TECHNICAL BULLETIN 70 ISSN 0070 - 2315

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\-'~~:~;-~~05 ON TIlE FEASIBILITY OF CHEMICAL CONTROLOF DISEASES OF

BARLEY AND WHEAT VARIETIES GROWN AT SEVERAL ENVIRONMENTS

A. Hadjichristodoulou and A Kari

AGRICULTURAL RESEARCH INSTITUTE MINISTRY OF AGRICULTURE AND NATURAL RESOURCES

NICOSlA CYPRUS

OCTOBER 1985

ON THE FEASIBILITY OF CHEMICAL CONTROL OF DISEASES OF BARLEY AND WHEAT VARIETIES GROWN AT SEVERAL

ENVIRONMENTS

A. HlIdjichristodoulou and A. Karl

SUMMARY

Disease control through foliar application or seed treatment with chemicals was studied in a number of trials during 1968-84, using several barley and wheat varieties. The most important diseases were: leaf rust, net blotch, powdery mildew and scald for barley,. and leaf rusts for wheat. Disease incidence in wheat was lower than in barley. In general, disease incidence was low, except under irrigation or high rainfall conditions. In barley, leaf rust. powdery mildew and scald were controlled by foliar applications of Dithane Z-78 (zineb) and Bayleton 25WP but their effect' . varied with variety, location and year. Seed treatment with Baytan Universal was not effective inmost cases. Disease inci­dence and yield losses were higher in barley than in wheat. Spraying increased yield of barley by up to 56%, depend­ing on variety and environment. but in most dryland trials there was no significant difference in yield between sprayed and control plots. Control of diseases increased yield more in some varieties than others. indicating variation in toler­ance levels among varieties. Athenais appeared tolerant to leaf rust. Sheaf weight, volume weight and lOOO-grain

. weight were also affected by diseases, but number of tillers per m2 and number of grains per spike were not affected. 11 is concluded that under rainfed conditions in Cyprus it is not economically justifiable to control cereal diseases chemically. However, breeding, cultural practices and other strategies should be used to control diseases in order to achieve high and stable yields under both low and high rainfall conditions.

INTROOUCI10N was sprayed with Bayleton against powdery mildew (Anonymous, 1980). In Mexico, where a rust

In Cyprus, cereals are g~own mostly under rainted epidemic on wheat existed in the late 1970's, spray­

conditions, and drought frequently reduces yields. ing of 115,000 ha with different conceritralions of However, 10-20% of the cereal area receives either Bayleton 25 WP and Iudar 70LC increased grain adequate rainfall or supplementary irrigation. _De­ yield by 31 % to 54% (Dubin, 1981).

spite the dry climate of Cyprus, diseases caused sig­nificant damage to cereals during the period 1930­ At the initiation of the breeding programme at

1960 (Hadjichristodoulou, 1981). the Institute in 1967 it was observed that several fol­iar diseases attacked the then commercially grown varieties and the most promising liries in the screen­Under the fluctuating environmental conditions of ing nurseries. Trials on chemical control of the ma­dryland areas, stability of performance is one of the jor diseases were initiated in 1968 and were aimed at main objectives of breeding programmes. Varieties

~elected to give high yield undef moisture stress con­ estimating yield losses. This information is useful in

ditions must have the potential to exploit also high assessing the imputs for the programme on breeding

rainfall conditions. Thus, it is important to eliminate for disease resistance.

any yield losses from diseases in order to achieve the full yield potential under all possible rainfall MATERIALS AND MEmODS conditions.

