Scaffolds Fruit Journal, Cornell University, New York State Agricultural Experiment Station; Art Agnello and Dave Kain, eds.

Insects | Diseases | General Information | Credits


Volume 7, No. 5                                                 April 20, 1998


COMING EVENTS

COMING EVENTS
                                                     43F       50F
Current DD accumulations (Geneva 1/1-4/20):          266       138
                    (Geneva 1997 1/1-4/20):          141        57
                (Geneva "Normal" 1/1-4/20):          145        60

Coming Events:                              Ranges:
Green fruitworm flight peak                       64-255    19-108
Tarnished plant bug adults active                 71-536    34-299
Rosy apple aphid nymphs present                   91-291    45-148
Pear psylla nymphs present                       111-402    55-208
Green apple aphid present                        127-297    54-156
Pear thrips in pear buds                         137-221    54-208
Spotted tentiform leafminer 1st oviposition      141-319    48-154
Obliquebanded leafroller larvae active           149-388    54-201
European red mite egg hatch                      157-358    74-208
Redbanded leafroller 1st flight peak             180-455    65-221
Spotted tentiform leafminer flight peak          180-544    65-275
McIntosh at pink                                 258-356    96-182

Phenologies (Geneva): Apple (McIntosh) - Early Pink
                       (Red Delicious) - Tight Cluster
                      Pear (Bartlett) - Green Cluster
                      Sweet Cherry (Darrow) - Bloom
                      Tart Cherry (Montmorency) - White Bud
                      Peach - Early Bloom
                      Apricot - Petal Fall
                      Plum - White Bud
          (Highland): Apple (McIntosh) - 25% Bloom
                      Pear (Bartlett) - Full Bloom
                      Plum (Stanley) - Petal Fall
                      Peach - Petal Fall
                      Apricot - Petal Fall

TRAP CATCHES (Number/trap/day)
Geneva:   
                                   4/2    4/6   4/13   4/16   4/20
Green Fruitworm                    0.7*   0.6      0      0      0
Spotted Tentiform Leafminer        0.2*     0   10.5    414     96
Redbanded Leafroller               0.2*     0    1.5    8.7    9.6
Oriental fruit moth (apple)          -      0    0.1*   0.3    0.9
Oriental fruit moth (peach)          -      0      0      0      0

Highland (Dick Straub, Peter Jentsch):
                                  3/27   3/30    4/6   4/13   4/20
Pear Psylla (eggs/leaf)            3.0    9.7    5.5    9.3    9.6
Pear Psylla (nymphs/leaf)            -      -      -    0.5*   0.7
Green Fruitworm                      0    3.0*   0.1    1.0    0.4
Spotted Tentiform Leafminer          0    0.1*   0.1    0.1    0.1
                                                            * 1st catch


Insects




BLOOMS WITH BITE

by Jan Nyrop and Dave Kain
Entomology, Geneva

The mite predator Typhlodromus pyri can give biological control of European red mite when the predator is conserved in apple orchards. Experiments have shown that, once established in an orchard, this mite can completely eliminate the need for miticides. While T. pyri is endemic throughout much of western New York, it can take as many as three years in specific orchard blocks for predator numbers to increase to the point where biological control is realized. Moving T. pyri from blocks where they are abundant to sites where more predators are desired (seeding) can speed this process.




Phytoseiid mite after feeding on European red mite

Instances will occur when it is necessary to use pesticides that are toxic to T. pyri to control other orchard pests. To combat the resulting disruptions of mite biological control caused by these pesticide applications, it has been suggested that orchardists establish sites to be used as mite "nurseries". These sites would not be treated with pesticides harmful to T. pyri and would be used as sources of predators that could be moved to orchards where predators are scarce; the practice of transferring them could therefore become an important ingredient of any integrated mite control program.

