  We use stacked spectra of the host galaxies of photometrically identified
type Ia supernovae (SNe Ia) from the Dark Energy Survey (DES) to search for
correlations between Hubble diagram residuals and the spectral properties of
the host galaxies. Utilising full spectrum fitting techniques on stacked
spectra binned by Hubble residual, we find no evidence for trends between
Hubble residuals and properties of the host galaxies that rely on spectral
absorption features ($< 1.3\sigma$), such as stellar population age,
metallicity, and mass-to-light ratio. However, we find significant trends
between the Hubble residuals and the strengths of [OII] ($4.4\sigma$) and the
Balmer emission lines ($3\sigma$). These trends are weaker than the well known
trend between Hubble residuals and host galaxy stellar mass ($7.2\sigma$) that
is derived from broad band photometry. After light curve corrections, we see
fainter SNe Ia residing in galaxies with larger line strengths. We also find a
trend (3$\sigma$) between Hubble residual and the Balmer decrement (a measure
of reddening by dust) using H${\beta}$ and H${\gamma}$. The trend, quantified
by correlation coefficients, is slightly more significant in the redder SNe Ia,
suggesting that bluer SNe Ia are relatively unaffected by dust in the
interstellar medium of the host and that dust contributes to current Hubble
diagram scatter impacting the measurement of cosmological parameters.
