Effects of 11 fungicides on endomycorrhizal development in sour orange

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Abstract
Eleven fungicides were examined in five tests for their effects on endomycorrhizal development in sour orange seedlings. Copper, metalaxyl, thiabendazole, captan, captafol, chloroneb, and formaldehyde were tested for their effects on Glomus etunicatus, and chlorothalonil, sodium azide, benomyl, and maneb were tested for their effects on G. mosseae. Captafol, chloroneb, metalaxyl, and captan did not adversely affect growth of mycorrhizal plants, although some adverse effect on the fungus was apparent with all rates of captafol and the high rate of captan. All rates of benomyl and thiabendazole reduced plant growth, and mycorrhizal infection and sporulation decreased as rates of thiabendazole increased. Plant growth was better and fungus sporulation higher than that of the mycorrhizal control in all sodium azide treatments. Copper at rates of 112 and 224 kg/ha significantly depressed plant growth but not infection and fungus sporulation. Maneb and chlorothalonil, which had no effect on G. mosseae at the low rate of 5.6 kg/ha, sharply reduced fungus sporulation and mycorrhizal plant growth at 11.2 and 22.4 kg/ha. Formaldehyde at three rates was toxic to G. etunicatus.