Transferring T. pyri entails removing wood (and foliage when present) from a source orchard to target trees. There are several timing possibilities, but in recent research trials, we found that bloom appears to be the preferable time to conduct this transfer. It has been noted that predators tend to concentrate in flower buds and the flowers themselves during bloom, most likely to feed on pollen. In our trials, predators were transferred from the source orchard to target trees by attaching five 20-inch-long branches collected from the source orchard to each of twelve recipient Red Delicious trees. Branches were chosen so that they each had approximately seven flower clusters. Transferring predators at bloom resulted in higher numbers of phytoseiids compared with transferring predators at tight cluster or at half-inch green.

Moving as few as 40 predators per tree resulted in substantial increases in predator abundance. Orchardists may not be willing to cut branches with flowers to transfer predators. In such cases, terminal branches cut later in the summer could be used; however, more branches will be required. Using winter prunings or branches cut early in the spring to transfer predators is not the most effective way of accomplishing this goal. While T. pyri overwinter throughout the tree, there are apparently many predators that overwinter on large branches or the trunk itself and that move into the canopy as foliage appears. Use of nurseries in which T. pyri are cultivated, and transfer of branches harboring T. pyri from these nurseries to target sites, should allow biological mite control to be more persistent on a farm-wide scale. The second season after seeding T. pyri and using nondisruptive pesticides in our IPM Demo blocks in western N.Y., predator numbers were at levels of more than 1/leaf by the end of August, and true biological control (that is, no oil or acaricides) of ERM is anticipated this year.


Phytoseiid mites feeding on European red mites

Unlike petroleum oils applied early in the growing season, oils applied during the summer can have an adverse effect on phytoseiid numbers. However, this effect is apparently only significant when high volumes of oil suspension are applied. Our opinion is that oil applied using conventional airblast sprayers will have only a minimal negative effect on phytoseiid numbers. As such, summer oil applications can be recommended as a way to help manage European red mite numbers if predator numbers are insufficient for biological control.



HONEY BEES, RENTAL FEES, AND POLLINATION CONTRACTS

by Nick Calderone
Entomology, Ithaca

Making a decent living in farming demands close attention to costs, and it is only reasonable that a grower will try to find the best price for each of the inputs that go into his or her crop production system. When it comes to honey bees, however, growers usually don't look inside the hives to see what they are buying, and even if they did, most wouldn't know a good hive from a bad hive. Most growers understand the need for quality hives, but don't have the expertise to determine that quality. The result is that the emphasis is usually on unit cost rather than the cost/benefit ratio, and the goal is generally to pay as little as possible. Downward pressure on prices does not always produce the highest quality. Beekeepers, faced with low rental fees, may have little choice but to split colonies so that they have more units to rent. Nobody really comes out a winner.

A lot has changed in the past few years. Most notable is a new system put in place by Cherryfield Foods, Inc., the largest producer of lowbush blueberries in Maine. Cherryfield Foods is a progressive, successful and rapidly growing concern. As new management practices have increased plant and flower density, they have also increased the need for honey bees. One of the reasons for Cherryfield's success is that it has a farm manager who recognized the role honey bees play in determining yield and quality. Cherryfield has adopted a very reasonable policy to ensure a sustainable supply of high quality honey bees for pollination - they pay well! That's right, they aren't shopping the bargain basements, they pay top dollar for the top hives. They take care of the beekeeper, and they take care of the bees. It's all spelled out in a simple contract. The basic points in the contracts are:

That's pretty much all there is. Cherryfield is happy with the results they have gotten, and so are the beekeepers. The contract is based on the carrot and the stick. Beekeepers that provide top quality colonies and make a good living; those that don't, either get up to speed or are weeded out to make room for those who will. Cherryfield ensures a ready supply of the very best colonies because they make it economically possible for the beekeeper to provide them. You can hold the beekeeper to a high standard and, if you pay a reasonable rate, they will be more than happy to do whatever it takes to keep your account. Ask your local county extension educator for sample contracts.

