EFFECT OF ECO-BIOLOGICAL FACTORS ON SUGAR CANE PRODUCTION IN IRAQ

I. M. Mansour I

Plant Pathology Research Institute, Agricultural '

Research Center, Giza, Egypt and

A. I. Allam I

Sugar Crops Research Institute, Agricultural Research Center, Giza, Egypt

j

ABSTRACT

Single and combined effects of the ecological factors, diseases and stalk borers-rot complex on the potential yield of cane and sugar were investiga- ted and compared with the obtainable yield of N Co 310 for four consecuti- ve crop-years (1976-1980) in Southern Iraq. The negative effects of frost, freezing and biological deterioration on juice qualities and mixed juice through milling was studied and sugar losses were quantified. Disease- environment interaction was also attempted.

The potential yield of cane in Southern Iraq is shown to be 254 tlhal - year. Unfavourable soil physico-chemical properties decrease this poten- tial by an average of 37,5 % . Another 18 O/O decrease can be due to climatic restraints. Ratooning and field management cause a 17 % decrease of the potential yield. Thus, sugar cane obtainable yield in Southern Iraq becomes 70,6 tlhalyear. The average actual yield of Iraq was 58,4 tlhalyear for the studied period. It represents 28% and 83% of the potential and abtainable yield, respectively. However, high yield of 70 or more tlhalyear can be obtained. Stepwise programs to yield 100-120 tlhalyear are feasible.

The stalk-borers, Chilo sp. and Sesamia sp. were recorded. Borer-rot complex causes a 10% reduction in N Co 310 yield. A 4,5-15,2 loss in Pol Yo juice is atributed to the complex. Estimated recoverable sugar (ERS) decreases by 20% and recovery becomes 7,9 instead of 9,9 tlsugarlt cane. Mill recovery for the period of the present study ranged between 4,7 and 7 t/sugar/100 t cane.

Diseases of sugar cane are enchanced by unfavorable environmental condition. Various organs of the plant are affected and subsequently symp- toms develop. Common rots, vascular diseases, systemic diseases, leaf spots, stripes and misshapen leaves are Seed-cutting rots are the most important disease problems. They negatively affect germination and stand, which result in a parallel decrease in yield. These rots are positively and highly pre-disposed by different unfavourable environmental conditions. Smut is the other important disease.

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INTRODUCTION

Agro-ecological studies help in predicting the behaviour of different crops under different agroclimatic zones. The effect of some of these factors on sugar cane production was partially investigated in North India (Panje, 1972), Iran (Sund and Clements, 1974) and Iraq (Sehgal et a l . , 1980).

The present study was initiated to quantify the effect of ecological factors (soil, water, climate), ecological and physiological disorders, the incidence and develop- ment of parasitic diseases on sugar cane. Also, the potential and actual yields of sugar cane in Iraq were compared with similar areas in the world. Earlier papers as by Panje (1972), from India, and other workers from other areas, have been more,concerned with qualitative effects on cane growth, than with the quantitative effect on yield and quality.

MATERIAL AND METHODS

Soil and Water

The research reported here was conducted during a four crop-year period (1976-1980). The methods used in the water and soil physical and chemical analy- ses are described and outlined by Richards, "954; and Sehgal et a17 1980. Soil salinity was measured as outlined by Richards (1954) and calculated as shown by Gowing and Rozeff "1972). The cation exchange capacity (CEC), the exchangea- ble cations and the organic matter content of the soil were also determined. The irrigation water was analyzed according to Richards (1954).

Meteorological Data

Solar radiation, temperature, wind velocity, relative humidity, rain and evapo- ration were recorded by using the standard apparatuses. In addition to the presen- 1 tation of the means for a twelve years period (1966-1977). I

I 1. Pyrheliometer (Belfast Co . , USA) fixed at a 2 m height over ground level, was I

used for total solar radiation recording. I 2. Thermo-hydrograph (Adolf Thies, Gottingen, W. Germany) was used for 1

measuring air temperature and % relative humidity (RH). I 3. Wind speed and velocity were determined by Casella Cub Counter Anemome- 1 1

ter. 4. Rainfall was measured by Case11 natural rain fall recorder124 h. 5 . Galvanized steel USWB, Class A ; 120,7 cm in diameter and 25 cm depth was

used for evaporating. The pan factor was equal to 0,9-1,O (Thompson, 1967 and Chang et a1 2 , 1967).

Potential Yield

The following international factors were used to calculate the sugar cane yield: 1 1. Crop or Canoby factor 0,83 2. Ratooning factor 0,90 3. Management factor 0,70

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Parasitic Diseases

The standard methods were used for identification of diseases and their causal organisms. Pathogenicity of different identified microorganisms was tested by using either direct inoculation into plants or indirect infestation through soil.

Chemical control of certain diseases was tried in vitro and in vivo. Bioassay techniques were used to test the uptake, translocation and residual effects of fungicides in the sugar cane plant.

Effects of different pathogens on sugar cane germination, stalk-, root- and cutting-rots, leaf spoting, wilt and dryness were examined. Effects of borers and associated microorganisms on cane yield and juice were quantified. The host- pathogen-environment interaction on disease severity and the extent of injury was recorded.

RESULTS AND DISCUSSION

I. Soils

The area of sugar cane production is situated in the southern part 'bf Iraq in Misan governerate at 31" 40' N and 47" 5' C . The physical properties of these soils show the presence of three distinct areas, i. e . , levee soils (adjacent and parallel to the river), basin soils (river delta) and haur soils (marsh or swamp lands). -

The mechanical analysis and texture of the three soils is presented in Table 1. Sand fraction decreases in basin and haur soils, while increases in levee soils. These soils are classified as silty clay loam (75%) and silty clay (25%).

Bulk density (see Table 1) varies between 1,36-1,38 g/cm3, in the surface la- yers. In subsoil layers, it increases to reach 1,52 g/cm"n haur soils and 1,58 g/cm3 in levee soils. Top soil non-capillary pores (0,009 mm) differs from 16,6% in haur soils to 27% in levee soils and to 27,3% in basin soils. This porosity provides proper conditions for root growth, gas exchange and water permeability. In sub- soil layers, porosity decreases to 4,3% in haur soils and 8,2% iii levee soils, which leads to less gas exchange, water permeability and limits root growth. Field studies showed that most of cane roots (70-90%) were confined in the surface 20 cm.

