Figure 1. ET/ETp ratio vs. canopy height.
Canopy height was also plotted as a function of time to determine when canopy height reached 120 cm (Fig. 2 ) . Canopy height reached 120 cm on about May 15 for the 1972 and 1973 growing seasons. Figure 2 represents cane growth data for both years. Using this information, a crop factor curve (Kco) for sugarcane NCo 310 in the Lower Rio Grande Valley was determined (Fig. 3 ) . These crop coefficients enable the prediction of the soil water depletion and the scheduling of irrigation from weather data (incident solar radiation and mean daily temperature).
Testing of Crop Coefficients
The soil water depletion schedule is usually started after a heavy rain or an irrigation when the soil water is near field capacity. ET estimates are determined daily. By subtracting ET from the available water supply and by adding precipitation and irrigation to the supply, a running balance is maintained so that the amount of available water in the soil profile at any time is known. When the available water in the soil is depleted to a predetermined amount, irrigations are initiated. This procedure also provides an estimate of how much water should be applied to replenish the soil with water.
The crop coefficients reported here were used for irrigation scheduling of three irrigation regimes during the 1973 and 1974 sugarcane crops at our USDA Research Farm and at 10 other sugarcane fields in cooperation with growers. The technique satisfactorily estimates crop water use.
Table 1 shows the irrigation dates as determined for the 60% allowable depletion treatment with the 4-, 5-, and 6-ft row spacings. The estimate dates vary from 1 to 2 days as compared with the measured soil moisture status. Figure 4 shows two moisture depletion schedules with reasonably close agreement between measured and estimated soil moisture. This degree of accuracy is well within the growers' practical needs.
1972 - 1973
Figure 2. Canopy height vs. time for two growing seasons.
% of Season Days after Effective Cover Figure 3. Sugarcane crop coefficient curve for Lower Rio Grande Valley of Texas.
189
Table 1. Irrigation dates for 60% water depletion estimated by evapotranspiration methods and measured by neutron probe for three different sugarcane row spacings during 1974.
4-ft row spacing 5-ft row spacing 6-ft row spacing Estimated Measured Estimated Measured Estimated Measured March 3 March 2 March 10 — - February 20 February 21 April 17 April 17 April 26 April 24 April 29
May 17 May 20 May 21 May 20 May 21 May 20 June 7 June 8 June 5 June 6 June 6 June 6 June 27 - — June 27 June 27 June 27 June 28 July 20 July 20 July 20 July 18 July 19 July 20 August 6 August 7 August 5 August 6 August 5 August 5 August 21 August 21 August 21 August 21 August21 August 21
Figure 4. Estimated and measured available soil moisture for two irrigation regimes.
The Jensen-Haise method of scheduling irrigations in the Lower Rio Grande Valley is a very useful water management tool for increasing water-use efficiency. The procedure is simple, and growers can easily develop their own scheduling programs.
REFERENCES
1. Buras, N., M. Dov Nir, and E. Alperovits. 1973. Planning and updating farm irrigation schedules.
J. Irrig. and Drainage Div., ASCE 99(IRI):43-51.
2. Chang, Hao, and J. S. Wang. 1968. Evapotranspiration and water requirement of sugarcane in Taiwan.
Proc. ISSCT 13:664-675.
3. Chang, Hao, J. S. Wang, and F. W. Ho. 1968. The effect of different pan ratios for controlling irrigation of sugarcane in Taiwan. Proc. ISSCT 13:652-663.
4. Cheema, J. J., and M. K. Moolani. 1970. Soil moisture in sugarcane. Indian J. Agric. Sci.
40(3):273-282.
5. Ekern, P. C. 1971. Use of water by sugarcane in Hawaii measured by hydraulic lysimeters. Proc.
ISSCT 14:805-812.
6. Gerard, C. J. 1974. Use of tensiometers and pan evaporation to irrigate sugarcane. Texas Agricultural Extension Service TC-No. 74-2.
