Bob Tritten

Recent weather
Our season is still running a full two weeks behind normal in terms of degree day totals. However, our harvest dates for our fruit crops have been and continue to be close to being “right on schedule” compared to normal seasons.

Soils over many parts of eastern Michigan have been dry over the last two weeks; in fact some areas have been dry for the last month to six weeks. As I look across the region, dry soils are currently impacting smaller fruit size on many varieties of apples.

Season weather review
Needless to say, the 2009 growing season has been a wild and wacky one in terms of weather. All season long our degree day totals were behind normal. As I look at our five year averages, it has been the coolest season in recent memory. For degree days base 50, we are running about 300 degree days behind last year’s cool season and over 400 degree days behind the five-year average. The most notable characteristic of this season was the persistent cool morning temperatures.

This cool season impacted many of our pest populations, some with higher populations than normal while others were reduced. Codling moth and Japanese beetle were the most notable fruit pests that were reduced due to this cool growing season. Insect pests that were on the increase due to the cooler season included apple maggot, woolly apple aphid and potato leafhopper just to name a few.

We had a really wet spring, which caused major challenges for apple growers trying to control apple scab. In mid-summer or so, we went into a pattern that was mostly dry. But when I look at the seasonal rainfall averages, we are just about on par with the five-year averages across the region. Most areas had between 18 and 22 inches of rain from March 1 to date.

We had some winter injury, which continued to pose a problem for fruit growers throughout the season. The winter injury caused collapse of some of our more sensitive tree fruit crops, most notably peaches. Cold weather occurred in mid-January, and then again in early February. Many of the MAWN weather stations recorded low temperatures in the -20 to -24°F range. This caused some peaches to collapse shortly after bloom, while other trees continued to collapse all the way through harvest time. This winter damage was least pronounced in the Romeo area, which I thought had gone unscathed. However they started to see this peach tree collapse later than other growers, in mid- to late July. This tree collapse continues today.

In some respects, this past winter injury was similar to a cold weather event and the resulting winter injury in the winter of 1994. For the next few years, peach growers will be removing peach blocks earlier than expected and also do a fair amount of replanting over the next three years to maintain peach production.

Southeast Michigan GDD totals for March 1 to September 21
Location	GDD42	GDD45	GDD50
Commerce (Oakland)	3491	2995	2227
Emmett (St Clair)	3355	2869	2127
Flint (Genesee)	3372	2889	2149
Lapeer (Lapeer)	3366	2884	2146
Petersburg (Monroe)*	3617	3114	2347
Romeo (Macomb)	3505	3009	2244

*Missing data has been estimated from Hudson and Toledo for July 23 – 31, 2009

Looking at apples
Apple harvest is in full swing across the region. We have an excellent crop of apples this season. Growers have finished up, for the most part, picking McIntosh and are picking Gala and a few blocks of Cortlands. The final picking of Honeycrisp also took place over the last few days. Growers are at a point now that they can see that they have a tremendous crop of apples to harvest over the next six weeks. For the most part, harvest labor has been more than adequate this year. The major challenge for apple growers down the road will be lack of bins and cooler space. As indicated earlier, fruit size is a problem in some of the unirrigated blocks across the region, most notably at this time for Gala and Empire.

Major apple pests
Codling moth pressure was the least that I have seen in my 31 seasons in working with apple growers in this region. Population pressure was down right from the start, and continued all the way through the season. In mating disruption blocks, growers were able to dramatically reduce insecticide inputs because mating disruption worked so well. In conventional blocks, it was difficult for many growers to see the rise in trap catch numbers for the first and second generations, again mainly because pest pressure was so low.

Apple maggot populations were very high this season. In nonsprayed and poorly sprayed blocks, I am finding a significant amount of apple maggot infected fruit. Apple maggot emerged a bit ahead of normal; at most farms they were out the first couple days of July. Apple maggot pressure seemed to follow soil moisture supplies. After each rain event, most growers had a good catch of apple maggot, primarily on yellow sticky traps, but also some red balls. At many farms, growers saw trap catch numbers that were very high, even unheard of.

Potato leafhopper populations started to build fairly early in the year, and continued to build throughout the summer. In fact, I continue to see potato leafhoppers flying in many apple blocks. In apples, it caused some severe leaf curling, particularly in new planted trees. It certainly was a good year for potato leafhopper.

Aphid populations were also very high this year, particularly green apple aphids. Aphid populations exploded in early June, and continued to plague many growers much later into the season than they typically do. While we did have good predator populations this year, in many blocks predator populations were not strong enough to completely control green apple aphid populations.

Woolly apple aphid populations were up this year, particularly late in the season. As I am harvesting apple maturity project samples in many blocks of apples, I continue to see woolly apple aphids congregating around the fruit stems and leaf axils. This is a pest problem that many growers will need to contend with next season.