Permeability of surface layers of haur and basin soils varied between 19,2 and 4 cm/day, respectively. Infiltration values of 0,9 and 1,6 cm/h were observed for basin and haur soils, respectively. The decreased to 0,2 cmlh after less than 3 h of inflow.

This may be attributed to the presence of an impermeable crust on the saline basin soils and/or the high level of CaC03 (relatively water insoluble) in addition to the 2 : l type rnontomorillonite clay.

Water storage capacity per meter depth, based on the volume of capillary pores in different layers of the soil profile and quantified as a difference in the amount of water held between 0,33 and 15,0 bar tension, was 12,3; 15,3 and 15,9 cm in haur, levee and basin soils, respectively (see Table 1). These capacities are consi- dered moderate and favourable for the growth of most crops.

Results of chemical analysis showed that pH values ranged between 7,4 and 8,2. Electric conductivity (ECe) varied in different soils and at different depths in the same soil from 1,3 to 37,4 mmhos/cm (see Table 1). It increased by depth, which may be due to increased Ca Co3. The data showed that ECI in soil extract increases in the surface layers to 37,4 and 25 mmhoslcm in basin and haur soils,

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respectively. Also, the CaCO3: CaSO4 was high. Cation exchange captcity is moderate as compared to that of clays. Furthermore, Ca++ and M~ were dominant and followed by Nai, which increases in sub soil layers. Exchangable sodium % (ESP) ranged from 1,8 to 2235% and the water table varied between 1 and 2 m from soil surface.

~ ~ b [ ~ 1. Chemical and Physical properties of sugar cane soils in Southern Iraq

Soil Locality

Proporties Levee Basin Haur

Sand % . 2-74 1-10 66-20

1-3 Silt % 55-65

32-6 42-43

Cloy % 44-25 1,38-1,58

57-54 Bulk density g / ~ m 3 1,37-1,52

7,5-27 1,36-1,52 Soil porousity (0,009) 8,2-27,3

2-66,2 4,3-16,6 Permeability (cmlday) 4-7,l

1,3 2,5-19,2

Infiltration (cmlhaur) 15,3

0,9 Water holding capacity 15,9

1,6

7,5-7,9 12,3

% ph 7,4-8,0 7,5-8,2 Electric conductivity (mmhoslcm) 1,3-3,3 1,9-37,4

29,5-31,3 2,0-25,O

Ca 'C03 21,O-24,5 0 2

24,2-27,l Gypsum

1,8-8,7 0,9

2,l-22,5 0 2

ESP 10,2-24,3 3,2-4,1

CEC % 20,6-24,4 0,50-0,30 30,O-35,4

Water table (meter) 0,O-0,3 Si-SiCL 0,o-2,0

Soil texture * * SiCL-Sic SiCL-Sic

* Range of 100 samples. * * Loam - L., Clay -C, and Silty - Si.

Effect of Salinity on Sugar Cane Yield

The negative effect of soil salinity of the surface layer (33 cm) on N co 310 and c p 44 - 101 varieties was obvious. A high significant decrease of 5,37 TC/ Feddan (4 200 m2)leach unit of salinty (mmhoslcm) increase was obtained as shown by the regression equation:

P = 35,15 - 5,37 x

where is the estimated yield of cane Per feddan and x is the degree of salinity (mmhos/cm).

This decrease equals 14,5% of cane tonnage Per unit area. Accordingly it shows that the yield of N Co 310 decreases by 25% at an E C of 2,8 and by 500/0 at 5,6 EC. A significant negative correlation (r = -0,474 *) was shown between salinity and yield of cane.

Water Characters

The electric conductivity of irrigation water has a mean of 0,75 mmhos/cm all year round (Table 2). This mean decreases to 0,5 mmhoslcm during flooding period (March to May) and increases to 1,0 mnhoslcm during dry period (October

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respectively. Also, the CaC03: CaS04 was high. Cation exchange ca acit is moderate as compared to that of clays. Furthermore, Cat+ and Mge+ :ere dominant and followed by Na+, which increases in sub soil layers. Exchangable sodium % (ESP) ranged from 1,8 to 22,5% and the water table varied between 1 and 2 m from soil surface.

Tabla I . Chemical and Physical properties of sugar cane soils in Southern Iraq

Soil Proporties

- Levee Basin Haur

Sand % , 2-74 Silt % 66-20 Cloy % 32-6 Bulk density &m3 1,38-1,58 Soil porousity (0,009) 7,5-27 Permeability (cmlday) 2-66,2 Infiltration (cmlhaur) 1,3 Water holding capacity 15,3

% nh 7.5-7,9 - r

Electric conductivity (mmhoslcm) Ca 'CO, su sum ESP CEC % Water table (meter) Soil texture * *

Locality

* Range of 100 samples. * * Loam - L., Clay -C, and Silty - Si.

Effect of Salinity on Sugar Cane Yield

The negative effect of soil salinity of the surface layer (33 cm) on N CO 310 I and CP 44 - 101 varieties was obvious. A high significant decrease of 5,37 TC/

Feddan (4 200 m2)/each unit of salinty (mmhos/cm) increase was obtained as shown by the regression equation:

9 = 35,15 - 5,37 x

I where ? is the estimated yield of cane per feddan and x is the degree of salinity (mmhos/cm) .

This decrease equals 14,5% of cane tonnage per unit area. Accordingly it shows that the yield of N Co 310 decreases by 25% at an EC of 2,8 and by 50% at 5,6 EC. A significant negative correlation (r = -0,474 *) was shown between salinity and yield of cane.

