Petal fall is the point when the majority of petals have dropped from the developing fruitlets and commercial beehives have been removed from the orchard. This may be the most critical stage of the season for insect pest management decisions. Pests present now pose a direct threat to the fruit intended for eventual harvest. Orchard sprays include a wide array of selective or broad-spectrum materials, therefore, it is imperative to pay close attention to worker re-entry intervals required for some pesticides.

The plum curculio may have been in the orchard for some time, but now that females are mated, they will be begin to lay eggs in fruit. The damage from this egg laying is a crescent shaped scar on the fruit. Typically, most plum curculio damage will be found first on trees bordering fencerows or woodlots. The orchard owner may be able to direct you to hot spots based on past experience. Obliquebanded leafroller larvae are over a half-inch in length and may move to feed on fruit as well as foliage. Fruit damage appears as surface chewing that may be deep into the flesh. Green fruitworm may also be active at this time, and because the damage is similar, identification of the larva is important. Tarnished plant bug is difficult to monitor because it spends much of its time in the ground cover. Adults move into trees and feed on developing fruit, leaving a distinctive funnel-shaped dimple. Rosy apple aphid colonies are declining by this time, but damage of fruitlets will now be evident as stunted, deformed fruit.

Oriental fruit moth eggs will be hatching in this time and bore into the actively growing terminal, causing terminal flagging. Green apple aphids will be moving to actively growing terminals. Predators such as syrphid fly and lacewing larvae may also be found feeding in aphid colonies. European red mite adults will begin laying eggs, which will appear on the underside of fully expanded leaves. The predator mites may be present and their abundance will be important for making management decisions. It is therefore important to make accurate identification.

Continue to monitor traps for Oriental fruit moth and document weekly counts. Traps and lures may have to be replaced at this time. Continue to monitor traps for codling moth and note the first sustained catch for biofix purposes.

Apple scab and powdery mildew continue to be active and the symptoms are more readily apparent. Fireblight damage will begin to show up as darkened, wilted and oozy strikes on fruit clusters, or brown wilted terminal shoots resembling a shepard’s crook in appearance.

To assess pest populations, you will inspect fruit clusters, terminals and leaf samples. Select a total of 100 fruit clusters, 100 terminal and 100 fully expanded leaves from inside and outside of 10 to 20 trees throughout the block. Inspect each sample and record the total number of each kind of pest and pest damage present.

USDA announced that a referendum will be conducted May 20 to 31 to determine support for proposed amendments to the tart cherry Federal Marketing Order (FMO). Ballots will be mailed by USDA to all known tart cherry growers and processors in the order's production area. USDA has indicated to the CIAB that the amendments approved by the industry will be made effective for this season.

One proposed amendment would lower the production threshold -- the basis for which districts within the production area are subject to volume regulation -- from 15 million pounds to six million pounds.

Other proposed amendments would: make shipments of cherry juice and juice concentrate to certain markets eligible to receive diversion credit; change provisions related to alternate board members serving for absent members at board meetings; make all processed cherries subject to assessments; and eliminate the requirement that different assessment rates be established for different cherry products. Other amendments pertain to allocation of board membership; clarification of order provisions relating to exemption and diversion; release of cherries in the inventory reserve; and the use of crop estimates other than the official USDA crop estimate in developing the board's marketing policy.

The amendments to the order will become effective only if approved by at least two-thirds of those growers voting in the referendum, or by growers producing at least two-thirds of the volume of tart cherries represented in the referendum, and grown during a period set by USDA. To be eligible to vote in the referendum, growers must currently be tart cherry producers, and they must have produced tart cherries in the production area during the period June 1, 2000, through May 31, 2001. In addition, processors of tart cherries who have frozen or canned more than 50 percent of the total volume of cherries would have to vote in favor of the amendments for them to be issued.

Click on date (May 10, 2002) and PDF for Adobe format.

