2018 Strawberry Season Update #3 - Aphid Flight

In this week's aphid trapping and monitoring we found our first winged strawberry aphids. This aphid species is the primary vector of the strawberry viruses (strawberry mild yellow edge virus and strawberry mottle virus) found in Nova Scotia. During the strawberry aphid flight period strawberry fields are at their highest risk of becoming infected with viruses, as winged strawberry aphids can travel long distances carrying viruses to previously uninfected fields. Because of this it is crucial to continue to monitor and scout for winged and wingless strawberry aphids in your fields. 

Winged strawberry aphid.

It is also important to continue to manage for strawberry aphids during this period. Since we are in the middle of harvest there are limited products available for fruiting fields but there are a few tools with short (0 day or 1 day) pre-harvest intervals. For information on control options please see Perennia's Strawberry Management Guide 2018.

Pest Update 2 September 2017

Spotted Wing Drosophilia (SWD) counts have been steadily climbing in all traps, whether located in or outside of the crop.  As can be expected, captures remain higher for traps located along the field borders.  However, we have been observing sustained captures and gradual increases in trap numbers located within the crops, over the past few weeks. To date, we have observed adult SWD emerge from blueberries, raspberries and blackberries. Although up-to-date GDD calculations suggest that temperatures are average (if not slightly below) for this time of year, we do know that this is when SWD populations will spike and one can easily see trap captures go from double digits to over a 1000. Monitoring the crop with traps and fruit collection and testing for infestations is critical at this time.  (Dr. Deb Moreau, Entomologist, AAFC)

Strawberry aphid is the main vector of strawberry virus diseases in Nova Scotia.  Strawberry aphid monitoring began in early spring and will continue into the fall as part of a provincial funding program with HNS and Perennia.  Populations have remained low throughout the summer in managed strawberry fields across the province.  With that said, we typically see a "blip" in September of increased numbers, so be sure to continue to protect next years fields. 

The large raspberry aphid is the primary vector in NS of bramble viruses that are responsible for decline in cane vigor and decreased fruit quality.  Monitoring activities have found them in commercial fields and at field edges in wild bramble.  Their size makes them easy to scout with the naked eye.  They can be found at the tips and undersides of newly expanded leaves where tissue is supple.  Given the prevalence of wild bramble that are potential sources of virus, it is important to monitor and protect fields if you have a confirmed population of aphids.

Large raspberry aphid.

Potato leafhopper was first found in early July and has now been found throughout the Annapolis Valley and the south shore (Erika Bent, APM Agricultural Pest Monitoring Consulting Ltd).  Adults (see photo) and nymphs are present in apple orchards, strawberry and raspberry fields.  Feeding by the leafhoppers results in yellowing and crinkled leaves (see photo) and they are able to transmit aster yellows and green petal in strawberry.  Nymphs and adults can be found by looking on the undersides of the leaves; nymphs walk sideways when disturbed.

Potato leaf hopper adult on strawberries.

Potato leaf hopper damage in strawberries
(photo credits: Erika Bent).

Sharp-nosed leafhopper is able to transmit stunt in highbush blueberries.  Erika Bent (APM Agricultural Pest Monitoring Consulting Ltd.) has been finding adults on yellow sticky traps throughout the Annapolis Valley over the past couple weeks.  Controlling the leafhopper will help reduce the spread of stunt, but not eliminate it.  Infected plants should be removed and destroyed.

Aphid monitoring project update – July 22nd, 2013

Is the aphid flight collapsing or not?  Updating the winged aphid counts from my last report on July 5th, you can see in the Valley/Western region that there was a sharp drop in total winged aphids and strawberry aphid the week of July 8-12 but a partial rebound last week. More encouraging, the total winged strawberry aphids depicted by the red line dropped over both of the weeks. The Central/Eastern regional data is also showing some week to week volatility but the general trend does appear to be down. I expect these trends to continue and that the flight will collapse in the two regions over the next week or so. We will see…..

Aphid monitoring project update – July 5th, 2013

If I could give this newsletter a title that would capture my main message it would be “stay vigilant”. We are still in the high risk flight window for virus transmission and we continue to catch significant numbers of winged aphids in our traps around the province. However, we are also in the thick of harvest and it is easy to let down our guard during this time. Unfortunately, this is not the time to do so as those winged aphids could well be carrying virus and spreading it/them through your fruiting and newly planted fields. 

Note in the graphs below that the aphid flight began on June 10th in Valley/Southwest NS and that total winged aphid catches are still rising after four weeks. Fortunately, less than 10% of these catches have been strawberry aphid, the primary vector that spreads the viruses, with only 5% in this week’s data. The aphid flight in Central/Eastern NS began on the week of June 17th, a full week later than Valley/Southwest, and 4% of these catches have been strawberry aphid, a slightly lower percentage than Valley/Southwest overall.  It will be interesting to see when the flights collapse in the two regions but my expectation is around mid-July in the Valley/Southwest and late July in Central/Eastern. Until then we have to maintain our vigilance on strawberry aphids management and monitor and spray as required.

