In this issue
§ Should fertilizer rates be reduced when freezes reduce crop levels?
§ Using your sprinkler system to protect blueberries from freezes
§ Mustang Max insecticide labeled for use in grape and berry crops
§ Section 18 label for Spartan 4L on strawberries
§ Enviro-weather tip: Create shortcut to key reports
§ Regional reports
§ Weather news
We are glad to find that much of
Fruit crops utilize varying amounts of nitrogen (N) and potassium (K) to grow and mature a full crop of fruit. If the fruit crop is lost or reduced by freeze damage, the nutrient needs are also reduced to some degree. Here are some thoughts on fertilizing following frost damage.
The amount of nutrients that accumulate in the fruit of apples, stone fruit, grapes and blueberries is one estimate of how much fertilizer can be reduced if the crop is frosted out (Table 1). The N content of the fruit ranges from 8 lb per acre (blueberries, cherries) to as high as 50 lb per acre (15 ton per acre peach crop). The K contents range from 8 to 80 lb per acre. A good rule of thumb for grapes is that 5 lb K are contained in each ton of fruit. In the event of a total crop failure, fertilizer rates can be reduced by at least these amounts. Since plants obtain only part of their nutrient needs from added fertilizer (the rest from soil reserves), fertilizer rates can be reduced even more in some cases.
|
Table 1. Nitrogen and potassium removed from fruit plantings in
harvested fruit (lb per acre). |
|||
|
Crop |
N |
K |
References |
|
Apples |
18-20 |
30-80 |
1,5,8 |
|
Blueberries |
8 |
8 |
4,6 |
|
Cherries |
8 |
16 |
9 |
|
Grapes |
28 |
30-40 |
2,3 |
|
Peaches |
50 |
80 |
7 |
If the fruit of apples or grapes is lost to frost, N rates can be reduced by 50 percent (on lighter, sandier soils) to 100 percent (heavier, fertile soils) of typical applications. If the entire crop of cherries, peaches or blueberries were lost, N rates can safely be reduced by a third on sandier soils, to as much as a half on heavier soils. Reduce rates proportionately in the case of partial crop failures.
The effect of crop loss on K requirements is difficult to estimate. Fruit are strong sinks for K, so the K demand is clearly reduced when no crop is produced. Frost-damaged plantings on heavier soils likely will not benefit from K additions this year. Plantings on sandy soils with a low K reserve or where tissue analysis has indicated a need for K, may benefit from K, but will require lower rates, perhaps half of the typical application. Applications of K could be discontinued this year where K levels in the soil are moderate to high, and an annual maintenance application of K is typically applied.
References:
1. Batjer, L., B. Rogers, and A. Thompson. 1952. Proc. Amer. Soc. Hort. Sci. 60:1-6.
2. Hanson, E. and G. Howell. 1995. HortScience 30:504-507.
3. Williams, L. and P. Biscay. E. 1991. Amer. J. Enol. Vitic. 42:113-117.
4. Hanson, E., and J. Retamales. 1990. Proc. N. Amer. Blueberry Res. Work. Conf.
5. Haynes, R., and K. Goh. 1980. Plant and Soil 56:445-457.
6. Retamales, J., and E. Hanson. 1989. J. Amer. Soc. Hort. Sci. 114:920-923.
7. Rogers, B., L. Batjer, and H. Billingsley. 1955. Proc. Amer. Soc. Hort. Sci. 66:7-12
8. Van Slyke, L., O. Taylor, and W. Andrews. 1905. NY Agric. Expt. Sta. Bull. 265:205-223.
9. Vang-Petersen, O. 1984 (Danish study).
Blueberry growers can protect against spring freezes by using sprinklers to reduce damage to blueberry flowers. Sprinklers do not protect blueberries in all circumstances. In 2002, many growers used sprinklers to protect their blueberries when they were at swollen bud and the temperatures were forecast to fall to the upper teens. Sprinklers will not protect crops under these extreme conditions. Sprinklers are used near bloom time when the flowers are visible and the lows are forecast to be in the upper to mid 20s. Unless your system is specifically designed to provide a lot of water in a short period of time, it is doubtful that it will protect below 24ºF. (view photo)
The system's irrigation rate and uniformity determine the
freeze protection that sprinkler systems can provide. More water is needed to
protect at lower temperatures and higher wind speeds (see accompanying table).