As strawberry rows become green, regular monitoring for pest and beneficial mites is the best way to ensure that pest mite populations don’t reach damaging levels. Although growth of mites is faster during warm years, experience from last spring shows that they can reproduce in plantings during cool conditions. Mites reproduce quickly, with multiple generations each year. Knowing what to look for and how to manage these pests can ensure that mites do not get to a level that can damage leaves and reduce yield. The two main mite pests in Michigan strawberry are the cyclamen mite and the two-spotted spider mite.

Two-spotted spider mite is the most common mite pest of strawberry (and brambles), and is yellowish-white with two dark spots. These mites feed by rasping on the underside of leaf tissue, and their feeding causes bronzing that becomes visible on upper surfaces. Infestations in Michigan strawberries rarely become high enough to warrant the cost of an acaricide treatment, but regular monitoring can help to determine whether populations get to this point.

For a complete sample, examine 60 trifoliates per field taken in a zigzag pattern across the field, and count the number of leaves with mites. The threshold is 25 percent of leaves infested (15 of 60 leaves with mites), but predatory mites can efficiently reduce pest mite growth. Even one predatory mite per ten twospotted spider mites is sufficient to control populations without the need for miticides. Predatory mites are visible on the underside of leaves, usually in association with pest mites, where they can be seen actively searching the leaf surface. Preservation of these natural enemies is the best way to prevent two-spotted mite problems, so if populations build too high, insecticides and miticides should be selected that preserve the predators.

In a recent field trial in Michigan strawberries, a synthetic pyrethroid (Danitol) was shown to quickly kill the pest mites, but because predatory mites were also killed, twospotted mite densities rebounded within two weeks of the application. In contrast, predator mites survived in plots treated with selective miticides that only killed mite eggs and immatures (Savey) or adults (Agri-Mek), and the pest populations did not rebound. This result shows the importance of protecting predators when treating for two-spotted spider mite. Regular monitoring can help determine whether chemical control is necessary and whether predatory mites are present in enough numbers to control pest mites for you. If selective miticides are used, they generally take some time to have their effect, and so application earlier in the population development may help gain control.

Cyclamen mite is a tiny (1/100 inch), tear-drop shaped mite, causing distorted leaves, blossoms and fruit in strawberry from its feeding on young tissues. If symptoms are found, verification that this mite is present is needed before controls should be considered. Infestation is typically found on the youngest tissues in the crown of the plant, but a magnifying lens is needed to see this species. Cyclamen mite is a common pest of greenhouse crops, and can be brought into a farm on infested transplants, so inspection of new plantings is particularly important. If infected plants are found, the area of infestation is usually quite localized and these areas can be targeted. A registered miticide should be applied to infested areas immediately pre-bloom, using high gallonage (400 gallons per acre is recommended) to get residue down into the tightest cracks where cyclamen mites are found. A second application 10 to 14 days later may be warranted to ensure that control is achieved. Waiting until mid-summer will reduce the chance of gaining control of cyclamen mites because of the difficulty gaining penetration of the canopy once it closes in.

Adult two-spotted spider mite has two dark spots

Predatory mite Neoseiulus fallacies is active on leaf surfaces

Striking differences in winter survival of canes were observed in a summer raspberry (cv. Tulameen) fungicide efficacy trial conducted in 2001 in South Lyon, MI. All plots received five fungicide sprays in the summer of 2001 (Table 1). Untreated plots served as a control. All fungicides significantly reduced anthracnose, leaf spot, and spur blight severity in 2001. Abound and BAS 516 (both strobilurins) provided excellent control of cane and foliar diseases as well as fruit rots. These fungicides are not yet labeled for use on raspberries, but may be within the foreseeable future. Captan + Benlate, and Nova also provided good control.

Upon examination on May 8, 2002, most of the canes in the untreated plots displayed dead buds and brown internal discoloration. In contrast, most canes in the fungicide-treated plots showed normal development with two to three leaves per bud. All fungicide treatments were similar, though the Captan and Benlate treatment showed a little higher incidence of canes with dead buds.

