IPM In Action
Hero Insects Save The Day
Our first experience of seeing the power of nature and the ability of beneficial insect species to successfully control pests was in 2004 with the arrival of the lettuce aphid (Nasonovia ribisnigri). The lettuce industry was devastated by this tiny aphid never before seen in Australia. Crops worth millions of dollars were being ploughed in, tough interstate quarantine laws were introduced, and growers had to learn to deal with a pest no other country has been able to control without chemicals.
Field trials were set up on a Government Research Station at Forthside in Northern Tasmania. This trial clearly demonstrated that it was entirely possible to grow a commercial crop of lettuce without the use of harsh broad spectrum chemicals. Even though the lettuces were completely infested with these aphids throughout the trial period, just prior to harvest the population decreased dramatically due to a build-up of natural predators.
Following the success of the trials, Houston’s Farm adopted the same approach to controlling the aphids with excellent results. The success story continues today. Our chemical use remains at a minimum which encourages an increase in beneficial insects. This in turn keeps the lettuce aphid under control. The defence against this pest is further strengthened by the introduction of new lettuce varieties which have resistance to the currant lettuce aphid bred into them.
Rest And Starvation Overcomes Mite
Though tiny in size, the Spinach Crown Mite poses a constant threat to spinach crops. There are no chemical options for effectively controlling this pest which eats the leaf and leaves it misshapen. Our work with IPM Technologies highlighted the solution was in fact to starve the mites. These mites feed on the youngest leaves in the crown of the plant. The damaged cells die and the cells in the surrounding tissue keep growing, which causes leaf distortion. As the mite eats the leaves in the heart of the spinach, they also release a toxin into the plant which contributes to the distortion of the leaves. These days we ensure we have a six week fallow gap between all rotations to avoid the build-up of Spinach Crown Mites. As no crops are planted during the six weeks, the mites have nothing to feed on and most die during this period. We have also decreased the use of broad spectrum insecticides which has resulted in predatory mites and small predatory beetles increasing in numbers. With this increase in predators we have found that they are able to control the few spinach crown mites that survive the fallow period leaving the next spinach crop largely free of mites.