The invention relates to the use of triazolopyrimidines of the formula I In which: R1, R2 are hydrogen, alkyl, haloalkyl, cycloalkyl, halocycloalkyl, alkenyl, alkadienyl, haloalkenyl, cycloalkenyl, halocycloalkenyl, alkynyl, haloalkynyl, C3-C6-cycloalkynyl, phenyl, naphthyl, or a five- to ten-membered saturated, partially unsaturated or aromatic heterocycle which contains one, two, three or four heteroatoms from the group consisting of O, N and S, where R1, R2 may be substituted as defined in the description or R1 and R2 together with the nitrogen atom to which they are attached may form five- to eight-membered heterocyclyl or heteroaryl which is attached via nitrogen and may contain one, two or three further heteroatoms from the group consisting of O, N and S as ring members and/or may be substituted as defined in the description; L independently of one another are halogen, alkyl, haloalkyl, alkoxy, haloalkoxy, alkenyloxy, cyano, C(═O)A1, S(═O)mA2, NRcRd or NRc—(C═O)—Rd, where A1, A2, Rc, Rd and m are as defined in the description; L1 is halogen, alkyl or haloalkyl; L2 is nitro, a group —C(S)NR3R4, a group —C(═N—OR5)(NR6R7) or a group —C(═N—NR8R9)(NR10OR11); X is halogen, cyano, alkyl, alkoxy, haloalkyl or haloalkoxy; R3, R4, R5, R6, R7, R8, R9, R10 and R11 are independently of one another selected from the group consisting of hydrogen, alkyl, cycloalkyl, alkenyl and alkynyl, where the 4 last-mentioned radicals may be substituted as defined in the description; or R3 and R4, or R6 and R7, or R8 and R9 or R10 and R11 together with the nitrogen atom to which they are attached form a four, five, or six-membered saturated or partially unsaturated ring which may be substituted as defined in the description; n is 0, 1, 2 or 3; and the agriculturally acceptable salts thereof, novel triazolopyrimidines, crop protection compositions comprising at least one compound of the formula I and at least one solid or liquid carrier, and a method for controlling phytopathogenic harmful fungi.