Nut Growers Handbook

The following reference guide for hazelnut growers was prepared by Jeff Olsen, OSU Extension Agent. It is intended as a guide for growers throughout the year and is an annual feature of the Nut Growers Society Proceedings. Each year the information is updated to current conditions and practices.

Note: For further information contact your County Extension Agent.

 

Hazelnut Production Calendar

Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec
Pruning X X X
Fertilizing X X
Moss & Lichen X X
Winter Moth X X
Flail X X X X X X
Cultivate X X X X X
Weed Control X X X X
Sucker Control X X X X X
Omnivorous Leaftier X X
Foliar Boron Application X
Aphid Control X X X X
Leafroller Control X X
Obliquebanded Leafroller X X X X
Sun Scald Protection X
Filbertworm X X
Bacterial Blight Control X X
Leaf & Soil Analysis X
Pre-Harvest Care X X
Harvesting X X
Management X X X X X X X X X X X X
Eastern Filbert Blight X X X

Details on the above operations follow in the order listed.

New Plantings

Before planting a new orchard one should give serious consideration to varieties, orchard design, orchard site (soil and slope suitability), pre-plant soil management, etc. Some varieties are much more sensitive to Eastern Filbert Blight (EFB). See Figure 1 for a relative ranking of EFB susceptibility. With new plantings one should consider mixing in a number of pollen compatible varieties with suggestions at the present time leaning towards the new EFB resistance gene pollinzer varieties released by OSU, which are Gamma, York, Felix, Eta and Theta. Here is a list of new varieties with the Gasaway resistance gene and their recommended pollinizers:

Jefferson = 40% Felix, 20% Eta, 40% Theta
Dorris = York, Felix and Yamhill
Yamhill = Dorris, Gamma, Felix and York
Sacajawea = Gamma, York, Lewis, Halls’ Giant, and Yamhill
Wepster = York, Gamma, Yamhill, Felix and OSU 880.027

Figure 1. Relative ranking of hazelnut cultivars to EFB susceptibility based on observational data obtained from Corvallis, OR and Vancouver, WA field plots.

Susceptible Intermediate Resistant Highly
Resistant
  • Daviana
  • Barcelona
  • Tonda di Giffoni
  • Jefferson
  • Ennis
  • Butler
  • Gem
  • Eta
  • TGDL
  • Hall’s Giant
  • Lewis
  • Theta
  • Casina
  • Willamette
  • Clark
  • Gamma
  • Negret
  • Sacajawea
  • Yamhill
  •  Tonda
  • Wepster
  • Romana
  • York
  • Felix

The first few years after planting are important. One must consider training, sunburn protection, rodent damage, managing soil moisture, blight control, etc.

For further detailed information please refer to the hazelnut publications listed at:  http://extension.oregonstate.edu/yamhill/orchards

 

Pruning and Training New Trees

The training of the young hazelnut tree begins by heading the tree at a height of 30 to 36 inches.  This allows the first scaffold branches to develop at a proper height.  Experience has shown that heading the tree higher than the 36 inches tends to make the young tree top heavy and prone to wind whipping.

After the first growing season the process of scaffold selection can begin.  The goal is to select 3 to 5 scaffold branches that are evenly spaced around the tree.  Hopefully you can get some vertical distance between branches.  Avoid selecting two branches that are emerging from the trunk at the same height.  This situation would ultimately make for some weak branches, as they grow older.

After the scaffold branches are selected, it helps to come back the following year and support them by removing any strong competing branches.  Once the scaffolds get a “head start”, they usually do all right.  After the scaffolds have been established, trees are generally left alone.  Excessive pruning of young trees can delay or reduce their early yields.  After the trees are around ten years old or older, they may require more corrective pruning, depending on their vigor and spacing.

 

Pruning Mature Trees

Prior to the widespread presence of Eastern Filbert Blight our OSU recommendation had been to prune hazelnuts on a five-year rotation, one fifth of the orchard each year.  We recommended that you remove about half of the fruiting wood on each tree pruned.  Now growers channel their time and money into EFB blight removal instead of production pruning programs.

Regular pruning helps to reinvigorate that tree for years to come.  The research on pruning showed yield increases with regular pruning.  It was also shown to be a good was to avoid biennial bearing or higher yields alternating with lower yields the next year.  Catkins are a good indication of where the fruiting wood is in a tree.