Most systems in
|
Irrigation rate (inches/hour) to protect buds under different wind
and temperature conditions |
|||
|
Temp (F) |
Wind speed (mph) |
||
|
0-1 |
2-4 |
5-8 |
|
|
27 |
.10 |
.10 |
.14 |
|
26 |
.10 |
.16 |
.30 |
|
24 |
.12 |
.24 |
.50 |
|
22 |
.16 |
.30 |
.60 |
|
18 |
.20 |
.40 |
.70 |
Most systems cannot easily be changed to deliver more water and protect to lower temperatures. Increasing the operating pressure is not advisable because the volume is not increased substantially (increase from 60 psi to 80 psi may provide only 15 percent more water). Higher pressure can also break lines. Higher pressures also generate considerable mist and change the uniformity of application. Larger nozzles can be installed in some systems, but only if the capacity of the mainlines, well and pump can handle the added volume. For example, 9/64-inch nozzles that deliver 0.12 inches water per hour require 60 gallons per minute per acre of blueberries. Switching to 5/32-inch nozzles would deliver 0.15 inches per hour, but require 68 gallons per minute per acre. Even if systems can provide adequate volume to protect from temperatures in the low 20's, breakage from ice accumulation can be considerable.
Blueberry flower buds and flowers become more sensitive to cold as they develop. Swollen but closed buds tolerate 15 and 20ºF. At tight cluster or early pink bud (individual flowers are visible but still tight in bud), injury will occur between 18 and 23ºF. Once flowers have separated from one another but the corollas (petals) are still closed, 22 to 25ºF may be lethal. By the time the corolla is half their full length, they are damaged at 25 to 26ºF. Fully open flowers are killed at 27 ºF. The most sensitive stage is just after the petal fall, when 28ºF may cause damage.
Dr. Mike Mainland from
Another consideration is wind. Don't attempt to frost protect if the combination of wind and temperature will exceed to capacity of your system to protect (see accompanying table). Dr. Mainland suggested studying the weather forecast closely, and hanging colored flagging in the field to indicate wind strength.
When irrigation begins, air temperatures are initially reduced due to evaporative cooling. The amount of cooling depends on the relative humidity. If the air is very dry (dew point 15 to 20ºF), start the irrigation when the air temperature drops to 36ºF. If the relative humidity is high (dew point above 24ºF), start irrigating when air temperature falls to 34ºF.
Stop irrigating when the ice is melting and temperature is rising. Ice breaking free from branches indicates water is forming under the ice and it is likely safe to quit. Normally this is when temperatures are above freezing and rising. Beware of sudden dips in the temperature soon after sunrise.
Some frost avoidance can be gained by keeping the soil surface clean of vegetation, moist and packed. Moist soils have a large capacity to capture and store heat energy during sunny days, and release heat to maintain air temperature during cold nights. Weeds, sod and plant residues insulate the soil from the sun and reduce heat capture. In addition, tall grass and weeds raise the effective ground level. This is important since cold air is heavier than warm air, and settles along the ground and in the lowest areas of fields. If fields are covered with foot tall grass or weeds, flower buds a foot higher in the canopy may be injured during a frosty night. Mowing fields with tall weeds is worthwhile.
