Apple Pest Report: Thursday,
May 3, 2007
Vol. 15 No. 2
Growth stage
In
Using the 10-day weather forecast, and climatic average temperatures beyond May 10, Orchard Radar estimates the following dates for key McIntosh bud stages are Highmoor Farm this year as follows.
|
McIntosh (and similar cultivars) Growth Stage |
Estimated date |
|
Tight Cluster |
May 8 |
|
Open Cluster |
May 10 |
|
full Pink (extended
petioles) |
May 14 |
|
King Bloom |
May 19 |
|
Full Bloom |
May 21-22 |
|
95% Petal Fall |
May 28 |
|
100% Petal Fall |
May 30 |
|
Fruit Set |
June 2 |
Of course, those dates can shift early or later if unusually warm or cool weather predominates. The estimates are updated twice daily at http://pronewengland.org/AllModels/MEmodel/me-Monmouth-Bud.htm
Once buds reach Half-inch green, there is risk of phytotoxicity and fruit russetting if copper is applied. Several growers expressed concern about sub-freezing temperatures that occurred on Thursday, April 26 after they had applied copper. The biggest risk seems to have been in Sanford, Lewiston-Auburn, and East Waterford where apples were at Quarter-Inch Green and the low temperature was around 26F. Fryeburg, Kents Hill, and Lincolnville actually got colder (24-25F) but apple buds in those locations were also less vulnerable as they were not much past Green Tip. My guess is that while it was cold enough to leave a heavy coating of frost in some locations, temperatures were not close enough to the critical values to cause significant damage even with oil and/or copper coverage on the buds. In addition, the buds should have been preconditioned for additional cold hardiness. Except for April 24, buds had been exposed to low temperatures in the 30’s or 20’s every night for weeks preceding the freeze on April 26.
An Easter freeze hurt tree fruit crops from South Carolina to Michigan. In many locations, apple trees were farther along than we are now when night temperatures dipped as low as 19F.
Here are the critical low temperatures for apple growth stages (from 2006-2007 Pennsylvania Tree Fruit Production Guide).
|
Growth stage |
10% Kill Temp. F |
90% kill |
|
Silver Tip |
15 |
2 |
|
Green Tip |
18 |
10 |
|
Half-Inch Green |
23 |
15 |
|
Tight Cluster |
27 |
21 |
|
First Pink |
28 |
24 |
|
Full Pink |
28 |
25 |
|
King Bloom |
28 |
25 |
|
Full Bloom |
28 |
25 |
|
Post bloom |
28 |
25 |
Apple Scab
The rain on April 27-30 represented less than 1% of the season’s primary scab infection potential.
The current 8-day forecast out does not show over-50% chance of rain on any day until May 10. The long term forecast out to May 16 indicates tendency for warm, dry weather. The apple scab fungus requires rain to initiate new infections. Growers who can respond quickly could wait until there is rain in the forecast before renewing fungicide protection. You don’t really buy protection against apple scab by applying fungicide; you rent it by the day. If the cost for fungicide, fuel, labor, and equipment wear to apply fungicide totals $40 an acre and that coverage will be depleted within 7 days due to foliar growth, chemical breakdown, and/or rain, then that protection costs about $6 per acre per day. Not having protection out there when you don’t need it is a way to minimize costs. But the risk of getting caught by an unexpected rain has to be considered.
Scab ascospore maturation and apple foliar regrowth will continue during the wait for the next rain. Scab infection potential is a function of ascospore maturity, amount of foliar growth less than about 4 days old, and conditions during the wetting event (leaf wetness duration and temperature).
When the next rain does arrive, it will bring with it all the scab infection potential developed since the previous rain. If, for example, the next rain did not occur until May 10, then about 6% of the season’s total scab infection potential could be expressed. If the next rain is not until May 15, then the number jumps to about 22%. Of course, we could get lucky and have a short rain with enough wetting to release ascospores, but not long enough to keep apple leaves wet for scab infection to occur. But scab has not survived millions of years by getting fooled by short rains very often.
Now that scab risk is increasing (and at an increasing rate), getting caught without protection would require a postinfection fungicide application. If that happens, Scala and Vangard are two options for early season kickback (postinfection) scab control up to Tight Cluster or Pink. These materials are not preferred after Pink because they are less effective at warmer temperatures (> 70F) and are not as effective as other options in protecting against fruit scab. But they do provide 48 hour postinfection activity for early season infections.
