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Pest Monitoring: Proper use of Pheromone Traps

Monitoring for pests and diseases is a fundamental first step in creating a proper integrated pest management (IPM) program. Targeting pests at the right time with the right product can save you money, make your pest control program more effective, and help preserve the beneficial organisms on your farm. There are many ways to monitor for insect pests in your orchards and vineyards and one popular method is pheromone traps. First of all, remember that pheromone traps are NOT the only method you should use to monitor for any pest. They are a useful tool but they are not a stand-alone method. Relying solely on pheromone traps for your monitoring information is hazardous to your crop! Having said that, pheromone traps are a useful tool but need to be used correctly. If you are in an area where there is a regional monitoring service and ‘Agriphone’ messages are available, you can rely on that for general guidelines, but you may want to monitor your own farm as well.
Pheromones are chemicals produced by some species of insects (probably in way more species than we now know) to communicate with members of the same species. Frequently, these are ‘sex pheromones’ which a female produces to attract a mate. Pheromones are most well known for Lepidoptera (moths and butterflies) and these chemical messengers can be commercially produced by synthesizing and blending the appropriate chemicals For pheromone trap use, the pheromone chemicals are commonly forced into a rubber ‘septa’ (a small rubber cap), which can be placed in a sticky trap to attract male moths.

Storage and handling

Pheromone ‘caps’ (lures) should be left in their sealed packages until a day before use in the field. Pheromone blends are species-specific and insects are sensitive to minute quantities of pheromones. When handling pheromone lures (or any other pheromone product), wear disposable gloves to avoid cross-contamination with other products.
Even if you are handling only one kind of lure, use disposable gloves or disposable forceps or you will contaminate the lure and it will be less effective than it should be.
Pheromone lures should be stored in their sealed packages in a fridge until use unless directed otherwise by the manufacturer.

Placement in the field

Sticky traps should be hung before the lures are placed in them. Put the traps at least 40m apart and if you are trapping for more than one kind of insect, use separate traps for each kind of lure and keep them at least 40m from any traps set up for monitoring other species. Five traps placed in a line in your orchard or vineyard should be sufficient for each kind of insect being monitored. Mark the location of the traps with bright flagging tape but keep the tape away from the trap so it doesn’t become stuck in it. Use the jumbo-sized twist tie provided with the sticky traps to put the trap up firmly so it doesn’t spin in the wind. Label your traps as well especially if you are monitoring for different insect species at the same site. Always use different traps for each insect type that you are monitoring – do not use more than one kind of lure per trap.

It’s preferable if you can figure out a reliable way to suspend the lure in the trap without it touching the sticky surface. However, this practice can be both time consuming and frustrating. If the trap is firmly affixed to the tree, vine, or wire, the lure can be placed in the bottom of the trap and will not roll around too much.

Some guidelines for placement of traps for commonly monitored pests:

Pest # of traps Separation Height Trap line placement
Oriental fruit moth

5

40 m

1.2 – 1.5 m

From edge to interior

Grape berry moth

5

40 m

On 2nd wire

Varies with site – 10m from likely source of infestation is a good start

Oblique-banded leafroller

*2

40 m

Mid-canopy

Wherever easily accessible in blocks with a history of damage

*With OBLR, you are monitoring for first catch, so fewer traps are needed. Established protocol says 2 traps, but we would tend to suggest at least 3.

Replacement

If traps get full of dirt, other insects or leaf bits, or if they sag from being wet for too long, they should be changed. Mass emergences of midges near large lakes often fill the sticky surface and cleaning them all off would remove all the sticky substance anyway. Transfer the pheromone lure to the new trap. Lures last for different lengths of time; if a replacement time is not printed on the package, assume that they last about 6 weeks. Pheromone lures definitely do not last all season! Try to replace the lures between generations of the monitored pest. It’s best to take the lures out of their package for a day or two before putting them in the traps because lures tend to give off a large ‘flush’ of pheromones when packages are first opened. This can result in abnormally high numbers of moths being caught making interpretation of data difficult.

Monitoring the traps

Traps should be checked twice a week on the same days each time. Once a week is not often enough because you will not get a good approximation of peak flights. Scrape out moths and other insects with a small spatula or scraper. Make sure you know what insect you are looking for and record the numbers you find every time. Do not rely on your memory!

