The trial was carried out at Bikolo nursery in Mecha district, North-Western Ethiopia, where the disease was prevalent. The site was located 11˚33'45" North latitude to 37˚16'14" East longitude and at an altitude of 1850 m.a.s.l.

The test contained seven treatments: Carbonchlor 50% SC, Benline 50% WP, Bellis 38% WG, Carbonchlor 50% SC combined with Bellis 38% WG, Benline 50% WP combined with Carbonchlor 50% SC, Benline 50% WP combined with Matco 72% WP and un-sprayed check. The fungicides were applied based on the manufacturers’ recommendation rate i.e., 20 ml and 20 mg per 10 liters of water for liquid and solid formulations, respectively. In order to spray fungicides thoroughly, Knapsack sprayer was used for applying. And the timing of application was started at the onset of the disease and had been continued at fourteen days of interval until one week left for harvesting. And during application, to avoid drift problem the plots under application were protected with plastic sheet supported by four wooden poles.

A Randomized Complete Block Design (RCBD) with three replications was the design applied. Consequently, 21 sweet orange trees of Jaffa variety were chosen for the test as experimental unit.

Disease severity was estimated both on leaves and fruits of the tree. On leaves, it was estimated on eight randomly selected terminal shoots from the upper and lower halves of the canopy in four directions (North, South, East and West) of each selected tree [7]. And it was computed based on a zero-to-four scoring scale, where 0 = no symptoms, 1 = 1% to 25%, 2 = 26% to 50%, 3 = 51% to 75% and 4 = above 75% of leaf area infected [8] [9].

On fruits, disease severity was assessed on 5 to 40 randomly selected intact fruits in four directions of each tree [7]. And it was recorded using the following zero to four scoring scale, where 0 = healthy, 1 = less than 5%, 2 = 5% to 20%, 3 = 21% - 50% and 4 = above 50% of fruit surface affected [10].

For analysis, severity grades were converted into percentage severity index (PSI) and calculated using the formula suggested by [11]:

PSI = Sum of   all numerical ratings Total no . of observations ∗ Maximum disease score ∗ 100

From the severity data, AUDPC for each treatment was calculated as described by [12] as follow:

AUDPC = ∑ i = 1 n [ ( x i + x i − 1 ) / 2 ] [ t i − t i − 1 ]

where, x_i = Present disease severity;

x_i-1 = Previous disease severity;

t_i− t_i-1 = Time difference between two consecutive disease severities; and

n—is the total number of days disease severity was assessed.

The efficacy of fungicides was calculated using [13] formula:

EF ( % ) = X − Y X ∗ 100

where,

X—Disease severity in control plots;

Y—Disease severity in treated plots.

All recorded data were analyzed by analysis of variance and tested for comparison of treatments at 0.01/0.05 level of probability using least significant difference (LSD). SAS separate analysis of variance, version 9.2 was the statistical package used for analysis [14].

Significant variations at (P ≤ 0.05) were detected between Matco 72% WP + Benline 50% WP and Bellis 38% WG + Carbonchlor 50% SC, Carbonchlor 50% SC only and Bellis 38% WG. Whereas, there were no significant variation observed among Matco 72% WP + Benline 50% WP, Benline 50% WP only and Carbonchlor 50% SC + Benline 50% WP. Likewise, significant variation was not observed among Benline 50% WP only, Carbonchlor 50% SC + Benline 50% WP, Bellis 38% WG + Carbonchlor 50% SC, Carbonchlor 50% SC only and Bellis 38% WG (Table 1).

Furthermore, differences among treatments on the recorded mean disease severity of leaves over time were discerned. Consequently, minimum mean disease severity (PSI) of leaves (1.73%) was recorded in Bellis 38% WG treated trees. However, maximum severity (PSI) (18.15%) was observed in the control plots (Figure 1).

However, on fruits the highest disease severity (35.66%) was recorded in unsprayed trees. And it was zero in all fruits of trees treated with different fungicides (Table 2).

The day ^⁎126 after the first fungicides spray, is the mean of the three replications; means followed by the same letter are not significantly different by LSD (P < 0.05).

^⁎⁎170 days after the first fungicides spray is the mean of the three replications.

Low rate of AUDPC (Area Under the Disease Progress Curve) was computed by Bellis 38% WG that was (149.38) followed by Carbonchlor 50% SC (220.92), Bellis 38% WG combined with Carbonchlor 50% SC (292.25), Benline 50% WP combined with Carbonchlor 50% SC (536.55), Benline 50% WP (594.44) and Matco 72% WP combined with Benline 50% WP (867.30). Whereas, it was (1736.56) by the unsprayed check (Figure 2).

Based on the efficacy level of the fungicides, the highest level of efficacy (90.46%) was produced by Bellis 38% WG treated trees followed by Carbonchlor 50% SC (86.50%), Bellis 38% WG + Carbonchlor 50% SC (82.00%), Carbonchlor 50% SC + Benline 50% WP (67.89%), Benline 50% WP (65.62%) and Matco 72% WP + Benline 50% WP (49.48%) (Table 3).