Earlier research of the Horticulture Innovation Citrus Gall wasp project (CT15006) has demonstrated the efficacy of late-spring application of several systemic insecticides for citrus gall wasp control on navel orange trees. However, late-spring application of a systemic insecticide with a 4-month withholding period is not an option for Valencia trees in the southern states, as the fruit is harvested during mid-October to April. Our research team (Jianhua Mo, Craig Swanbury, Andrew Creek, Steven Falivene and Scott Munro) has investigated summer to autumn applications of systemic insecticides to find an option for gall wasp control in Valencia trees. The insecticides trialled were Confidor Guard® (9 mL/tree), Samurai® (12 g/tree) and Movento® (40 mL/100 L plus Hasten® at 50 mL/100 L). The results of applying these three insecticides were compared with those on untreated control trees in replicated trials.
Only Samurai® at 8g/tree is registered under permit for the control of citrus gall wasp in citrus. All other chemicals tested are not registered for citrus gall wasp control but are registered for citrus for other pests. Always follow label or permit recommendations.
April applications of Samurai® and Movento® reduced gall wasp emergence by more than 50% (see the left panel in the figure below). Confidor Guard® also reduced gall wasp emergence, but the effect was not as clear cut.
In a separate trial, we investigated three different timings of Movento® application to Chislett summer navel trees. All three timings (from 25 January to 5 April) significantly suppressed gall wasp emergence (see right panel in figure below). The 23 February and 5 April applications were the most effective, reducing emergence by 95%.
Movento® and Samurai® show good potential for gall wasp control in Valencia trees during late-summer and autumn. They reduce gall wasp numbers in the next season by killing the wasp larvae inside the galls. It is worth noting that, in autumn, trees have well-developed galls, and when insecticides are applied the galls appear to develop normally into winter but the wasp dies at a later stage of their development. Trials are currently in progress to confirm the results and evaluate the lower permit rate of 8 g/tree for Samurai®.