Another consideration is that moist soils have a higher heat
capacity than dry soils, and packed soils absorb more heat than recently
cultivated soils. It is not worthwhile to cultivate just before a frost. Some
growers attempt to irrigate during the day prior to predicted frosts in order
to increase the capacity of the soil to absorb heat. This may be of some value
if water is applied early in the day, and there is ample sun to warm the wet
soil. Irrigating late in the day or on cloudy days will not increase soil
temperatures and provide more heat at night. The bottom line is that clean,
moist and packed soil surfaces absorb the most radiant energy during the day,
and protect from frost by releasing this heat during the night.
A new registration announced this week allows use of FMC’s pyrethroid insecticide Mustang Max on grapes and berries. The berry crops listed include blueberries and raspberries, but not strawberries. The label lists a 4 oz per acre rate and a 1 day PHI for grapes and berries, with aerial application allowed. In grapes, this product is labeled for control of leafhoppers. In berry crops, the label lists activity against leafrollers and root weevils.
This label has come before MSU researchers have had a chance
to evaluate performance of Mustang Max in
There is also a new supplemental label designed to allow producers with existing product to use it on the expanded list of crops. Both labels should be available at agrochemical distributors, or can be obtained from the FMC website.
A Section 18 Emergency Exemption has been issued for use of Spartan
4L on strawberries in
Create a shortcut on you desktop to your favorite Enviro-weather report. Here’s an example for users of Internet Explorer. If you are keeping track of apple scab infection periods, go to the apple scab report for your station and right click anywhere on the screen. A menu will pop-up, select “create short” from the menu. The next time you want to access a current apple scab report just open the short cut on you desktop and you will go directly to the report.
Please note that the Section 18 exemptions announced for Argy-Gent and Mycoshield in our April 10, 2007 issue should have been identified as specific exemptions rather than crisis exemptions. The rest of the article content remains the same and is accurate. (view revised article)
For the last two weeks, temperatures were cool with lows near freezing and highs near 40 for the week after the early April freezes and plant development virtually stopped. The last five days have been warm and pleasant with highs climbing into the 80s Sunday (April 22). We accumulated as many GDD (25 base 50) on Sunday as in the previous two weeks. Next week’s forecast is for cool, wet weather. We have had little rain and soils are drying out.
March 1 through April 22 April
1
Location GDD 42 GDD 45 GDD 50 GDD 50
SWMREC 316 246 158 60
Lawton 365 294 199 79
Fennville 273 209 130 50
Insect activity increased with the return of warm conditions. Growth and warmer temperatures make it easy to determine the extent of the injury. It is apparent that damage from the Easter freeze was very variable due to site and variety differences. Apple leaves show significant injury, but stone fruit leaves, which emerge later, show little damage. We will be assessing the injury for some time to come.
Apricots are beginning to leaf out. There is no crop.
Peaches are blooming. A good crop of peaches means that growers need to think about thinning. A few growers are using ropes to blossom thin peaches. Growers are also pruning. Oriental fruit moth pheromone traps should be out. Pheromone disruption of the first generation works better in mature orchards than in young plantings. Sustained flight and egg laying begins at about 250 GDD base 45. Our first flight probably began Saturday 230 GDD at SWMREC, but cooler temperatures may shut down the flight. Pesticide sprays are targeted for 150 to 170 GDD base 45 after Biofix, this timing would be the middle of next week. Tarnished plant bug adults have been seen in trees during warm weather. If we get warm rains growers need to protect against brown rot.
Tart cherries are blooming. It appears that the crop has been reduced by 75 percent. Some of the open flowers have good pistils. Many buds have not moved much since the freeze, indicating they are dead, others are opening, but the flowers are deformed. As the leaves emerge and unfold they become susceptible to cherry leaf spot. Growers with little if any crop may want to use copper as their primary cherry leaf spot material to reduce their fungicide costs and maintain a healthy leaf canopy for as long as possible.