The news on sterol inhibitor resistance seems to keep getting worse. Dr. Wolfram Koeller has published another comprehensive article in the NY Scaffolds Newsletter. http://www.nysaes.cornell.edu/ent/scaffolds/2007/070430.html#disease
In that article, Dr. Koeller states that second-generation sterol inhibitor (SI) fungicide Indar is significantly better than the first generation SIs (Nova, Rubigan, Procure) for postinfection scab control. The number of previous SI applications in orchards where resistance was found by recent testing ranged from 40-60. Dr. Koeller also provides some cautions about relying on the “number of previous SI uses” rule as a guide to the chance of resistance in untested orchards. Used in combination with a low-rate protectant fungicide, SI resistance may be masked by the protectant fungicide doing the bulk of the work until high infection pressure overwhelms what the low rate protectant can provide on its own. He concludes that discussion with “The only current advice we can offer is that whenever SIs in mixture with mancozeb have shown 'signs of weakness', SIs should not be used during the next season, and that leaf samples with scab lesions should be submitted for sensitivity tests”.
But where there is not SI resistant scab, the SIs can provide 96 hour post-infection control. Strobilurin fungicides (Sovran, Flint, Pristine) offer 48-72 hour kickback.
Syllit (dodine) provides
18-24 hour postinfection control.
In NY, scab resistance to dodine is considered too widespread to
recommend its use. It has been used
successfully in Maine long after its utility had diminished in NY, but without
fungicide resistance testing in a given orchard there is no way to define
resistance status in that orchard.
If conditions allow application within 18-24 hours after an infection
begins, even captan, mancozeb (Dithane, Penncozeb, Manzate, and Manex) and Polyram
(metiram) have been shown to provide post-infection control. Unfortunately, weather conditions often
make application within the first 24 hours after an infection begins
impractical.
Given the concerns about all of the postinfection materials, protection in place before the next infection period is definitely the preferred approach, with post-infection control reserved for emergency situations.
Here are excerpts from a
table of comments on the different apple fungicides from the 2007 Michigan
Fruit Management Guide. To the see
the full table, go to http://web1.msue.msu.edu/epubs/pestpubs/E154/10-Tree_Fruit_Fungicides.pdf. I’ve edited some of the statements
with additional ratings in the Cornell 2007 Pest Management Guidelines for
Commercial Tree-Fruit Production.
Ratings assume use at full rate.
Note that New England growers have achieved excellent scab control
basing captan intervals on the assumption of 7 days protection, with the
possible exception of rapid growth spurts during Pink and Bloom when a shorter
interval might be called for.
|
Inorganic |
|
|
Sulfur |
2-3 days forward primary scab. Use after bloom starts can reduce
fruit set. May cause fruit russet
and yield reduction when used in high temperature conditions. Should not be used within at
minimum 7 days before or after an oil application due to phytotoxicity
concern. |
|
Copper |
3-4 days primary scab. |
|
Anilinopyrimidine |
|
|
Vangard (cyprodinil) & Scala (pyrimethanil) |
48 hours post-infection
activity. Do not control other key apple
diseases. |
|
Strobilurin |
|
|
Flint (trifloxystrobin) |
Use no more than 2-3 consecutive
applications for resistance management.
(Other sources not using a strobilurin more than twice before
switching to a different chemistry. Also maximum number of applications per
season is 4.) 5-6 days primary scab. Post-infection activity is less
than the 96-100 hours stated on the label. (Cornell rates strobilurin post-infection
range as 48-72 hours, and 48 hours in orchards with SI resistant scab). Post-infection control not as good as
sterol inhibitor fungicides were before SI-resistant strains developed. Back-to-back sprays do not
increase post-infection control. Reduce spore production on
existing scab lesions, but use of strobilurins for post-symptom control not
recommended because it will hasten resistant strain development. Better at primary scab control than
at stopping secondary scab when lesions are already visible. To control existing lesions,
works better when combined with captan, which also helps with resistance
management. Also control powdery mildew,
sooty blotch, flyspeck, black rot, and are fair against bitter rot. Flint 14 day PHI, Sovran - 30
day PHI. |
|
Pristine (pyraclostrobin
and boscalid) |
Pristine is a two-fungicide
combination of a strobilurin (pyraclostrobin) and a carboximide
(boscalid). The strobilurin
activity is the same as for Flint and Sovran. The boscalid provides better
protection against bitter rot and postharvest rots caused by Botrytis and
