Upcoming Pest Events | Phenologies | Entomology | Horticulture

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Upcoming Pest Events | Phenologies | Entomology | Horticulture

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Upcoming Pest Events | Phenologies | Entomology | Horticulture

   Now that we've had a few days of summer to compensate for last week's deep winter reprise, maybe we can get down to business and actually have a bit of spring.  Tree (and insect) development is not quite to where it should normally be by now, but some semblance of typical pest progression should prevail for the next weeks, so the following checklist of prebloom arthropod activity might be kept in mind as you set up your management duties.  In all these cases, remember to practice responsible pesticide use in consideration of any bees being rented, used or otherwise relied upon during the pollination season.

   Mites: Oil applications should go on before we reach pink in apples or white bud in pears, and as there's not much freezing weather in the extended forecast, any calm period of sufficient duration would be a suitable spray window.  Start with 1.5-2.0% at first, and reduce to 1.0-1.5% as the trees reach tight/green cluster.  Also, don't forget the usefulness of this tactic in stone fruit plantings (cherry, peach and plum) with a history of ERM.  In apples, Savey and Apollo can be delayed until pink, and if everything else runs away with your time and a miticide application before bloom is impossible, consider Agri-Mek or Zeal at petal fall in problem blocks.  Besides saving some time during the hectic prebloom period, this is also a sensible rotation program for purposes of resistance management.

   Rosy Apple Aphid: In particularly susceptible varieties (Cortland, Ida Red, Golden Delicious, R.I. Greening), a material such as Lorsban or Supracide can provide effective prevention through tight cluster, and will pick up any San Jose scale at the same time.  Actara is also a good prebloom fit for rosy apple aphid and other pests besides, including leafminers and early plum curculio.  You'll also get some incidental rosy control if you're using Esteem for scale at this time.

   San Jose Scale: Besides the Lorsban and Supracide noted above, delayed dormant oil applications will do a good job of reducing scale populations.  If you're not treating for rosies but are concerned that SJS might be increasing in some blocks, Esteem is an insect growth regulator with good activity on scale.  The label calls for it to be mixed with oil, so if you're applying oil for mites anyway, this might be a tactic to try in severe cases.

   Dogwood Borer/American Plum Borer: A coarse spray of Lorsban directed at trunk burr knots between half-inch green and petal fall is the most effective tactic against both species, which can be a problem in dwarf plantings.

   Pear Midge: The first adults generally appear when Bartletts and Clapps are in the swollen bud to tight cluster bud stage, but no successful egg-laying occurs until the flower buds are a little more developed.  In pear blocks with a history of midge infestation, concentrate on those portions of the orchard most protected from the wind by trees, high ground, or buildings, as the midges tend to be most numerous in these spots.  Organophosphates like Guthion are the most effective materials; 2 sprays are recommended, one between swollen bud and first separation of the sepals, and another 7 days later (or at white bud, whichever comes first).

   Pear Psylla: If you're just starting on your oil sprays, one application at 2% or two at 1% until white bud should provide adequate protection against egg deposition until an insecticide spray might be elected.  Actara, Assail, Calypso and Esteem at white bud or after petal fall have all shown good activity in suppressing psylla numbers.  Agri-Mek used shortly after petal fall has given good control if applied correctly (well-timed, adequate coverage, combined with an oil adjuvant), and split applications of Nexter or Provado, also starting soon after petal fall, will help keep nymph numbers down through the early summer.

   Oriental Fruit Moth: The first adults could start flying during the next two weeks, depending on how much of a warming trend we get, but we don't necessarily recommend pheromone disruption against this brood in peaches or apples, as your plum curculio sprays will serve double duty against OFM as well.  However, be prepared to start these at petal fall even in peaches, as shuck split will be too late to get the first egg-laying moths.

   Black Cherry Aphid: In (sweet especially) cherry plantings with a history of infestation by this pest, which curls and stunts leaves, a prebloom inspection for these shiny black metallic insects can warrant an application of Thionex or a pyrethroid (Warrior or Asana).

   Tarnished Plant Bug: Early season feeding by overwintered adults in peaches can damage flower buds and cause bleeding of sap from twigs and shoots.  If you note several bleeding sites per tree, a pink application of a pyrethroid can offer some control.  In apricots, you have a choice of either Asana or Warrior.

Upcoming Pest Events | Phenologies | Entomology | Horticulture

   Planting trees should begin in earnest early this week, with the perfect weather and soils having had sufficient time to dry out.  Last week we talked about tree quality – a very important component in starting a new orchard.  Now that we have the site properly prepared and have obtained the right tree and variety, have chosen the planting system and spacing, we need to think about the actual planting procedures.

   The goal is to have the tree grow rapidly enough to exactly fill the allotted space and begin to fruit as soon as possible without limiting tree growth.  If the variety, rootstock, and spacing are chosen properly, yield should reach maximum potential within 4–5 years with minimal pruning and tree training.  To accomplish this we need to achieve moderate tree vigor.  Experienced horticulturists instinctively know what this level of vigor is!  Extension growth between 12–24 inches is usually acceptable in the early years, and eight to 15 inches as trees mature and start to carry a crop.

   Vigor is more easily controlled when fully feathered trees are planted, especially when minimally pruned, since the root system is insufficient to provide all the nutrients and water that the developing tops require.  And excess vigor is controlled in later years by early cropping.

Fig. 1. Planting fully feathered trees helps manage tree vigor

   Planting un-feathered whips requires additional management, and spacing and tree vigor need to be considered more carefully.  Since the root system is in better balance on these trees, it can provide luxury water and nutrients to the rapidly developing shoot growth.  In the second leaf, the root system can fully support the top and there is no crop to help control the tree's vigor, resulting in vigorous growth.  Not until the third leaf will crop begin to help control tree vigor.  Generally, whips are more vigorous and more likely to cause crowding problems in high-density orchards.

   Varying planting depth is a well-known method for controlling vigor.  The rule of thumb is that the more rootstock that is exposed above the ground level, the weaker the tree growth.

Fig. 2. Plant trees so that 4 to 8 inches of the rootstock are above ground level.  The more of the rootstock shank that is exposed, the less vigorous the tree will be.

It has been a common practice to plant trees with graft unions high above the ground level on vigorous varieties or systems with very high densities and tight spacings.  In fact, in Europe in the Super Spindle planting systems, trees were commonly placed on the soil surface and soil mounded up over the roots, rather than being planted.

   Hrotko (2004) showed that after 10 years of M.26 rootstock having 8 inches of rootstock exposed above the ground, canopy volume was reduced 60% and trunk size 50%.  With 4 inches exposed, canopy volume was reduced 30% and trunk size 35%.  Similar results were obtained with other rootstocks.

         Scion rooting has been a very common problem when the graft unions were planted very close to or below ground level.  It has resulted in very large trees, lack of precocity, and poor fruit quality of not only the affected tree but those surrounding it.  Be sure to always adjust graft unions after planting to prevent scion rooting.

Reference cited
K. Hrotko and L. Magyar. 2004. Effect of Depth of Planting/Budding Height and Solar Radiation Exposure of M.26, MM.106 Rootstocks and B.9/MM.111 Interstems on the Growth and Yield of 'Idared' Apple Trees. Proc 1st ISHS Rootstocks for Deciduous Fruit.  Acta Hort 658: 69-73.

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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
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