7. Israelson, 0. W., and V. E. Hansen. 1962. Irrigation Principles and Practices. John Wiley and Sons, New York. 447 p.
8. Jensen, M. E., and Howard Haise. 1963. Estimating evapotranspiration from solar radiation. J.
Irrig. and Drainage Div., ASCE 89(IR4):15-41.
9. Jensen, M. E., and Howard Haise. 1965. Estimating evapotranspiration for various crops using solar radiation. Proc. Open Tech. Conf. 16 pp., Sprinkler Irrigation Association, Kansas City, Missouri.
10. Jensen, M. E., Howard Haise, D. C. N. Robb, and C. E. Franzoy. 1970. Scheduling irrigations using climatic - crop - soil data. J. Irrig. and Drainage Div., ASCE 96(IRI):25-38.
11. Jensen, M. E., J. L. Wright, and B. J. Pratt. 1971. Estimating soil moisture depletion from climate, crop, and soil data. Trans. Amer. Soc. Agr. Engs. 14:954-959.
12. Kingston, G. 1974. Evaporation pans for scheduling sugarcane irrigations. Cane Growers' Quarterly Bull., April 1974, pp. 117-120.
13. Kovda, V. A., C. Van den Berg, and R. M. Hagan. 1973. Irrigation, Drainage, and Salinity.
Hutchinson and Co., LTD., UNESCO, pp. 206-253.
14. Mongelard, J. C. 1968. The effect of different water regimes on the growth of two sugarcane varieties. Proc. ISSCT 13:643-651.
15. Penman, H. L. 1948. Natural evaporation from open water, bare soil, and grass. Proc. Roy Soc.
193:120-145.
16. Thornthwaite, C. W. 1948. An approach toward a rational classification of climate. The Geographical Review, 38:55-94.
17. Van Bavel, C. H. M., and T. V. Wilson. 1952. Evapotranspiration estimates as criteria for determining time of irrigation. Agr. Eng. 33(1):417-420.
191
PINEAPPLE DISEASE IN SOME FIELDS ASSOCIATED WITH POOR GERMINATION OF SEED CANE IN LOUISIANA1/
Shaw-ming Yang
U.S. Sugarcane Field Laboratory, Southern Region, ARS, USDA Houma, Louisiana 70361
ABSTRACT
Poor stands occurred in commercial sugarcane fields in Louisiana in 1974 and 1975. Field observations were followed by sampling of ungerminated seed pieces of 3 cultivars (CP 52-68, CP 65-357, and L 62-96). Samples were taken from sandy loam and heavy clay fields planted with hot-air-treated and untreated seed pieces. Symptoms suggested the presence of pineapple disease, red rot, and stem rot.
Isolations made from ungerminated seed pieces yielded fungi belonging to 11 species and 7 genera. Of these isolates, only those causing pineapple disease (Ceratocystis paradoxa), red rot (Colletotrichum falcatum), and stem rot (Fusarium moniliforme) affected germination. C. paradoxa was isolated from 86%
of 169 ungerminated seed-piece samples from sandy loam and from 38% of 112 samples from heavy clay. The fungus was also obtained from 93% and 35% of soil samples of sandy loam and heavy clay, respectively.
C. falcatum was isolated from 2% of 169 ungerminated seed-piece samples from sandy loam, and from 13% of 112 samples of seed pieces from heavy clay. This fungus was not obtained from soil samples. The results suggest that pineapple disease contributed to poor stands, particularly in sandy loam.
INTRODUCTION
Poor stands of 3 sugarcane cultivars, CP 52-68, CP 65-357, and L 62-96, were observed in 1974 and 1975 in some fields of Valhi, Inc., in Houma and Thibodaux. Both hot-air-treated and untreated seed pieces were involved. Many ungerminated seed pieces showed a black discoloration and disintegration of the central core; others exhibited a red to reddish brown internal discoloration. The internal discolor- ation of the ungerminated seed pieces suggested that fungal pathogens were involved.