Let’s talk about aphid management options at this point in the season. If you used the Admire soil drench option on your new fields earlier in the season it will be wearing off after 3-4 weeks and will no longer be protecting your new plants. As noted above we are still in the flight period of strawberry aphid and we need to spray regularly at least until this flight collapses. Options include Thiodan/Thionex and Cygon/Lagon and each should have activity for about a week. Hopefully the flight will collapse by mid-July and only a couple of sprays would be required.

What about fruiting fields? Well, we only have one control that has a short enough pre-harvest interval to be used during harvest and this is Assail (1 day PHI). It can be applied twice per season so you should only apply it if monitoring warrants its use. Excellent post-harvest options include Admire (2 foliars allowed assuming it was not applied previously as a drench), Thiodan/Thionex, and Cygon/Lagon.

Thank-you for your cooperation during the virus sampling over the last three weeks. Results are still coming in so I cannot give a comprehensive report at this time but stayed tuned and hopefully by my next newsletter I will have something for you. In the meantime, I am trying to communicate test results to individual farms as I receive them but am somewhat behind on this. If you are especially eager to know your results you can speed up the process by contacting me directly.  Until then “stay vigilant”!

Aphid monitoring project update – June 4, 2013

As reported in the May 31^st update, virus symptoms have been expressing over the last two weeks and I have been asked what the symptoms look like. The picture below is very typical of the symptoms and note that older leaves tend to be a normal green while the newest leaves emerging over the last few weeks are the ones showing the symptoms. These have a generalized chlorosis (yellowing) that is focused more on the leaf margins. Also, these new leaves tend to be stunted and often twisted and misshapen. Other problems (cyclamen mites, herbicide injury, nutritional deficiencies, etc) can cause similar symptoms but if you do see symptoms as described, and shown below, please contact me as soon as possible.
 

Virus symptoms in Mira – spring 2013

 

Aphid Monitoring Project Update - May 31st

It’s been two weeks since my last project update and no news is good news in this case! Cooperating growers were actively applying controls (where necessary), and have done a tremendous job managing strawberry aphid populations during this time. Controls that have been used so far that seem to be working well are the Admire soil drench as well as the foliar application, and Thiodan. A few growers have applied Cygon or Assail this week but we will need to wait until next week to assess their effectiveness.

Although cooperating growers have done a great job managing their strawberry aphid populations over the last two weeks both of the project biologists have reported catches of winged strawberry aphids this week in matted row fields. The numbers have been very low but this does appear to be the beginning of the “spring flight” period for strawberry aphid this season.

What does it mean if winged aphids are found on your farm? In some cases this may mean that appropriate controls were lacking or were not effective and I would encourage the application of new controls as soon as possible as winged strawberry aphids are a much greater risk for virus transmission. On the other hand, on one farm where a winged strawberry aphid was found there were no wingless aphids so it is possible (and likely probable) that the winged aphid that was caught flew in from an outside source – an adjacent strawberry farm, home garden strawberry patch, or from wild strawberries. This notion reminds us that not all commercial strawberries farms are direct cooperators in the aphid monitoring project and that home-gardeners and wild strawberry sources of aphids are also excluded from our monitoring work. With regard to the former, I encourage all cooperators to talk to their neighbors and encourage them to monitor for strawberry aphid and apply controls if warranted. They may also direct them to contact me for advice as I may have a better idea of virus risk in their area. With regard to the possible source of strawberry aphids coming from home-gardeners or wild strawberries there is not a lot we can do other than continue to monitor our aphid populations and apply controls as we feel are needed.

What do winged strawberry aphids look like? There have been a few calls this week regarding suspicious looking winged insects found while scouting strawberry fields. Winged strawberry aphids actually look quite different from the wingless forms so a picture (Figure 1) and description is worthwhile. Firstly, they still have the knobbed hairs that distinguish the strawberry aphid from other aphid species. Also, they are more fly-like in appearance with a darker, more streamlined body with a distinct head, thorax, and abdomen as indicated in the picture below. Finally, the eyes are compound and black.

Figure 1.  Picture of winged strawberry aphid

The final part of this update concerns virus testing conducted over the last week and a half. As reported earlier, we cannot do reliable virus testing early in the spring because virus titre levels are too low and we have to wait until temperatures warm-up and there is significant new plant growth. With the cold late spring this has meant that we have not been able to see any symptom expression (from 2012 infections) or do any lab testing until very recently. I began seeing virus-like symptoms about two weeks ago and have verified by lab testing that our two problem viruses are more widespread and at higher levels around the province than I had expected (or hoped). This reinforces the importance of our aphid monitoring and control work so please keep up the good work. I truly believe that with good management we will quickly return to normal production levels.
 

