FRASER FIR PEST CONTROL PORTAL
Focus on Elongate Hemlock Scale
EHS is the hardest to control pest of Fraser fir. However, other pests are typically successfully controlled when EHS is being controlled. Combining cultural controls with chemical controls will provide the best results.
Cultural Controls
None of the following cultural controls will eliminate problems with EHS. However, they can all help reduce problems with scales.
Reduce the Use of Nitrogen
Pests often become more of a problem if the host plant receives excessive nitrogen fertilizer. That nutrition translates into nutrition for the pest, causing it to reproduce better. In Fraser fir Christmas trees, there appears to be a connection between EHS and nitrogen fertilizer. As many fields have a strong clover component in the ground cover which will supply nitrogen, the use of nitrogen fertilizer throughout the rotation is not needed. Not fertilizing younger trees with nitrogen may reduce problems with EHS in young trees.
Parasitic wasp on
yellow sticky card
Reducing Pesticide Use
The EHS has many natural enemies including lady beetles and parasitic wasps. The use of broad spectrum insecticides such as Dimethoate and the synthetic pyrethroids (Asana, Astro, Sniper, Talstar, Wisdom) will kill these along with the pest, allowing the EHS to reproduce and quickly rebound. Therefore, it is important to only use these broad spectrum materials when they are really needed to control pests. Use these materials in the fall whenever possible to have the least impact on natural predators.
Culling Heavily Infested Trees
Even the best controls of EHS will only kill about 95% of the scales. That means on heavily infested trees where there are 10 or more scales per needle and the majority of the needles are infested, there will still be enough live scales to perpetuate a problem. By cutting down and removing the most heavily infested trees, you will be removing a significant source of reinfestation.
When Chemical Control is Necessary
Judging if EHS is bad enough to control is difficult. There are currently no treatment thresholds. In some cases, EHS has been present in fields at low levels for several years without getting worse. However, in most cases, the incidence of scale does increase over time.
If EHS has been found in your trees, consider switching control of all pests to times and materials that will control the scale as well. Good control in younger trees will also be easier than in trees exceeding six feet.
Chemical Control of EHS
To date, the best controls of EHS are either Safari or a combination of Asana + Dimethoate. Both of these combinations will also control BWA any time of year. Treating for EHS also provides an opportunity for controlling all the other pests of Fraser fir such as RBM, BTA, Cinara aphids and SSM depending on the chemical used and the time of year applied. Therefore, the various windows for EHS are discussed along with the other pests that can be controlled as well as the pesticide options.
Living EHS can be found on 3 and 4 year old needles back in the canopy of the tree. It appears that even the highly systemic Safari performs best when applied with adequate coverage. Use a high pressure sprayer and create a mist that will move back to the underside of 3 and 4 year old needles.
Mistlbower applications have typically not successfully controlled EHS. However, mistblower applications with Asana + Dimethoate have kept EHS from spreading to other trees even when applied prior to bud break. Applications with Safari with a mistblower are still being evaluated, but there is potential for better control using a mistblower with this product. For growers with limited acreage, a backpack mistblower is an effective way of applying materials for EHS control.
At this time, trunk applications with Safari for EHS control are still experimental. Rates and application timing are being investigated. The benefit to this method of application is that there is little to no impact on natural predators and pollinators. However, control of other pests of Fraser fir would still be necessary.
June – RBM Treatment Window
This is also the most effective time for treating EHS. However, controls during this time will also have the most impact on natural enemies of scale. If you have RBM though, this is definitely the time-frame you should be looking at.
| Pests Controlled | Treatment Description | Treatment Window |
|---|---|---|
RBM |
ASANA + DIMETHOATE: Using this combination will control EHS (requires both products), RBM (from the Dimethoate), BTA (from both products) for next year and BWA (from the Asana). This combination may make HRM worse the following spring, so be sure to keep scouting for mites. Dimethoate provides a knock-down of SSM and HRM. Long-term control of these mites depends on many factors. Typically HRM is becoming less active by June because temperatures are rising. Therefore, HRM control is usually not a problem. But if SSM in particular is a problem, consider adding another miticide that controls eggs. For options see: Focus on Mite Control. | Shoot elongation - June
|
EHS |
SAFARI: Safari by itself will control EHS and BWA. If mites are a problem, consider adding a miticide that controls eggs. For options see: Focus on Mite Control. | |
RBM |
SAFARI + DIMETHOATE: Using this combination during shoot elongation will provide good control of both BWA and EHS without causing either SSM or HRM to become more of a problem. Safari control of BWA will take several weeks and EHS control may take several months. Dimethoate also provides a knock-down of SSM and HRM. Long term control of these mites depends on many factors. Typically HRM is becoming less active by June because temperatures are rising. Therefore, HRM control is usually not a problem. But if SSM in particular is a problem, consider adding another miticide that controls eggs. For options see: Adding Mite Control. When Dimethoate is applied in June, the BTA is killed before it has a chance to reproduce and lay the egg for next spring. |
Summer to Early Fall (July through early September)
Treating in the summer also gives good control of EHS. Deciding when in this treatment window to treat is difficult. Scale control is better earlier in the summer. The longer treatment is delayed into fall, the more likely scale control will be compromised. However, there are several good reasons for waiting. First of all, it’s usually cooler and easier to spray. Secondly, there will be less impact on natural predators. In addition, Cinara aphid control on trees going to market will be better and BTA control for the following spring will be better. Targeting an August application appears to be the best way to control all pests.
