Susceptibility of the diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae) to acetamiprid and selected insecticides by foliar treatment and strategy for resistance management

2015

English

The dependence on pyrethroids and organophosphates to control the diamondback moth (DBM), Plutella xylostella (L.) (Lepidoptera: Plutellidae) on cabbage and cauliflower in Ghana since the 1990’s, and the absence of effective resistance management strategies has led to reported cases of widespread development of DBM resistance to these insecticides since 2002. The study was undertaken to identify alternative insecticides to the pyrethroids and organophosphates, and recommend a strategy that would effectively manage DBM resistance to insecticides in Ghana. The susceptibility of the DBM to acetamiprid (neonicotinoid), chlorfluazuron (benzoylphenyl urea) and Bacillus thuringiensis subsp. kurstaki Berliner (Btk) (microbial) was compared with susceptibility to esfenvalerate and phenthoate, which were selected as reference pyrethroid and organophosphate compounds, respectively. The Osaka susceptible strain of DBM and the leaf-dipping method were used. The results showed that esfenvalerate was most toxic after 72-h treatment. However, when the end-points for the insecticides were considered, chlorfluazuron was the most toxic after 168-h treatment and Btk the next most toxic after 96-h treatment. Acetamiprid was the least toxic to the DBM by foliar treatment. The low toxicity of acetamiprid would subject the DBM to a low selection pressure, and as a result delay the development of resistance in the pest. Acetamiprid should, therefore, be a preferred alternative for DBM control in Ghana. Chlorfluazuron and Btk by virtue of their toxicity against the DBM and favourable safety levels should also be a preferred alternatives for DBM control in Ghana. An effective resistance management strategy against the DBM in Ghana would be the rotational use of acetamiprid, chlorfluazuron and Btk for DBM control since these insecticides show no cross-resistance to each other.

Ninsin, K. D.