Once again, regarding aphid management options, please visit Perennia’s Strawberry Insect and Disease Management Schedule at http://perennia.ca/Pest%20Management%20Guides/Fruits/2013/Strawberry_Guide_2013.pdfor you may wish to review Pam Fisher’s (Berry Specialist, OMAFRA) article on aphid management at http://www.omafra.gov.on.ca/english/crops/hort/news/hortmatt/2013/03hrt13.pdf

 

Aphid Monitoring Project Update - May 15th

Monitoring plots have been set-up around the province and leaf and sticky trap samples are now being collected regularly. Egg hatch was underway last week on many farms and we are now finding aphids on new leaves. As noted in my earlier report, the majority of aphids that we are finding are Chaetosiphon species which are the vector for the two viruses that have caused so many problems over the past year. This is a concern and many growers are opting to apply a control as a precaution against virus increase and spread.

The leaf sampling procedure we are using involves collecting 60 random leaves from each field/block and conducting the aphid counts in our lab under 20-30X magnification. The leaf samples should be immature, partly unfolded leaves as these are the target for young aphids. The strawberry aphid is distinct from other species in that it has knobbed hairs on its body and the knob at the end of each hair often appears to glisten from light reflection (see photo below).

The good news is that we have not found any winged aphids yet but we did observe an aphid that was starting to grow its wings this morning. It was collected May 14th from an early matted-row field that had been covered by row cover for a month and was 2 weeks ahead of other fields. Perhaps this is an early warning as to when we might expect an aphid flight in matted row fields without row cover. Needless to say, winged strawberry aphids are a much higher risk for virus spread.
Once again, regarding aphid management options, please visit Perennia’s Strawberry Insect and Disease Management Schedule here!

OR you may wish to review Pam Fisher’s (Berry Specialist, OMAFRA) article on aphid management here.

Aphid Monitoring Project Update - May 7th

This is a brief update on the “strawberry aphid monitoring project” that is underway for this growing season.

Overall the project is proceeding very well. Student biologists have been hired and are located at Perennia’s Bible Hill and Kentville offices respectively.  Also, an aphid identification training session was held on Monday April 30th at the Kentville Research Station, led by Dr. Deb Moreau of AAFC and with excellent support from Erika Bent and Rachael Cheverie.

Monitoring plots have been established at most targeted sites around the province with the remaining ones being set-up over the next two days. Samples have also been collected from most sites and some counts have already been conducted.

Interestingly, we have already learned quite a bit of new information. Firstly, we did not know if there would be any overwintering nymph or adult aphids and surprising to me we have not found any. In contrast we have found an abundance of overwintering aphid eggs, with much variability in numbers from field to field and farm to farm. So, for this year at least aphids appear to be overwintering primarily as eggs. In my opinion this is a good thing because with the late spring, hatch has been delayed and thus population build-up is going to be delayed. This gives us time to plan our aphid management strategies and in turn our virus management should be optimized this season.

What about the aphid egg hatch? Well, our first confirmation of newly hatched nymphs came from an ‘Annapolis’ block in Central NS that was covered in row cover and this was on Friday, May 3rd. Our first confirmation of nymphs in uncovered matted row system was in an early ‘Wendy’ block on a sandy soil in the Annapolis Valley and this was on Monday, May 6th. Several other aphids were observed while setting up plots today in the Annapolis Valley so the spring hatch is underway here in the Valley. We are uncertain how long the hatch period may be but I would expect it to occur fairly rapidly on a given site because it is largely based on heat accumulation and this should be fairly uniform in a given field.

Finally, what about aphid species?  Unfortunately, the bulk of the aphids found thus far, from the Annapolis Valley and Central NS, have been ‘strawberry aphid’, the vector that transmits the viruses that were identified in the province last year. Other species have been found as well but the majority of aphids counted thus far have been the strawberry aphid and this is a concern as surveys from the 1960’s reported very few strawberry aphids at that time. Things have definitely changed and we need to monitor and manage this new pest if we are to prevent the spread and increase of the problem viruses.

Individual farm monitoring results will be communicated by phone or email. No news is good news but if you can’t wait please feel free to contact me at my cell number 902-670-4892.

Regarding aphid management options, please visit Perennia’s Strawberry Insect and Disease Management Schedule here!

Also, you may wish to review Pam Fisher’s (Berry Specialist, OMAFRA) article on aphid management here.

Stayed tuned for my next monitoring report on Monday, May 13th.