1. Bacterial Spot of Pumpkins and Squash
Elaine Roddy
Vegetable Crop Specialist
OMAFRA, Ridgetown

2. Xanthomonas Cucurbitae
Michigan
Ohio
Indiana
Illinois
Georgia
Ontario (2012)

3. Elgin County, 2014

5. Pumpkin cv. Gladiator
a) sunken, advanced lesions on pumpkin ‘Gladiator’
C. Trueman, University of Guelph – Ridgetown Campus

6. Survival
Wind?
Seed
Soil
(2 years)

7. Bactericides (Copper, etc…)
Management Options
Rotation
Clean Seed
Bactericides (Copper, etc…)
?????

8. Butternut Squash cv. Ultra

10. Compared with Angular Leaf Spot
X. Cucurbitae
P. syringae pv. Lachrymans

11. Butternut Squash cv. Ultra
d) sunken lesions on butternut squash Ultra
C. Trueman, University of Guelph – Ridgetown Campus

12. Butternut Squash cv. Ultra, ‘blister-type’ lesion
e) blister lesions on butternut squash Ultra
Uncharacteristic, but X. cucurbitae was confirmed from this lesion type (lab test)
Butternut Squash cv. Ultra, ‘blister-type’ lesion
C. Trueman, University of Guelph – Ridgetown Campus

13. Table 2. Incidence of cucurbit leaves with bacterial spot (X
Table 2. Incidence of cucurbit leaves with bacterial spot (X. cucurbitae) symptoms in an inoculated field trial, Ridgetown, ON, Plants were inoculated on Aug 12.
Crop
Cultivar
Incidence (% leaves)
Aug 21
Sept 3
Sept 16
AUDPC
Pumpkin
Gladiator
36 a
37 a
77 a
1221 a
HPX
14 bc
27 ab
60 b
827 ab
Baby Pam
22 ab
43 a
69 ab
1152 a
Butternut
Ultra
62 ab
1110 a
Atlas
11 bc
19 ab
35 c
541 b
Cucumber
Vlasstar
1 c
0 b
0 d
4 c
The trial was inoculated with X. cucurbitae on Aug 12.

14. Figure 2. Incidence and severity of bacterial spot on cucurbit fruit, and % rotten fruit by weight at harvest, Ridgetown, The trial was inoculated with X. cucurbitae on Aug 12. a a a a a a a a a b b b b
C. Trueman, University of Guelph – Ridgetown Campus

15. Seed Disinfestation Strategies
Chlorine
25 oz of chlorox (5.25% sodium hypochlorite) and 100 oz water and 1 tsp Sylgard 309
Use one gal of solution per lb seed
Hot water
Water bath at 37 C for 10 minutes then 50 C for 20 minutes then cold water bath for 5 minutes.
Dry heat (food dehydrator)
71 C for 120 hours
Dry heat (oven)
85 C for 72 hours

16. Dry Heat Treatments

17. Results – Waltham Squash
Dry heat treatments were not repeated
Both chlorine and hot water effectively removed X. cucurbitae from the infested seed.
Chlorine seed treatment reduced emergence by 5%.
Additional slight delay in emergence in the chlorine treatments (9%)

18. Thank you
Cheryl Trueman and Phyllis May University of Guelph – Ridgetown Campus Paul Goodwin University of Guelph Tina Simonton, Nathalie Smith and Anissa DeWulf Summer students Horticulture Crops Ontario OMAFRA Grower Co-operators