Current DD Accumulations

Apogee Application Actions

Apogee is now registered for use in Massachusetts for fireblight suppression and growth control. Blocks with a history of fireblight or excessive growth are candidates for Apogee application in 2001. Some important points to keep in mind when using Apogee include:

Apogee must be applied before new shoot growth exceeds 3 to 4 inches in length. The petal-fall period (1 to 2 inches shoot growth) is a good time to target your first Apogee application.

Apogee should be applied at 6 ounces per 100 gallons dilute spray. A follow-up application at 4 to 6 ounces may be necessary for season-long growth control—this should be applied just before or as growth resumes following the first application.

Apogee should be used with a surfactant and spray water should be tested for hardness. Hard water should be softened with AMS or a commercial softening agent. Do not apply Apogee with calcium sprays.

Apogee may increase fruit retention—keep this in mind when thinning Apogee-treated block(s). (On the flip side, this may be desirable when poor set is anticipated, and directions for reducing June drop are on the Apogee label.) Also, Apogee and gibberellin-based PGR's such as Provide and Promalin (and Accel) may combine to result in excessive fruit retention. Avoid using Apogee and these products in the same block at the same time.
Apogee should not be used on Empire until an observed fruit russetting issue has been resolved.

For more information on Apogee, see ‘F-127R Apogee—A New Growth Retardant for Apples,' http://www.umass.edu/fruitadvisor/factsheets/factsheets.html.

Growth Control Short Course: Part II

Trunk ringing is a similar but more aggressive growth control technique than scoring. Whereas scoring uses a narrow blade tool (such a linoleum knife) to cut a narrow circle around the apple trunk, ringing uses a more vigorous tool such as a saw blade, chain saw, or a special ringing knife to remove more of the bark and vascular tissue. This results in greater disruption of the flow of nutrients, water, and hormones from root to shoot. Net result: more reduction in growth. But, because ringing is such a disruption to the tree, it should be used sparingly and only in situations when you need to have a dramatic reduction in growth. With less vigorous tools, such as a ‘Wheeler' saw blade, the ringing cut (like scoring) can be a complete circle around the tree. But, with more aggressive cutting tools such as a ringing knife or chain saw, two cuts halfway around the tree spaced a few inches apart, are more appropriate. As with scoring, ringing is best done shortly after bloom when new shoot growth is 4 to 6 inches in length. And ringing cuts are made on the trunk anywhere from ground level to the first set of scaffolds. Either ringing or scoring is a useful growth control technique in years when light fruit set is anticipated, such as when frost has significantly reduced crop potential. See the Growth Control Factsheet.

Don't Like the Weather? Wait a Minute, It'll Change…

Record heat in the 90's last week brought most Massachusetts orchards into a state of early bloom. Who would have thought we'd be in bloom now just a couple short weeks ago when orchards were at green-tip at? Also, the sudden heat brought peaches into bloom at about the same time as apples. Unfortunately, early bloom predisposes us to frost injury, and sure enough, the combination of dry, cold air that spilled in over the weekend resulted in widespread frost Monday (5/8) morning. At the UMass HRC in Belchertown, a low temperature of 27 F (at a lower elevation) was recorded. Significant browning of apple petals was observed by mid-morning. According to a WSU fact sheet,
(http://www.pan.co.wa.us/wsuext/coop/treefrt/applebud.html), at full bloom 10% of apple fruit buds will be killed at a temperature of 28 F. At 25 F., 90% kill would occur. Clearly, the HRC and many Massachusetts orchards fall somewhere between. The amount of frost damage and resultant crop reduction will certainly affect thinning decisions. If the crop is reduced substantially—which is still yet to be determined—it will be a good year to exercise one of the growth control options (scoring, ringing, Apogee) discussed in the latest HF issues. Also, reports from Connecticut indicate that temperatures the morning of May 8 were in the low 20's—unusual, as there were apparently colder than in Massachusetts. Although time will tell, many Connecticut growers are already facing a potentially significant apple crop loss. Stay tuned.

Tarnished Plant Bugs

Through early pink, TPB entry into most orchards was moderate to light, as judged by captures on sticky white rectangle traps and visual observation of tree canopies. During the very warm weather of last Wednesday through Friday, however, there was a noticeable influx in several orchards. A case in point was Prokopy's small orchard in Conway. This orchard was surrounded by sticky clear plexiglas panels, 2 x 2 feet mounted vertically on poles and placed about 6 yards outside of perimeter-row apple trees. These panels were intended to capture incoming plum curculios (see below). Surprisingly, they captured a lot of TPB: about 25 per trap from Wednesday through Friday. Trees were at mid to full pink. This suggests that TPB are perhaps considerably more abundant as well as later in arriving in orchards compared with recent years. Fruit are most susceptible to scarring by TPB when attacked from late pink through a week or so after petal fall. A petal fall spray against plum curculio should help somewhat in preventing further TPB injury, even though some injury may already have occurred.

