S.D. Codified Laws § 55-5-8
The trustee shall diversify the investments of the trust unless, under the circumstances, the trustee reasonably believes it is in the interests of the beneficiaries and furthers the purposes of the trust not to diversify. Regardless of concentration or lack of diversification, the trustee need not diversify if the trust instrument or court order allows or directs retention of assets forming part of the trust corpus and no trustee is liable to a beneficiary to the extent that the trustee acted in reliance on the provisions of the trust instrument or court order. If a trust instrument or court order allows or directs a fiduciary to invest in a specific investment, type of investment, or investment concentration, no trustee is liable to a beneficiary to the extent that the trustee acted in reliance on the provisions of the trust instrument or court order.
SDCL 55-5-8