Sweet cherries are at full bloom. Most trees have more bloom higher in the tree, but many of the pistils are dead. Damage seems to be very variety specific. Cultivars on dwarfing rootstocks were more advanced and suffered more damage. There will be good crop of sweet cherries in some orchards and few if any cherries in others. Copper is phytotoxic to sweet cherries and should not be used. If we get warm rains, growers should protect against brown rot.
In plums, European plums are blooming. Oriental plums are in the shuck. Growers should be protecting against black knot and brown rot.
Apples are at pink and open cluster. Early varieties such as Idared and Zestar began to bloom Sunday. Green leaf tissues are growing and showing typical crinkled freeze injury. Most cluster leaves show severe damage. Early varieties were severely affected by the freeze two weeks ago. Later developing varieties suffered much less damage. We can see differences in the growth of individual flowers in damaged clusters. Some growers are applying oil sprays for European red mite control, but we have found few mites or mite eggs. Spotted tentiform leafminers and red-banded leafrollers are flying. There have been no apple scab infections since April 4. With the beginning of bloom, we will be updating our Code-A-Phones with fire blight conditions whenever there is a risk of fire blight in the region. Growers can also check for apple scab and fire blight at the Enviroweather website. http://www.enviroweather.msu.edu/
Pears are blooming and suffered no damage in the freeze.
Blueberry fruit buds are swollen. The crop potential looks good. Damage from two weeks ago is restricted to early varieties that have some brown dead flower buds. Exposed green leaf tissue shows browning at the tips and damaged tissues are more susceptible to mummyberry. Mummyberry mushrooms are out.
In grapes,
Strawberry leaves were singed, but the plants are putting out new leaves and the trusses have emerged from the crown of the plant. White flower buds can be found in many fields.
Fall raspberries are putting up new shoots. Shoots that have emerged before the freeze are singed and damaged. Summer raspberries were also hurt. Advanced shoots were damaged or killed, but new growth is emerging.
Cranberries are beginning to green up on the edges of the beds and buds are beginning to swell.
Growers are pruning and clearing brush and applying early season fungicide sprays.
The next Monday Fruit Update
meeting will be, Monday April 30, 5:00
PM, at the Fruit Acres Farm in
Our “stop and go” season seems to be back in the go mode at the moment. It seems as if we’ve had the kind of spring with two weather extremes: very cold or very warm. With warm temperatures over the weekend, our growth has leapt ahead once again. Our season is running about five days ahead of normal in growth stages and degree day totals.
Over the last two weeks, I’ve had a greater chance to assess the damage from the Easter freeze event. The crops that were most severely damaged included sweet cherry, tart cherry, early plums and possibly strawberries. Even though the flower buds looked very tough last week at this time, it has truly been amazing to see that many appear to be viable. However, I am concerned about some off-color in many of the flower buds that might be an indication of more severe problems down the road. The best I can do at this time is to say that time will tell.
|
|
|||
|
Location (County) |
GDD42 |
GDD45 |
GDD50 |
|
Commerce ( |
281 |
210 |
127 |
|
Emmett (St Clair) |
243 |
179 |
106 |
|
|
280 |
209 |
126 |
|
Lapeer (Lapeer) |
276 |
206 |
125 |
|
|
315 |
241 |
152 |
|
Romeo ( |
279 |
208 |
126 |
Apples have moved
ahead to a point where we are at pink in the south part of the region and tight
cluster to early open cluster from
Pears are at open cluster to popcorn at this time. I saw a few pear psylla flying yesterday morning. They were certainly out in greater numbers in the afternoon due to the warm temperatures.
Peaches are at pink bud for most varieties to first bloom on some of the early flowering types. On good peach sites there is a good crop of peaches this year. However, on other sites there is extensive bud and branch kill from winter injury. This cold event most likely took place in late January or early February.
Sweet cherries are continuing to push along, with most farms at white bud or popcorn to early bloom. Much of the bloom, however, appears to have been damaged from the Easter freeze event. Damage is in the range of 40 to 90 percent.
Tart cherries are at early white bud for the most part, with a 30 to 50 percent crop loss.