I I Water Characters

The electric conductivity of irrigation water has a mean of 0,75 mmhos/cm all year round (Table 2). This mean decreases to 0,5 mmhos/cm during flooding period (March to May) and increases to 1,O mmhos/cm during dry period (October

and November); the p H ranges between 7,3 and 7,5. The Ca++:Mg++ ratio reaches 1,17, while it decreases to 0,40 in the ground water. This result indicates that calcium precipitates through soil profile as insoluble carbonate or relatively insoluble sulphate. Salinity of this water is moderate and can be used for irriga- tion under good drainage conditions. Hence, soil water is characterized by high E C (13,45 mmhos/cm). Thus, this irrigation water can be classified as medium- salinity but low-sodium water (C2-S1) Richards (1954). It contains a very low level of sodium and has no effect on soil structure or conversion to alkalinity.

Table 2. Irrigation Water Properties (Majar El-Kabir River, Tigris Branch) and Ground Water

Properties * Irrigation Water Ground Water

E.C. (mmhos/cm) 0,75 13,45

PH 7,5 7,30 Cations (meq/L) Naf 2,s 73,30 Ca++ 3,5 2,70 Mg+ + 3 8 6,70 Ca to Mg 1,17 0,40 Anions (meq/L) C1- 1,47 80,5 HC03- * * 0,7 SO4-- 1,80 * *

* Average of 100 samples. * * Not recorded.

II. Climate

Results (Table 3) show that growing sugar cane in Iraq is subject to an exceptional range of climatic conditions. The monthly mean solar radiation ran- ged between 248,6 and 547,8 g/cal/cm3/day for December and June, respective- ly. The highest radiation was accopanied by the highest evaporation rate and the highest wind velocity.

Evaporation reaches maximum average value of 15,9; 15,6 and 14,6 mllday during June, July and August, respectively. The yearly mean rainfall reaches 178,4 mm, 71% of it falls during winter and 29% during spring and autumn. While summer (July to September) is completely dry. This dry period is associated with high air temperature. Maximum relative humidity is 77,9% during January and the minimum is less than 45,30% during June. Wind spead increases during spring and summer to a maximum average of 8,2 mileslh and minimum average reaches 3,5 milelh.

Summer months have average daily maximum temperature of over 47,2"C (record extreme 51) and winter months commonly have several days of frost (average extreme minimum -1,5"C, record extreme -4°C). Thus, the area repre- sents a climatic type of arid (with no water surplus), megathermal (less hot) with temperature efficiency regime normal to first megathermal (Ed. A'2 a ' l ) (Thorn- wait system lo, 1948; as modified by Vernemrnen ", 1969).

These exceptional range of climatic conditions affect sugar cane growth and interact with parasitic agents causing disease development and spread. Besides, high and low temperature cause many physiological and environmental disorders.

Table 3. Climatic Conditions in Southern Iraq (Misan), Average of the Period 1966-1968 1

Temperature "C Relative Wind Total Solar Evaporation Month humidity speed rain radiation

Max Min Mean % milelhour mmlmonth Gmlcal mmlday

January 22,2 0,l 10,6 77,9 4,5 42,8 251,l 2,6 February 25,7 1,3 13,3 71,2 4,5 29,8 302,5 3,1 March 30,8 5,2 18,7 63,6 5,5 17,O 371,3 5 3 April 36,9 10,8 22,2 60,7 5,3 24,l 437,8 8 2 May 43,6 16,9 30,l 52,O 5,4 6,3 448,6 11,2 June 46,8 21,4 33,7 45,3 8 2 0,o 547,8 15,9 July 47,2 21,9 34,8 45,5 7,7 0,o 508,8 15,6

i 1 I I

August 46,8 21,lO 34,O 48,4 6,4 0,o 481,l 14,6 I

September 44,8 17,4 31,l 50,5 5,4 0,o 437,8 11,3 October 39,9 12,O 25,O 60,4 4 4 6 342,7 6,7 1 i November 32,9 4,5 17,8 67,5 3 3 11,9 257,9 3,7 December 26,2 1,3 13,l 74,l 4 .41,9 248,6 2,7 I

Monthly mean 37,O 11,2 23,7 59,8 5 ,4 178,4 386,3 8,4

A) High Temperature Effect

Temperature over 45°C accompanied with high wind velocity and high evapo- ration during summer months cause direct injury to the cane plant. The plant water balance is disturbed and plants sliow wilt appearance. Under severe condi- tions leaves of certain varieties (i.e N 50-211) dry-up, CP 44-101 exhibits a degree of field tolerance and shows only tip burn due to these conditions. This disorder increases during dry seasons and is pronounced under saline conditions. This leads to stunted internodes, increased fiber, decreased juice and extraction ratio. Pithiness appears in late-harvested fields resulting in more bagasse and bagassilo in the clarifiers.

B) Low Temperature Effect

The results show that temperature below 7°C accompanied by high relative humidity and/or rainfall are deterent for cane ripening in Iraq. Also, rain and high relative humidity are necessary for spores of pathogenic fungi to germinate and penetrate the plant. Certain seed rots are favored by low soil temperatures before plant seedlings germinate and emerge. Thus, affect disease development and spread.

A perusal of the data (Table 4) show the effect of frost and freeze on the 1 growth of certain sugarcane varieties. The N Co 310 and CP 48- 103 showed a moderate degree of tolerance, while POJ varieties, B.41-227 and Co 419 were 1 susceptible to sub-freezing temperatures (00-4°C). Mild frost damage caused par- I tial destruction of the chlorophyll on young and mature leaves of cane, a condition which can be confused with mosaic symptoms.

The effect of sub-freezing on juice qualities of N Co 310 js shown in Table 5. Results show a substantial decrease of brix, Pol and purity readings from 19%; 16,2% and 85% before freeze to 17%; 13,3% and 78%, respectively, after 14 weeks from freeze occurrance. This impaired milling efficiency and reduced the average estimated recoverable sugar (ERS) by one t sugar/100 t crushed cane.

/Table 4. Effect of Low Temperatures (Fros * and Freez *") on Sugar Cane Growth in Southern Iraq

Rates of Effects Cane Variety

Plant Cane 1st Ratoon 2nd Ratoon

N Go 310 1 1 1 Co 419 3 2 4 B 41-227 3 3 4 C1 41-223 2 2 3 CP 48-103 1 1 * * * CP 52-68 1 2 2 US 59-16-1 2 2 * * * POJ 2827 POJ 2967 POJ 3016

3 a 3 4

POJ 3067 PR 980 2 2 2

* 0°C. * * 1,5"C. 1, 2, 3 and14 indicate moderate, weak, very weak and highly susceptible respectively.