| Pests Controlled | Treatment Description | Treatment Window |
|---|---|---|
EHS |
DIMETHOATE + ASANA: Using this combination will control EHS (requires both materials) and BWA (from the Asana). EHS control through August is sufficient to virtually eliminate the white produced by the male and to keep males from developing in the home on cut trees. Both products should control Cinara aphids in market-size trees. Asana will reduce problems with BTA for the following year by reducing egg viability. Some growers have also added a bifenthrin product such as Sniper during this timeframe to increase BTA control. The synthetic pyrethroids such as Asana and Sniper may make HRM worse the following spring, so be sure to keep scouting for mites. Treating in August has provided the best controls of twig aphids for the following spring. This risk is lessened the longer in the season you wait to apply. Dimethoate also provides a knock-down of SSM and HRM. Long-term control of these mites depends on many factors. If SSM in particular is a problem, consider adding another miticide that controls eggs. For options see: Focus Mite Control. | July through early September
|
EHS |
SAFARI: Safari used by itself will control EHS and BWA. EHS control through August is sufficient to virtually eliminate the white produced by the male and to keep males from developing in the home on cut trees. There will be no negative impacts on mites. Impacts on EHS natural enemies are less than for other products and these impacts will continue to be reduced the longer in the season you wait to apply. If mites are a problem, consider adding a miticide that controls eggs. For options see: Focus on Mite Control. | |
EHS |
SAFARI + SNIPER (or other bifenthrin product): Safari plus a bifenthrin product such as Sniper, Talstar or Wisdom will control EHS (from Safari), BWA (from both products), and BTA for the next spring, Cinara aphids and SSM (from Sniper). EHS control through August is sufficient to virtually eliminate the white produced by the male and to keep males from developing in the home on cut trees. The synthetic pyrethroids such as Sniper may make HRM worse the following spring, so be sure to keep scouting for mites. This risk is lessened the longer in the season you wait to apply. |
Spring Prior to Bud Break
| Pests Controlled | Treatment Description | Treatment Window |
|---|---|---|
EHS |
ASANA + DIMETHOATE: To successfully control EHS in the spring, wait to as close to bud break as possible to allow as many crawlers to hatch as possible. This combination will control BTA for this year when applied before budbreak (from both products), BWA (from the Asana), and will give a knock-down for SSM and HRM (from the Dimethoate). The synthetic pyrethroids such as Asana may make HRM worse the following spring, so be sure to keep scouting for mites. Long term control of these mites depends on many factors. If mites are active, consider adding another miticide that controls eggs. For options see Adding Mite Control. There will not be BTA control for the following year. | Prior to bud break - April
|
EHS |
SAFARI: Safari by itself will only control EHS and BWA. Control of EHS may be better with Safari during the June to early September treatment windows. | |
EHS |
SAFARI + DIMETHOATE: Adding Dimethoate to Safari will provide BTA control for the current year when applied before or even two weeks after bud break. The Dimethoate will also provide SSM and HRM knock-down. Long term control of these mites depends on many factors. If mites are active, consider adding another miticide that controls eggs. For options see Adding Mite Control. There will not be BTA control for the following year. | |
EHS |
SAFARI + SNIPER (or other bifenthrin product): Safari plus a bifenthrin product such as Sniper, Talstar or Wisdom will control EHS (from Safari), BWA (from both products), BTA (from Sniper) for the current year when applied before bud break, and SSM control (from Sniper). The synthetic pyrethroids such as Sniper may make HRM worse the following spring, so be sure to keep scouting for mites. There will not be BTA control for the following year. |
Additional Pest Focus Pages:
- Focus on rosette bud mite control — If rosette bud mites are your problem, look no further for the control of all pests except Cinara aphids in market size trees.
- Focus on balsam woolly adelgid control — No rosette buds or scales but you do have woollies? Look here for control.
- Focus on aphid control — Nearing harvest? RBM, EHS and BWA not a problem? Then the balsam twig aphid and Cinara aphids are your number one concern.
- Focus on mite control — Mite control can be added on any time other pests are being controlled. Look here for added information on mite control.
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