Biological control is a great alternative to chemicals
/by Talia Plaskett
Growers of all sorts – including greenhouse growers – have experienced the headache of having to control for pests and disease in their crops. While the typical control method has been chemical sprays that target key points of a pest’s metabolism, there’s been a significant change in management strategies during the past few decades. The shift toward a more ecosystem-based strategy has gained traction and allows growers to diversify when dealing with pest and disease issues.
Biological control uses naturally occurring insects, bacteria, and fungi to control pests and disease. Through extensive research, these agents have been found to occupy the habitats that pests need to thrive. They infect or predate the pests that damage crops, resulting in reduced population size. We now have a diversity of tools to manage the biotic stresses our crops inevitably face.
When it comes to managing pest populations, biological control is a great alternative to conventional chemicals. Unlike conventional chemicals, there are no post-harvest or re-entry intervals associated with biological control. There is also no risk of developing pesticide resistance when relying on biological control, meaning conventional sprays can be effectively used in emergency situations in which crop performance and yield are threatened. In addition, some biological control products have positive secondary side effects. For example, increased overall immunity, higher-yielding plants, and better uptake of nutrients and water have been witnessed as the results of applying certain beneficial microbes to the root systems of plants.
Biological control, although a fantastic tool, cannot realize its full potential on its own. It requires a few other key components to be successful. These are collectively known as “integrated pest management” (IPM). IPM is the strategic use of all the tools in your toolbox to manage pests and disease in your grow space. It consists of prevention, scouting, identification, response, monitoring, evaluation, and record keeping.
A major aspect of a successful IPM program is prevention. By implementing certain biosecurity protocols for all greenhouse staff members, you can significantly reduce pest and disease pressure. Practices such as quarantining incoming plant material, wearing clean work clothing every day, using clean growing media and supplies for every production round, and implementing strict order-of-entry protocols can reduce pest movement into a greenhouse and movement throughout the greenhouse. This serves as your first line of defence against any biotic stress in your grow space.
Another important tool in your IPM toolbox is scouting. You need to know what pests are in your crop and in what quantity. Insects can be monitored using yellow or blue sticky cards. Ideally, these are replaced weekly so that you can assess the current state of the crop. Indicator plants, which are highly susceptible to pest and disease infestation, are another way to monitor your growing space.
Making regular checks throughout the crop canopy is also very important. Know which areas of the plant to focus on. For example, whiteflies are typically found on the growing points of the plants while aphids like to hang out on the underside of more mature leaves. A plant’s crown and roots are the best places to check for root disease. Some pests, such as whiteflies, are easily displaced by jostling the plant while others, such as Spider mites, are not. Checking all these boxes regularly is key to preventing a major infestation.
Once you get a sense of what’s happening in your crop, you can respond with the application of an appropriate biological control. However, your job is not done at that point. Following this release with regular crop checks is crucial to management. Is your biological control working? Are you seeing a reduction in the pest you’re looking to get rid of? Is the new growth looking healthier than the old growth? By scouting, you can answer these questions and adjust accordingly. If the control isn’t working, it’s back to the drawing board. Why did your biologicals fail? Were they released properly? Was it the appropriate response to the problem? Are there incompatibilities (environmental, predatorial, target stage of life, etc.) in your grow space?
Biological control agents on their own aren’t going to be the holy grail of pest and disease management. By instituting biosecurity protocols for all employees, you reduce the initial pest and disease load. By monitoring the pre- and post-release of your control measures, you know exactly what is present, what life stage it’s in, and how much of it there is. By keeping detailed notes throughout the season, you can track seasonal fluctuations and hotspots throughout the greenhouse in order to better tackle issues in the coming year.
Each tool in your IPM toolbox must be given the attention it deserves. One weak link in the chain leaves the whole system vulnerable. It’s important to consider this when you’re planning your next crop and its pest management strategy. A well-maintained greenhouse ecosystem is well worth the effort. It’s just a matter of consistency, fine-tuning, and practice.
(Talia Plaskett is a protected crop specialist with Perennia Food and Agriculture Inc.)