In 1968-9 a trial was conducted at Athalassa in Control strategies for cereal diseases in Cyprus in­ which two spray treatments (spraying with Dithane

clude breeding for disease resistance or tolerance, Z-78 (zineb) and no spraying),two N fertilizer rates, and the replacement of varieties by new ones every 5.0 and 7.5 kg N/donum (one donum=134Om2) and few years in order to prevent the development of two varieties (Athenais and Sel B 55-22) were tested epidemics (Hadjichristodoulou, 1981). Chemical in a split-split plot design wi~h five replications. Nine control has not been used because of the low yields sprays were applied at about weekly intervals to under moisture stress conditions though in other control rust. Sprayed and control plots occupied the countries, e.g. Western Europe, it is routine prac­ main plots, N levels the sub-blots and varieties the tice. In 1975,41% of the barley acreage in the U.K. sub-sub-plot (12m2). A similar trial was conducted

in 1969-70 at Athalassa with Athenais and Sel B 55­22 barley, and Psathas, Kyperounda and Tripolitico durum wheat. The design was a split-plot with six replications. Sprayed and Control treatments oc­cupied the main plots and varieties. the sub-plots (1.6m2). Fertilizer rates were 5kg Nand 6 kg P205 per donum.

In three seasons, 1980-3, six trials were conducted with three barley varieties, namely the local Athenais, the recently released Kantara (Had­jichristodoulou et al., 1980), the promising line Mari/CM67 CMB72-140-8Y-IB-3Y-lB-IY-OB, and a mixture of susceptible lines. Three of the trials, one in each season, were sown at Athalassa under irrigation to secure normal plant growth. Three rainfed trials were sown at Laxia, Dromolaxia and Akhera in 1981-2 under farmers' conditions. The de­sign was split-plot with six replications. Three treat­ments (spraying with Bayleton 25% WP, 67 g/donum), seed treatment with Baytan Universal, and Control) occupied the main plots and varieties the sub-plots (7m2). Fertilizer rates were 6 kg N ana 4 kg P205/donum.

In 1983-4 two trials with 12 varieties were sown at Drorrtolaxia, one early and one late, and one at Laxia. The design was a split-plot with three replica­tions. A sprayed treatment and the control occupied the main plots, and varieties the sub-plots. Fertilizer rates were 6 kg Nand 4 kg P205/donum.

In all tfials of 1980-4 rust was controUed by Bayle­ton WP25. Other diseases (powdery mildew, net blotch and scald) were controUed only in certain trials. Two sprays were applied, one at boot stage and the other 20 days aft,er heading.

Data on diseases were recorded using the method described by Hadjichristodoulou (1981), The method proposed by Loegering (1959) was used for stem rust, leaf rust and stripe rust. Two scores were taken: severity as percent infection of the plant de­tennined by visual observation, and response as the type of infection designated as follows: 0 (no visual infection on the plant); R (resistant, necrotic areas with or without minute uredia present); MR (mod­erately resistant, small uredia present, surrounded by necrotic areas); MS (moderately susceptible, medium size uredia without necrosis but possibly with some distinct chlorosis: S (susceptible, large

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uredia without necrosis and with little or no chlorosis present); X (intermediate). Severity and response were then combined together, e.g. tR indi­cates trace severity of a resistant infection. For the numerical evaluation of the data the response type was given scores as follows: zero for no infection (0),0.2 for R, 0.4 for MR, 0.6 for X, 0.8 for MS and 1.0 for S. The severity percentage was multiplied by the response score to calculate the coefficient of in­fection (CI) of each plot. The CI values from diffe­rent replications or locations were averaged to give the Average Coefficient of Infection (ACI).

Records on foliar diseases other than rusts, namely powdery mildew, scald, net blotch etc., are presented with two numbers, the first recorded on a scale of 0-9 and representing the height of plant in­fected, and the second the percentage of leaf area covered by the diseases.

In 1968-70 rust was recorded as percent of leaf area covered by the disease. Grain yield and 1000­grain weight were recorded in all trials. In some trials sheaf weight and N content of the grain were also' recorded.

RESULTS

1968 -70 triaJs

In 1968-9, which was a high rainfall season (425 mm), zineb application increased grain yield, sheaf weight, volume weight and lOOO-grain weight (Table 1). A 4.4% increase in N content of the grain was not significant at the 5% level of probability. Leaf rust incidence was very low (0-5%)in the sprayed plots and very high (90%) in the control plots. Net blotch was not controlled by the chemical used.

Table 1. The effects of spraying with zineb on agronomic traits of two barley varieties (Athenais, Sel B 55-22) in 1968-9.

