Phytotoxicity resulting from a combination of a pre-emergence herbicide and a pesticide seed dressing in maize (Zea mays L.)

Abstract

This study was prompted by reports from maize producers, indicating phytotoxicity to occur when using pre-emergence herbicides in combination with seed dressings under cold conditions on sandy soils. A greenhouse experiment was conducted in which the insecticide imidacloprid and the herbicide flumetsulam/s-metolachlor were compared as single treatments and in combination to an untreated control. Two temperature regimes and 10 cultivars were used. Throughout the observation period, no visual symptoms of phytotoxicity in the sense of chlorosis, necrosis, stunting, scorched leaves, malformation of plant parts and/or whiplashing of the growth points occurred. A pronounced negative effect of the insecticide/herbicide combination was observed on seedling emergence and on dry mass of plants, contra-indicating the combined use of these products with cultivars PHB3442, PAN6710, NS9100, CRN3414 and PAN6777 in sandy soils. The combination appeared to be particularly hazardous under cold conditions. However, it would be commercially acceptable to use either flumetsulam/s-metolachlor or imidacloprid unmixed on all cultivars tested.

Keywords:

• maize
• phytotoxicity
• pre-emergence herbicides
• seed dressings