Plums are at full bloom for some of our earlier flowering types; however, most are at white bud to first bloom.
Strawberries are showing good leaf growth over the last week. Many of the earliest emerging leaves were burnt from the freeze. I am seeing some odd discoloration in the bud of this year’s crop. This will take some additional time to assess.
Raspberry buds were burned quite severely from the Easter freeze event. Summer fruiting raspberries are beginning to show some regrowth. Fall raspberries are emerging from the soil, most canes that were up prior to the freeze were burned off.
Blueberries are at half-inch green. I am finding some damage in early flowering varieties of blueberries over the last week as they have begun to grow.
Grapes are beginning to show some regrowth at this time, with most being at early bud swell.
Growth over the last two weeks was at a standstill up until the last few days where growth really started again with the 70 plus degree temperatures. Apples are mostly at a tight cluster stage. Sweet cherries are just starting to bloom. Peaches will be blooming soon as well.
At this time, freeze damage to apples doesn't appear
to be extensive, with about 25 percent bud damage being seen. That means that
out of the 6 flower buds in a cluster, one or two or even three are damaged, but
the others are fine. With no further freezes, this will translate into a very
good crop of apples. Damage to sweet cherries is variable depending on site and
variety. We're estimating about 30 to 50 percent of a crop at this time. There
is some damage in the tart cherries in the
Growers are still wrapping up winter pruning of apples and removing brush from blocks. Ground applied fertilizer applications should be starting soon, and foliar applications of boron and zinc could be added to help buds that have cold damage. If you are using EBDC fungicides, you are probably getting enough added zinc and don't need to add any more. Tree planting should start soon.
The only apple scab infection has been the light one that occurred just before the cold weather moved in. Some light rain moved across the area Monday, April 23, but didn't result in an infection period. Some areas did not see any rain at all.
Oriental fruit moth should be flying at anytime. Early aphid species should be found soon. Green fruitworm should be flying soon. Overwintering European red mite eggs are very difficult to find at this time, even in blocks that had some bronzing at the end of last year. Perhaps they were damaged by the winter weather.
Blueberries in
the
Our study on the environmental impact of deicing salt on blueberry fields showed that, despite the implementation of the Ottawa County Road Salt Management Program, we are observing extensive flower bud kill in blueberry fields located alongside US 31 and M-45 highways. Damage estimates showed 100 percent bud kill up to 100 ft away from those heavily salted roads. In secondary roads, damage goes from no damage at all to 30 percent. However, in general, we are seeing less damage than in 2006. This could indicate that there is some progress in limiting the impact of road salt applications.
In the last two weeks we had a variety of weather conditions. From April 11-15, snow and cold temperatures were more suited for the January scene than April. Since than, the temperatures have been on the rise approaching more seasonable values. This has had an impact on vegetation development. Since Saturday and Sunday (April 21-22) when the temperatures were into the 70’s, trees were going through phenophases in a matter of hours.
Apples were in about half-inch green before Saturday and now, they are showing tight cluster.
Pears are in cluster bud with the beginning of flower separation.
Peaches are starting to bloom with less than 5 percent open flowers.
Plums are showing white bud,
Tart cherries are in tight cluster.
Sweet cherries are showing first white.
West
As of Sunday, April 22
|
Location |
GDD42 |
GDD45 |
GDD50 |
Rainfall since 4/1 |
|
Hart |
216 |
162 |
95 |
1.53 |
|
Ludington |
136 |
99 |
94 |
1.73 |
|
Manistee |
205 |
154 |
81 |
1.38 |
Rain on April 18-19
was an apple scab infection event
for Manistee/Bear Lake and Ludington areas.
Trees are approaching
bloom time and with that a prime time for black knot spore discharge and
infections. From now on, fungicides like Captan, Bravo (until shuck split) or
Topsin-M sprays will aid in disease control.
