Create a aov_4() that will test if there is an effect of time in one particular variable of a particular treatment (eg. my data > if plant height changed from week 1 to week 3?)

code : mod1 <- aov_4(LoliumC ~ Week + (Week|ID), data = LocustDataControlRM_txt)

Error in aov_car(formula = as.formula(formula), data = data, fun_aggregate = fun_aggregate, :
dv needs to be numeric.

Cant work out how to make dv numeric