A RESEARCH RESPONSE

by Dick Straub
Entomology, Highland

The recent furor surrounding EPA's implementation of the Food Quality Protection Act has led us all to believe, in the worst-case analysis, that OP's will eventually be unavailable to combat many of our most important apple pests. Obviously, this would be extremely detrimental to our management programs for two pests in particular - plum curculio (PC) and apple maggot (AM). Because no practical non-OP alternatives are currently available for these two pests, we (Straub, Reissig, Nyrop and Agnello) sought and were awarded grants from USDA's Northeast Pesticide Impact Assessment Program, the NYS Apple Research and Development Program, and the NYS Apple Research Association to investigate alternative management strategies. The research will concern three major objectives:

Even though there appears lately to be some modicum of rational thought diffusing into EPA regarding the FQPA, the campaign to either eliminate or greatly curtail OP and carbamate usage will remain. The search for alternatives and alternative management tactics must begin in earnest. The investigators are indebted to ARDP and ARA for their support; and to cooperating apple growers, without whose assistance we could not attempt to satisfy these objectives.


Diseases

BROWN ROT

by Wayne Wilcox
Plant Pathology, Geneva

With many stone fruits in bloom and abundant rain last week, growers already should have applied a blossom blight spray. However, it's not too late for a few brief reminders about brown rot control, for both blossoms and fruit.

WEATHER. Brown rot likes it warm and wet. Ideal temperature is about 70 to 75°F. If inoculum is plentiful, significant infection can occur after only a few hours of wetness at these temps, but as temperatures get lower and/or inoculum gets scarcer, progressively longer periods of wetness are required. We certainly had suitable conditions for blossom blight infections in western and central NY last week.

INOCULUM. In relative order of importance, the main sources of blossom blight inoculum are mummies retained in the tree, mummies on the orchard floor, and nearby wild or abandoned stone fruit trees. On peaches, twig cankers that developed from infected fruits last summer also can be very important. If you had more brown rot than usual last summer, expect to have more inoculum than usual this spring.


FRUIT SPECIES SUSCEPTIBILITY. Apricots and sweet cherries seem to be the most susceptible to blossom blight, sour cherries the least. Peaches and plums are somewhere in the middle. Remember also that the very young fruit (before pit hardening) of all species EXCEPT sour cherries are fairly susceptible to infection during wet weather conditions, and the usual influences of temperature and inoculum pressure should be considered. Sometimes these early infections show up immediately, but often they remain latent until the preharvest period when they suddenly seem to appear from nowhere.

Thus, the first few weeks after petal fall CAN be an important time for protecting young fruitlets. However, many labels make no provision for brown rot control between petal fall and preharvest, although some do allow sprays during this period for control of other diseases (peach scab, cherry leaf spot). Read the labels carefully and treat as needed.

FUNGICIDE CONSIDERATIONS. There are three general categories of fungicides for brown rot control:

  1. Protectants (Captan, Bravo, sulfur). These must be present before a wetting period occurs and need to be reapplied fairly regularly (depending on the material) if they are washed off by rain. Captan is not the best material for blossom blight, but it's often good enough unless disease pressure is very high, and it's cheap. It does have some drawbacks: (a) 4-day reentry period; (b) phytotoxic to some sweet cherry and plum varieisties; (c) new rates established in the early 1990's are not always effective, e.g., the 4 lb/A rate for cherries is inadequate on larger trees, especially sweets which are highly susceptible to brown rot.
  2. Bravo has several positive and negative properties that should be considered: (a) less prone to washoff than captan; (b) more expensive; (c) can't be used beyond shuck split; (d) best material available for control of black knot on sour cherries and plums. If weather is wet at petal fall/shuck split and disease pressure is high, a Bravo spray should provide good residual protection against brown rot infection of young fruitlets and black knot where needed.