These recommendations could now be used on hazelnut varieties that are free of EFB infections. Pruning can be simple.  There are only two types of pruning cuts:  1) “heading”, which is cutting a portion of a branch off, and 2) “thinning”, which removes the whole branch.  Heading cuts tend to cause a flush of rank shoot growth below the cut.  Oftentimes this rank re-growth is not productive for a few years.  Too many heading cuts can actually cause less light to get into the tree; it can have a sort of blanketing affect on the outside of the tree.

On the other hand, thinning cuts tend to open the tree up to sunlight penetration, which is necessary for nut set.  Most of the pruning cuts that we do on mature trees should be thinning type cuts.  Make your cut to a lateral branch.  This helps channel the re-growth, and it allows you to make a healthy pruning cut.

A healthy pruning cut is one that does not leave a stub, but does leave the branch collar intact.  The branch collar is that raised area at the base of every branch.  The branch collar contains specialized cells that serve to seal off a pruning wood.  This helps to prevent wood rot fungus from infecting the branch through the pruning wound.

Hazelnuts are very susceptible to wood rot fungus.  And the larger the cut, the more likely the chances are for wood rot infection.  It has been proven recently that paining the pruning wound does not help prevent wood rot fungus.  But, making the pruning cut where it will keep the branch collar intact is the best thing that you can do to prevent wood rot fungus from entering the tree through the pruning wound.

Many mature hazelnut orchards need to be reduced in height.  Orchards that are too overgrown present challenges to thorough spray coverage at the tops of the trees.  They also shade out much of the sides of the trees so that the crop is restricted to the very tops of the tree.  All of the nuts are produced on the top one third of the tree, with the other two thirds being just support scaffolding.  This is not a very efficient tree form.  We would like to recapture that second one third of the tree and make it productive.  The bottom third will always be just support wood on older orchards.

When you face the job of reducing tree height chose a level that you want to bring the tree down to.  In most overgrown orchards you would be cutting off about 10-15 feet in height.  Allow for a range of height, since you are not going to give the tree a “flat top”.  Remember that you are going to cut to lateral branches that are within the range of height that you are aiming to achieve.  They are not likely to be all at the same height.  Your goal in a rotational pruning program is to reduce the fruiting wood by half on the trees that you prune.  By starting with height reduction cuts, you are likely to be very near your goal after making them.

 

Fertilizing

Fertilize mature trees according to leaf analysis and lime the orchard according to a soil test. Leaf tissue analysis should be taken in the month of August. Take leaves from the mid-shoot of current season’s growth. Taken enough random samples to represent the whole orchard, and total at least 50 leaves per sample. A soil test can be taken at any time of the year. But, try to have your results in hand by the fall of the year when lime and potassium can be easily applied when the orchard floor is still firm. Both soil and leaf tissue tests are important tools to calibrate your fertilizer program. The OSU Extension Service offers the EM 8786, “Nutrient Management Guide for Hazelnuts”, which is available free of charge to help growers interpret their leaf and soil test results for hazelnut fertility management.

Normal requirements for a mature tree are 1 1/2 to 2 lb. of actual nitrogen per tree broadcast (depending on tree densities). If the nitrogen is applied in a 1 to 2 foot band under the drip line, you can use 20-30% less nitrogen. Nitrogen fertilizer rate will depend on the age of the orchard. Younger trees obviously need less. Improper fertilizer applications to new trees can kill them. For young trees make sure that the fertilizer is distributed over the ground’s surface rather than depositing in one location. Newly planted trees could benefit from small amounts of controlled release fertilizer, similar to that used when they are grown in pots in a greenhouse.  Most growers apply nitrogen (1/8 lb. per tree) in the second year. The rates can be gradually increased as the trees age. A normal full rate can be applied to a 12-year old tree. Nitrogen should be applied as urea in March, coincident with bud break.

Potassium required may range from 6 to 10 lb. per tree banded at the drip line. While nitrogen is often an annual need for all orchards, potassium is only occasionally applied, based on leaf and soil analysis results. When tests show a need, it can be fall applied since potassium is slower acting and not as mobile in the soil as N.