* * * No second ratoon plants.

Table 5. Average Effect of Freeze on Juice Qualities of NCo 310 During 1977-1978 Season for the Period 21-12-77 to 5-4-78 in Southern Iraq (Misan) '

Weak Date Brix Pol Sugar % Flnal Sugar

Purity Cane Recovery YO

6 * * * 2511 19 16,2 85 13,O 0,85 11,l

Average 18,2 15,O 82,O 12,O 0,83 9,9

7 * * 112 19 15,s 83 12,6 0,83 10,5 8 * * * 8 2 19 15,4 81 12,3 0,81 10,O 9 * * * 15,2 19 15,l 79 12,l 0,79 9,6

10 * * 22,2 19 14,6 77 11,7 0,77 9,0 11 * * * 113 19 14,3 75 11,4 0,75 8 6 ,

12 * * * 813 19 14,3 75 11,4 0,75 8,6 13 * * . 1513 18 13,5 75 10,s 0,75 7,s 14 * * * 2213 18 13,7 76 11,0 0,76 8,4 15 * * * 3913 18 13,9 77 11,l 0,77 8,6 16 * * 514 17 13,3 78 10,6 0,78 8,3

Average 18,5 14,4 77,6 11,5 0,78 0,78

' Average of 48 samples, fifteen stalks each. * Freeze occurred (-140 for six hours) on 17-1-1978 morning.

* * True reading (laboratory estimated each three weeks). * * * Calculated readings from the true readings using the linear regression.

C) Temperature Effect o n Bud Germination and Stalk Elongation

Bud germination completely ceases during December and January when avera- ge temperature decreases to 10,6OC. Incomplete germination results in low number of plantstunit area and the spread of winter and spring weeds.

Ninety % of the stalk length occurs from March (19°C) to September (25°C). Sixty % of this elongation occurs during June, July and August, when the average temperature rises to 33°C or more. The rate of stalk elongation was closely associated with ambient temperature. Thus the effective period of growth is 6 months (mid-April to mid-October). Under more favourable conditions, cane plane reaches its final length within nine months from mid-February to mid- November as in subtropics.

I Parasitic Diseases

The present surveys of sugar cane diseases in 1raq show the presence of:

A) Virus Diseases

1. Mosaic Mosaic was recorded in k a q since the begining of sugar cane cultivation in 1968. Under Iraqi environmental conditions, sugar cane varieties differ in their susceptibility from highly susceptible (PR 1013 and PR 1059) to moderately susceptible (N Co 310). Current surveys showed that disease severity is co- rrelated with air temperature. The disease was severe on susceptible varieties during spring. Mosaic symptoms are masked during summer when temperature rises. In highly susceptible varieties, discoloured areas are conspicuous, sharply defined and may coalesce together producing wider areas covering most of the leaf lamina. These symptoms can be easily confused with iron chlorosis or with salt damage.

2. Ratoon Stunting Few ratoon plants of N Co 310, showed the purple dots in the nodal region of the base1 internodes. It is noticed that late ratoons, are visibly stunted.

B) Fungi Diseases

1. Rind Disease (Pleocyta sacchari) , The disease was first recorded in Iraq during 1975. Pleocyta sacchari attacks

standing plants of N Co 310 in early spring causing pasal stalk rot and rind discolouration, followed by the appearance of characteristic fruiting structures. It plays a major role in seed-cuttings deterioration and reduction in germina- tion. It invades the stalks and seed-cuttings through wounds. Then mycelia grow under the epidermis forming a circular or spherical cushiony mat with a hollow center encheathed with a layer of condiophores and spores. Fruiting structures emerge causing cracks in the epidermis outer surface. The fungus, also forms sclerotia in the tissues of infected plants. Under Iraqi ecological conditions. Pleocyta sacchari inhibits seed-cuttings ger- mination resulting in severe infection and failure of germination. Also, agro- machines aggravate this situation, especially in late plantings during October and November. The disease causes poor germination and rot infection results in death of the few germinating buds.

2. Pokkah Boeng (Gibberella moniliformis) Charasteristic symptoms of pokkah boeng disease were visible in recent sur- vies. In mild infection the disease affects only the leaves of tolerant varieties: CP52-68, CP57-603 and CL41-223. Top rot appear on susceptible varieties, 1'OJ 3067, POJ 2827, C o 290 ap&B 41-227; Co.421, Go 976, B 36-161, B 43-62 and B 37-172 show considerable degrees of tolerance. Symptoms are favou- red by a wet weather proceeded by hot and dry season.

3. Seed-cutting Rot-complex In Iraq, Fusarium and Pleocyta sacchari are the most injurious fungi. Other isolated fungi are Verticillium sp., Rhizopus sp., Penicillium spp., Aspergillus spp., Alternaria sp., Nigrospora sp. and Curvilaria sp. Cane varieties showed degrees of susceptibility to these fungi and rot develop- ment. Young plants show wilt appearance due to root-rot. Fungal filtrate of different organisms shows suppressing or inhibiting effect on root development and germination. This effect may be either of contact or systemic nature which has to be elucidated.

4. Leaf Spots (Helminthosporium sp.) Eye spot disease caused by Helminthosporium sp. appears on nature plants at the end of summer and during winter. A severe infection occurred in 1976 on seedlings growing from seeds imported from Brazil. Red to brown spots appeared on the leaves and coalesce together and the leaves wilt and dry. In advanced stages the seedling dies.

5. Rhizosphere fungi and Actinomycetes Current studies showed that Fusarium spp., Verticillium sp., Pythium sp., Alternaria sp., Aspergillus sp., and Rhizopus sp. were the common fungi isolated. The actinomycetes Streptomyces, Nocardia and Micromonospora were also isolated. Pathogenicity test showed that Fusarium spp., and -Pyt- hium sp. were able to infect cane grown in infested soil. Germination land root production were decreased. Sugar cane varieties showed different de- grees of symptoms due to their susceptibility. Germination and root produc- tion were affected in some varieties while wilt was pronounced in others. ' Fungal filtrates showed no effect in some cases, in others they showed either a contact of systemic effect suppressing root production and germination. Dif- ferent actinomycetes were antagonistic to fungal growth.