A combination of disease and cold injury during the winter or early spring may have contributed to these differences. While it is not clear which disease was primarily involved, spur blight and anthracnose are likely causes. Severe leaf spot could have further weakened the canes and predisposed them to cold injury. These results show that good control of cane diseases can increase the chances of winter survival in summer raspberries. This may be particularly important in raspberries highly susceptible to cane diseases, sensitive to cold injury, or are planted in a cold spot.

Table 1. Efficacy of fungicides against cane and foliar diseases in raspberries, South Lyon, MI, 2001.

^xValues shown are actual means; statistical analysis was performed on log (x)-transformed data.

^yValues shown are actual means; statistical analysis was performed on log (x+1)-transformed data.

^zColumn means followed by the same letter are not significantly different according to Fischer’s protected LSD test (P# 0.05).

Several grape growers have asked about disease control strategies when part of the crop is on primaries that were not killed by frost and part is on secondary buds that began growth after the frost. This creates a problem because you have two populations of buds that will bloom and fruit that will ripen at two different times, one behind the other. Growers who did not suffer a lot of loss will continue to spray as they normally would. Many other growers will be waiting until they see the crop potential of the buds that grow after the frost to decide on a disease control strategy.

This spring's cool, wet weather is ideal for diseases such as black rot, powdery mildew and phomopsis. Most growers will not spray early before they see the crop, so there will be active disease lesions later as the secondary buds open. These later flower clusters will be exposed to fungal spores from both overwintering sites and this year's new infections. If you think you have a marketable crop as the secondary buds open, you need to apply a protectant early. I still believe that the two bloom sprays, pre- and post-bloom, are the most important for controlling fruit rot, but since some fungicides are not labeled for use after bloom, this means that the post bloom spray for the primary flowers is a prebloom spray for the secondary flowers. Do not use a material that is restricted after bloom once flowers have opened in the vineyard. The broad-spectrum materials that we normally use as post bloom sprays make excellent prebloom materials also; they are just more expensive.

So instead of a pair of sprays you may end up using three, so that you can apply a post bloom spray to both groups of bloom the early and the late. The second post bloom spray is important also, and whether or not growers apply it will depend on the size of their crop and how much disease is out. For more susceptible varieties like Niagara and wine grapes, the decisions will be hard to make. Since most growers will be reducing their fungicide applications to a bare minimum, disease pressure will be high.

It is very important that growers assess the crop potential of their vineyards as soon as possible. If you have a marketable crop, an application of a broad-spectrum material early during shoot growth may reduce disease pressure later in the season and help reduce the disease inoculum later in the season when grape diseases can really explode. If you have little or no crop, disease control is not an issue unless you want to reduce the overwintering populations, and this is more a function of weather and growing conditions than fungicide choice early in the season. All grape growers will need to choose their sprays wisely.

Another week of cool weather, with highs in the low 60’s and 50’s with lows in the 40’s slowed plant growth. The weekend was cold and wet resulting in a major infection period for most fruit diseases. Rainfall totals for the week were 2 to 4 inches. Soils are wet with soil temperatures around 50° F. Cool soil temperatures mean that foliar mineral nutrition symptoms are pronounced and growers worry about applying foliar sprays to correct this. These symptoms will go away when the soil temperatures warm up. Cool conditions similar to last week are forecast for next week. There is a chance of showers Thursday and Friday (May 16-17). The weekend is forecast to be cool.

Growers are spraying fungicides trying to maintain coverage between rains. A good rule of thumb is that half of a protectant material will be washed off in half an inch of rain. Systemic materials are usually absorbed quickly and wash off is not a problem if the material has dried and been on for a few hours. These cool, wet conditions are excellent for bacterial diseases caused by Pseudomonas species, such as blister spot in apples, bacterial canker in stone fruit.

In tart cherries, there was another infection period for cherry leaf spot this weekend. It is hard to gauge pollination and fruit set. We should have a better idea as the fruit comes out of the shuck. These cool, wet conditions are excellent for bacterial canker in tart cherries. Growers who did not apply copper before bloom may want to make an application now to reduce the spread of this disease. The same cool, wet conditions that cause bacterial canker also increase copper uptake and phytotoxicity. Avoid over applying copper by repeating treatments. Copper is redistributed on the surface of the plant during rain. A single application can go a long way.