Trees more than 3 years old may well begin showing a response to boron. Boron, when applied as a soil treatment, is usually applied at a rate of 5 to 7 lb. actual B per acre. Most growers apply boron as a foliar spray at the rate of 1 lb. of actual B per acre, which is discussed in detail later. As a soil application, boron can be toxic when concentrated so it should always be applied broadcast.

Experiments show that liming acid soils will make potassium, nitrogen, and magnesium more available to the trees. A soil pH of 5.6 or less might be limiting. Agricultural or dolomitic lime will work its way slowly into the upper portions of a soil when the surface is under flail management. Dolomitic lime can be used if a magnesium deficiency is present in the orchard.

 

Moss & Lichen

The most serious problem caused by moss and lichens is excessive limb breakage due to heavy snow and ice buildup. Copper and lime sulfur sprays can reduce the amount of moss in the trees. A bordeaux mixture of 12-12-100, or 6lb. of tribasic copper per 100 gal. of water, or 3.5 galllons of lime sulfur (29%) per 100 gal. of water is effective. While it’s suggested to wait until early March to apply these treatments, the treatments can be applied earlier in the winter season. Thorough, saturating rates must be applied to kill the moss or lichen. Once the moss and lichen are killed they will slowly slough off the tree. Consider applying Bordeaux for your first EFB spray, and get double duty by controlling moss and lichen as well.

 

Orchard Floor Management

The flail is used on orchard ground cover beginning in late April or early May. The flail is used to chop the vegetation down to the surface of the soil. The flail helps chop up leaves and small twigs in the spring as well as early drops of blank nuts before the harvest period.

The growth of the vegetation will dictate how often the floor should be flailed; four to six flailings are usually required per season. By using herbicides in the tree row, flailings are only needed on the alleys between tree rows. Extended applications of the herbicide strip can result in flailing being done in one pass and in one direction. This saves time and money for the grower.

Some growers use herbicides to delay or kill growth in the alleys (a term called “chemical mowing”) to reduce the number of times the orchard floor is flailed. The recommended rate of glyphosate to use for chemical mowing the cover crops is 6 to 8 ounces per treated acre. For best results add 1.7 pounds of ammonium sulfate per 10 gallons of spray solution. Flail all growth to within one-fourth inch of the soil to minimize competition for moisture. Flails that are 8 to 9 feet wide and a tractor with at least 40 h.p. are commonly used. It’s sometimes desirable to flail after harvest to mulch leaves and eliminate old crop nuts, which can attract rodents. On steep slopes where erosion is a problem a cover crop would be desirable. This could be flailed to not less than 1 inch in height.

Flailing can encourage certain weed problems among the grass cover. Low growing prostrate perennials like false dandelion survive the flail action. Broadleaf herbicides are helpful in this situation to eliminate those weeds.

 

Cultivation

It is sometimes desirable to cultivate and level in new orchards for one or two years before using the flail. Cultivation in orchards should start as soon as soil is dry enough to work and cultivate only enough to control weeds and never at a depth of more than 4 inches. Prepare a level and compact orchard floor as early as possible to avoid loss of moisture. Roll the orchard floor firmly prior to harvest.

 

Weed Control

Weed control is usually associated with the flailing program where herbicides are banded down the tree row. Chemicals registered for use in hazelnuts fall into general classes. Our pre-emergent materials with residual benefit include simazine,  Karmex, Solicam, Devrinol and Surflan. Those post-emergent examples without residual effect would be: Gramoxone, glyphosate,  Goal, and Rely. Casoron has a combined post emergence with residual effect.

Some pre-emergence and post-emergence materials can be combined to get a knock-down and hold-down effect with one application. Follow directions on materials containers for restrictions (such as new vs. established plantings) and best results. Chemical registrations change, so growers should check for the PNW Weed Management Handbook for the latest recommendations.  The PNW Weed Management Handbook is available online at http://pnwhandbooks.org/weed/.

