Response of several crop plants and weeds to maleic hydrazide

The results in brief …

Maleic hydrazide has been found to have selective herbicidal action on weedy grasses. Young plants are more susceptible to injury by it than are old plants. This relation of maturity to injury applies to crop plants as well as to weedy grasses.

Maleic hydrazide is particularly toxic to grass species. It affects plants when applied at low concentration; it causes growth abnormalities; it apparently acts on plant meristems at a distance from the point of application. For these reasons, it is concluded that maleic hydrazide has hormone properties.

Addition of a wetting agent increases the effects of maleic hydrazide, presumably by improving the contact with the plant tissues.

Many vegetable crops show growth inhibition from maleic hydrazide treatment; growth abnormalities occur on some. On tomato, the abnormalities resemble virus symptoms.

A common response to maleic hydrazide is anthocyanin pigmentation. This might result from carbohydrate accumulation in the leaves.