Making the most of natural predators in your brassica crop

The terms “IPM” and “IPM Friendly” have been used for some time in the horticulture market, and more recently in the fodder brassica market. As Nick George, Area Business Manager for FMC points out, there is an awareness of IPM (Integrated Pest Management) but it is often misunderstood, and this is particularly the case for fodder brassicas. The introduction of the selective insecticide Exirel® in 2014 has played an important role in developing a greater understanding of both the pest species and beneficial species of insects in New Zealand fodder brassica crops.

IPM uses three pest control methods together in a compatible way. The combination of which can provide a better outcome than any one method on its own. The three methods are:

Biological control – the use of beneficial insects that naturally occur in the crop and making sure they are not disrupted by using pesticides that may impact their various life cycles.

Cultural control – any farm management technique that disrupts the pests and enhance the beneficial population. Examples maybe the variety of the crop selected and its insect tolerance, timing of planting, weed control along fence lines or the use of irrigation.

Chemical control – IPM is not about eliminating all pesticides but rather using them in an effective way that minimises disruption to beneficial species. It is important to understand the impact each product has on every beneficial species at each of their life stages.

There are many selective insecticides available, however, that does not mean they are safe to all beneficial species. After gathering relevant data on every product and its impact on beneficial species, Nick says you will see Exirel® at the top of the list.

The number and variety of beneficial insects in fodder brassica crops around Canterbury are generally underestimated Nick says. The key beneficial insects that disrupt pests in NZ fodder brassica crops are parasitic wasps, hoverfly larvae, brown lacewing adults and brown lacewing larvae. Exirel® is safe on these beneficial insects while still effectively controlling diamond back moth caterpillar, cabbage white butterfly caterpillar, soybean looper caterpillar, European leaf miner and grey cabbage aphid (suppression).

As you can see, Exirel® insecticide provides targeted cross spectrum activity on all key chewing and sucking pests in fodder brassica crops without harming key beneficial insects. Nick also explains that it has an innovative mode of action that ensures pests stop feeding rapidly after application for excellent crop protection. Translaminar activity and local translocation allow the insecticide to reach further into the crop canopy and control insect pest species that were not immediately targeted by the spray application.

Understanding insect pests and beneficial species at each crop stage means a plan can be implemented from establishment through to late crop stages. Broad spectrum insecticides still have their place at early establishment of the crop when beneficial insects are minimal. This allows best use of selective Group 28 insecticides (Exirel®) at mid/late stages of the crop to avoid risks associated with Group 28 resistance.

Once the crop is established, apply Exirel® at the first sign of pest pressure to minimise pest impact on yield and reduce the spread of insect transmitted disease while at the same time helping the establishment of beneficial populations. Don’t mix or use dual insecticide active ingredients, have a plan for each crop stage, monitor the crop and apply the right single active ingredient for the pest and beneficial species present. Continue throughout the season to monitor the crops for signs of beneficial activity such as mummified aphids and parasitized caterpillars along with overall reduction in pest population. Your Luisetti Seeds agronomist will be able to help with this.

Some North Canterbury farmers will also be pleased to hear that Exirel® is now registered for aerial application by helicopter. Accurately calibrated spray equipment and a minimum of 50L/ha of water must be used. When the crop canopy has begun to close or the crop is heavy, 80 – 100L/ha is a better water rate.

Understanding IPM and knowing your bugs, along with the selective insecticide Exirel®, can provide a lower cost, more sustainable fodder brassica crop. Talk to your local Luisetti Seeds agronomist about the use of IPM in your fodder brassica crop this season.