Symptoms and distribution of blossom blight in alfalfa seed production on the Canadian Prairies

Figures & data

Fig. 1 (Colour online) Symptoms of severe blossom blight on alfalfa caused by Botrytis cinerea (left) and Sclerotinia sclerotiorum (right)

Table 1. The incidence of Botrytis cinerea (Bc) and Sclerotinia sclerotiorum (Ss) in and on alfalfa flowers at eight sites on the Canadian Prairies in 1995

Province & Region	# of fields	Early bloom		Mid Bloom		Late bloom
		Bc	Ss	Bc	Ss	Bc	Ss
Alberta
- Peace River	16	nd	nd	nd	nd	78	8
Saskatchewan
- Northcentral	5	nd	nd	58	1	64	8
- Northeast	2	nd	nd	65	0	59	0
- Central	2	nd	nd	71	15	11	6
- Northwest	2	nd	nd	64	0	42	0
Manitoba
- East	2	23	5	nd	nd	nd	nd
- Central	1	0.5	6	nd	nd	nd	nd
- Interlake	2	2	1	nd	nd	nd	nd

nd = not done.

Table 2. Incidence (mean % and range below) of Botrytis cinerea (Bc) and Sclerotinia sclerotiorum (Ss) in or on alfalfa flowers at early, mid, and late bloom at ten sites on the Canadian Prairies in 1996

Location	#. of fields	Early bloom		Mid bloom		Late bloom
		Bc	Ss	Bc	Ss	Bc	Ss
Alberta
- Peace River	13	17	22	40	24	34	17
		(8–44)	(6–63)	(3–75)	(4–64)	(0–70)	(4–47)
- South	12	4	15	12	13	4	11
		(0–8)	(3–50)	(3–30)	(0–48)	(0–8)	(0–53)
Saskatchewan
- Northwest	3	25	23	24	33	30	12
		(7–44)	(8–36)	(0–40)	(5–69)	(8–51)	(5–18)
- Northcentral	4	15	18	41	35	54	15
		(4–31)	(1–33)	(15–93)	(10–58)	(18–100)	(9–21)
- Northeast	9	8	13	8	17	58	28
		(3–20)	(0–38)	(0–33)	(0–58)	(20–99)	(3–63)
- Central	3	11	26	9	8	7	8
		(0–19)	(0–67)	(0–26)	(0–13)	(7)	(8)
- Southeast	4	6	21	14	28	67	28
		(3–10)	(4–53)	(10–20)	(8–59)	(31–93)	(7–63)
Manitoba
- Eastern	2	5	0	nd	nd	58	23
		(5)	(0)	nd	nd	(15–100)	(5–40)
- Southern	2	13	9	nd	nd	69	54
		(5–20)	(5–13)	nd	nd	(38–100)	(30–78)
- Interlake	2	2	4	nd	nd	35	44
		(0–3)	(0–8)	nd	nd	(18–52)	(33–55)

nd = not done.

Table 3. Flower infestation (mean %, with range in brackets below) by Botrytis cinerea (Bc) and Sclerotinia sclerotiorum (Ss) in commercial alfalfa seed fields in Alberta and Saskatchewan in 1997–1999

Location	# of fields	Early bloom		Mid bloom		Late bloom
		Bc	Ss	Bc	Ss	Bc	Ss
1997
Alberta
- Peace River	6	76	12	68	6	72	4
		(30–95)	(5–23)	(15–96)	(2–10)	(28–93)	(0–12)
- South	8	1	7	3	4	1	2
		(0–3)	(0–25)	(0–8)	(0–10)	(0–5)	(0–5)
Saskatchewan
- North	5	3	2	3	6	17	10
		(0–5)	(0–3)	(0–13)	(0–28)	(0–58)	(0–38)*
- Central	2	5	15	3	7	1	9
		(0–10)	(13–18)	(3)	(3–10)	(0–3)	(0–18)
- South	3	7	0	0	2	0	0
		(3–10)	(0)	(0)	(0–5)	nd	nd
1998
Saskatchewan	17	1	8	8	10	17	1
		(0–3)	(0–15)	(0–30)	(0–35)	(0–93)	(0–4)
Manitoba	7	13	23	21	22	1	5
		(0–25)	(0–50)	(0–50)	(0–50)	(0–31)	(0–38)
1999
Saskatchewan
- North	20	5	28	nd	nd	5	26
		(0–28)	(0–77)	nd	nd	(0–30)	(0–65)
- Central	5	2	29	nd	nd	15	21
		(0–4)	(21–45)	nd	nd	(10–19)	(16–25)
- Southeast	2	0	30	nd	nd	0	21
		(0)	(25–35)	nd	nd	(0)	(13–28)

nd – not done.

* One heavily infested field, most others had little or no infection.

Fig. 2 (Colour online) Regional summary of blossom blight severity from 1993 to 1997 in the major alfalfa seed production areas of the Canadian Prairies; southern Alberta, the Peace River region of northern Alberta, north-eastern Saskatchewan, and central Manitoba. Section pattern represents incidence; white section = not assessed, fine vertical line = low, heavy transverse lines = moderate, black section = severe

Table 4. Incidence (% and range) of floret infestation with Botrytis cinerea (Bc) or Sclerotinia sclerotiorum (Ss) in 10 irrigated alfalfa seed fields in southern Alberta, 2014–2017

Year	# of fields	Early bloom		Mid bloom		Late bloom
		Bc	Ss	Bc	Ss	Bc	Ss
2014	2	4	22	1	2	6	20
		(4)	(22)	(0–2)	(0–4)	(3–10)	(0–40)
2015	2	5	11	3	4	12	19
		(2–7)	(7–14)	(3–4)	(1–7)	(3–21)	(12–26)
2016	2	3	27	9	22	34	16
		(2–4)	(19–35)	(4–15)	(19–26)	(32–36)	(15–17)
2017	4	44	14	nd	nd	71	5
		(6–81)	(7–21			(54–92)	(2–11)

N.B. Infection was assessed on florets selected at random from the raceme and surface-sterilized), rather than the oldest floret plated without treatment.

nd = not done.

Table 5. Incidence (% and range) of floret infestation with Botrytis cinerea (Bc) or Sclerotinia sclerotiorum (Ss) in 21 commercial alfalfa fields in Saskatchewan, 2000–2003

Location & Year	# of fields	Early bloom		Mid bloom		Late bloom
		Bc	Ss	Bc	Ss	Bc	Ss
2000
- North	2	8	66	nd	nd	6	9
		(6–9)	(38–73)			(3–8)	(3–14)
- Central	2	12	54	nd	nd	5	3
		(12–14)	(38–64)			(0–9)	(0–6)
2001
- North	4	1	5	nd	nd	2	7
		(0–3)	(2–10)			(0–3)	(0–25)
- Central	3	3	1	nd	nd	3	2
		(0–10)	(0–3)			(1–7)	(1–3)
- Southeast	2	0	7	nd	nd	2	2
		(0)	(5–8)			(0–4)	(0–4)
2002
- Northeast	2	nd	nd	3	3	0	9
				(0–5)	(0–5)		(1–16)
- Southeast	1	nd	nd	3	5	0	29
				(3)	(5)	(0)	(29)
2003
- Northeast	3	nd	nd	0	23	0	27
				(0)	(20–27)	(0–1)	(23–34)

nd = not done.