Pacific Pests, Pathogens and Weeds - Online edition

Pacific Pests, Pathogens, Weeds & Pesticides

Tomato - residual herbicide (379)

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  • Unknown distribution. In Oceania, symptoms of toxicity recorded in Fiji (possibly), Papua New Guinea, Vanuatu. On tomato. Residual herbicide a possible cause.
  • Damage: twisting of leaves, bunching of terminate growth, stunting of plants.
  • Reasons for residual herbicide and toxicity include: (i) soils (sandy, low clay) that fail to bind, e.g., glyphosate; (ii) frequent applications; (iii) applications at high concentrations; (iv) applications of phosphorus fertilizer (competing with glyphosate for soil binding sites); (v) addition of other herbicides to increase residual activity.
  • Control:
    • Avoid land where glyphosate applied frequently and/or at high rates, or wait at least 40 days between last application before re-planting
    • Make sure sprays only contains glyphosate, i.e., no other chemical present to increase possible residual activity in soil.
    • Alternatively, carry out a bioassay (see below): transplant test seedlings (tomato) across area prior to planting entire crop. Inspect for toxicity after 7-14 days.
Common Name

Tomato - residual herbicide effects.

AUTHOR Grahame Jackson
Information from How much glyphosate? (2016) The Land. (; and Cornish PS (1992) Glyphosate residues in a sandy soil affect tomato transplants. Australian Journal of Experimental Agriculture 32: 395-9. (; and from Herbicide residues in soils - are they an issue? Northern. GRDC. Grains Research Development Corporation, Australian Government. (

Produced with support from the Australian Centre for International Agricultural Research under project HORT/2016/185: Responding to emerging pest and disease threats to horticulture in the Pacific islands, implemented by the University of Queensland and the Secretariat of the Pacific Community.

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