 

Sucker Control

Hand suckering is a job of the past. Most growers use chemicals for the control of suckers, spraying when the suckers are six to nine inches tall. Most orchards require three to four treatments per year. Gramoxone can be mixed at a rate of 1 quart per 100 gallons and sprayed to wet the foliage. Best results are obtained when sprayed in cloudy weather or late evening. Use only the 2,4-D amine formulations that have a label for sucker control on hazelnuts (Saber or OrchardMaster). Mix 2,4-D at the label rate and use a spreader-sticker. Failure to treat at the proper time may still require that the sucker be cut out. Rely and Aim are also registered for sucker control in hazelnuts.

 

Omnivorous Leaftier

Leaftier larvae hatch from over-wintering eggs in April and May and are carried into orchards by the wind on silken threads. Larvae feed on developing buds, often resulting in destruction of the terminal growth.

This feeding results in malformed trees and a delay in overall tree growth. The key to control is early detection. This may be very difficult since the damage is often already done when the larvae can be seen. Growers might consider a preventive treatment in the first week of May and again two to three weeks after. Insecticides applied when the larvae are very small will protect new plantings.

 

Winter Moth

Winter moths hatch in late winter and the light green larvae feed on buds and leaves. There is only on generation each year. The leaves take on a torn and tattered appearance. Control sprays of Lorsban must be applied early to prevent their damage. Growers often see the damage one-year and then treat for the winter moths in the following late winter.

 

Foliar Boron Application

Several years of plot work have shown that foliar boron will increase hazelnut set as much as 33.5% in orchards with very low boron levels. The best time to apply boron is in mid-May to early June. Since boron is toxic when used in excess, care should be taken not to apply more than 1 lb. actual boron per acre to mature trees. This would translate to 5 lb. of solubor per acre. Boron should not be used on trees less than five years of age.

The amount of water used is not important. Good results have been recorded with solution rates from 20 to 200 gal. per acre. It is not necessary to use a spreader-sticker with solubor sprays.

Boron applied at this rate tends to build up over time. Get a leaf analysis periodically. Hold off on annual boron applications when the leaf analysis shows a boron reading of over 200 ppm. The positive effects of boron are greatest with low-leaf boron levels. Recent work shows that the boron in the buds in the spring is not closely related to August leaf samples.

 

Aphid Control

There are now two species of aphids in hazelnut orchards in the Pacific Northwest.  They are the filbert aphid, Myzocallis coryli; and the more recent arrival, the hazelnut aphid, Corylobium avellanae.  Aphids have been a problem in some years.  Aphids have been a problem in some years. However, the introduction of the filbert aphid parasite, Trioxys pallidus has reduced aphid problems. If natural predators do not keep them under control, insecticides can reduce their numbers. Studies have shown that heavy aphid infestation can reduce crop yield by 8-10%. OSU’s IPM program in hazelnuts calls for aphid sampling to begin April 1. Choose three terminals per tree and count aphids on the newest fully expanded leaf on each terminal. The action threshold for aphids per leaf is as follows: April 20, May 20, June 40, July 40, with an increasing population. Also look for aphid mummies, which are a sign of the presence of Trioxys pallidus activity. If mummies are found and you are near the action threshold, hold off on spraying and sample again in a week.

The OSU Extension Service now has a Hazelnut Pest Management Guide that is updated annually. Obtain a guide for hazelnuts from your Extension Office in regard to materials, rates, and timing.

 

Leafroller Control

Heavy infestations of leafroller may result in yield reductions. Spraying is done in late April or early May to control this pest. Some growers find treatments necessary once every three years to keep the populations in check. Check your orchard for infestation before applying control materials. Check three terminals per tree and three leaf clusters per terminal. Spray for larvae when there is a 20-25% infestation level.

 

Obliquebanded Leafroller

Infestations of this relatively new pest have resulted in nut losses in a limited number of orchards. The tiny larvae feed on developing nuts resulting in stained, misshapen and aborted nuts. There are two generations a year. The first flight of moths occurs in mid-June. Larvae from this hatch are most damaging. A second generation of moths emerges in September. The larvae from this second generation feed briefly and then winter over until spring.

If an orchard has a history of OBLR damage, pheromone traps are suggested to determine the time of sprays. Insecticides should be applied soon after traps catch 40 moths per trap per week at the peak of the adult flight and larval damage is detected on the nut clusters.

 

Sun Scald Protection

Sun scald can be particularly hard on young trees whose tops are not yet large enough to shade the trunk. It generally occurs on the south and southwest sides of the tree in the first three or four years after planting. Use trunk collars or tree paints to protect against sun scald. Use the white water based exterior latex paints diluted 50-70%. If paint is used, be sure to paint to the soil line.