  3. Dicarboximides (Rovral and Ronilan). Although once the Cadillac materials for brown rot control, these fungicides are in their golden years. Ronilan has significant label restrictions, and the new Rovral label limits its use to the blossom period only (note that old product may also be used preharvest, according to its label directions). Both provide protectant and limited systemic activity. Significantly, they also interfere with the production of brown rot spores from infected tissues, so they are useful in slowing down the spread of an epidemic. Basically, these have become blossom blight fungicides, and expensive ones at that. It's nice to have alternatives to the SI fungicides for resistance management purposes, but cheaper alternatives (e.g., captan) make more sense unless high disease pressure--like last week for sweet cherries--warrants dicarboximide use.
  4. Sterol inhibitors (Elite, Indar, and Orbit). Elite is labeled only on cherries, peaches, and nectarines: blossom sprays, postbloom through postharvest on cherries (for leaf spot and powdery mildew), and 0-21 days preharvest (0 day PHI). Indar is labeled on apricots, cherries, nectarines, and peaches: blossom sprays, postbloom through postharvest on cherries (leaf spot) or postbloom through harvest on peaches (scab), and 0-21 days preharvest (0 day PHI). Orbit is labeled on apricots, cherries, nectarines, peaches, and plums: blossom sprays, and two preharvest sprays 0-21 days before picking (0 day PHI).

In my trials over the years, all three of these materials have provided excellent control when sprayed fruit have been challenged with brown rot inoculum shortly after the final application. These differences have often been significant; e.g., when sour cherries were inoculated 9 days after the final spray of 1997, disease incidences were: unsprayed = 72%, Elite = 24%, Orbit = 17%, Indar = 1%.

For resistance management purposes, try to use a non-SI during bloom if you're planning on using SI's preharvest. Using SI's during bloom plus preharvest won't burn them out over a season or two, but it all adds up after awhile.

TIMING APPLE FUNGICIDE SPRAYS AROUND BLOOM

by Dave Rosenberger
Plant Pathology, Highland

Timing apple fungicide sprays from the pink bud stage through petal fall is often difficult because of all the factors that need to be considered. Virtually all apple orchards in the state are sprayed with an insecticide at petal fall to control plum curculio, and a fungicide is naturally included in this petal fall spray. The difficulty in timing pre-petal fall fungicides involves forcing the spray interval to "come out right" so that trees are fully protected through bloom but are due for another fungicide spray just as petal fall rolls around. The arrival of petal fall is as unpredictable as the weather, so optimizing fungicide sprays during bloom involves a mix of luck and skill.

SI fungicides (Rubigan, Nova, or Procure) provide a bit more flexibility for timing sprays than do traditional contact fungicides because of the eradicant capabilities of the SI's. Drs. Wilcox and Kovach demonstrated that SI fungicides, when used in combinations with a contact fungicide, will control scab effectively in low-inoculum orchards if the fungicides are applied at tight cluster, pink, petal fall and first cover. This strategy is described on pages 79-80 in the 1998 Pest Management Recommendations for Commercial Tree-Fruit Production. Using this 4-spray program, the back-to-back sprays at petal fall and first cover provide eradicant activity against infections that may have occurred during the latter part of the bloom period when fungicide protection may have been exhausted.

The 4-spray SI fungicide program can only be used in orchards that were virtually scab-free the previous year. Even then, the 4-spray program may be a high-risk strategy in years where the period between pink and petal fall stretches beyond 12 days. In the absence of a short-bloom period, what are the options to consider when fungicide coverage runs out midway through bloom?

The most important consideration in timing fungicides during bloom is ensuring that trees are adequately protected during this period of peak susceptibility. Ascospores are usually still abundant at pink and early bloom stages, and any primary infections that became established early in the season will begin producing conidia during bloom. Fruit and foliage are extremely susceptible. "Stretching" spray timing just a few days so one can reach petal fall can be a costly mistake if trees are left unprotected during critical bloom-time infection periods.


General Information



GOING BY THE NUMBERS?

Moving right along, we offer the following errata:



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:

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Photographs courtesy of New York State Integrated Pest Management Program