Upcoming Pest Events | Trap Catches | Pest Focus | Insects | Diseases | Erratum

Upcoming Pest Events | Trap Catches | Pest Focus | Insects | Diseases | Erratum

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Upcoming Pest Events | Trap Catches | Pest Focus | Insects | Diseases | Erratum

Geneva: Lesser Peachtree Borer trap catch increasing.
San Jose Scale and Lesser Appleworm first trap catches.

Highland: High levels of Plum Curculio ovipositional damage occurring this
week.
Very high levels of European Apple Sawfly damage in McIntosh and
Ginger Gold, with larval feeding and frass exuding from fruit.
Pear Psylla adults of 2nd generation increasing in number; increased
egg laying observed. Nymph populations have fallen below action
threshold. Egg hatch of 2nd generation beginning.
Black Cherry Aphid causing leaf curl on sweet cherry.

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Upcoming Pest Events | Trap Catches | Pest Focus | Insects | Diseases | Erratum

Geneva Predictions:
Roundheaded Appletree Borer
RAB adult emergence begins: May 30; Peak emergence: June 12.
RAB egglaying begins: June 7. Peak egglaying period roughly: June 28 to July 12.

Codling Moth
Codling moth development as of May 30: 1st generation adult emergence at 15% and 1st generation egg hatch at 0%.
1st generation 3% CM egg hatch: June 8 (= target date for first spray where multiple sprays needed to control 1st generation CM).
1st generation 20% CM egg hatch: June 16 (= target date where one spray needed to control 1st generation codling moth).

Obliquebanded Leafroller
1st generation OBLR flight, first trap catch expected: June 10.

Oriental Fruit Moth
Optimum 1st generation second treatment date, if needed: May 30.

Spotted Tentiform Leafminer
1st generation sapfeeding mines optimum sample date: around May 25, when a larger portion of the mines have become detectable.

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   Summer arrived beating the bass drum over the weekend, and although arthropods respond positively to hotter conditions, pest management decisions tend to be more straightforward than they are during cool and wet weather, as things tend to happen on a more predictable schedule.  If there's such a thing as a normal schedule, insects and mites are probably a bit ahead of it already, so this may increase the likelihood a lot of management decisions might have to be made all at once.  The following are updates on some of the traditional crop protection scenarios during this period.  Dates in parentheses, where present, are the mean date of occurrence in Geneva, according to our recent records.

Plum Curculio (May 24 - scars present)
   Curcs have only so much egg-laying activity programmed into their behavior, and it's directly related to the temperature.  The warmer the post-petal fall period, the quicker they get done, so the warm 7-10 days we have in the long-term forecast could mean that a petal fall plus possibly one additional spray at 1st cover will adequately protect most of the region's orchards until the ovipositing is finished.  We'll keep you posted, but most orchards should definitely receive their petal fall spray this week.  Jim Eve reports finding fresh scars in his trees near Naples, and the NEWA Apple Pest DD Calculator (http://www.nysaes.cornell.edu/ipm/specware/newa/appledd.php) puts curculios somewhere about one-third of the way through their egglaying activity as of last night.  If you additionally have Rosy Apple Aphid colonies active in your trees, consider using Actara or Calypso now, both of which have good activity against both species.

European Apple Sawfly 
   Traditionally confined to the eastern half of the state, but steadily making westward progress in recent years, the adults will be laying eggs on or near newly set fruitlets starting at petal fall, so the plum curculio applications will do double duty against this pest as well.

Obliquebanded Leafroller (June 10)
   We have yet to catch the first obliquebanded leafroller adult in western N.Y., but populations in the Hudson Valley should be something like a week ahead of us, so don't be surprised to begin seeing them this week.  Depending on the location, larvae can be found now in many stages of development, from the relatively small to the pupal stage in some of the more advanced sites.  This would therefore be an advisable time to be sure a pheromone trap is hung in problem apple blocks, to fix the date of first emergence in your specific area.  Recall that we recommend sampling at 600 DD (base 43°F) after the first adult catch, to determine the need and timing for treatment.  For problem orchards with a reliable OBLR history where sampling is generally not needed, egg hatch (which equates to the first occurrence of susceptible larvae) occurs 350 DD (more or less) after the 1st adult catch.  It pays to keep an eye on the daily highs and lows for your area if you are doing your own trapping, as it's likely that our "normal" first sampling date of July 5 won't turn out to be necessarily appropriate this year. In orchards still not too removed from petal fall and containing large larvae, an application of a B.t. product (e.g., Dipel, Deliver) or Intrepid at this time can help diminish the population for better management during the summer.