Grain Sheaf Volume l00Q-grain yield weight weight weight

Treatment (kg/donum) (kg/donum) (kglhl) (g)

Control 442 b 1247 b 58.9 b 37.4 b Zineb 552 a 1528 a 62.0 a 42.8 a

The interaction zineb x variety was significant for sheaf weight and grain yield (Fig. 1). In the case of Sel B 55-22, zineb increased sheaf weight by 32% and grain yield by 30% (P=0.05). In the case of Athenais, significant increases were obtained in grain yield (17%) but the increase in sheaf weight (13%) was not significant. A comparison of the two varieties showed that in the control plots the sheaf and grain yields were not significantly diferent but in the sprayed plots Sel B55-22 outyielded Athenais in both grain and sheaf yield. Control of rust also in­creased grain size of both varieties. The lOoo-grain weight (average of both varieties) increased from 37.4 g to 42.8 g. Volume weight also increased from 58.9 kg/hi to 62 kg/hI. Variety x T·reatment interac­tion for volume weight was not significant.

In the 1969-70 trial at Athalassa (180 mm rainfall) leaf rust incidence was for the barley varieties 6.3%

Table 2. Coefficient of infection (CI) for treatments.

to 8.3% in the sprayed plots and 73.3% to 83.3% in the control plots, and for the wheat varieties 1.5% to 1.8% and 6.3% to 10.8%, respectively. Spraying with zineb did not affect yields significantly in five of the six varieties. In the case of variety Sel 855-22, however, yield of sprayed plots was 367 kg/donum, 27% higher than that of control plots. Sheaf weight was not affected by zineb in any of the varieties.

1980 - 3 trials

Data of the 1980-3 trials on the effect of chemicals on leaf rust (Table 2) and on yellow rust, powdery mildew and scald (Table 3) show that sprays with Bayleton controlled these diseases but seed treat­ment was not effective in most cases. There were significant differences among varieties on disease re­sistance, as shown by their scores in the control

leaf rust of four barley varieties under three

Mari- Precipitation

Season Location Treatment Athenais Kantara CM67-CMB· Mixture" (mm)

1980-1 Athalassa Control (Irrigated) Seed treated

Sprayed

198[-2 Athalassa Control (Irrigated) Seed t rea ted

Sprayed

Laxia Control (Rainfed.) Seed treated

Sprayed

Dromolaxia Control (Rainfed) Seo:d t rea ted

Sprayed

Akhera Control (Rainfed) Seed treated

Sprayed

1982-3 Athalassa Control (Irrigated) Seed trea ted

Sprayed

Mean Control ACI Seed t rea ted

Sprayed

. MARI-CM67-CMB72- \40-SY -I B-3Y-IB-l Y-OB Mixture of susceptible varieties.

5.2 4.7 1.7

24.7 13.3 03

200 \9.0 00

340 28.0 14.0

10.0 8.7 3.5

200 \6.6 0.5

18.9 15\ 3.3

3.5 33 1.\

1.8 0.7 0.0

0.4 04 0.0

4.0 4.0 3.3

0.7 0.5 04

0.6 0.9 0.\

1.8 1.6 08

203 21.0 5.3

140 U5 0.0

126 8.6 00

45.4 433 106

3l 1.3 0.8

14.6 17.3 03

183 \7.5 28

26.5 210 73

24.0 19.4 0.0

220 15.3 0.0

42.6 393 127

12.7 10.7 13

22.6 \9.3 0.3

25.0 20.8 36

325

+ Irrigation

190 +

irrigation

226

266

273

228

+ Irrigation

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plots. Kantara was the most resistant variety for leaf Differences among locations in 1981-2 for leaf rust rust, with an Average Coefficient of Infection (ACI) incidence were significant as shown by the ACI v;lJ­1.8 compared to 18-25 for the other varieties. Bayle­ ues of control plots of all varieties (Table 2). Also ton reduced leaf rust ACI to 0.8 for Kantara and differences in ACI among years at the same location 2.8-3.6 for the other varieties. Yellow rust incidence were significant as shown by the ACI values of con­observed only in 1980-1 and 1982-3 at Athalassa trol plots at Athalassa during 1980-3. Differences (Table 3) shows that Athenais was the most resis­ among years are also shown for leaf rust, powdery tant, with ACI 2.6 compared to 27-46 of the other mildew and scald (Table 3). vaneties. Powdery mildew and scald incidence was low in all years (Table 3), and Bayleton reduced it In the irrigated and rainfed trials of 1980-3 differ­significantly. ences in grain yield between treatments were not

Table 3. Disease scores (ACI) for yellow rust, powdery mildew and scald for four barley var­ieties under three treatments.