Penicillium. 0 day PHI. Excellent choice for the
season’s final fungicide application. |
|
Sterol inhibitor All
also control powdery mildew and cedar apple rust. Prone to resistance. |
|
|
Nova (myclobutanil) |
3-4 days primary scab
protection. 96 hour post-infection activity
at high rate and no SI resistance. |
|
Procure (triflumizole) |
2-3 days primary scab. 48-72 hour post-infection
activity at high rate and no SI resistance. |
|
Rubigan (fenarimol) |
2-3 days primary scab. 96 hour post-infection activity
at high rate and no SI resistance. |
|
Thiophanate, aka Benzimidazole |
|
|
Topsin M (thiophanate methyl) |
Similar profile as Benlate (which
is no longer available). Scab resistance is a problem in
MI and NY, resistance status not known in Maine. Good for flyspeck, sooty blotch,
black rot. |
|
Dithiocarbamate aka EBDC |
|
|
Dithane, Manzate 200, Penncozeb (mancozeb) and
Polyram (metiram) |
5-6 days primary scab
protection. Very good retention and
redistribution. 18-24 hour post-infection
activity. |
|
Carbamate (related to, but distinct from, EBDCs) |
|
|
Ferbam Granuflo (ferbam) |
Related to EBDCs. 3-5 days primary scab
protection. No post-infection activity. Good retention and
redistribution. Leaves unsightly residue if
applied close to harvest. Lenticel enlargement and
russeting of Golden Delicious. Gritty texture can cause pump
and nozzle wear. |
|
Ziram |
Only fair for scab control. Similar scab activity as ferbam. Good control of flyspeck and
sooty blotch. Only fair against
black rot and bitter rot. |
|
Thiram |
No longer registered for apples. |
|
Guanidine |
|
|
Syllit (dodine) |
24-36 hours postinfection activity
(NY rates as 18-24 hours). Scab resistance is a problem in
MI and NY, resistance status not known in Maine. Inactivates spore production on
existing scab lesions with two high rate applications one week apart. |
|
Phtalimide |
|
|
Captan, Captec (captan) |
5-6 days primary scab
protection. 18-24 hour post-infection
activity. Very good retention and
redistribution. Should not be used within at
minimum 7 days before or after an oil application due to phytotoxicity
concern. |
Other Diseases
With
opportunity for copper application to suppress Fire Blight bacterial growth
behind, the disease management focus until King Bloom is almost exclusively on
apple scab. However, now is a good time
to imagine a possible scenario where during bloom we have a forecast for three
days with high temperatures in the mid-70s, or two days with highs above 80F,
followed by rain. If such weather
is forecast, you would want to apply an antibiotic (e.g. Agrimycin, Streptrol,
Firewall) within 72 hours (preferably 48 hours) before, or within 12-24 hours
after the rain begins. Now is the
time to check with your pesticide supplier to see if you would be able to acquire
an antibiotic on short notice. If
that looks doubtful, then it is time to consider the investment you have in
highly susceptible rootstocks (e.g. M26, M9) and cultivars (Braebrun,
Growers who have had
problems with Powdery Mildew (PM) may want to consider PM in their fungicide
selection for applications between Tight Cluster and First Cover, but PM is
usually a minor problem in
Insects and Mites
Half-inch Green to Open Cluster is the optimum timing to apply oil to smother European red mite eggs. As the eggs get closer to hatch and as warmer temperatures prevail, their respiration rate increases and so does their susceptibility to oil. Apple tissue susceptibility also increases as buds development progresses. Use a rate of 2 gallons oil per 100 gallons dilute spray until Tight Cluster. At Tight Cluster reduce the rate to 1.5 gallons, and if applying between Tight Cluster and Open cluster use a 1.0 gallon rate. Oil also helps to suppress San Jose Scale.
Oil can be applied in concentrate spray like other pesticides and can be concentrated to keep the same amount of oil per acre as if you were making a dilute spray. But coverage is all important with oil application and efficacy will decline if the application is at more than 3X (i.e. less than one third the amount of water needed for a dilute application. If you do decide to spray at higher than 3X concentration, do not concentrate the oil more than 3X. Penn State advises combining with surfactant (spreader) to reduce chance of oil mixture with other pesticides “buttering out”. Numerous sources, including oil product labels, recommend adding oil last when making a tankmix, and to add the oil when the tank is ¾ full of water with active agitation until it is sprayed out. Hold off on applying oil if there were subfreezing temperatures in the 24-48 hours before, or forecast shows a risk of freezing temperatures in the 24-48 hours following the application. If cold or wind prevents you from applying oil, there are alternatives like Apollo, Savey, Zeal, and Agri-Mek that you use at Petal Fall to keep mites in check without having to resort to rescue treatments.
