Progress Towards Systemic Fungicides

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Abstract
Developments in the past decade are reviewed. All the compounds considered possess direct fungitoxicity and none appear to depend on modifying the host plant, chemically or physically, to control diseases. Water solubility is low to very low. Yet these compounds, when sprayed, enter aerial tissues, and, on reaching plant roots, enter via non-living tissue and pass into the xylem. They are swept upwards in the transpiration stream, to an extent depending on the properties of the compound, and may accumulate in the margins of leaves. They do not appear to enter organs, such as petals, that do not transpire, nor are they re-exported from leaves to new growth. Any downward translocation in the phloem, if it occurs with any of these compounds, is of no practical significance. The range of plant diseases controlled by some compounds is confined to powdery mildews; other compounds control several types of disease, and some, especially among the benzimidazoles, control a very wide range indeed. None offer control of important diseases due to fungi classed as phycomycetes, with one exception confined in practice to hop downy mildew. Major advances have been achieved in the control of losses in storage and transit of fruit, and of seed-borne diseases in cereals and grasses. Strains of certain fungi have emerged that are very tolerant of certain compounds, and this is a cause for concern regarding the future of these compounds, most of which inhibit mycelial development by interfering with some biosynthetic process. Although not strictly acaricidal, some of the compounds can reduce mite fecundity and the fertility of the eggs laid.