Season Disease Location Treatment Athenais Kantara Mari-CM67 Mixture

1980-1 Yellow Athalassa Control 2.7 70.0 46.6 725 rust (irrigated) Seed treated ~ .3 675 42.5 62.5

Sprayed 00 08 0.0 0.0

1982-3 Athalassa Control ~.) 125 6.6 20.0 (irrigated) Seed treated ]. :) 8.3 58 22.5

Spra yed O() 00 0.1 00

Mean Control 2.f, 41.3 26.6 20.0 ACI Seed treated .1 ~ 379 242 22.5

Sprayed 110 0.4 0.05 0.0

1980-[ Powdery Atha[assa Contro[ ~/lr+- 3/7" ~/I5" 5/3f," Mildew (irrigated) Seed treated tr 2/6 3/8 4/14

Sprayed (J 0 n 0

1981-2 Control 2/5 2/1, 3/5 3/5 Seed treated 2/~ tr 2/5 3/5 Sprayed tr tr 0 tr

1982-3 Control 2/5 tr 2/2 4119 Seed treated :'13 tr tr 4/17 Sprayed III 0 0 2/2

1980-1 Scald Athalassa Control (J 3/4 2/2 3/4 (irrigated) Seed t rea ted (J 2/4 tr 2/6

Sprayed (J 0 () 0

1981-2 Control (J 3/9 0 3/6 Seed treated (J 2/4 0 3/5 Sprayed (J n 0 tr

1982-3 Control (J 3/6 1/2 5114

Seed treated () 3/7 III 4/8 Sprayed (J 2/2 0 2/2

. tr: trace the first number indicates the height of plant infected: the second Indicatcs the percentage of infection .

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significant in most cases (Table 4). The effect of treatment varied with variety and trial. There was no significant difference in any of the trials with Athenais. With the other varieties differences were significant in two of the six trials. On average over six trials, grain yield of sprayed plots of the four var­ieties was up to 10.1 % higher than that of the con­trols. In the three irrigated trials the range of in­crease was 2.7 to 13.7%.

In 1980-1 Bayleton spraying increased volume weight from 57 to 63 kg/hi in Kantara, from 65 to 68 kg/hi in Mari/CM67-CMBl72-140-8Y-1B-3Y-1B-IY­OB and from 55 to 60 kg/hi in the Mixture. No sig­nificant effects were found in the other years. The lOoo-grain weight of sprayed plots was higher only for two varieties in one of the six trials. The increase

was from 39.6 to 48.5 g for Kantara and from 30.6 to 35.9g for the Mixture. Bayleton did not affect crude protein content in any of the trials. Number of grains per tiller increased significantly only for the Mixture in 1980-1, from 42 in the control plots to 63 in the sprayed plots. Plant height, heading date and tiller number were not affected significantly by con­trolling the diseases.

1983 - 4 trials

Precipitation in the 1983-4 rain fed trials was 257 mm at l..,axia and 331 mm at Dromolaxia. Bayleton controlled leaf rust and scald (Table 5) but not pow­dery mildew, spot blotch or net blotch. Disease inci-

Table 4. Grain yield (kg/donum) of four barley varieties under three treatments dur­ing 1980-3

Variety

Season Location Treatment Athenais Kamara Mari-CM67 Mixture

1980-1 Athalassa Control 720 a 633 b 893 a 663 b ([ rrigated) Seed I rea led 7~0 a 659 b 869 a 719 b

Sprayed 808 a 877 a 858 a 850 a

1981-2 Athalassa Control 10(X) a 1091 a 1103 ab 1140 ab (Irrigated) Seed treated 1002 a 1078 a 985 b 1028 b