Stone Fruit Aphids
   Although green peach aphids are not always a serious pest every year, colonies of these greenish, smooth-looking aphids have been noted in Wayne Co. peach blocks, along with their damage.  They cause curled leaves that may turn yellow or red in severe cases, and more importantly, they are vectors of Plum Pox Virus, which still has not been documented in N.Y., fortunately.  The young aphids begin to hatch about the time of peach bloom and remain on the trees for 2-3 generations, until early summer, when they seek other hosts (mainly vegetable truck crops).  Green peach aphids suck the sap from the new fruits and twigs, and are also found on plum, apricot, cherry, and many ornamental shrubs.  These insects are difficult to control; fortunately, Provado has a stone fruit label, and this would be our recommended option, where needed.  Lannate and Thiodan are alternatives, but are possibly less effective.  Applications are recommended before excessive leaf curling occurs, in order to maximize the spray's effectiveness.  Also, keep an eye out for black cherry aphid in your cherry trees after shuck fall.  If colonies are building up on the foliage, recommended materials include Provado, Sevin and Imidan (tart cherries only).

Cherry Fruit Flies (June 16)
   No adults have been reported caught on sticky board traps, but because of the zero tolerance in cherries for insect damage or presence, it's prudent to begin sprays in your cherries now (for this pest as well as for curculio).  Guthion, Imidan (tart cherries only), Sevin, Diazinon or the pyrethroids are all effective treatments.  Sevin and Imidan will also control black cherry aphid.

Lesser Peachtree Borer (May 25)
   A possibly errant first adult was caught on May 15 in Geneva, although no more were seen until today, but the flight always starts right around Memorial Day.  Remember to get your trunk and scaffold sprays on peaches and cherries during the first 10 days of June if borers are a problem in your blocks.  An effective alternative is Isomate-L for pheromone disruption.  Now is still not too late to hang the ties (100-150/acre will disrupt both species -- Peachtree Borer appears about mid-month -- in our region).  This pest increases the severity of Cytospora canker infections in peaches and is often found within the canker; by feeding in the callous tissues, it interferes with the tree's natural defenses against the disease.  Infestations can be determined by the presence of the insect's frass, which resembles sawdust, in the gum exuded from the wound.  In peaches, you can use Lorsban 4E, Thionex, Asana, Ambush, Pounce, Proaxis or Warrior for this application.  In cherries, use Thionex, Asana, Pounce, Ambush, Proaxis, Warrior or Lorsban (tarts only) 75WG or 4E, as a trunk spray ONLY; do not spray the fruit, and observe the proper PHIs for these respective materials.

European Red Mite 
   Mite populations have been slow to build so far this season, but adults have been noted in some orchards, which means that they'll be laying summer eggs that will hatch into potential problems before long.  The pre-bloom period was uncharacteristically favorable for early season oil or miticide applications this year; however, if you failed to take advantage of these opportunities before bloom, it's not too late to use one of the preventive ovicidal materials such as Savey, Apollo, Agri-Mek, or Zeal in problem blocks or where you may have noted ERM eggs.  Also, this year, recall that a new miticide has been registered in NY apples and pears - Kanemite (Arysta) is new chemistry that has both stomach and contact activity against all mite stages, and can also be used in-season to control threshold populations (2 applications permitted per season).

  In situations where European red mite pressure or the crop's sensitivity to them haven't necessarily justified an early season treatment with any of the above options, this is the time of year when a summer oil program also might be considered as an alternate preventive approach, particularly considering this species' slow start during the spring.  Our field research trials have shown the effectiveness of using a highly refined oil in a seasonal program to control mites throughout the summer. Some examples of these products are PureSpray Spray Oil 10E or BioCover UL or PureSpray Green (all from Petro Canada), Stylet-Oil (JMS Flower Farms), and Omni Supreme (an ExxonMobil product formulated using Orchex 796 and distributed in our area by Helena); others are labeled, such as Damoil (Drexel) and Mite-E-Oil (Helena) although we haven't tested all brands.  Note that Sunspray Ultra Fine Spray Oil (Sun Refining & Marketing, Philadelphia) is no longer registered in NYS.