6. Culmicolous Smut (Ustilago scitaminea) Culmicolous smut caused by Ustilago scitaminea is one of the most known diseases of sugar cane. During February and March, 1980, the first infection was observed in few fields of N Co 310, in Iraq. The charasteristic whips

I appeared profusely and early in ratoons but scarcely and late in plant crop. Infection ranged between 0,5 and 5%. Then, the disease was apparent in the whole area (5 000 ha) by May, 1980. Infection also occurred on CP 44-101 and was severe in some fields of N Co 310. CP 52-68 showed field resistance. Sanitary precautions were taken to limit disease spread and reduce infec- tion. Disease severity and spread indicate its presence since more than two years.

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C) Bacterial Diseases

1. Red Stripe (Xanthomonas rubrilineans) Red stripe disease caused by Xanthomonas rubrilineans is recorded in Iraq. The disease infects several varieties. Clear symptoms occur on Co 290, CP 57-603, CL 41-223, B 37-172 and POJ 30-67. The commercial variety N Co 310 is moderately tolerant. Disease symptoms are observed during all

months of the year, but its severity differes by the season. Symptoms are very conspicuous during February and March after cool weather and frost. Hence, symptoms are favored by periods of high humidities of spring rain. Symptoms appear as longitudinal stripped streaks parallel to the midrib. Leaf sheat may be infected. The disease frequently causes top rot, specially after frost. Buds and stalks may also be infected. Infected joints are stunted and shrinked. Wet craks appear on infected joints, which may later dry and shown brown colour. Then, joints show internal cavities.

D) Control of Seed-cutting Rots

Control of different rots was achieved through improvement of cultural practi- ces and the use of fungicides, in Iraq; as follows:

1. Cultural Practices Rots of seed-cuttings were markedly reduced by: a) Restricting new planting to the end of October. b) Using apparently healthy cutting for planting. c) Avoiding harmful wound to cuttings, caused by agromachines. d) Enhancing germination by using thin soil cover. e ) Improvement of drainage and reducing salinity.

2. Chemical Control In vitro studies showed that the systemic fungicides Benlate (E. I . du Pont de Nemours), Vitavax captan and Vitaxax thiram (Uniroyal), and Falisan (orga- nic mercury) were the most effective on most fungi. However, their effective concentrations differed. Benlate gave excellent results and 10 ppm. Morocide

I

I (Hoechest) showed a selective action against Pleocyta sacchari. It is also effective against common spider mite Tetranicus sp. a major sugar cane pest in the area. Basamid (Dasomit 98%, BASF) at 1 000 ppm showed high activity against Cephalosporium aeromonium and Pythium sp., and a selective action against Furarium spp. isolated from the rhizosphere. The results showed that Benlate was absorbed by the roots of sugar cane and moved upside the plant. Juice of different 60 day treated plant organs was either fungistatic or fungitoxic to Pleocyta sacchari. Juice toxicity increased as the rate of fungicide increased. Toxicity was detected in shoot organs. Vitavax compounds were phytotoxic to cane plant at all rates. Benlate presisted in soil and was detected up to 120 days. In vitro it stimula- ted root primordia and growth of roots and shoots. Vitavax compoundes were persisted only for 80 days in soil. Fundazol (Benomy of Chinion Pharamaceutical and Chemical Works Hungary) at 10 ppm was toxic to Pleocyta sacchari in vitro. While KWG 519 15 DS 15 A and Bayloton (Bayer) at 50 ppm were only fungistatic. Fundazol was absorbed and translocated in the cane plant. The other two compounds were phytotoxic and suppressed root production. The three compounds controlled rind disease at 500 ppm and persisted in soil upto 120 days.

1 IV. Microbial Deterioration of Mixed Juice

Leuconostoc sp. , Streptococcus sp. , Alcaligerles Viscola.ris, Saccharomyces sp. , Candida sp. , P, sacchari, Aspergillus spp., and Fusarium spp. were isolated from mixed juice. Artificial inoculations with bacteria and yeasts either singly or in combination showed that combined inoculation induced deterioration in sterile juice similar to that naturally occuring. Leuconostoc induced the most deteriora-

tive effect followed by Saccharomyces spp. and Candida. However, certain isola- tes of Saccharomyces were more effective than Leuconostoc sp.

V. Borers and Associated Microorganisms

A 10% \ reduction \in\,stalk \weight was\\atributed to Chilo sp. and : Sesarnia sp. and associated microorganisms. Infested stalks lost 4,5-15,2% sucrose due to infestation and bioconversion. Apparent purity was reduced by 6% while redu- cing sugars were increased by 41% during February. Deterioration was propor- tional to infestation intensity.

Certain fungi, most likely chlamydospore producing fungi were detected in vascular bundles of infested tissues. The red spider mite, a major sugar cane pest

i n area, overwinters in borer tunnels and have a positive role in the dissemination of microorganims.

Fusarium spp., Aspergillus spp., Penicillium spp., Rhizopus sp., Alternaria sp. , and Pleocyta sacchari were isolated from rotted tissues infested with borers. Leu- conostoc, Xanthomonas and Erwinia were also obtained from the same tissues. Also, Leuconostocr and Saccharomyces were isolated from juice of bored plants.

Sugar cane area is at 31'40' N and 47'5' E in South of Iraq and economically considered at the marginal borders of sugar cane growing belt. However it ro- sembles most of the sugar cane growing areas of the world. The present results show that ecological factors (soil, water and climate) limit the actual yield as compared to potential yield. The latter is calculated according the following assumptions:

1. One t of cane is obtained per 1 ml of irrigation waterlhalyear. 2. Pan evaporation (EO): Evapotranspiration (ET) = 1 : 1. 3. Total consumption of water by sugar cane in Iraq = 306,5 cm31year. 4. Crop factor during close-in stage = 0,83. Thus transpiration water = 306,5 x

x 0,83 = 245,4 cmlhalyear.