Sprayed 995 a 1060 a 1135 a 1225 a

Laxia Control 644 a 663 a 642 a 582 a (Rainfed) Seed treated 630 a 707 a 702 a 559 a

Sprayed 622 a 683 a 678 a SSt a

Dromolaxia Control 70S a 701 a 618 ab 503 a (Rainfed) Seed treated 676 a 635 a 514 b 562 a

Sprayed 713 a 720 a 680 a 614 a

Akhera Control 569 a 567 a 567 a 486 a (Rainfed) Seed treated 569 a 591 a 589 a 481 a

Sprayed 630 a 5lf7 a 584 a 508 a

1982-3 Athalassa Control 824 a 801 b 971 a 973 a (Irrigated) Seed treated 908 a 925 a 921 a 994 a

Spayed 918 a 950 a 1025 a 1042 a

Mean of all Control 744 7~3 799 725 locations for Seed treated 754 766 763 724 three years Sprayed 781 815 827 798

Mean for three Control 848 R42 989 925 years under irrigation Seed treated 883 887 925 914 at Athalassa Sprayed 907 962 1006 1039

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dence varied with variety; for the control plots, the that of the control plots. For individual trials the in­range of ACI for leaf rust was 0.8-13.3, 0.9-13.3 and crease in yield was 20.1%,17.7% and 12%, the lat­0.4-31.0 in the three trials (Table 5). Kantara (Vt) ter not being significant at the 5% level (late sown was the most resistant to leaf rust. Bayleton reduced trial at Dromolaxia). The increase in yield resulting ACI to almost zero for all varieties. The mean ACI from the chemical control of diseases was significant of 12 varieties was 7.24-12.5 in the control plots and only in some varieties (Fig. 2). In the combined 0.1-0.2 in the sprayed plots. analysis of the three trials, yield increases were sig­

nificant in eight of the 12 varieties. The effect of Bayleton sprays on scald was not

consistent in any of the varieties (Table 5). For ex­ample, for V7' percent infection of scald at The effect of spraying varied also with environ­Dromolaxia was reduced from 33 to 13% in the nor­ ment. For V2 (Athenais) and Vll sprayed and con­mal sowing date and from 13 to 11 % in the late trol plots gave similar yields in the aU three trials. sown trial, but it was not affected significantly at The disease level of Athenais was high, especially Laxia. At this location, scald incidence was low and ACI of leaf rust, which was among the highest with the effect of Bayleton sprays was not significant in a score of 12, 13.3 and 31.0 in the three trials (Table

most cases. 5). Leaf rust and scald incidence of V 11 was rela­tively low, hence the effect of spraying was not sig­

Incidence of the other foliar diseases, powdery nificant. For none of the varieties was the effect of mildew, spot blotch and net blotch, was low, below spraying significant in all three environments. For 7% in most varieties.' some varieties, spraying increased yield at one or

two environments. By comparing the data in Table 5 The mean grain yield of sprayed plots over the and Fig. 2 for Kantara (VI) it is evident that in two

three trials was 479 kg/donum, 16.5% higher than trials at Dromolaxia, where spraying reduced the

Table 5. Disease scores (ACI) for leaf rust and scald for twelve varieties under two treatments.

Variety" •

Season Disease Location Treatment VI V2 V3 V4 V5 V6 V7 VS V9 via VII VI2

1983·4 Leaf rust Dromolaxia' Control 08 13.3 80 93 SO 5.3 9.3 120 10 80 0.0 53 Sprayed 0.0 0.0 0.5 02 00 0.2 00 0.2 0.0 0.5 0.2 0.0

Dromolaxia" Control 0.9 12.0 [0.7 8.0 0.7 93 107 120 17 133 0.7 10.7 Sprayed 00 0.2 0.0 0.2 0.0 0.2 0.0 02 00 0.2 0.0 02

Laxia' Control 0.4 310 200 173 106 4.0 40 280 OS 193 4.0 10.6 Sprayed 0.0 0.4 0.5 0.2 0.2 00 0.2 00 00 0.5 0.5 0.0