If you are not sure EXACTLY what your target insect looks like, find out. OMAFRA specialists, local entomologists and crop consultants can either identify your catches or direct you to good reference material for insect identification. The reason that this is so important is that even though pheromones are species specific, traps do sometimes catch other insects either passively (they’re just flying through) or actively because of a close similarity in some species pheromones. A pheromone is really a blend of chemicals and the major constituents may attract a non-target moth. The important point is that you want to be counting only the pest you are monitoring. Record your trap catches every time and graph the numbers if you can – it helps to visualize what the numbers mean.

Interpreting the numbers

The numbers you record from pheromone trap catches tell you a couple of things about the pest but don’t expect them to give you the whole picture. They do tell you when a particular pest is present in the adult form in your area. That’s important for some pests as is ‘biofix’ or sustained first flight for other pests. By graphing the total numbers caught in your traps on each monitoring day, you can also see whether the numbers of adults is rising or falling. This can help you determine the best timing for control measures. The numbers caught in your traps do not always tell you enough information about the overall pest pressure to be used as thresholds for action. Timing of sprays is most accurate when information is gathered from a number of sites – regional monitoring programs are extremely useful in this regard.
Using the three pests from the previous table as examples, here is a rough idea of how to use the information from pheromone trap catches to time control sprays. (Note: if you are using mating disruption products for control of any pests, this information does not apply to you). Insecticide sprays are directed towards newly hatched larvae, not the adults. For both GBM and OBLR, decisions at some points are not based on pheromone trap data. Monitoring in other ways for these and all pests is a vital part of pest management.

  • For OFM, treatment should occur 3 to 6 days after peak flight depending on the weather (especially temperature – for first generation in the spring, the timing would usually be around 6 days after peak flight but only 3 days after peak for later generations).
  • First generation GBM do not normally cause economic damage except in sites with a history of severe infestations. The first insecticide for second generation GBM is timed 5 to 7 days after the first significant upswing in trap catches for that generation. Third generation flight activity is often sporadic so border sprays can be applied when traps indicate activity and complete vineyard sprays are determined by cluster monitoring for larval activity.
  • For OBLR in apples, the first spray is timed in the spring when larvae are found feeding in terminals. Pheromone traps are placed in the orchard after petal fall and the timing of treatments for the first summer generation (late June to early July) is just prior to first egg hatch. This occurs at 170 – 210 degree days Celsius ( base 6.1ºC) after ‘biofix’ (first sustained flight). To calculate the degree days, use this calculation: DDC = (Max. daily ºC + Min. daily ºC / 2 ) – 6.1º C for each day and add the DDC until threshold (170 – 210 DDC) is reached. In this case, the pheromone traps are used primarily to determine ‘biofix’.

Don’t worry if there are moths still being caught in your traps after a spray is used. Your spray for most moths is targeted at the new larvae as they emerge from their egg. Adult moths will still be flying from other locations and males will continue to be caught in your traps. That is not an indication that there was any problem with the effectiveness of your spray. When you do spray, post the information so any pest scouts can observe the appropriate reentry period when they come to monitor your trap lines.
When you’re not sure what the numbers mean, seek guidance from experienced crop consultants and pest management specialists.

Summary

  • Handle and store pheromone lures appropriately or they will not be effective.
  • Replace traps and lures when needed and do not expect lures to work for a whole year.
  • Place the traps so that they do not interfere with each other or with traps for other insects.
  • Monitor faithfully and regularly and keep careful records.
  • Be able to identify your target pest and find out what other common insects look like.
  • Do not rely on trap catch numbers alone for pest management decisions.
  • Attend pest scout training sessions, read ‘Pub. 360’ and find other information sources to learn more about pest monitoring.

Special note for growers using mating disruption products

Pheromone traps have a very different use if you are treating your entire vineyard or orchard with pheromones for mating disruption (MD) of a particular pest. Full marks if you immediately said “but they won’t work in a pheromone-treated site!”. Of course they won’t work – or at least they should not catch any moths in a pheromone treated area (a few are likely to be caught on field edges). The pheromone spray or ‘twist-ties’ fill the surrounding area with pheromones, making it hard for males to find females and also making it hard for males to find the lures. That is exactly why you should still use the traps – as an indirect measure that the MD is working! Do not rely on trap catches alone to be sure that MD is protecting your field! We cannot stress that point enough. Remember- the traps are for catching males, they tell you nothing about the number of mated females that may be flying in from elsewhere. Regular, careful monitoring for signs of crop damage is imperative to be sure your site is protected. Actually, that’s good advice for everyone, not just those using MD products.

(Source – http://www.omafra.gov.on.ca/english/crops/facts/pheromonetraps_proper.htm)

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