You’ve likely noticed by now that thrips populations are especially high because of the hot, dry summer. Many growers are noticing their usual biocontrol programs can’t keep up, and further defenses are needed this year.
The use of mass trapping strategies may be the key to getting an edge over thrips. This post discusses the latest research on mass trapping of thrips in ornamentals, including patterned sticky tapes and the use of pheromones.
Mass Trapping: What is is?
Mass trapping uses a high density of attractive traps to reign in large pest populations or prevent outbreaks. Typical traps include: coloured sticky tape and cards, pheromone traps and trap plants.
The trap should be more attractive to the pest than the crop, thereby preventing thrips from intercepting the crop. Thrips primarily use visual cues when choosing a host crop. That certain colours and patterns cause more “excited” responses from light receptors within thrips’ eyes can be taken advantage of when designing traps.
Research shows that thrips are most attracted to flower or circle shaped patterns, and to yellow and blue color wavelengths. (Though there is ongoing is disagreement in the scientific community as to which colour is actually better at attracting thrips).
The norm in the industry – plain yellow or blue sticky tape/cards – take advantage of colour, but ignore the potential of patterns. Recent industry trials suggest patterned tapes (Fig 1) can catch up to 450% more thrips. However, these trials were conducted a highly temperate region (where thrips may be more active).
Tests in Ontario greenhouses are imperative before we can make conclusions about the usefulness of patterned tape for our industry.
Patterned Tape: Is it Worth the Hype?
During the course of this high-thrips summer, we set out to determine if patterned tapes are worth switching to. We compared plain yellow and blue tapes to their patterned counterparts (all tape was from the same manufacturer and donated by Plant Products Inc). We also tested the back side of the patterned tapes for attractiveness (the pattern is only printed on one side, but shows through somewhat).
Preliminary results are fairly clear (Fig 3). In Ontario greenhouses, thrips catches are highest in our plain yellow treatment – at least 2x higher than all other treatments. Further, adding a pattern didn’t appear to help at all.
However, our results don’t necessarily mean blue tape isn’t useful. Different hues of blue in different products may prove more attractive.
Blue tape is also often recommended when flying biological control agents are used (such as those for aphids or whitefly). Some studies show that parasitoids are less attracted to blue than yellow (meaning fewer should get stuck on blue tape). Decisions on what tape to choose ultimately involve assessing both thrips pressure and money spent on flying biocontrol agents.
Similarly, future products with patterns may yet prove useful – based on published research, traps with flower shapes are the most likely candidate.
Pheromones to Improve Thrips Catches on Traps:
Other “additions” to sticky traps may also boost effectiveness. Preliminary studies by Dr. Rose Buitenhuis’ Lab at Vineland show higher thrips catches when thrips “lures” are added to sticky cards (Fig 4). These lures contain thrips aggregation pheromones; originally marketed as an improved monitoring tool, lures may have applications for improving mass trapping.
Other Tricks for Effective Traps:
Placement of sticky tape or cards is also very important. Targeting entry points and so called “hot spots” within the greenhouse can be more effective than random placement.
Tape and cards should also be placed JUST above the crop canopy for thrips – this may mean periodically moving the traps to maintain optimal positioning. Putting out ENOUGH traps is also a key factor in mass trapping. As an example, 120 large-size cards (4 per bench) in a 15000 sq.ft. zone has been a successful density in some commercial mum operations. This is equivalent to 8 large cards/1000 sq.ft. Other helpful tips and tricks can be found in this 2014 article in Greenhouse Canada Magazine.
By paying attention to color, placement and density of mass traps, and considering adding pheromone lures, you can maximize the number of thrips removed from your greenhouse, allowing your thrips biocontrol agents to gain the upper hand again. Now go stick it to ’em!
This post written by S. Jandricic and OMAFRA summer student Mitch Eicher-Sodo. Mitch has been conducting research trials under the supervision of Drs. Jandricic and Carlow, and is looking to pursue a career in protected crops. The authors would like to thank all the commercial greenhouses that participated in the trial.