1983-4 Scald Dromolaxia' . Control 8/40 51tr 8/17 8/27 S/45 S/28 8m S/20 sm 6/tr SIS 7/8 Sprayed 5/20 tr 6/25 0/5 0/20 6/12 6/lJ 4/5 7/2S tr tr 6/tr

Dromolaxia" Control 7/22 Ir 7123 0/27 7130 7/1S 6/lJ 6113 7130 6/5 5/3 5/7 Sprayed 7113 tr 5/8 6/0 0/20 6/S 6/11 6/6 711S 3/3 515 51tr

Laxia' Control 6/5 tr 0/4 0/7 4/7 3/4 5/4 3/5 6/3 0/2 4/5 4/4 Sprayed 5/3 3/5 3/3 313 3/5 5/4 5/4 5/2 4/5 513 5/3 6/tr

, Normal sowing date in fallow field Late sowing date in a field sown with barley the previous season

'" Vl=Kantara, V2=Athenais, V3-V12 are new lines selected for high performance after four years of testing.

6

E . NS:J 500 NS NS NS NS c o 400 1)

300

percentage infection by scald from 22% and 40% to 13% and 20%, yield was increased significantly. By S

Sheaf weightcontrast, at Laxia, where scald incidence was low, 1600

yield differences between sprayed and control plots E :Jwere not significant. Kantara was resistant to leaf 1500 C

rust. Fig. 1 and Table 5 show the effect of chemical a A

1) 1400control on diseases and can explain the effects on

0'

grain yield also for the other varieties. x:: 1300

1)

The relative ranking of the 12 varieties in the 120 .,.II>

sprayed plots was not the same as in the control >-Grain yieldplots, because of the differences among the varieties 600

Sin losses from diseases. However, the top yielding c

lines could be selected in both treatments, as shown '1l

in the mean yield data over three trials (Fig. 2). l') 500

DISCUSSION

The present trials, which were conducted under 400

fdifferent environmental conditions (1-4 trials in each

Control Z ine b of four seasons during 1968-84), showed that, as ex­pected (Mathree, 1982), percent infection varied with disease and environment. Leaf rust was the Fig. 1. Effects of spraying with zineb on sheaf. and main foliar disease on barley with a considerably grain yield of Athenais (A) and Sel B55­high severity under irrigation or high rainfall condi- 22(5) barley, 1968-9.

A

(a) Me a n of the Uyee trials (b.c ,d) o Control, ~ SpraYlld NS

:~~t . 400

300

NS NS

(b) Laxla.normal sowing date 6001

(e) Dromolaxia, late sowi ng

'L..I....J.LL.J...JL...L---.l....Juu.....L.l.LL.L..J..I~U-k:..L..l.....I..LL.J...~~.I'-I......I....l.l:..L.....l....I..I/:..L..l..J.LJ....I...lL.I_

c (d) Dromolaxia,normal sowing date

'" 700

l') 600 NS

500

NSNS:~~~I >­ 300

V1 V2 V3 V4 V5 V6 V7 VB V9 V10 Vl1 V12 M

Fig. 2. Effect of Bayleton sprays on grain yield of 12 barley varieties in (VI = Katltara, V2=Athenais, V3-V12 new lines as in table 5).

three trials. 1983-4.

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tlons, such as in 1968-9 at Athalassa (450 mm). lnci­dence of yellow rust was also important in the 1980-1 season at Athalassa. Powdery mildew, net blotch and scald were less important. However, annual disease records of the Institute's breeding program show that scald becomes increasingly im­portant in Cyprus, especially on some susceptible varieties.

Control of diseases by foliar sprays of zineb or Bayleton was efficient in most cases and reduced significantly the percentage of infection, but seed treatment was not effective in most cases. By con­trast, in Greece, seed treatment controlled powdery mildew in barley and increased yield up to 10% (Skorda, 1981).

