Compositions and methods for increasing the efficacy of pesticidal compositions are described herein, including synergistic pesticidal compositions comprising: benzovindiflupyr, bixafen, boscalid, cyproconazole, fenpicoxamid, fenpyrazimine, florylpicoxamid, flutriafol, fluxapyroxad, isopyrazam, isotianil, kresoxim-methyl, metrafenone, oxathiapiprolin, penflufen, penthiopyrad, picoxystrobin, prothioconazole, pydiflumetofen, revysol, sedaxane, trifloxystrobin, pyraclostrobin, azoxystrobin, chlorothalonil, cyprodinil, metalaxyl, epoxiconazole, propiconazole, difenoconazole, fludioxonil, mancozeb, tebuconazole, valifenalate, in combination with a C4-C10 saturated or unsaturated aliphatic acid and methods for delivery of pesticidal active ingredients. Some pesticidal compositions and methods as described are directed to compositions and methods for increasing the efficacy of fungicides. Some pesticidal compositions and methods as described are directed to compositions and methods for increasing the efficacy of nematicides. Some pesticidal compositions and methods as described are directed to compositions and methods for increasing the efficacy of insecticides. Methods for enhancing the activity pesticidal active ingredients in pesticidal compositions in use are also described.