Foliar-applied pesticides

Finally, for foliar-applied pesticides, the target plant system may impede the uptake and movement of the pesticide to its biological target. 

Each of these issues will be discussed in turn, although not all are relevant for both soil- and foliar-applied pesticides. Furthermore, the extent to which pesticides are vulnerable to the above loss mechanisms will depend on the precise chemistry and mode of action of the pesticide concerned. 

The need to match the UV absorption spectrum of the pesticide, plus developing a solution that fits the use profile of the product (e.g. soil-applied, vs. foliar-applied, etc.) means that most solutions to UV stability are particular to the pesticide protected. A significant obstacle to the extensive use of UV stabilisers is their often significant cost (relative to the pesticide), as well as the high application rates applied. Furthermore, the improvements seen to date have... 

There now exists an extensive literature on the uptake and translocation of herbicides in plants. In this brief review, it is intended to elucidate the general principles that govern the transport of pesticides in plants. The transport behavior of the different classes of herbicides will be considered, together with ways of using physicochemical properties to predict the likely behavior of new chemicals. It should be noted that the processes of sorption in soil, of cuticular penetration in the case of foliar-applied compounds, and of metabolism in the plant all influence the availability of herbicides for uptake and redistribution in plants, and these factors are the subjects of separate chapters in this book. Interpretation of the literature on systemic transport usually needs substantial consideration of these additional factors. 

Somewhat water-soluble pesticides such as acid herbicides will be washed from foliar surfaces and into subsurface soils by rainfall. For example, dislodge-able turf residues of 2,4-D after a 2.54-cm rainfall have been reported to be only 1-5% of those found at 4-8 h after application (Nishioka et al., 1996 USEPA, 1997c). However, dew or rain on aged turf residues may increase their dislodgeability (Nishioka et al, 1996). OP insecticides are semivolatile and will vaporize from surfaces after applications. Chlorpyrifos vaporizes rapidly from lawns if applied in aqueous formulations. Diazinon, which is used on lawns as well as indoors, dissipates even more rapidly. However, the persistence of OP... 

In some situations, foliar treatments can be avoided by using a prophylactic soil-applied pesticide. Treatment of potted plants, especially ornamentals, may be by an admixture of granules to the potting compost, by dipping the roots into a slurry of pesticide at planting, or by a subsequent drench. However, all these treatments have a limited persistence, and are only aimed at protection during the first two to six weeks of plant development. 

Micronutrients can be applied in many ways including foliar application, seed treatment, root dipping of transplanted seedlings, and application with pesticides. However, the most popular method is to apply the micronutrients in admixture with the primary nutrient... 

It is common practice to combine foliar application of micronutriails with pestidde sprays or with foliar application of primary nutrients. When two or more materials are combined for foliar application, care must be taken to ensure that the materials are compatible. Many pesticides are incompatible with solutions of micronutri-ents. Incompatibility means that some chemical or physical change takes place that renders the mixture unusable or harmful. In general, micronutrient solutions should be applied separately unless compatibility is shown. 

Uses Conditioner improving the compatibility of liq, and foliar fertilizers with pesticides as well as combinations of different herbicides applied as a single spray sol n. 

The most popular nonpressurized nitrogen solutions are prepared from urea and ammonium nitrate and contain between 28 and 32% of nitrogen. No special equipment is needed for their storage and application they are easier to mix and to handle than solids, have low distribution losses, can be accurately placed, are suitable for foliar and aircraft application, and are excellent carriers of micronutrients as well as of pesticides and herbicides. As a result, about 60% of U.S. fertilizer nitrogen is now applied in fluids, and the use of solutions is becoming also more widespread in Europe. ... 

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