In view of this, the potential yield of sugar cane in Iraq is 254,5 tlha. It is a I high figure. However, it is similar to that given by Irvine (1979) for Half

Tappeh, Iran. The physiologists, in Australia, found that the maximum potential yield of sugar cane is 280,O tlhalyear (Irvine, 1979). Sehgal et a1 (1980), in Iraq, found that the potential yield is 216,O t/ha/year.

The constrains to reach this potential yield in light of the present results are:

1. Soils Sehgal et a17 (1980) found the characters of the soil of Iraq have the ability to produce 50-70% of the potential yield, which is equal to 127,O-190,5 with a mean of 158,7 tlhalyear. This is in agreement with the present results, when soil salinity 'does not exceed 2,8 mmhos. Eachs inacrease of saturated base; E C mmhos decrease the production by 12,8 tlhalyear .

I 2. Water I In Iraq, chemical characters of irrigation water is suitable for the mean pro-

duction of sugar cane. However, it may affect soil salinity under ineffective I drainage. Irrigation water affects production if it decreases below 300 cm/ha/ year because of the close relation between water quantities and cane yield.

3. Climate Solar radiation of the area is sufficient for dry mater production Bonner (1962) mentioned that plants need 250 g cal/cm2/day of solar radiation to form

321

the dry matter, providing suitable temperature. Decreased temperature be- low 12,2"C suppresses the vegetative and root growth of sugar cane. Under Iraqi conditions, low temperatures during winter (December, January and February) reduce the growth rate to its minimum. This period is 25% of the growing season and inhibits the ability of the plant to benifit from radia- tion in the early spring. This agrees with Panje (1972) in North India where low t e m p e r a t u r e s d u r i n g w i n t e r s u p p r e s s t h e g r o w t h by a b o u t 25%. Additional reduction is due to low soil temperature at the end of winter and the beigning of spring (March). This supports the results on germination and stalk elongation (Table 5) and agrees with Sund and Clements (1974) in Iran. This confirms our assumption that the growth season, in Iraq, does not exceed 9 months (middle February to middle Novem- ber). Where 90% of the total growth occurs within 6 months (middle April to middle October). It is clear, in subtropics, that yield is less than yield of the tropics. This is nearly close to what Panje (1972) found. Accordingly, the climatic condi- tions in Iraq cause 33% decrease in the potential yield of sugar cane. Consi- dering the climatic conditions, the yield becomes'*112,0 tlhalyear.

4. Ratooning factor This factor is universally estimated by 0,9. Accordingly, the potential yield of sugar cane in Iraq is 100,8 tlhalyear.

5. Management Effectiveness of management in cane farms is estimated by 70%. So it causes additional reduction in the potential yield under the obove soil, climatic conditions and ratooning factors equal to 30%. The potential yield for the area becomes 70,6 tlhalyear. Despite of other factors, under the above conditions, the obtainable potential yield in Iraq is about 70,6 tlhalyear. From the forgoing discussion and results, it appears that the obtainable poten- tial yield under Iraqi conditions: 70,6 tlhalyear is 27,9%/maximum production 254,O tlhalyear and can be achieved providing optimum conditions for produc- tion. I t is known that mean yield in Hawaii is 37,0%/potential yield (280,O t/ halyear. The mean yield for the years 1970-1979 in Iran was 112 tlhalyear (40% potential yield; 280 tlhalyear declines to 230 t because of unfavourable climatic conditions) (Irvine, 1979). In Iraq the actual yield for the seasons 1976-1977 to 1979-1980 was 47,2; 60,4; 66,2 and 66,4 tlhalyear and was nearly close to the obtainable potential yield (70,6 tlhalyear). However, in some fields it reached 120 and 176 tlhalyear indicating the poten- tial of steping-up production by improving soil characters, water management, and cultural practices (Sehgal et al, ' 1980). It is interesting to know that the universal average yield is 60,0 tlhalyear.

6. Pests and diseases Considering pests and diseases, the difference between maximum production (120-176 tlhalyear) and the actual average yield for the seasons 76-77 to 79-80

.(58,4 tlhalyear) could be partially attributed to bioeffects beside the effects of other factors, i.e.weeds, wild pigs, and rodents. In spite of the difficulties encountered in quantifying the effects of pests and diseases. The present study showed a 10% reduction in yield of N Co 310 due to borer and associa- ted microorganisms. In addition to the above effects, there are other effects of plant diseases on yield, i .e. , reduced germination, stunted plants, and impaired and injuried shoot growth. Also negative effects on juice qualities and processing.

Effect of the interaction of ecobiological factors on juice qualities Ecological and biological factors mainly affect juice and its qualities. Final recoverable sugar from millable cane is 9,9 ton white sugar1100 t crushed cane. However a reduction of 1 t sugar is due to freeze and another ton is lost due to borers and associated microorganisms. Thus, total reduction of 2,O t1100 t crushed cane is apparent and the final recovery becomes 7,9 t sugar 100 t cane specially when freeze occurs. The total apparent and unapparent losses during processing range between 0,8-1,O t sugar. The final recovery declines to 6,9 upto 7 , l t sugar1100 t crushed cane. The average production of the Misan Factory for the years 76-80 was 4,7 to 7,O t1100 t cane, which is close to the above figures. This confirms the present results of the effects of the ecobiological agents and biota with the actual yield. The results also emphazises that Iraq is a marginal agricultural and production zone for sugar cane. There, the eco-biological factors limit the possibility of reaching yields similar to that in tropics. Howe- ver, there is a possibility to raising the recent production to 100-120 tlhlyear. This is what has been already achieved in Iran, under conditions similar to Iraq (Sun and Clements, 1974 and Irvine, 1979). It agrees with Irvine (1979) reporting that the actual yield in Iran and Hawaii is 49% and 37% of their potential (230 and 280 tlhalyear), respectively.

