I'm a new bee to R programming. My problem is, how do I get the standard deviations for each concentration (0,1,5,10,15,20 mg/L) to get displayed on the plot?

Here's my code:

72 timer LC50
> LC50_72hR<-read.csv(file.choose(),dec=".",sep=" ", header=TRUE)
> LC50_72hR
Concentration Total Dead
1 0 20 1
2 0 20 1
3 0 20 1
4 1 20 4
5 1 20 2
6 1 20 5
7 5 20 7
8 5 20 11
9 5 20 10
10 10 20 11
11 10 20 16
12 10 20 15
13 15 20 16
14 15 20 18
15 15 20 20
16 20 20 19
17 20 20 20
18 20 20 20
> LC50_72hR<-drm(Dead/Total~Concentration,weights=Total,fct=LL.2(),type="binomial",data=LC50_72hR)
> summary(LC50_72hR)
Model fitted: Log-logistic (ED50 as parameter) with lower limit at 0 and upper limit at 1 (2 parms)
Parameter estimates:
Estimate Std. Error t-value p-value
b:(Intercept) -1.40548 0.16443 -8.54734 0
e:(Intercept) 4.09353 0.49499 8.26987 0
> plot(LC50_72hR)
> ED(LC50_72hR,c(10,50,90))
Estimated effective doses
Estimate Std. Error
1:10 0.85734 0.2242
1:50 4.09353 0.4950
1:90 19.54538 3.2559

How do I put std dev on my plot?