PART 1. A CHECKLIST
The effective use of biologicals (bios) requires a different approach and philosophy than for chemicals. Biological control agents are better at preventing than curing pest and disease problems.
Use of tools such as ‘action thresholds,’ which guide the timing of pesticide sprays when pest populations reach a certain level, don’t work for biocontrol. Why? Because if you wait until these thresholds are reached before initiating a biocontrol strategy, it’ll be too late; pest populations will be too large to be brought under control using a biological agent.
The efficient use of biocontrols requires different assumptions and timing of actions. In addition, rarely does one biological serve as a ‘stand-alone’ control agent; rather, they need to be deployed within a system that supports their success. This first article highlights key aspects of a pest management system and future content that will provide more detailed insights to the use of biocontrol, in particular for thrips.
THE SYSTEMS APPROACH
There are many interactive variables that affect the growth of greenhouse crops, the incidence and impact of pests and diseases, and the performance of biological and chemical controls. These include:
- the type of crop and crop growth stage.
- production practices and inputs.
- external environmental conditions (temperature, humidity, light).
IPM FROM START TO FINISH
It is important to prevent insect and disease pressure from the very beginning of crop production. The best pest management plans start before young plants come into the greenhouse and are adapted to the different crop production stages. While an IPM program must be conceived and implemented for the entire production cycle, different approaches may be considered for different phases in the crop cycle.
Preparation: “Think before you act.” Take a critical look at the plant species and cultivars you are planning to grow, your fertilizer, irrigation schedules and general layout of the greenhouse. This will help identify potential problems. Part 2 of this series will go into more details, but here are some thoughts to keep in mind:
- What do you know about the plants you will be growing?
- What do fertilizer and irrigation have to do with pest problems?
Although most greenhouse crops are on high-fertilizer regimes, not all plant species require these elevated rates. Research suggests that in some crops, fertilizers can be reduced by 33 to 75 per cent without affecting the quality of the finished plants, and reducing their susceptibility to pests.
As well, plants that are over-watered or water-stressed are more susceptible to pests. More research is needed to provide recommendations on balancing plant growth and pest resistance.
- Based on previous years, where are the trouble spots in your greenhouse operation?
Propagation: “Begin as you mean to go on.” Part 2 of this series will address the principle of starting clean. This is one of the basics of an IPM program and propagation is the ideal place to nip pest problems in the bud.
- How clean are your cuttings or plugs?
- Front-loading of bios: Propagation is the time to build up your ‘army’ of biocontrol agents.
- At this stage, thrips biocontrol programs rely on predatory mites and biopesticides such as BotaniGard and Met52.
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Production: When the plants are moved out of propagation into the production area, it is time to think about how pests get into this area of the greenhouse and how to continue the biocontrol program initiated during propagation, tweaking it where necessary. Needless to say, scouting is essential to determine if your strategy is working and to detect any unexpected visitors.
- Screening (see Part 2 of this series) and mass trapping (see Part 5 of this series) are two ways to deal with pests coming in from outside.
- For thrips biocontrol in production, predatory mites are still the best agents.
- Inevitably, at some point during production, you will have to deal with a pest outbreak.
- In some cases, one or more applications of pesticides are needed to bring pest levels down to a manageable level for bios, or to control a pest that can’t be controlled biologically.
Finishing: What to do when you are close to shipping and you still have too many pests in your crop? Luckily, there are a few rescue options:
- If you still have a few weeks left before shipping, it may be worth increasing the release of biocontrol agents, or to add a different biocontrol agent to the mix.
- Another common practice is to do one or two “clean-up sprays” of pesticides.
Evaluation: When the last plant is shipped and the greenhouse is cleaned, it is time to evaluate the efficacy of the IPM program. Are you happy with the results? What worked and what didn’t? What needs improving? And most importantly: how much did it cost? This is one of the reasons why keeping records is so essential. You will be able to compare crops over multiple years and to decide where to invest your biocontrol budget for maximum results.