REFERENCES

Bonner, J . (1962): The Upper Limit of Crop Yield Science, 137(3523):11-15. Chang, Jen-Hu, Campbell, R . B, Brodie, H. W. and Baver, L. A. (1967): ~ v a ~ o t r a n s ~ i r a t i o n Resgarch at the HSPA Experiment Station. Proc, of the XI1 Congress of the ISSCT, Puerto Rico, pp. 10-24. Gowing, D. P. and Rozzef, H . N. (1972): Appraisal of Soil Salinity for Land Reclarnatlon in Lower Iraq. Proc. of the XIV Congress of the ISSCT. Louisiana, pp. 762-765. Irvine, J . E . (1975): The Wonder of Haft Tappeh. Sugar Jour, 42(5):24. Panje, R. R. (1972): Cultural Methods for Sugar Cane Production in the Sub-tropics. Proc. of the XIV Congress of the ISSCT. Louisiana, pp. 621-627. Richards, L. A . (ed.) (1954): Diagnosis and Improvement of Saline and Alkaline Soils. US Dept. Agric. Handbook No. 60, 166 p . Sehgal, J . L . , Allam, A. L., Gupta, R . P. and Ata Aziz (1980): The Suitability of the Soils of Mesopotamian Plain for Sugar Cane Cultivation. Proc. of the XVII Congress of the ISSCT. Philippines, pp. 132-151. Sund, K. A. and Clements, H . F. (1974): Production of Sugar Cane Under Saline Desert Condi- tion in Iran. Hawaii Agr. Exp. Sta. Bull., 160, 64 p. Thompson, G . (1967): The Relationship of Potential Evapotranspiration of Sugar Cane to Environmental Factors. Proc, of the XI1 Congress of the ISSCT. Puerto Rico, pp. 1-9. Thornwaite, C. W. (1948): An Approach Towards a Rational Classification of Climate. Geog. Rev., 28:55-94. Vernemmen, C. (1969): Bijdrage tot de studie van de klimast classificatie van C. W. Thornwaite. D. Sc. Thesis. State Univ. Ghent (Belgium), 476 p.

Effect of the interaction of ecobiological factors on juice qualities Ecological and biological factors mainly affect juice and its qualities. Final recoverable sugar from millable cane is 9,9 ton white sugar1100 t crushed cane. However a reduction of 1 t sugar is due to freeze and another ton is lost due to borers and associated microorganisms. Thus, total reduction of 2,O t1100 t crushed cane is apparent and the final recovery becomes 7,9 t sugar 100 t cane specially when freeze occurs. The total apparent and unapparent losses during processing range between 0,8-1,O t sugar. The final recovery declines to 6,9 upto 7 , l t sugar1100 t crushed cane. The average production of the Misan Factory for the years 76-80 was 4,7 to 7,O t1100 t cane, which is close to the above figures. This confirms the present results of the effects of the ecobiological agents and biota with the actual yield. The results also emphazises that Iraq is a marginal agricultural and production zone for sugar cane. There, the eco-biological factors limit the possibility of reaching yields similar to that in tropics. Howe- ver, there is a possibility to raising the recent production to 100-120 tlhlyear. This is what has been already achieved in Iran, under conditions similar to Iraq (Sun and Clements, 1974 and Irvine, 1979). It agrees with Irvine (1979) reportiqg that the actual yield in Iran and Hawaii is 49% and 37% of their potential (230 and 280 tlhalyear) , respectively.

REFERENCES

Bonner, J . (1962): The Upper Limit of Crop Yield Sclence, 137(3523):11-15. Chang, Jen-Hu, Campbell, R . B, Brodie, H . W. and Baver, L. A . (1967): ~ v a ~ o t r a n s ~ i r a t i o n Resgarch at the HSPA Experiment Station. Proc. of the XI1 Congress of the ISSCT. Puerto Rico, pp. 10-24. Gowing, D. P. and Rozzef, H. N. (1972): Appraisal of Soil Salinlty for Land Reclamation In Lower Iraq. Proc. of the XIV Congress of the ISSCT. Louisiana, pp. 762-765. Irvine, J . E. (1975): The Wonder of Haft Tappeh. Sugar Jour, 42(5):24. Panje, R. R . (1972): Cultural Methods for Sugar Cane Production in the Sub-troplcs. Proc. of the XIV Congress of the ISSCT. Louisiana, pp. 621-627. Richards, L. A. (ed.) (1954): Diagnosis and Improvement of Saline and Alkaline Soils. US Dept. Agric. Handbook No. 60, 166 p. Sehgal, J . L., Allam, A. L . , Gupta, R . P. and Ata Aziz (1980): The Suitability of the Solls of Mesopotamian Plain for Sugar Cane Cultivation. Proc. of the XVII Congress of the ISSCT. Philippines, pp. 132-151. Sund, K . A , and Clernents, H. F. (1974): Production of Sugar Cane Under Saline Desert Condi- tion in Iran. Hawaii Agr. Exp. Sta. Bull., 160, 64 p. Thompson, G. (1967): The Relationship of Potential Evapotranspiratlon of Sugar Cane to Environmental Factors. Proc. of the XI1 Congress of the ISSCT. Puerto Rico, pp. 1-9. Thornwaite, C. W. (1948): An Approach Towards a Rational Classification of Climate. Geog. Rev., 2855-94. Vernemmen, C . (1969): Bijdrage tot de studie van de klimast classiflcatle van C. W. Thornwaite. D. Sc. Thesis. State Univ. Ghent (Belgium), 476 p.

EFFETS DES FACTEURS ECOBIOLOGIQUES SUR LA PRODUCTION DE CANNE A SUCRE EN IRAQ

I. M. Mansour Institut de recherches sur la pathologie vCgCtale, Centre de recherches agricoles,

Guizkh, Egypte I

et A. I. Allam

Institut de recherches sur les cultures sucrikres, Centre de recherches agricoles, Guizkh, Egypte

Les auteirs ant' examine les effets simples et combines des facteurs 6cologiques, des maladies et du complexe borers-pourriture de la tige sur le rendement potentiel en cannes et en sucre, tout en les comparant avec le rendement possible de la varietk N Co 310 durant quatre recoltes conskcuti- ves (1976-1980), dans le sud de 1'Iraq.