Fungal pathogens associated with seed-piece rot are well documented in the literature (1, 2, 6, 8, 1 0 ) . In Louisiana the red rot (Colletotrichum falcatum Went, the imperfect stage of Glomerella tucumanensis (Spec.) v. Arx et E. Muell) is considered the most important seed-piece disease (1, 2, 6 ) . Pineapple disease (Ceratocystis paradoxa (Dade) C. Moreau) occurred occasionally in seed pieces planted in poorly drained soils in winter (6). The other seed-piece rots, such as Fusarium (6) and Phytophthora (10) rots, rarely occurred.
The black discoloration and disintegration of the central core in most of the ungerminated seed pieces indicated the involvement of C. paradoxa rather than C. falcatum in the poor stands of the three cultivars. Studies were, therefore, initiated to determine the fungi associated with the poor germination.
MATERIALS AND METHODS
Ungerminated seed pieces of 3 sugarcane cultivars, CP 52-68, CP 65-357, and L 62-96, were collected from fields showing poor stands. Date of planting, soil type, whether hot-air-treated or untreated seed pieces, total number of seed pieces collected from each location, and date of collection are shown in Table 1. Untreated seed pieces of CP 52-68 and L 62-96 planted in sandy loam soil were not available.
Isolation of fungi from ungerminated seed pieces. Seed pieces were washed in tap water and in 0.1%
HgCl2 solution, then split aseptically with a knife. Four pieces of tissues (0.5 x 1.0 cm) were removed aseptically from each internode and immersed in 0.1% HgCl2 solution for 2 min and rinsed twice in sterile water for at least 5 min. The tissue pieces were incubated in petri dishes at 25 or 30 C for 2 to 7 days either on potato dextrose agar (PDA) amended with 200 ppm streptomycin or on acidified oatmeal agar (OMA). Pure cultures of isolated fungi were maintained on PDA or 0MA in test tubes for identification and for pathogenicity tests.
Fungi recovered from soil. Two sandy loam soil samples and two heavy clay soil samples were collected from fields with poor stands. Pathogenic fungi were isolated from sugarcane stalk tissues which had been incubated with the soil samples. Twenty pieces of freshly cut stalk tissues without rind (1-2 x 0.5-0.8 cm) of CP 65-357, added to a sieved soil sample (2 mm mesh) in a polyethylene interlocking seal bag (25 x 25 c m ) , were incubated at 25 C for 1 to 2 weeks. The stalk tissues were then removed from the bag, washed in running tap water, rinsed in sterile distilled water 3 times, and placed on PDA amended with 200 ppm streptomycin or on acidified OMA in petri dishes. The plates were incubated at 25 or 30 C for 2 to 7 days. Fungi grown from the tissues were transferred to PDA or OMA in test tubes for identification and pathogenicity studies.
1/ Research at this location is done in cooperation with the Louisiana Agricultural Experiment Station.
Ten one-node seed pieces of CP 65-357 were also planted in the sandy loam soil and heavy clay soil in pots. The planted seed pieces were kept on a greenhouse bench for 6 weeks. Numbers of ungerminated seed pieces were recorded. Fungi were isolated from the ungerminated seed pieces by the method described above.
Pathogenicity tests. Either spore suspensions or pieces of mycelium on agar of a selected isolate were used to inoculate 3 to 5 stalks of each cultivar by the puncture method (2). Stalks inoculated with sterile water or sterile agar were used as controls. The inoculated stalks were incubated at 20 to 22 C for 4 weeks before the discoloration of internal tissues was recorded. The fungi were reisolated from the inoculated stalks.
RESULTS
Isolation of fungi from ungerminated seed pieces. Eleven species belonging to 7 genera of fungi were isolated. The relative frequency of C. paradoxa, C. falcatum and Fusarium moniliforme (Fusarium seed-cane rot pathogen) and other Fusarium species isolated from the ungerminated seed pieces is shown in Table 1.
