May 20, 2019

GDD Update May 20, 2019

Well, this is different – sun and heat!  Based on the weather alerts popping up on my radio, some people got lots of rain this weekend, which continues to make everything difficult.

Most reports are ‘missed that window for weed/insect management, planting, etc…’.  Peter Brooks wondered what the effect of all the rain on GDD based insect models is.  I suspect the effect is less on their development and more on our ability to deal with them.  Now, for something that pupates or overwinters in the soil, there might be an effect.  Harder to escape muddy soils?

On the disease side, there is definitely an effect of a wet spring.  We’ve seen too much Phytophthora in the past to not know it is exacerbated by waterlogged soils.  And George Hudler is noted in the Branching Out newsletter for May 17 as saying that leaf, needle and rust diseases are expected to be at high levels in 2019.  He thinks Rhabdocline and Swiss needle cast are as high as he has seen in many years.  (I have heard comments about Rhabdocline this year after not hearing any for quite a while.)

So this is a year to make sure you get good coverage for your needlecast sprays.  Remember Brian has seen good results treating for the first time at 1.5 – 2 inch elongation of shoots for Swiss needlecast, later than the traditional recommendation.

Growing degree days for the farms I am following range from 85-345.  Where do you fall?  Find out at NEWA: http://newa.cornell.edu/index.php?page=degree-day-calculator

 

Things to be scouting for now or soon:

Douglas fir needle midge – adults emerge 200-400

Gypsy moth  – eggs hatch 90-448

Pine needle scale – first generation crawlers emerge 298-448

I don’t get many requests for information on sawflies, but if you have them (and there are several species), they may be emerging now (78-220 for European pine sawfly).  Treatment is usually spot treatment only and often only in the last few years before sale.  Unfortunately, Bt doesn’t work on sawflies.

Have a great week!

May 13, 2019

GDD update May 13, 2019

GDD is inching up.  Not much has changed from the update last week.  The range of GDD for the growers I am working with on this project is 56 – 260.

 

Do any of you note the GDD for budbreak for the different tree species you grow?  Maybe a project for me for next year.  It would be helpful to know, wouldn’t it?  Source may affect it but perhaps we could get a range.

 

Supposed to get to 84 in Ithaca on Sunday.  The bigger problem for you at the moment may be getting in to your fields to scout with all the rain and little sun to dry things out.  We had to throw in the towel (and a soggy towel it was) on sampling for insects this week.

 

Have a great week!

 

May 13, 2019

GDD update for May 8, 2019

One thing I was reminded of this week – things can change quickly!  Especially when you get busy!

Monday I was out in our beneficial habitat plots setting up pitfall traps and helping with sweep netting.  We are certainly catching bugs – especially where there are flowers, and even weeds count (oh, yes, we have weeds).  We can’t identify them all yet but there are definitely beneficials out there already.  We caught several pink spotted ladybeetles – an excellent aphid parasite that you want if you have balsam twig aphid.

Why am I telling you this? Not just so you can be happy I spent a day away from my desk (Yes!) but because it suggests 2 things:

  • Flowering plants – beneficial habitat plots or weeds (if they aren’t interfering with production practices) – will draw the good guys in to your plots where they will feed on the pests you don’t want.
  • If you are applying pesticides, knowing the effects on beneficials will help you avoid killing them off.  This information isn’t that easy to find but if you want to know what I can find on a particular pesticide, send me a note and I will do my best (and include the information in these notes).

A quick review of where most people are:

Balsam twig aphid eggs will be hatching for many of you (30-100 GDD) and the best control is between egg hatch and bud break.

Balsam woolly adelgid treatment is before bud break (no GDD available).

Cooley spruce gall adelgid nymphs on Douglas fir or spruce are still in a treatable stage for some locations (22-91 GDD)

Douglas fir needle midge adults will be emerging from the soil (200-400) soon and heading out to lay eggs on your trees.  Yellow sticky cards will tell you exactly when.

Elongate hemlock scale adults can still be controlled if your trees are still dormant (7-120) but no-one is yet at the stage of treating crawlers (360-700)

Gypsy moth larvae will be hatching (90-448 GDD) and the Bt applications work best on small larvae.

Pales weevil and Eastern pine weevil treatment still possible for some (7-121 GDD and 7-100 GDD respectively)

Pine needle scale eggs should be scouted  (98-248 GDD) but I wouldn’t expect crawlers to be out for anyone quite yet (248-448)

Spruce spider mite eggs should be hatching – or already done (50-121 GDD)

White pine weevil – getting close to the end for everyone if you aren’t already there (7-58 GDD).  The next step is to cut out the shepherd’s crooks caused by the larval feeding.

