The summer months bring increasing pressure from insect pests in vegetable crops around the country, particularly onion thrips which thrive in December’s warmer conditions.

When temperatures average around 25°C, onion thrips take 13 days to develop from an egg to an adult. When temperatures average 30°C, this development takes only ten days.

Begin monitoring onion crops for thrips early to identify when the population begins to increase. This helps select the appropriate insecticide and application timing.

Early spray options to target establishing populations include Confidor®, Benevia® Insecticide and Solvigo®. Once the thrips population starts to increase at a faster rate and greater control is required, switch to products such as Sparta®. Trial work completed by Fruitfed Supplies over the last couple of years in Pukekohe and Canterbury show that Sparta is effective at controlling onion thrips. Other options also include Proteus® or Ascend®.

Thorough coverage is vital with your chosen insecticide as thrips are commonly found in the centre of the plant where leaves are close together. It’s recommended to use a wetter or spreader, such as Du-Wett®, to improve insecticide contact with the pest.

Onion thrips are prone to developing resistance to insecticides, and some strains are already resistant to synthetic pyrethroids and to a small number of organophosphates. Carefully consider product options and rotate active ingredients from different insecticide groups.

Onions are primarily grown for export and many classes of insecticide are under review internationally. Always check with your exporter if there are any products which cannot be used for your intended export market due to Maximum Residue Levels (MRL) or because an insecticide (or group of insecticides) is banned in that market.

For more information on controlling onion thrips or insect resistance management, contact your Fruitfed Supplies Technical Horticultural Representative.