Among seed-piece samples from sandy loam soil, C. paradoxa was isolated from 146 seed pieces and occurred most frequently. In decreasing order of frequency, other fungi isolated were Trichoderma spp. (including T. harzianum Rifai aggr. , T. koningii Oud. aggr. , T. pseudokoningii Rifai aggr., and T.viride Pers. ex Gray aggr.), Fusarium spp. (including F. moniliforme and F. solani (Mart.) Appel & Wr. 24 samples), Penicillium spp. (21 samples), Aspergillus niger Van Tieghem (11 samples), C. falcatum (3 samples), and Rhizoctonia solani Kuhn (1 sample). Among the seed-piece samples from heavy clay soils, Trichoderma spp.
(55 samples) was isolated most frequently, followed in decreasing order by C. paradoxa (42 samples) , A. niger (32 samples), Penicillium spp. (18 samples), C. falcatum (16 samples), Fusarium spp. (14 samples), and R. solani (2 samples).
Table 1. Sugarcane cultivars, with or without heat treatment of seed canes, date of planting, soil types, number of ungerminated seed pieces collected, date of collection and frequency of 3 seed-piece pathogens isolated from the ungerminated seed pieces.
With or No. Frequency of pathogens isolated2/
Cultivars without Date Soil ungerminated Date Cerato- Colleto- Fusarium monili- hot-air planted type seed pieces samples cystis trichum forme and other treatment1/ collected collected paradoxa falcatum Fusarium species
L 62-96 + 8/20/73 Loam 33 3/19/74 .62 0 .21 L 62-96 + 8/20/73 Clay 27 4/ 3/74 .33 .04 .11 L 62-96 - 8/20/73 Clay 17 3/19/74 .41 .06 .29 CP 52-68 + 8/19/73 Loam 45 4/ 3/74 .89 .02 .11 CP 52-68 + 8/19/73 Clay 35 4/ 3/74 .43 .03 .27 CP 52-68 - 9/22/74 Clay 33 1/21/75 .33 .39 .06 CP 65-357 + 9/20/73 Loam 28 3/19/74 .86 .05 .13 CP 65-357 + 8/21/74 Loam 43 11/25/74 1.00 0 .17 CP 65-357 - 8/21/74 Loam 20 11/25/74 .95 .05 .14 1/+ indicates seed pieces had been treated at 58 C inlet temperature for 8 hr before planting;
- indicates no heat treatment.
2/Frequency of fungal isolates was expressed as the number of internodes from which isolates were obtained divided by the total number of internodes of one cultivar from one location.
The red rot pathogen was isolated rarely from the ungerminated, hot-air-treated seed pieces of the 3 cultivars and infrequently from ungerminated, untreated seed pieces of CP 65-357 and L 62-96. The pathogen was observed in almost half of the ungerminated, untreated seed pieces of CP 52-68 collected from heavy clay soil. Phytophthora was not isolated from ungerminated seed pieces.
Fungi recovered from soil. Seven species in 3 genera of fungi were recovered from soils. The isolated fungi were C. paradoxa, F. moniliforme, F. solani, T. harzianum, T. koningii, T. pseudokoningii, and T.
viride. C. paradoxa was detected in 93% and 35% of tissues buried, respectively, in sandy loam and heavy clay soils. Fusarium spp. were recovered from 28% and 43% of tissues placed in sandy loam and heavy clay soils, respectively. Species of Trichoderma occurred in 75% and 100% of tissues, respectively, buried in sandy loam and heavy clay soils.
Seventy percent and 35% of one-node seed pieces planted in sandy loam and heavy clay soils did not germinate in 6 weeks in the greenhouse. C. paradoxa was isolated from more than 70% of the ungerminated seed pieces. C. falcatum was not isolated from the ungerminated seed pieces.
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Pathogenicity tests. All tested isolates of C. paradoxa were moderately to severely pathogenic to stalks of the 3 cultivars. The isolates of C. falcatum attacked stalks of CP 52-68 and CP 65-357 slightly to moderately. The reaction of L 62-96 to C. falcatum was not consistent; some stalks were moderately susceptible, while others were resistant. Stalks of the 3 cultivars were also attacked, though slightly, by the isolates of F. moniliforme. The buds of infected internodes were killed by these 3 pathogens. Although F. solani and species of Trichoderma occasionally spread to adjacent internodes from the site of inoculation, they did not kill the buds. The isolates of C. paradoxa, C. falcatum and F.
moniliforme were recovered from the inoculated stalks.