   Our approach is to make three applications, on a preventive schedule, immediately after the petal fall period, before mite populations have a chance to build.  The first application can be any time from petal fall to 1-2 weeks later, followed by two additional sprays at 10-14-day intervals.  The oil is not concentrated in the tank, but rather mixed on the basis of a rate per 100 gallons of finish spray solution; in most cases, we recommend 100 gal per acre.  A rate of 1-2 gal/100 should maintain control of most moderate populations.  Don't apply without leaving at least a 10-14-day interval before or after a captan spray.

San Jose Scale (June 19 - 1st crawlers)
   Minute SJS adult males emerge in the spring from beneath scale covers on the trees, usually during bloom, and mate; 1st catch in Geneva was today.  The females produce live crawlers within 4-6 weeks of mating; these make their way to new sites and insert their mouthparts into the tree, secreting a white waxy covering that eventually darkens to black.  SJS infestations on the bark contribute to an overall decline in tree vigor, growth, and productivity.  Fruit feeding causes distinct red-purple spots that decrease the cosmetic appeal of the fruit.  Insecticidal sprays are most effective when directed against the first generation crawlers, specifically timed for the first and peak crawler activity, which are usually 7-10 days apart. 

In the Geneva area, first crawler emergence has tended to occur sometime around mid-June.  The NEWA Apple Pest DD Calculator predictions are for this to occur in 7-10 days around western NY, which means slightly sooner in the Hudson Valley.  Lorsban used to be the standard recommended treatment for scale, and since it's no longer labeled for summer use, we're fortunate to have Esteem 35WP available, which is quite effective against this pest.  It should be applied at 4-5 oz/acre at first crawler emergence; a low rate (0.25% or 1 qt/100) of a highly refined summer oil (see above) has been shown to improve penetration and, therefore, control.  The remaining OPs such as Guthion and Imidan, as well as Provado, are alternative options.

Oriental Fruit Moth 
   We're calling biofix April 29 to May 3 in western NY.  In problem blocks (i.e., those with a history of more than 1-2% fruit infestation since 2002), the first spray against the first larval brood in apples is recommended at 350-375 DD (base 45°F) from biofix, which corresponds with 50-60% hatch.  The records as of today (courtesy of the NEWA Insect DD Calculator) show the DD accumulations to be: Appleton, 326; Sodus, 345; Williamson, 360; and Albion, 366.  Therefore, this week would be a timely window for such a treatment.  If you're applying petal fall sprays, you should be covered by most materials that are effective against plum curculio.  If you're more than 7-10 days past your PF sprays and need something specific against OFM, Assail, Calypso, Intrepid and Avaunt are recommended options in apples, and Asana or Warrior in peaches.

Pear Psylla 
   These insects have also been slow to start this season, but the warm temperatures will doubtless spur the production of summer nymphs.  Particularly if you weren't able to get an oil spray on before bloom, populations of 1-2 per leaf would be an indication of the need for a prudent application of Agri-Mek at this time; alternatively, Assail, Actara, Calypso, Esteem, Provado, Nexter, Asana and Warrior also have varying degrees of effectiveness against this pest, usually negatively correlated with past history of use.

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Upcoming Pest Events | Trap Catches | Pest Focus | Insects | Diseases | Erratum

   Leaf spots on fruit trees are caused by a wide variety of pathogens and abiotic factors.  Most growers can identify typical leaf lesions caused by apple scab, cedar apple rust, powdery mildew, and cherry leaf spot.  However, when leaves develop small, nondescript brown leaf spots or small shot holes, even experienced plant pathologists often have difficulty identifying the causes. 