Tarnished plant bug is the major insect pest concern in the prebloom period. If you don’t have monitoring traps, finding three or more buds oozing sap from TPB stings per tree is an informal treatment threshold. Many orchards do not receive prebloom insecticide treatment for TPB without any noticeable damage, but in some years in some orchards TPB damage without a prebloom insecticide can be noticeable. Warm dry springs may favor more TPB activity in apple orchards. The forecast for May 7 – 10, Monday – Thursday next week, looks like “TPB weather”, so keep an eye out for damage.
Other insect pests to watch for are rosy apple aphid (RAA), especially on Cortland, IdaRed, JonaGold and Golden Delicious. If you find more than 1 RAA infested fruit cluster per tree in checking 10 fruit clusters per tree on 10 trees, then treatment may be economically justified. Winter moth, green pug moth, and green fruitworm caterpillars are hatching out now and may also warrant control if there is feeding damage on more than 5% of fruit clusters. RAA or the prebloom caterpillars usually do not require treatment, but they there are always exceptions.
Insecticides and Honeybees
It is always a good idea to make pollination arrangements as early as possible, and that is especially true this year. In addition, your beekeeper may be especially interested in discussing insecticide use while the bees are in the orchard. There is concern that the neonicotinoid insecticide group (which includes Actara, Assail, Calypso, Clutch, and Provado) may be a contributing factor in the recent concerns about honeybee Colony Collapse Disorder.
Here are recommendations for growers using honeybee pollination in a letter published on April 23, 2007 by Maryann Frazier of Penn State. She is one of the lead scientists in the effort to help beekeepers meet this new challenge. The full letter provides much more information, and is online at http://maarec.cas.psu.edu/CCDPpt/RecGrowersUsingNeonics1.pdf
“Recommendations for
Growers
• Know the
pesticides you are using and their toxicity to bees (do not depend on third
party to provide this information).
• READ the
LABEL AND FOLLOW THE LABEL DIRECTIONS.
• Never use a neonicotinoid
pesticide on a blooming crop or on blooming weeds if honey bees are present.
• The use of a
neonicotinoid pesticide pre-bloom, just before bees are brought onto a crop is not recommended. If one of these
materials MUST be used pre-bloom (for example at pink in apples), select a
material that has a lower toxicity to bees (acetamiprid or thiacloprid) and
apply only when bees are not foraging, preferably late evening.
• Do not apply
these materials post bloom (example petal fall) until after the bees have been
removed from the crop.
• Blooming
time varies depending on varieties. Bees pollinating one variety or crop may be
at risk while another post-bloom crop or variety is being treated with
insecticides. Also while crops may have completed blooming, bees may be
visiting blooming weeds in and around crops. Be aware of these situations and
avoid the application of pesticides on a non-blooming crop if there is risk of
drift onto blooming crops and weeds if bees are present. If a spray must be
applied, use the least toxic material and apply only when bees are not
foraging.
• Protect water sources from contamination by pesticides. If necessary, provide a clean source of water close to colony locations prior to their arrival in the orchard or crop.”
Unfortunately, the alternative insecticide options (e.g. organophosphates such as Imidan and Guthion; Sevin; and pyrethroids such as Ambush, Pounce, Baythroid, Danitol, and Warrior) all have higher mortality ratings against honeybees than the neonicotinoids. But there are more questions than answers at this point. If there is a relationship between neonicotinoids use and CCD, it may be due to behavioral effects that were not measured in previous rating schemes of honeybee mortality associated with insecticide residue present when honeybees are working in orchards.
Looking ahead to Petal Fall insecticide selection, the Cornell Pest Management Guidelines for Commercial Tree-Fruit Production gives Avaunt a lower honeybee mortality rating than the other alternative products listed above, and Avaunt has a 3 rating (on a 1-3 scale, with 3 being the best) against plum curculio and leafhoppers, along with a 2 for codling moth and other internal fruit feeding Lepidoptera caterpillars. If you need to leafminer control at First Cover, SpinTor is an effective non-neonicotinoid option.
Sprayer Calibration, Pesticide Dosage, Tree Row Volume
In the previous Apple Pest Report I wrote that the default assumption for pesticide rates when stated on a per acre basis is for an acre of trees requiring 400 gallons of water (GPA) for a dilute application. Here is what I found in checking labels and apple management guides from Pennsylvania, New York, and Michigan to see how consistent that assumption was across different labels and in different apple producing states.
Out of 19 apple
fungicide labels:
5 were explicit in stating a 400 GPA basis (Captan 50WP, Ferbam Granuflo, Nova,
Topsin M, Ziram).