Leafminers

Only a couple of monitored commercial orchards have shown over-threshold captures of LM adults on sticky red rectangles stapled to tree trunks. We are not convinced, however, that captures on these traps are truly indicative of the threat that LM may pose this year. Again, Prokopy's orchard may be illustrative. That orchard had about 3 miners per leaf at leaf fall last October, nearly 100% being spotted tentiform LM. Through early bloom, captures on vertical red trunk traps have averaged about 0.3 LM per trap and on sticky horizontal red rectangles in the tree canopy about 1 LM per trap. These numbers are far below what we would expect, given the fairly substantial autumn population. Was there high mortality of LM over winter or has adult emergence been delayed well beyond normal, possibly owing to the late snow cover and the very dry weather since snow melt? Time will tell. But in our judgement, this may be a year when LM could surprise us and show up in considerable numbers as sap-feeding miners much later than usual. If true, then treatment may need to be directed against second-generation LM in late June.

Mites

Red mite eggs have hatched but it's still too early to tell the size of hatched populations. Over the next week or two, we'll have a better idea. Given the relatively light numbers of overwintering eggs and the favorable (compared to some other years) conditions for applying oil, we shouldn't be seeing too many first-generation nymphs or adults.

Sawflies

Few adults caught in most monitored orchards. If adults aren't there during bloom, injury won't be a problem. So it appears like a light sawfly year.

Plum Curculio

In one of our unsprayed research blocks, we've already caught nearly 200 PC adults (through May 7) on odor baited traps designed to intercept adults on their way from overwintering sites into orchards. These traps are placed just outside perimeter rows of apple trees. In one commercial-orchard block, we're already averaging about 2 PC per trap for traps placed on perimeter-row apple trees. The big influx came last Tuesday through Friday, on precisely the same dates it came last year.

We now know from our trapping studies that PC immigration is driven by high temperature, whereas our direct observations have shown that PC injury to fruit is driven by decreasing barometric pressure in combination with high humidity or rainfall (especially at night), provided temperature is 60oF or more.

So PC has arrived in Massachusetts orchards--even the latest-maturing ones. If the weather remains unfavorable for injury to fruit, then a perimeter-row spray at petal fall may provide enough protection. If the weather turns toward higher humidity and rainfall, then a whole-orchard spray at petal fall may be advisable.

Fire Blight Is Fickle

The key to managing fire blight, as with most problems, is determining the risk and the cost/benefit of treatment. Making that sort of analysis this year has more variables than a Shuttle launch, but let's try anyway.

First, consider the easy variables: blight history and tree susceptibility. The history of fire blight is very important. In general, if you have had fire blight in the orchard over the past two years, then that is a high-risk situation. Fire blight in orchards around the region the previous year indicates moderate risk. In Washington, the Cougar Blight model (http://www.ncw.wsu.edu/fbmdl98f.htm) uses this sort of criteria alone to determine risk levels. To keep it simple, consider any risk in or near your orchard in the past two years to represent a significant risk.

Tree susceptibility is determined by the cultivar and rootstock, the age, and the amount of new growth. Young trees have relatively more young, new tissue. Many new cultivar and rootstock are very susceptible to fire blight. In addition, young trees can't absorb much damage from fire blight. Last year's epidemic in southwest Michigan hit Gala and Fuji particularly hard. Honeycrisp and Ginger Gold area quite susceptible, as well as the more established Paula Red, Jersey Mac and Jonagold. (See Mark Longstroth's web site for information on last year's Michigan epidemic: http://www.msue.msu.edu/vanburen/fb2000.htm). Also bear in mind that English cider varieties, and some of the older heirloom varieties like Roxbury Russett are highly susceptible to blight. And of course our common pears, Bartlett, Bosc and Clapp's are very susceptible.

Now, consider the more difficult part, the weather. The temperature variable was relatively easy: abnormally hot. That drove the models that predict bacterial populations to say that with bloom, we would have dangerous levels of bacteria around. With bloom and high levels of bacteria, then the only missing element is moisture. Rain was predicted.

Then, the rain variable became difficult. Showers were spotty and not very long. The question everyone had to ask was, did the blossoms get wet? If they did, then everything else was in place so that high-risk blocks had the potential for fire blight. If they didn't, then the potential for blight was low. In any case, streptomycin would have to have been applied within two days of the infection to have any effect. We are beyond that now.

And what has happened since? Well, it got cold, really cold. Frosty cold. If there is any good news about this, it is that that the cold knocked the population of blight bacteria back to virtually ground zero. If it came at the expense of half the crop or more, I'm not sure that we gained anything.

What about Apogee? Apogee controls the shoot blight phase of fire blight (NOT the blossom blight phase) by slowing growth. The problem with deciding whether to use Apogee is that you don't know whether blossoms were infected by the time you need to apply the Apogee. Apogee on trees that have not yet filled in their spaces is problematic, because it stops new growth. On the other hand, if the risk of fire blight is very high, perhaps it makes sense to sacrifice growth and avoid death of the trees. On larger trees, where Apogee might make sense as a growth regulator alone, the call is a lot easier.

Scab Sticks Around

The dry warm weather has meant that there has been scab maturation without any real spore release. Squash mounts from a couple of sets of leaves confirms this thinking. There's a lot of scab inoculum around. As a result, the next wetting period could be a heavy infection period. Prepare accordingly!