   Fortunately, the nondescript leaf spot diseases in the Northeastern United States rarely cause economic losses, even when their appearance temporarily disfigures the tree canopy.  The fungi causing apple leaf spot diseases either do not have secondary cycles on leaves or they are easily controlled with fungicides and appear only when fungicide protection is disrupted by extended spring rain events.  Abiotic leaf spots that develop shortly after petal fall are often attributable to agrichemical mixtures that have caused localized phytotoxicity.

   Following are some of the most common causes of early season leaf spots and clues for determining their causes.  This article focuses on leaf spots that may appear in May, June, and July.  Leaf spots with other causes and symptoms sometimes appear during August and September, but they will not be discussed here.

   Frog-eye leaf spot, caused by Botryosphaeria obtusa, is the stereotypical leaf spot disease on apples.  Frog-eye leaf spots are round, dark brown spots, 2-5 mm in diameter, with an almost black border and a tan center (Fig. 1). 

Fig. 1: Frog-eye leaf spot on Cortland showing typical tan lesions dark brown edges.

Individual leaves may have a single spot or as many as 30 to 50 spots.  Frog-eye can usually be differentiated from other kinds of leaf spots by its non-random distribution and its association with nearby inoculum sources.  In sprayed orchards, frog-eye leaf spots are usually concentrated in the vicinity of mummified fruitlets that were retained after fruit thinning.  Fruitlet mummies can be colonized by B. obtusa and then provide inoculum for infecting the leaves the following season.  Spores are dispersed by splashing rain between tight cluster and about second cover.  Frog-eye is most common on apple cultivars such as Cortland, Northern Spy, and Honeycrisp, that retain many fruitlets after chemical thinning (Fig. 2)

Fig. 2: Severe frog-eye leaf spot on Cortland showing a fruitlet mummy (center of photo) that provided inoculum for infections.

However, all cultivars may retain thinned fruit in years when weather conditions fail to promote rapid abscission of thinned fruitlets.

   Frog-eye leaf spot may cause premature drop of severely affected leaves, but most damage from frog-eye is cosmetic.  The same fungus that causes frog-eye leaf spot also causes black rot fruit decay, but there is no evidence that leaf spots contribute to fruit infection.  Instead, the inoculum for fruit infection comes from the same fruit mummies that provide the inoculum for leaf infection.  Thus, frog-eye on leaves can be viewed as an indicator for conditions that may have favored infection of fruit, but the leaves themselves do not contribute directly to the development of black rot on fruit.  Black rot infections in fruit may remain quiescent until fruit ripen because green fruit contain inhibitors that prevent fungal growth.

   Most fungicides control frog-eye leaf spot, but the SI fungicides (Rubigan, Nova, Procure) and the 3 lb/A rates of mancozeb or Polyram are less effective than captan, Flint, and Sovran.  Severity of leaf spotting around fruitlet mummies may be affected by the fungicide program that was used the previous season because fungicides used after thinning may prevent the fruitlets from becoming infected as they dry out during summer.  However, the relationship between spray programs, colonization of retained fruitlets by B. obtusa, and inoculum levels within trees has not been documented for most of the fungicides currently available.

   Rust-induced leaf spots develop when cedar apple rust and hawthorn rust infections are killed either by subsequent application of SI fungicides (Fig. 3) or by host incompatibility reactions (Fig. 4)

Fig. 3: Rust-induced leaf spot on Ginger Gold leaves where an SI fungicide was applied to incubating rust lesions. Note chlorotic lesions (black arrows) with pinpoint necrosis in centers where rust infections have not yet been invaded by other pathogens.

Fig. 4: Rust-induced leaf spot on an unsprayed rust-resistant selection from the Geneva breeding program. Severely affected leaves are turning yellow and will drop during June.

SI fungicides applied within 96 hr of the start of wetting periods will eliminate rust infections before they can cause visible damage to leaves.  However, if SI fungicides are applied more than 4 days after infection, leaf cells invaded by the rust fungi will die even though the rust fungus is eradicated.  These killed leaf cells result in small 1-2-mm diameter leaf spots that are tan or brown, sometimes with a tiny orange rust fleck in the center of the leaf spot.  Similar lesions can appear on McIntosh, Empire, Liberty, and other rust-resistant cultivars if trees are subjected to high levels of rust inoculum in the absence of fungicide protection.  On the rust-resistant cultivars, fungal development is arrested by the genetic resistance of the host rather than by fungicide activity, but the resulting leaf spots are similar.