In regards to brown rot or blossom blight on stone fruit, it is
inevitable that a certain percentage of fruit remains on the trees after the
harvest and becomes subject to late-season infections and one of the primary
inoculum sources. All mummies still on the trees will be a source for blossom
blight infections. Meteor and Balaton, being susceptible to European brown rot,
will require a few extra sprays starting at white and through bloom. Sweet cherries are showing white and
will starting to bloom soon if the warm weather continues. Once in bloom, they
will require protection with one of the available materials (Elite, Indar,
Nova, Orbit).
Peaches are in full pink to early bloom. This is the time when we can use one of the copper formulations to control bacterial leaf spot (Xantomonas arboricola pv. pruni). Keep in mind that copper may cause phytotoxicity if the equipment calibration is not proper thus delivering a higher rate of copper that will result in serious damage. Research has shown that Cuprofix, KOCIDE 2000, KOCIDE 101, KOCIDE DF, CHAMP WP, BASICOP etc. may be used in early applications (pink, 5-10% open blossoms) as well as “low-rate” formulations of copper like Tenn-Cop 5E may be used in post bloom sprays. Tenn-Cop 5E may be used as alternate spray for Mycoshield 17W on 7-14 day-interval depending on frequency of precipitation.
GDD42 - 192
GDD50 - 76
The weather was very warm this past weekend with Sunday (April 22) reaching into the 80’s. The temperatures cooled down to more April-like on Monday, and the rest of the week will follow suit.
In tree fruit, the damage in the Northwest still seems a bit too early to call for an overall estimate. At this time, we have reported some damage in tarts and sweets, but it does seem to be spotty throughout the region. If the weather continues to cooperate and we have good pollination conditions, we anticipate a good crop in the region.
Some bud mortality occurred in grapes as a result of the April freeze, but overall the area vineyards did not suffer badly from that weather event. Bud death in winter due to poor cane maturation and powdery mildew infection is significant in some vineyards.
Apple: Early Tight Cluster
Pear:
Sweet Cherry: Hedelfingen: Green Tip: Gold and Napoleon: Bud Burst
Tart Cherry: Montmorency: Green Tip; Balaton: Early Bud Burst
Apricot: 25% Bloom
Grapes: Chardonnay: Scale crack
With this recent wet weather, a few stations in the region have reported low infection levels for apple scab. East Leland, Kewadin, Northport, Benzonia, the NWMHRS areas all had enough moisture and warm temperatures to initiate an apple scab infection period. We have observed low levels of apple rust mites, two-spotted spider mites and green apple aphids in apple.
Bud swell is just underway; most producers have completed pruning and tying. Growers planning on dormant sprays for disease control need to get these applications on soon. No pest insects have been seen to this point, although beneficials such as lady bugs and spiders have been seen in vineyards, and honeybees are collecting sap from pruning cuts.
Following a period of mild temperatures and a resumption of
growing degree day accumulations late last week, cooler temperatures will
return for much of this week as an upper air troughing feature settles in across
the region. Fair and dry weather will dominate across the state on Tuesday
(April 24), with an increase in clouds by late in the day. An area of low
pressure approaching from the west will bring a widespread area of rain to
parts of
Best chances for rain Wednesday will be across southern sections, where some 0.5 to 1.0 inch totals are possible. Rainfall totals will rapidly fall off from south to north across the state, with most of the northern Lower and Upper Peninsulas remaining dry. The upper air troughing feature will lead to a continuing chance for showers Thursday through Saturday, although areal coverage and amounts will remain light at best.
A frontal system will bring the next best chance for
widespread precipitation by Sunday. Daytime temperatures will fall back to the
low 50's north to near 60 south, gradually warming to the 60's to near 70 by
Sunday. Low temperatures will range from near 30 north to the low 40's south,
warming to the 40's to low 50's by Sunday. Medium range forecast guidance
suggests the eventual return of a troughing feature across the western
New