Naptalam
Naptalam is a selective preëmergent herbicide, first registered in the US in 1949, to control sundry annual broadleaf weeds and grasses. Naptalam is a phthalic acid, though it is commonly also in sodium salt form. It's also an aryl carboxylate, a phthalamate compound and an amide. It is also used in Australia and Canada. In 1974, the USA used in agriculture.
Naptalam is unstable at temperatures over 180 °C or pH over 9.5.
Naptalam's mode of action makes it a Group P or Group 19 herbicide under the HRAC classification. It is absorbed through the weed's primary roots and seeds.
Application
Naptalam has been used on soybean, peanut, cucumber and melon crops, and ornamentals. Typical application rates are 2 to 6 lbs per acre,. Formulations are usually water based liquids, or granular. While primarily preëmergent, naptalam may also be sprayed postemergently in some cases. Preëmergently, it should be applied within 48 hours of planting; weeds already emerged will usually not be controlled. Light incorporation may help if the soil is dry. Postemergently, it is done before plants start to vine. It may stunt the crop growth, but it should return to normal. Emerged weeds may be stunted too, but are not usually controlled.It has been sold under the tradename "Alanap-L" and "Rescue" in the US, and has been manufactured by Uniroyal, Chemtura and Vertac. "Alanap-3" is a 240 g/L formulation sold in Canada.
Environmental behaviour
In soil, naptalam is absorbed through the roots and translocated to the leaves. Soil mobility is high in fine sand, sandy loam, and silt loam; soil retention is increased with CEC and organic matter content.Naptalam's toxicity is low for birds, fish, and aquatic invertebrates, presenting minimal hazard.