Association of apple powdery mildew (Podosphaera leucotricha) and anthracnose (Neofabraea malicorticis) epidemics with environmental factors and agronomic practices in Chencha highlands, southern Ethiopia

Table 5 Categorization of independent variables and disease contingency for powdery mildew and anthracnose severity in Chencha, southern Ethiopia, during the 2021 and 2022 cropping years

Variable	Variable class	Number of fields	Powdery mildew severity (%)		Anthracnose severity (%)
Variable	Variable class	Number of fields	≤ 26	> 26	≤ 24	> 24
Altitude^a	< 2700	50	35	15	38	12
Altitude^a	≥ 2700	114	50	64	56	58
Year	2021	82	49	33	52	30
Year	2022	82	36	46	42	40
Survey site	Farmers field	160	83	77	90	70
Survey site	State farm	4	2	2	4	0
Age of tree	≤ 5 years	4	3	1	4	0
	5 – 10 years	18	8	10	12	6
	10 – 15 years	48	30	18	32	16
	> 15 years	94	44	50	46	48
Source of planting material	Non-government	148	74	74	84	64
Source of planting material	Bureau of Agriculture	16	11	5	10	7
Growth stage	Fruit development	84	53	31	53	31
	Fruit maturity	70	28	42	40	30
	Flowering	10	4	6	1	9
Cropping system^b	Mono-cropped	46	11	35	12	34
	Mixed with enset	20	6	14	8	12
	Mixed with horticulture	70	50	20	42	28
	Mixed with cereals	16	8	8	12	4
	Mixed with legume	12	10	2	10	2
Apple tree management	Earthen up + compost 1 × /year	80	14	66	36	44
Apple tree management	Earthen up + compost 2 × /year	84	71	13	58	26
Precipitation (mm)	< 1000	139	82	57	90	49
Precipitation (mm)	≥ 1000	25	2	23	5	20
Relative humidity (%)^c	< 90	140	80	60	89	51
Relative humidity (%)^c	≥ 90	24	6	18	5	19
Temperature (°C)^d	< 22	128	80	48	87	41
Temperature (°C)^d	≥ 22	36	6	30	7	29
Disease status^e	High	38	10	28	1	37
	Medium	74	45	29	44	30
	Low	52	31	21	49	3
Disease management	Pruning + sanitation	52	49	3	38	14
	Sanitation (no pruning)	44	23	21	24	20
	No management	68	13	58	31	37
Weed management^f	Good	112	64	48	73	39
	Intermediate	34	16	18	18	16
	Poor	18	5	13	4	14
Yield (t/ha)	≤ 15	19	0	19	0	19
	15 – 20	48	12	36	12	36
	20 – 25	36	17	19	27	9
	> 25	61	56	5	56	5

^aAreas of 2300–2700 and ≥ 2700 m.a.s.l are classified as highland and extremely highland, respectively, in Ethiopia
^bMono-cropping indicates planting apple varieties only; mixed with enset is apple varieties planted with enset; mixed with horticulture is apple varieties planted with potato, cabbage, spices, aromatic herbs, onion, shallot, garlic, and carrot; mix cropped with cereals is planted with wheat, barley, and triticale; and mix cropped with legume is apple varieties planted with fava bean, field pea, and common bean
^cRelative humidity (%) < 90 and ≥ 90 is the percentage of relative humidity below and above optimum, respectively
^dTemrature (°C) < 22 and ≥ 22 indicates less than and greater than the optimum temperature of both diseases (Xu and Butt 1998; Xu 2021), respectively
^eHigh, medium, and low disease status indicate high, medium, and low disease infection in the whole observation of orchard, respectively
^fWeed management was recorded as good, intermediate, and poor, referring to weed free, few weeds, and no weeding, respectively