 

FILBERTWORM CONTROL

This is the most serious insect problem of hazelnuts in Oregon. It is an annual problem and in many cases must be sprayed for each year. Traps can be used to help determine if the adults are present, if their numbers are sufficient to cause significant damage and when the population is most active. Notices indicating the beginning of moth activity are sent to growers through the OSU Extension Service. Treatment dates are usually close to July 10 and again about three weeks later. Farm supply dealers will have pheromone (sex attractant) traps available to help monitor male filbertworm moth activity in the orchard. Growers should place pheromone traps in the orchards in early June. The recommended rate is four traps for the first 10 acres and one for each additional four acres. They should be placed in the top 1/3 of the tree canopy. The action threshold is two to three moths in each trap, or when a cumulative total of five moths is collected in any one trap. Thorough application of recommended rates of chemical is usually necessary for control.

 

Blight Control

Common Bacterial Blight

Filbert bacterial blight is a serious disease problem seen mostly in young trees up to six years in age. It has been observed on older trees that are under significant stress.  Copper sprays are recommended for application in late August through September but before fall rains begin. Bordeaux, 6-3-100; Kocide DF at 16-24 lb. per acre, C-O-C-S WDG at 12-16 lb. per acre, or Nu-Cop 50 DF at 16-24 lb. per acre.

Eastern Filbert Blight

Eastern Filbert Blight is a fungus disease caused by Anisogramma anomala. It is spread by the wind. The disease causes small football shaped pustules that line up vertically on infected branches. Spores are spread within and between trees via wind and rain. The initial infection occurs on leaf tissue in the spring. The fungus has a life cycle of two or more years. There is a latent period of 12 to 15 months where no symptoms are detectable in an infected tree.

Current control recommendations encourage vigilant scouting for new infections, removal of infected wood, and applications of protectant fungicides. There are two main scouting times, late summer and winter. Branches that are girdled by the disease will show “flags”, which are branches with dead leaves on them. When an infection is found it should be pruned off at least one to three feet beyond the visible symptoms. The more susceptible varieties like Ennis should favor the three-foot level, while the less susceptible varieties can be pruned about one foot back.

The first fungicide sprays should be applied around bud break in the spring, and repeated every 10 to 14 days. Bud break is defined as that stage when half of the buds show a separation of the leaves out of the buds. Refer to the Pest Management Guide for Hazelnuts in the Willamette Valley, OSU Extension Bulletin EM 8328 for specific rate recommendations and a diagram of bud stages.

 

Pre-Harvest Care

One last flailing just before solid nuts begin to drop in early September will grind up blanks and twigs that have dropped and will put the orchard floor in a proper condition for harvesting. If orchards are clean-cultivated, the final leveling, smoothing, and rolling should be done at this time.

 

HARVESTING

All commercially grown hazelnuts are harvested mechanically. Sweeping is the first process which should clean the tree row with air blast or mechanical fingers and deposit the nuts in a narrow windrow in the center of the row. Sweep only fast enough to keep ahead of the pickup machines. Otherwise, worm castings and moisture hamper harvest.

A harvesting machine follows which lifts and separates the nuts from the leaves, twigs, etc. and deposits them in a tote box or trailer. Some growers use trailers with bottom drops that they open over drop pits. The nuts are conveyed out of the pit and into bulk trucks for delivery to the cleaning and drying plants.

If totes are used, a third person follows on a fork lift tractor to move tote boxes out of the orchard. This type of operation can harvest around 15 acres of orchard per day. Less sophisticated and less expensive equipment is used in smaller orchards or neighbors work together to increase efficiencies.

 

Mangement: A Year-Round Concern

After harvest

Check receipts and expenses for the year to determine advisability of buying equipment and supplies in the same tax year.

Winter

Increase knowledge of the industry and its operation; overhaul equipment; develop changes to be initiated in operation; review operational timetables; plan for correction of any errors made in last year’s operation.

Spring

Make adjustments in your operation as needed; start planning for harvest, marketing, etc.

Summer

Keep on top of cultural practices and finish harvest and market preparations.