The effects of chemical control on yield varied with variety, enviroRmen t and especial! y the level of disease infection. For example, in a wet season in which leaf rust infection was 90%, yields of sprayed plots were significantly higher than control plots but in four dry seasons (1969-70 and 1980-3) yield differ­~nces were mostly not significant. However, in all trials mean yields were higher in sprayed than con­trol plots. The mean increase in y;eld of barley was 25% in 1968-9,3.7% in 1969-0,7.0% in 1980-3 and 16.5% in 1983-4, which is generally lower than in countries where chemical control is practised (Anonymous, 1980). For individual varieties and trials the 'yield increases were up to 38.5% in 1980-3 and up to 56% in 1983-4. Thus, though yield losses were' variable and were on average low, in special cases of high disease incidence they were very high.

Sheaf weight, volume ':Veight and lOOO-grain weight were also reduced by diseases in some trials. [n similar studies in the U.K., Jenkyn et at. (1983) reported significant reduction .in grain yield and lOOO-grain weight but not in number of ears or number of grains per ear. Grain size was the yield component most frequently affected by diseases. Foliar diseases, especially rust, affect the photosyn­thetic capacity during grain filling, thereby reducing grain size. The number of tillers/m2 and number of grains per tiller are set before the appearance of rust, and hence they are not adversely affected.

The differences in the relative ranking of some varieties in the sprayed and control plots can be

8

attributed to differences in susceptibility to the vari­ous diseases. Differences in tolerance of varieties may also cause differences in the relatiye yield of varieties when recorded on sprayed or control plots. An example of such a case is offered by Sel B55-22 and Athenais (1968-9 trial); both varieties were sus­ceptible to rust, but the disease affected the yield of Sel B55-22 more than that of Athenais, which also showed its tolerance to leaf rust in 1983-4.

Stategies for the control of cereal diseases were discussed by Hadjichristodoulou (1981). Cultural practices such as proper rotations, burning of cereal crop residues and seed treatment, which is effective against some seed-borne diseases, may be used in controlling diseases (Leonard and Martin, 1963).

Breeding for disease resistance is considered the most effective method to control cereal diseases, although it is not always successful. Even in countries with advanced breeding programmes and long history in breeding for disease resistance, com­mercial varieties may be susceptible to one or more diseases. One of the reasons for this is the interac­tion between host and pathogen, as a result of which new races develop which attack new resistant var­ieties. This study showed that under dryland condi­tions yield losses from diseases are not consistent and in most cases are not significan t. However, it is necessary to select for resistance or tolerance of var­ieties to the predominant diseases. The case of Athenais, which although susceptible to leaf rust is a successful variety in Cyprus and other countries, suggests that a certain level of disease infection may be acceptable, provided the variety is high yielding.

ACKNOWLEDGEMENTS

The authors gratefully acknowledge the assistance of L. Daniel, G. Alexandrou, Chr. Theodorides, M. Mouzouris, A. Pharmakides and A. Demetriou in field and laboratory work.

REFERENCES

Anonymous. 1980. Bayleton. The programme approach to cereal foliar diseases. Courier. BA YER. Vol. 19. 1/80 pp3-7.

Dubin. H.J. 1981. Causes and consequences of the 1976-77 wheat leaf rust epidemic in Nvrthwest Mexico. Annual Re­view of PhylOpalhology 19: 41-49.

Jenkyn. J.F.. M.E. Finney and G.V. Dyke 1983. Effects of nit­rogen fertilizer and tridemorph on mildew. growth and yield of spring barley 1975-7. Journal of Agriculillral

Science. Cambridge 101:517-546.

Hadjichristodoulou, A. 1981. Cereal diseases in Cyprus - Con­trol strategies. Technical Bul/elin 38. Agricultural Re­

search Institute. Nicosia. 12p.

Leonard. W.H. and J.H. Martin. 1963. Cereal Crops. The Mac­millan Company. N. Y.. 824 p.

Loegering. W.D. 1959. Method for recording cereal rust data. 1,,­lernalional Spring Wheal Rusl Nursery, 1959.

USDA. Washington

Mathree. D.E. 1982. Compendium of Barley Diseases. The American Phytopathological Society. St. Paul. Min­nesota. USA.

Skarda. E 1981. Powdery mildew of barley (Er)'siphe graminis) in Greece. In Proceeding s Barley Diseases and As­socialed Breeding .Melhodology Workshop, Rabat

(Morocco). USAID/CIMMYT/ICARDA, pp. 117-122.

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