ABSTRACT

We investigated sowing cotton into standing cereal stubble to reduce insect pest populations. Reducing Helicoverpa armigera and Aphis gossypii numbers through the use of standing stubble is a viable option, as it can limit the need for disruptive insecticides in early season cotton.

The abundance of A. gossypii throughout the trial enabled us to examine the effect of stubble on aphid population dynamics and the impact of natural enemies on the population. However, low H. armigera activity throughout the trial resulted in no significant difference between treatments for this pest.

Cotton sown into standing sorghum stubble had significantly fewer aphids than cotton sown into wheat stubble and cotton sown conventionally. Furthermore there was significantly more parasitism of A. gossypii by Lysephlebus testaceipes in cotton sown into sorghum stubble (53%) compared to cotton sown conventionally (15%) and cotton sown into wheat stubble (13%). It is apparent from this investigation that stubble, in particular sorghum stubble, has the potential to prevent aphids from colonising cotton plants. Plants sown into stubble had more squares.

The move towards an integrated pest management approach using a variety of tools and techniques to control pests such as H. armigera and A. gossypiiwill ensure that the cotton industry continues to be economically and environmentally sustainable.