11s on ktudie aussi les effets nkgatifs de la gelee, de la congelation et de la deterioration biologique sur la qualit6 du just et du jus melange au cours du broyage, tout en mesurant les pertes en sucre. L'interaction entre les maladies et l'environnement a 6tC observee aussi.

Le rendement potentiel annuel en canne a sucre dans le sud de 1'Iraq est estimk B 254 t/ha/an. Lorsque les propri6tCs physiques et chimiques du ' sol sont dkfavorables, ce potentiel se rCduit de 37,5% en moyenne. Les limitations climatiques peuvent Ctre B l'origine d'une diminution supple- mentaire de 18%. Les techniques culturales reduisent de 17O/0 le rendement potentiel. Le rendement possible en canne sucre dans le sud de 1'Iraq est donc de 70,6 tlhalan. Durant la piriode ktudiee, le rendement annuel reel dans ce pays a 6 t i de 58'4 tlhalan, soit 28% du rendement potentiel et 83% du rendement possible. NCanmoins, un rendement annuel de 70 t/ha/an ou plus peut Ctre obtenu. Des programmes par &apes peuvent Ctre mis en oeuvre en vue d'atteindre des rendement de'ordre de 100 a 120 tonnes B l'hectare par an.

Les auteurs ont detect6 la presence des borers ou foreurs des tiges Chile sp. et Sesamia sp. Le complexe form6 par les borers et la pourriture rkduit de 10% le rendement de la varikte N Co 310. Une perte de 4'5-15'2 dans le Pol % jus peut Ctre attribuie B ce complexe. Les estimations du sucre rkcupkrable diminuent de 20% et la recuperation est de 7,9 au lieu de 9,9 t de sucre pour 100 t de cannes. Pendant la pkriode etudiie, la rkcupkration

I au broyage a fluct uC entre 4,7 et 7 t de sucre pour 100 t de canne. I Les maladies de la canne a sucre ont augment6 lorsque l'environnement I a kt6 dkfavorable. Divers organes de la plante sont attaques, les symptd- / mes se manifiestant par la suite. Les auteurs ont observk les morves

communes, des maladies vasculaires, des maladies genkralisees, des feuilles 1 dCtCrior6es et couvertes de taches et de raies. La maladie la plus grave est 1 la pourrite des boutures, car elle nuit B la germination et a la croissance et

f A I. M. Mansour

1 rkduit le rendement. Ces pourritures se produisent plus facilement dans un I' environnement dkfavorable. I

!1

I I RESUMEN

Le charbon est aussi une maladie importante.

EFECTOS PRODUCIDOS POR FACTORES ECOBIOLOGICOS SOBRE LA PRODUCCION

DE CANA DE AZUCAR EN IRAQ

-:I

' 1 Instituto de Investigaciones sobre Patologia de las Plantas, Centro de Investigaciones 1 Agricolas, Giza, Egipto

Los efectos simples y combinados de 10s factores ecol6gicos, enfermeda- des y el complejo borers-pudricion del tallo, respecto a1 rendimiento poten- cia1 de caiia y azdcar se investigaron y compararon con el rendimiento obtenible de N Co 310 durante cuatro cosechas anuales consecutivas (1976- 1980) en el sur de Iraq. Los efectos negativos de las heladas, congelacion y el deterioro biol6gico sobre las calidades del jugo y del jugo mixto, durante la molida, se estudiaron asimismo y se cuantificaron las pkrdidas de azucar. Tambikn se estudi6 la interacci6n entre las enfermedades y el ambiente.

El rendimiento potencial de la caiia de azucar en el sur de Iraq se considera que es de 254 tlhalaiio. Las propiedades fisico-quimicas del suelo que son desfavorables reducen este potencial en una cifra promedio del 3 7 3 % . Otra disminuci6n del 18% puede deberse a restricciones climfiticas. La atenci6n dada a las cosechas de soca y a1 campo originan una reduccidn del 17% en el rendimiento potencial. D e este modo, el rendimiento obteni- ble en la caiia de azucar en el sur de Iraq alcanza la cifra de 76,6 tlhalaiio. El promedio del rendimiento real de Iraq fue de 58,4 tlhalaiio durante el period0 estudiado. Esto representa el 28% y el 83% del rendimiento potencial y obtenible, respectivamente. Sin embargo, se puede obtener un alto rendimiento de 70 o mis tlhalaiio. Son factibles 10s programas por etapas para lograr rendimientos de 100-120 tlhalaiio.

Los borers, o perforadores del tallo, Chilo sp. y Sesamia sp. fueron detectados. El complejo formado por 10s borers y la pudrici6n origina una reducci6n del 10% en el rendimiento de N Co 310. Una pkrdida de 4,5 a 15,2 en el Pol % del jug0 se puede atribuir a dicho complejo. El estimado del azucar recobrable disminuye en un 20% y el recobrado se convierte en un 7,9 en lugar de 9,9 t de azucar por 100 t de caiia. El recobrado en la

325

I

I

4 4 i i

Y A. I. Allam

Instituto de ~hvesti~aciones sobre Cosechas de Caiia de Az~icar, Centro dk Investigaciones Agricolas, Giza, Egipto

molida durante el period0 del presente estudio oscil6 entre 4,7 y 7 t de azucar por 100 t de cafia.

Las enfermedades de la cafia de azucar se incrementan debido a las condiciones ambientales desfavorables. Distintos 6rganos de la planta re- sultan afectados y despues se manifiestan 10s sintomas. Las pudriciones comunes, enfermedades vasculares, enfermedades generalizadas, manchas en las hojas, hojas rayadas y deformadas han quedado de manifiesto. La pudrici6n que se manifiesta en las estacas de semillas constituye el proble- ma de enfermedad de mayor importancia. Esto afecta negativamente la germinaci6n y el crecimiento, lo que origina una reducci6n paralela en el rendimiento. Estas pudriciones resultan mhs susceptibles de producirse debido a condiciones ambientales desfavorables. El tiz6n, o carbbn, es la otra enfermedad de importancia.