Resistant pests a global problem for ag sector

Resistance occurs when a change in the genetics of a pest population allows individuals to survive.  It develops in all agricultural pest groups, starting when a tiny number of pests survive a pesticide and become resistant. 

For most New Zealand growers this is not yet a big problem. Though there are pockets of resistant species in some sectors, a wide range of products are effective against pests. Such a range is crucial for managing resistance. But to keep a variety of products available, the makers must navigate a number of hurdles. 

One big hurdle is the high cost of developing new products and re-registering older pesticides. In NZ the process is compounded by the low level of data protection for new application registrations, thus putting pressure on the companies’ profits. 

To overcome this Agcarm is advocating a legislative amendment to achieve greater data protection, so encouraging companies to spend more on new product registrations and new technologies.

Another problem is the difficulty and cost to assess the level of resistance in weeds. For example, extensive trial and error is needed to identify the cause of resistance in weeds resistant to more than one product. This can be expensive and time-consuming for the crop producer.

Weeds are adaptable to many environments. For example, when lawns are repeatedly mowed close to the ground, weeds can overcome the lawn. No surprise that weeds can adapt to certain herbicides. Weeds are also highly reproductive, with seeds that can survive for long periods and disperse over long distances. 

Managing resistance requires an understanding of the factors that influence its development, and slowing or preventing the resistance from happening. Resistance should not be automatically assumed. A number of factors need to be ruled out: was the pesticide misapplied? Was the weather unfavourable?  Was the application poorly timed? Was crop management poor? 

When using fungicides, insecticides or herbicides, follow the label instructions, especially on rate of application. An experienced advisor can help develop a spray strategy, but if the manufacturer’s instructions are not followed, resistance is more likely. 

A good resistance strategy includes rotating pesticides, crop rotation, good hygiene and combining pesticide applications. Follow these five steps to manage pest resistance:

1. Apply pesticides according to the label – every time 

2. Expect some level of resistance 

3. Have a strategy to address resistance 

4. Identify the root cause by trial and error 

5. Get the right advice; talk to your supplier or distributor. 

Evolution and nature cannot be stopped, so keeping on top of resistance by using an integrated pest management strategy will mean one less problem for farmers. 

• Mark Ross is the chief executive of Agcarm.