Japanese beetles were another pest problem that was reduced due to the cooler than normal growing season. While the range of Japanese beetle infestation continues to expand across the region, spread seems to be slower this year than in most years. Also populations on individual farms were greatly reduced over most years’ populations.

European red mites and twospotted spider mites flared to above threshold levels in just a few apple blocks this year. For the most part, predators kept them under control.

San Jose scale populations continue to expand around the region. As growers are harvesting fruit, they are finding the red halo damage on apples. Growers need to make note of that damage this year to help control them during the dormant season next spring as well as in the next growing season.

Predator populations were very high this year across most of the region. There was an abundant food supply for them with high aphid populations and other insects as well.

Major apple diseases
Apple scab was a major challenge for fruit growers this spring and early summer. Many fruit growers used more fungicides during primary apple scab season than they had for any previous entire growing season. Many farms had to spray to control apple scab in less than ideal conditions. With our wet soils, it caused many orchards to be torn up and they are still badly rutted. Most growers had an average of 17 wetting events during primary apple scab season, which ended late this season on June 15 with many having eight to 10 infection periods. As I am harvesting apples this fall, I am finding most growers had some apple scab in the region, and there is also a fair amount of late developed pinhead scab that growers will need to contend with next year. In sampling for apple scab which occurred during the 2008 growing season, it was discovered that there is some sterol inhibitor fungicide resistance occurring across the region. Some additional sampling occurred during the 2009 growing season. Look for results of this sampling to be discussed during winter grower meetings.

Powdery mildew was seen earlier than normal in many apple blocks.

Fireblight was not much of a concern during the blossom time, but I did continue to see some fireblight strikes later in the season at several farms. There were just a few farms that had heavy fireblight infections this year.

Nectria twig blight was also seen in many blocks of apples this year. This caused some twigs to be killed. Many growers confused this disease for fireblight.

More tree fruit summaries
Pears had a fairly good crop this year. Pear psylla populations, while present the entire growing season, were much lower than normal. Pear scab was seen in a limited number of blocks late in the season. For some growers it was the first time they had ever seen pear scab.

Peach yield was reduced this season due to tree loss from winter injury. Most growers finished picking peaches the last week of August or the first week of September. Peach size was reduced at farms that were not irrigated and where fruit was not thinned well. As indicated earlier in this report, I continue at this late date to see peach tree collapse due to wood or cambium injury that occurred this past winter. I have made many recommendations to peach growers this season where they had enough injury that entire blocks need to be removed. Peach leaf curl was seen early in the year, and at some farms where growers had never seen it before. Controls for peach leaf curl need to be made this fall and then again early next spring. Peach scab was an issue at several farms this year. Bacterial spot of peaches was particularly bad in most blocks, causing extensive fruit damage and leaf drop. X-disease was an emerging problem this summer.

Sweet cherry harvest began earlier than normal at many farms across the region with a normal crop load at most farms. Some farms experienced brown rot due to extreme moisture conditions in springtime. In many sweet cherry blocks, fruit was not clustered well, some due to a long extended rain during a key pollination period. While cherry leaf spot was not a major problem in bearing plantings of cherries, it was particularly severe in many younger plantings which were not sprayed as often. I saw several blocks of young sweet cherries that had no foliage left in mid-August or so. These trees are prone to winter injury. While cherry fruit fly trap catch numbers were very high at some farms, most growers did not see any damage this year. I also recommended that many growers apply a post-harvest insecticide application to control late season cherry fruit fly.

Tart cherry yield was slightly below normal across the region. Some of the same pest problems and poor pollination conditions existed for tart cherries as I described for sweet cherries.

Plum harvest has wrapped up across the region early last week. Most farms had a fairly good crop of plums.

Small fruit
Strawberry yields were fairly good as I look across the region. The season started late at most farms, primarily due to cold morning temperatures. Growers reported that they needed to close many times throughout the season to allow more fruit to ripen. Potato leafhopper was a troublesome pest in strawberries this year, particularly for newly planted fields, and then for bearing fields after renovation. These unusual high populations of potato leafhopper continue to plague many growers until well into September. It is difficult at this time to tell if these high populations will be an issue in setting a crop of buds for next year. Late in the season powdery mildew infected many newly planted strawberries. Powdery mildew also causes some leaf curling, which was a bit confusing for many growers who felt like the problem was primarily caused by potato leafhopper.

Raspberry harvest continues for fall red raspberries. Most growers are having an excellent crop this fall. Again due to cool morning temperatures many fall red raspberry growers are commenting that they have had to close for a few days to allow fruit to ripen. Japanese beetle was not much of a pest problem in raspberries this year. Summer red raspberry yield was reduced this year due to some drought stress midway through the season at many farms. Potato leafhopper was a problem on fall red raspberries at many farms.

Blueberry yield was normal to above normal at most farms across the region. The season was a bit slow to get started, but once we had more heating during blueberry season it seemed as if it pushed the crop along fairly well. Due to drought conditions, many blueberry farms reported that their late season yields were disappointing, primarily due to small berry size.