Pears need protection against pear scab. Pear blister mites were found.

Spittlebugs are out in strawberries. Growers need to apply fungicides during bloom to reduce fruit rots.

Cool temperatures have persisted over Southeast Michigan causing little spring growth and also slowing our typical insect and disease activity. There are several new insects that I will report on, but their typical spring emergence has been much lighter than normal. There has been some scattered frost and freeze over the last week. Many areas of Lenawee and Monroe Counties received a large amount of rainfall on Sunday, May 12. Precipitation totals in that area are running around three inches. For folks further north rainfalls ranged from 0.6 to 0.9 inches. Our soils are very wet right now and will require a fair amount of heat and wind to dry them out. Speaking of wind, we’ve had very poor pollinating conditions over the last week. Extremely windy weather on May 9 and 10 resulted in only moderate honeybee flight and activity. Soil temperatures have dropped back a bit to the mid- to high 50’s most days. Cool conditions are forecast to continue over the next week with a chance of rain on Thursday and Friday (May 16-17).

Pear blister mites were found at one pear farm.

Peaches look very good at this time.

In tart cherries, we’ve had several infection periods for cherry leaf spot over the last week. It looks like we have fairly good set on tarts this year.

The sweet cherry crop looks very good at this time. Remember, they are susceptible to plum curculio as we near shuck split time, which will happen within the week. Brown rot is also a concern on both sweet and tart cherries.

In strawberries, I’ve seen a fair amount of black blossoms from frost and freeze injury, which occurred most likely on the morning of April 23. While the flower buds were still in the crown of the plant at that time, it appears that frost protection would have been needed. I can find black blossoms at most strawberry farms that I visited over the last week.

Raspberries are growing fairly slowly this year with leaves fully expanded, however, very little new shoot growth has occurred as of yet. Canby winterkill has been extensive at some farms.

Fall red raspberries are also growing fairly slowly with canes about three to four inches in length.

Blueberries are near bloom for new crop. Mummyberry trumpets are still being found. No mummyberry shoot strikes have been found.

Degree day accumulations are running near to slightly above normal for much of the Grand Rapids region.

We have had three infection periods of apple scab since the last Fruit CAT Alert issue. The first infection started May 6, ended May 7 and was a moderate infection for the Sparta area, but no infection for the Belding area. On May 8, rain moved in again and resulted in light to moderate infections for the areas around Grand Rapids. The most significant infection period so far this season started on May 11 and lasted for nearly 45 hours at temperatures averaging around 44° F. This rain resulted in a heavy infection for most of the area and rainfall totals ranged from 1 inch to 1.4 inches. Spore discharge has been light perhaps due to the very cool wetting periods.

Apple scab lesions can be found in abandoned blocks and are most likely from the April 27 infection period.

Concerning powdery mildew susceptible varieties should have materials added to the tank. This can be especially important now that we are in bloom. The cooler weather doesn’t usually favor mildew, but it has been wet and humid, which could lead to slow mildew infections and spread.

The weather did warm up a bit last week and epiphytic populations of fireblight bacteria started to increase. We had some moderate risk for blossom blight infections with early bloom that was out there and the rains that moved through last week. However, Maryblyt did not issue an infection, just high risk for one. The only blocks that warranted control were those with existing cankers where there might have been a higher level of bacteria present. Some high winds moved through late last week which did trigger a trauma blight situation, but I feel that even this was marginal because of the very cool temperatures.

More Oriental fruit moth have been caught in the Grand Rapids area in apple orchards. Numbers are not unusually high, but I did set a biofix for the district on May 10. Rosey apple aphids can be found on terminals in normal numbers. Obliquebanded leafroller larvae continue to be found in terminals in normal numbers. European red mite egg hatch is just starting to be found. Apple rust mites seem to be building in numbers, but no control needed at this time. No reports of codling moth trap catch. We should start finding it in the next seven to ten days in traps in high-pressure areas. Any mating disruption dispensers for codling moth should go up as soon as possible; sprayable pheromones can wait a little longer.

