deepak, S.. 375-390 in: Handbook of Phytoalexin Metabolism and. A., Amruthesh, K. N., Shetty, H. S. 2004. Effect of. Action. M. Daniel, and R. P. Purkayastha eds. Marcel. some phosphorous-based compounds on control of pearl. Dekker, INC. New York. 14. Tsai, J. N., Ann, P. J., Wang, I. T., Wang, S. Y., and Hu,. Chen, C. C. 1961. A species of Peronophythora gen.. C. Y. 2009. Control of Phytophthora late blight of potato. Nov. parasitic on litchi fruit in Taiwan. Special Publ.. and tomato with neutralized phosphorous acid. J.. Coll. Agric., Natl. Taiwan Univ. 10: 1-37.. Taiwan Agric. Res. 58: 185-195. (in Chinese with. Cohen, T., and Coffey, M. D. 1986. Systemic fungicides. English abstract). and the control of Oomycetes. Annu. Rev. Phytopathol.. 9.. 13. Saindrenan, P. and Guest, D. V.1995. Involvement of. Boesewinkel, H. J. 1976. Storage of fungal cultures in. millet downy mildew disease. Crop Prot. 23: 595-600. 7.. of Phosphonates in plants. Biol. Rev. 66:159-187.. Ann, P. J., Wang, I. T. and Tsai, J. N. 2011. Control of. 149-156. 5.. 11. Guest, D. I., and Grant, B. R. 1991. The complex action. 15. Wicks, T. J., Magarey, P. A., Waxhtel, M. F., and. 24: 311-338.. Frensham, A. B. 1991. Effect of post-infection. Fei, W. C. et al. 2010. Plant Protection Manual (fruit).. application of phosphorous (phosphonic) acid on the. Agric. Chem. Pest. Inst. Pub., Taichung, Taiwan, ROC.. incidence and sporulation of Plasmopara viticola on. 322 pp. (in Chinese). grapevine. Plant Dis. 75: 40-43.. 10. Forster, H., Adaskaveg, J. E., Kim, D. H., and.

(8) Control of lychee fruit rot by phosphorous acid. 摘. 97. 要. 安寶貞 1,3、蔡志濃 1、楊宏仁 2. 2011. 利用中和後之亞磷酸防治荔枝果實露疫病. 植病會刊 20: 90-97. (1 台中市霧峰區農業試驗所植物病理組；2 嘉義市農業試驗所嘉義分所；3 聯絡作者，電子郵件：pjann@tari.gov.tw；傳真：+886-4-2330-2803) 近年來，農試所研發一種簡單的方法配製亞磷酸中和液 (NPA)，將等重量之氫氧化鉀加入亞磷酸水溶液中和後使用。於 1999-2003 在田間施用 NPA，以評估其對荔枝果實露疫病的防治效果。在荔枝黑葉果實近成熟期，每隔 7 天噴布濃度 1000 mg/L 之 NPA 一次，共 2-3 次，相隔 7 天之後，再接種露疫病菌孢囊懸浮液（濃度為 200-500 spores/mL）。結果顯示，NPA 在田間防治荔枝果實露疫病之效果非常好，果實發病率可從 26.1-46.6%下降為 0.5-11.8%。同時，NPA 防治果實露疫病的效果與噴施三次 80% 鋅錳乃浦可濕性粉劑（稀釋 500 倍）的效果一樣好，無顯著性差異。此外，人工接種之結果顯示，在田間施用相同濃度的 NPA 2-3 次，同樣可以顯著降低採收後果實露疫病之發病率，從 12.2-96.6% 下降至 0-16%；還可以延緩果實露疫病病徵之出現達 2-4 日。然而，以相同濃度之 NPA 處理採收後的果實再接種露疫菌，則無法顯著降低果實之發病率，此項結果顯示，NPA 必須施用於田間才有防治荔枝果實露疫病之功效。關鍵詞：荔枝果實露疫病、Peronophythora litchii、病害防治、亞磷酸、誘導抗病.

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