Dear Friends;

Well here we are approaching another spring, which could be upon us quickly if temperatures continue to remain on the mild side. Time to once again begin thinking about spring training, planting new fields, pre-emergence herbicides, delayed dormant sprays, crown borer drenches, and fertilizers. Recent research in blueberries and Kotata blackberries has shed new light on fertilizer practices and timing. Plants do not appear to begin taking up nitrogen fertilizer from the soil until buds have opened and there is some leaf area to exert a tension or suction on the roots. Because of this, we no longer recommend applying nitrogen fertilizer in March, when heavy spring rains can leach it below the root zone prior to plant demand. To assure adequate nitrogen for fruit development, a split application made in April and June would probably be a good approach. Bernadine Strik (OSU Berry Crops Specialist) has recently completeled a 2 year study of nitrogen fertilizer uptake in AY Kotata blackberries which is particularly informative. A report of her work appears below. Although this work has not yet been done in raspberries or other blackberries, it provides some interesting insights into fertilizer uptake and movement in a perennial crop and can provide us all with some good "food for thought."

Nitrogen Management of AY 'Kotata's

We've just completed a two-year study to look at nitrogen uptake, movement and storage in AY 'Kotata' at the NWREC. We used Nitrogen-15 (N15), a stable isotope of nitrogen, because this special "labeled" fertilizer can actually be traced in the plant. We looked at AY production because it allows N to be studied when the crop is primarily in vegetative (off-year) and in reproductive (on-year) growth.

We treated 10-year-old 'Kotata' with N15-depleted ammonium sulfate (50 lb N/a) in Spring, 1997. Whole plants were destructively sampled throughout the growing season, partitioned into their various parts and dry weight, %N and % N15 obtained. In the second year, we only applied non-labeled nitrogen (normal fertilizer) so that storage and redistribution of the fertilizer N applied in 1997 could be measured; through soil testing, we knew that none of the labeled fertilizer applied in 1997 was still present in the soil in 1998. Whole plants were destructively harvested as in 1997. We could not obtain the entire root system.

Off-year plants produced 2-5 times the primocane growth, in dry weight, of on-year plants. Primocane growth occurred throughout the growing season in both off- and on-years, with 45 and 50% of the growth occurring after berry harvest, respectively; we've observed this before in 'Marion'. Note, however, that in red raspberry only 25% of primocane growth has been found to occur after berry harvest. This type of late-season growth appears to affect N uptake and use in trailing blackberry.

Off-year. In the year we applied labeled fertilizer (1997), plants took up N from the fertilizer (Nitrogen Derived From the Fertilizer - NDFF) from late April through at least July (Figure 1). N movement out of primocane leaves to roots was seen at the end of the season. Considering that the leaves were still pretty green in late October, there was probably even more of this "saving" of N before the leaves fall.

When N was applied in the off-year, 30% of the applied N was accounted for by October of 1997, excluding roots. This amounts to 15 lb N/a taken up; this amount was likely higher as we couldn't account for the root system. Very little stored N (from fertilizer applied in 1997) was used by off-year plants (Figure 1).

On-year. When we applied labeled nitrogen in the on-year, 1997, plants took up fertilizer N from April through July (Figure 2). By August, the on-year plants had taken 45% of the applied N, or 22 lb N/a not including the roots (36% of the N in the roots was derived from the fertilizer). The fertilizer N in the fruiting canes greatly decreased from August to October (N content decreased from 6.9 to 1.7 lb N/a), supporting remobilization of N to the roots before it is lost from the plant. This implies that if dying fruiting canes are going to be removed in an every-year production system, it would be best to wait as long as possible to minimize loss of N; of course this is only possible in EY-February trained fields. For AY production, blackberries are cut to the ground in October after an on-year, so the 4.8 lb N/a in the primocanes, primocane leaves, fruiting canes was lost from the plant, and only the amount in the crown and roots (unknown) remained.

Figure 1. Accumulation of new fertilizer N in 1997 and use of stored reserves in 1998 in 'Kotata' blackberry growing in the off-year.