   Leaf cells killed by the initial phases of rust infections provide an entry point for other less-pathogenic leaf spot pathogens such as Botryosphaeria, Alternaria, or Phomopsis species.  These fungi invade cells killed or damaged by failed rust infections and then move into adjacent healthy tissue, thereby enlarging the leaf spots until the individual lesions look like frog-eye leaf spots.  Rust-induced leaf spots can be distinguished from frog-eye leaf spots because the former are uniformly distributed throughout tree canopies, whereas the latter are clustered near inoculum sources.  Sometimes the original orange-yellow rust lesion remains visible in the center of rust induced leaf spots, whereas frog-eye leaf spots never have such bright orange centers. 

   Other leaf spots resulting from fungus-fungicide interactions can develop when SI fungicides, strobilurin fungicides (Sovran, Flint, Pristine), or Topsin M are applied to leaves that contain incubating apple scab or mildew lesions.  Scab spots that are arrested during the early part of the incubation period (roughly 5 to 8 days after infection) can produce "ghost lesions." (Fig. 5)

Fig. 5: 'Ghost lesions' of apple scab on a Jerseymac leaf that received at post-infection application of a strobilurin fungicide.

Ghost lesions are indistinct pale spots 2-3 mm in diameter that develop where the scab fungus disrupted normal cell functions before the fungus was inactivated by the fungicide.  The same fungicides applied just before scab lesions become visible can result in rusty, red-brown lesions that exhibit the usual size and shape of normal scab spots. (Fig. 6)

Fig. 6: Fungicide-arrested lesion of apple scab on a Jerseymac leaf that received an SI spray 13 days after infection.

   Post-infection application of the SIs and strobilurins can also cause "burned out" mildew lesions on leaves.  Mildew lesions arrested by fungicides can appear on the upper leaf surface as large chlorotic lesions with indistinct margins, or on the lower leaf surface as more sharply-defined red blotches. (Fig. 7)

Fig. 7: Fungicide-arrested mildew lesion on an apple leaf.

Portions of the leaf compromised by mildew may be more susceptible to subsequent invasion by secondary pathogens that may cause necrotic spots or larger irregular areas of leaf necrosis.

   Alternaria leaf spot appears as brown spots similar in size to frog-eye leaf spots.  Alternaria species can be isolated from leaf spots in many orchards, especially in late summer, but Alternaria leaf spot does not cause economic damage in the northeast.  In most cases, Alternaria is a secondary invader of damaged leaf tissue.  In North Carolina and Virginia, however, a severe form of leaf spotting known as Alternaria blotch spreads rapidly during summer and causes premature defoliation of affected trees.  Delicious is particularly susceptible.  The strain of Alternaria mali that causes defoliation in the southeast may be different from the common Alternaria mali present in northeastern orchards.  None of our fungicides are very effective for preventing Alternaria leaf spot or Alternaria blotch.

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Upcoming Pest Events | Trap Catches | Pest Focus | Insects | Diseases | Erratum

   Julie Carroll brought an error in the Tree Fruit Guidelines to my attention: The herbicides Roundup Original 2K and Roundup WeatherMax are listed in Table 51 (p. 233) under the active ingredient carfentrazone-ethyl.  They are actually glyphosate materials and so should have appeared several lines up in the appropriate a.i. category.

This material is based upon work supported by Smith Lever funds from the Cooperative State Research, Education, and Extension Service, U.S. Department of Agriculture. Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture.

Scaffolds is published weekly from March to September by Cornell University -- NYS Agricultural Experiment Station (Geneva), and Ithaca -- with the assistance of Cornell Cooperative Extension. New York field reports welcomed. Send submissions by 3 p.m. Monday to:

Scaffolds Fruit Journal
Editors: A. Agnello, D. Kain
Dept. of Entomology, NYSAES
P.O. Box 462
Geneva, NY 14456-0462
Phone: 315-787-2341 FAX: 315-787-2326
E-mail: ama4@cornell.edu

Online at <http://www.nysaes.cornell.edu/ent/scaffolds/>