Zimmerman pine moth – does anyone see this? – larvae are hatching now for some of you (121-246 GDD)

Does anyone get sawflies or pine bark adelgid?  As there are fewer pines grown as Christmas, we see fewer pine pests.  But they are still in the landscape trade.

A long one today since you got off easy last week!

 

Have a great week!

May 1, 2019

GDD Update 4.29.19

What a difference a day – or a year – makes.  We didn’t get the threatened snow in Ithaca but did get a good frost last night.  Just because I planted a few things (patience is not one of my virtues)?

 

And at the Cornell Orchards, the GDD today is 80 – last year on this date it was 13 and in 2017 it was 152.  So I guess we are at a happy medium.

 

Did anyone have snow?  Did anyone have buds out far enough to get nipped if you had a frost?

 

Not much change in GDD overall since last week – just 6 units if you all are included and 4 if we take out Long Island which had all the outliers. And no big jumps through May 4 – just creeping up. Doesn’t change any advice so I’ll make this a quick email!

 

Have a great week!

April 29, 2019

GDD Update April 22, 2019

For many, there isn’t a huge increase in GDD over the next five days.  Unless you are on the Island – or a few other places.  But we are steadily increasing overall.   I rather like slow springs….

 

Today’s topics ‘thresholds and ‘keep scouting!’

 

Thresholds are values – usually number of insects – that indicate it is time to take action to avoid economic loss.  They are complex to calculate as they can vary with time of year, crop, pest, etc.  Consequently, there are very few available for Christmas tree pests.  Two I have found are:

 

Spruce spider mite – 10 mites/branch scouted (usually with a tap test over white paper)

 

Balsam twig aphid – 3 aphids per tree,  when 10” of branch on 15 trees of similar age and size are scouted.

 

In addition to scouting now for spruce spider mite (50-121) and balsam twig aphid (30-100) – and remember to especially scout where you have had the pest before – you should be scouting for:

 

Cooley spruce gall adelgid (22-19) at base of buds on blue spruce or where there are bent needles or yellow spots on needles of Douglas fir

 

Elongate hemlock scale (if you are in the zone) – use sticky traps to catch adults (7-120)

 

Balsam woolly adegid – no GDD available – but scout for flat tops, gouting (swelling at nodes and ends of twigs) and very tiny adults covered in a white waxy covering on the trunk and branches.

 

Gypsy moth (especially if you have had it before) – you can pick off the egg masses before they hatch  (start about 90) and treat while they are still small (less than 1”) with Bacillus thuringiensis (Bt).  The small larvae can balloon off the tree onto neighboring trees so consider your wind direction and treat trees in that area.

 

Pine needle scale – check under the scale covers for maroon eggs. Treat when crawlers hatch later.

 

Zimmerman pine moth – larvae start to hatch 121-246 GDD

 

Are you still trapping for white pine weevil?  You maybe catching Eastern pine weevil – they are hard to tell apart.

 

Have a great week!

 

April 15, 2019

April 15 GDD update

The range of GDD for the group of growers in this project is from 4-67 – so you can see the variation by location!  And I expect things will start moving fast soon!

 

A reminder that insects don’t read books (or my emails) so scouting is always the best way to determine if an insect is present and at what developmental stage.  The GDD ranges give a suggested window for scouting.

Balsam twig aphid management 30-100

Cooley spruce gall adelgid management 22-81

White pine weevil management 7-58 GDD – a few areas have hit this deadline already and more will by April 20.  You might still catch Eastern pine weevils in the traps after 58 GDD and they are hard to distinguish from white pine weevil.

 

So many pesticide applications state ‘treat before/or after budbreak’.  I understand budbreak on a single bud – when the bud scales open and you can see the new needles inside.  But what about budbreak on a field basis – especially if you have different species or cultivars in the same species?  Just looking at some research papers, I found budbreak defined as:

  • The day when buds in the upper 1/3 of the crown showed green needles under the cap of the bud scales
  • Once one shoot broke its bud scale

 

Those are pretty different measurements.  So when would you treat for needlecasts, for example, as you are trying to protect new foliage – after budbreak?  Brian’s research on Swiss needlecast on Doug fir is showing that you can get good control starting spraying later when there’s about an inch of new growth and you don’t have to guesstimate bud break.  For control of needlecasts good coverage is essential.  Have you ever tested your spray coverage?

 

Some insects are good at avoiding contact insecticide applications.  Anything that forms a gall or feeds inside plant stems and those that have scale or waxy filament coverings are essentially wearing pesticide raincoats.  That’s why you need to apply the insecticide at their weakest development stage – before they get under cover.

 

 

Have a great week!