The average yield was 5.8 tons/a. Total N lost in fruit was 28 lb N/a with 30.5% of that new fertilizer N (1997) and 20.2% stored fertilizer N (1998) – we couldn't trace the origin of the rest of the N. In an on-year, stored N (1998) was mainly used for growth of fruiting laterals and fruit; again little went to primocanes (Figure 2).

Figure 2. Accumulation of new fertilizer N in 1997 and use of stored reserves in 1998 in 'Kotata' blackberry growing in the on-year.

In short, what we've found is that 'Kotata' plants took up fertilizer from late April through July. No fertilizer seems to be needed before primocanes emerge. To insure a N supply for uptake in these times, a split N application would be better than a single application if significant losses of N occur between the time of N application and the time of plant N uptake. The amount of N taken up by mature 'Kotata' plants, 15 lb N/a in the off-year and 22 lb N/a in the on-year, not accounting for roots, is considerably less than the OSU recommendations of 50 to 70 lb N/a. It is likely that off-year plants have more root growth and N uptake than on-year plant roots, which grow in competition with fruit. Within the crop, new fertilizer N was used primarily for "new" growth; primocanes in the off-year, and fruiting laterals and primocanes in the on-year. Very little stored N was allocated to the primocanes of the on-year plants. Results of this study suggest the need for fertilizer N in both the on-year, for fruiting lateral and fruit growth, and in the off-year, for new primocane growth. Remobilization of N from dying tissues (primocane leaves in the fall and fruiting canes) occurred. However, movement of N from dying fruiting canes was slow. Cutting off fruiting canes in August could lead to 6.9 lb fertilizer N/a lost compared to 1.7 lb N/a when removing canes in October. Note that other compounds (nutrients, carbohydrates, for example) may be being remobilized also.

We expect that 'Marion' in AY production would respond similarly to 'Kotata' in this experiment. This type of work needs to be done in EY 'Marion', perhaps looking at impacts of later fertilization, and in red raspberry which has a very different growth habit.

Many thanks to the Oregon Raspberry and Blackberry Commission for funding this study.

Pesticide Update

1. Washington and Oregon are requesting a Section 18 (Emergency Exemption Label) for caneberries for both Switch and Elevate this year. Without this Section 18, we only have the use of Captan, Ronilan, Rovral, Ferbam Granuflo for Botrytis control in raspberries, and Captan, Rovral, Or-Cal Ziram, and Ferbam Granuflo for Botrytis control in blackberries. A full label is pending for Switch in caneberries, but no one knows when this will actually happen. We'll keep you informed of the status of the Section 18.
2. Joe will also be requesting another Section 18 label for Brigade.
3. Since so many caneberry growers also have blueberries, I'll take this opportunity to announce that the Section 18 for Indar for control of mummyberry has been granted.

Delayed Dormant Sprays

Blackberries:

• Purple blotch – lime sulfur or fixed copped
• Septoria leaf spot – lime sulfur or fixed copper
• Cane and leaf rust – particularly a concern in Evergreen and Chehalem blackberry where a dormant lime sulfur spray is recommended at the dormant and green tip stage.
• Powdery mildew – particularly of concern in Boysenberry, where a dormant lime sulfur is recommended. Additional Benlate, JMS Stylet Oil, M-Pede, or sulfur (wettable or powder) applications may be necessary during the growing season
• Anthracnose – lime sulfur

Raspberries:

• Yellow rust – delayed dormant lime-sulfur, fixed copper, or Ferbam Granuflo.
• Spur blight – delayed dormant lime sulfur
• Anthracnose – delayed dormant lime sulfur or fixed copper.

I don't think it's possible to overstate the value of a delayed dormant spray in promoting cane health in the trailing blackberries.

Things to do – March

• Apply pre-emergence herbicides
• Drench crowns for crown borers, if necessary with 2 lb ai Diazinon or Guthion (only the Clean Crop label allows for an adequate rate of Guthion).
• Apply Ridomil for root rot control in raspberries, if necessary. The fungus doesn't become active until soil temperatures rise above 45 degrees F. Because Aliette is a foliarly absorbed material, it would not be applied until plants are leafed out.
• Apply delayed dormant sprays. Dormant and delayed dormant lime sulfur sprays are also important for control of red and dry berry mites.
• Complete all training and pruning.