2 explicitly mentioned 300 GPA (Rubigan, Sovran).
12 were not explicit about dilute gallons per acre (Dithane DF and M-45,
Penncozeb, Manzate, Polyram, Flint, Lime sulfur, Procure, Scala, Sulfur WP,
Syllit, Vangard).
The Michigan and
Pennsylvania guides assume 400 GPA unless the label explicitly states
otherwise. The New York guide gives
a rate per 100 gallons dilute that fits with a 400 GPA basis for some
fungicides (e.g. Captan) and a 300 GPA for others (Dithane and other EBDCs,
Scala, Vangard.)
Out of 37 apple
insecticide and miticide labels:
13 were explicit about using a 400 GPA basis (Agri-Mek, Calypso, Carzol,
Guthion, Imidan, Lannate, Proclaim, Sevin XLR, SpinTor, Apollo, Kanemite,
Nexter, Vendex).
3 were implicitly using a 400 GPA basis by comparing the Cornell rate per 100
gallons dilute rate recommendation with the rate per acre stated on the label
(e.g. the Provado rate per acre is 8 ozs. and Cornell recommends 2 oz. per 100
gals./dilute. The other two
products treated this way were Lannate and Vydate).
0 explicitly mentioned 300 GPA.
17 were not explicit about the GPA basis (Actara, Ambush, Pounce, Assail,
Avaunt, Aza-Direct, Baythroid, Centaur, Danitol, Dipel, Esteem, Intrepid,
Surround, Warrior, Acramite, Savey, and Zeal).
4 were oddballs (Asana – 200-600 GPA statement on label, 250 GPA by
comparing rate per 100 gals. dilute to the per acre rate; M-Pede mixture is by
volume % of tankmix regardless of acreage; Fujimite label stated 200 GPA, not
registered in Maine by the way; and Thionex was the high roller at 500 GPA!
As with
fungicides, the Michigan and Pennsylvania guides assume 400 GPA unless the
label explicitly states otherwise.
*************************
The agency that regulates pesticide registrations is the EPA – Environmental Protection Agency, not the Crop Protection Agency. Their interest is in protecting human health, and to protect the environment which is measured in acres. Whether you get a clean crop is not their main focus, so the clarity of dosage recommendations for use on apple trees is not a controlling factor in pesticide labeling.
Except for tree crops like apples, acres works fine for most other crops. But as a two dimensional unit, an “Acre” is not all that useful for describing pesticide dosage for a target site that can range from 3 foot high whips to 30 foot high mammoth trees. Basing dosage on a mythical 400 gallon per acre orchard might have made sense when tress of that size dominated the industry. But now it’s about as relevant as going to buy a suit and telling the clerk that you are 2/3 as tall and weigh half as much as Shaquille O’Neal. Calculating the Tree Row Volume dilute gallons per acre for each orchard block only takes minutes. Once you’ve done one block, you’ll find that the math is really quite simple. Having an accurate measure of dilute gallons per acre is essential in order to set up your sprayer to deliver the correct gallons per minute. If you haven’t done these calculations you are sending many dollars of spray to protect many more dollars of crop through a system you haven’t measured.
If you have questions about any of this, don’t hesitate to give me a call. Sprayer calibration seems to be a weak link in the management program for many orchards. Having a detailed IPM strategy can provide better crop security with minimum costs, but it rests on a foundation of accurate pesticide delivery when you need it. Over-spray and you waste money and risk overthinning, phytotoxicity, and illegal residue. Under-spray and you risk crop damage or expensive and time consuming corrective treatments. Accurate spray calibration is the path to a profitable, high quality crop, and perhaps less worry because you’ll have greater confidence that you are applying the right dosage with the right coverage.
New England Apple Pest Management Guide
The 2007 edition of the guide is supposed to arrive
by May 10. They will be sold
through Highmoor Farm.
Scouting Co-op and Orchard Radar
I still don’t have anyone hired to be the
Apple IPM Scout. If you know of a
person at least 18 years old with a Maine driver’s license, a clean
driving record, and who lives within commuting distance of Highmoor Farm,
encourage them to pick up an application at Highmoor Farm, or to give me a call
at 207-581-3882.
Sincerely,
Glen
Glen Koehler
Pest Management Office
491 College Avenue
Orono, ME 04473
Voice: 207-581-3882
Email: gkoehler@umext.maine.edu
Web: PRONewEngland.org
Fax: 207-581-3881
What we call the
secret of happiness is no more a secret than our willingness to choose life. -
Leo Buscaglia