Plum curculio is starting to cause some egg-laying scars in stone fruits, such as plum.

The weather continues to be unseasonably cold. At the beginning of the week we had hail that struck the area mainly in the southern and central part of the district. Though in some spots the ground was covered with more than an inch of hail, damage to the trees had been insignificant. The week ended with the mild frost event on May 11.

With apples getting into bloom, fireblight is getting more attention. So far, we did not have many days with temperatures at or above 65° F to trigger the multiplication of bacteria and oozing from the margins of the overwintering cankers. Growers need to assess their blocks for fireblight inoculum levels and determine the level of relative danger for the infection taking place. At this point, we are looking into delayed streptomycin application in anticipation of warmer temperatures and reaching the threshold for fireblight infection to take place.

There has been very little insect activity since last week. Our traps have been generally empty. No codling moth catches have been reported as of this time. Spotted tentiform leaf miners are just about the only insect that has been on a rise since last week.

In pears, the threat of fireblight infection is present though the temperatures are still very low for the infection to actually occur.

In many peach blocks, fruit set appears to be questionable though it is really too early to make any crop size assessments and predictions. No sustainable catch of Oriental fruit moth has been reported so we have not had all the parameters for a biofix date yet.

In plums, it is too early to say anything about the fruit set and crop potential yet.

Weather continues to be favorable for disease development in cherries. Very few plum curculios have been trapped.

GDD42 275

GDD50 128

Weather this past week has been very cool, generally windy with precipitation recorded on five of the seven days at the NWMHRS. Conditions for pollination have been very poor.

In apples, the recent rains of Sunday and Monday (May 12 and 13) provided enough wetness and high humidity to result in light to moderate infection period for apple scab, depending on your location. Spotted tentiform leafminers averaged seven per trap. Occasional apple grain aphids can be found.

Sweet cherry crop potential varies greatly by variety and site with Gold generally showing the least freeze damage; pollination conditions poor. Significant freeze damage reported to tart cherry crop last week in Utah. Northwest Michigan tarts are in early bloom. Leaf spot is a concern on sweet cherries and Balaton cherries that have leaves fully expanded. Montmorency does not, at this time, have enough leaf surface unfurled. The recent rains did not result in a leaf spot infection. Adult green fruitworm continue to fly.

Pear psylla nymphs are starting to hatch in pear orchards.

The wet, cool spring has been ideal for slugs. Many homeowners have reported them. Strawberry growers should be regularly scouting for this pest and take control action if necessary.

Northwesterly flow aloft was in full force across the Great Lakes region Tuesday morning (May 14), resulting in unseasonably cool and windy weather conditions. Following a brief respite Wednesday (May 15), this pattern is expected to become even more pronounced late this week into the weekend. Wednesday will be mostly sunny and milder, with high temperatures reaching back into the 60's to near 70 in most areas. By late in the day, however, clouds will be on the increase once again in association with a frontal passage from west to east across the region. Rainfall will be a possibility statewide late Wednesday evening into Thursday. A reinforcing shot of cool air will move across the state by late Thursday and persist into the weekend. Temperatures are expected to fall back to highs in the 50's to low 60's with lows in the 30's and 40's.

With abnormally cold air aloft above the region this weekend, mainly afternoon and early evening showers will be a continuing threat. Some of the precipitation could fall in the form of snow in northern sections of the state. Some moderation in temperature is possible by the middle of next week as an upper air-ridging feature now located across the Great Plains region finally shifts eastward.

The NOAA 6-10 day outlook for May 19-23 calls for below normal temperatures for this period, with near normal precipitation totals. In the 8-14 day period, the upper air shift mentioned above is taken into account, with temperatures moderating back to normal and precipitation increasing to above normal levels.