DISCUSSION
Although 11 species of fungi were isolated from the ungerminated seed pieces of the 3 sugarcane cultivars, only 3 species, C. paradoxa, C. falcatum, and F. moniliforme, were pathogenic to the buds of seed pieces. Isolates of C. paradoxa and C. falcatum were more detrimental to germinations of seed pieces than isolates of F. moniliforme. Species of Trichoderma and F. solani were slightly pathogenic to the inoculated stalks even though they did not kill the buds.
Ceratocystis paradoxa occurred most frequently in the ungerminated seed pieces of the 3 cultivars and in soils. This pathogen was especially common in ungerminated, hot-air-treated seed pieces and in sandy loam soil, whereas C. falcatum was observed only rarely in the ungerminated, hot-air-treated seed pieces. Although there are many factors influencing bud germination, C. paradoxa in soils is among the more important factors responsible for reducing the germination of hot-air-treated seed pieces.
Edgerton (6) reported that pineapple disease in Louisiana occurred only occasionally during winter when the temperature was low while the seed canes were more or less inactive. Isolation of C. paradoxa from more than 95% of ungerminated seed pieces of CP 65-357 and from soils collected in November, 1974, indicates that this pathogen could infect seed pieces of some present commercial cultivars in late August and early September. The pineapple disease in Puerto Rico also occurred mostly in the summer when the soil moisture was below 22.5% and the soil temperature was 22 to 32 C (7). This is the first report on the infection of planted seed pieces by C. paradoxa in the summer in Louisiana.
The severity of pineapple disease in planted seed pieces is greatly affected by soil and weather conditions that retard the germination of the buds or the growth of young shoots ( 6 ) . When seed pieces are planted in soils with low moisture in late August or early September, bud germination is delayed, and growth of £. paradoxa in seed pieces is favored.
Colletotrichum falcatum was isolated rarely from the ungerminated, hot-air-treated seed pieces. The rare isolation of C. falcatum suggests that C. falcatum was inactivated by heat treatment of the seed pieces. The inactivation of C. falcatum by hot-air-treatment of short seed pieces has been reported from India (9).
All the commercial cultivars of sugarcane in Louisiana are screened for their reaction to C. falcatum.
The 3 cultivars ranged from moderately susceptible to very resistant to C. falcatum (3, 4, 5 ) . The reaction of the 3 cultivars to C. paradoxa and F. moniliforme is still unknown. The results of present studies seem to indicate that the 3 cultivars are susceptible to £. paradoxa and resistant to F.
moniliforme.
REFERENCES
1. Abbott, E. V. 1931. Red rot as a factor in the planting program. Sugar Bull. 10(1):4 & 6.
2. Abbott, E. V. 1938. Red rot of sugarcane. U.S. Dept. Agr. Technical Bull. 641, 96 p.
3. Anonymous. 1958. Release of CP 52-68. Sugar Bull. 36:258.
4. Anonymous. 1969. Notice of release of sugarcane variety L 62-96. Sugar Bull. 47(20):3.
5. Anonymous. 1973. Notice of release of sugarcane variety CP 65-357. Sugar Bull. 51(20):4.
6. Edgerton, C. W. 1959. Sugarcane and Its Diseases. 2nd ed. Louisiana State Univ. Press, Baton Rouge, La. 301 p.
7. Liu, L. J., and Amelia Cortes-Monllor. 1972. Effect of temperature and moisture on various aspects of development, growth, and pathogenicity of Thielaviopsis paradoxa from sugarcane in Puerto Rico.
J. Agr. Univ. P. R. 56:162-170.
8. Martin, J. P., E. V. Abbott, and C. G. Hughes. eds. 1961. Sugarcane Diseases of the World. Vol. I.
Elsevier, N. Y. 542 p.
9. Singh, K. 1973. Hot air therapy against red rot of sugarcane. Plant Disease Reptr. 57:220-222.