May 20, 2008

In this issue

Tree fruit news

§ Dealing with frost and fruit crops

§ Winter injury in sweet cherry

§ Optimizing insecticide sprays for plum curculio

§ TNRC trapline data: Oriental fruit moth

Small fruit news

§ Timing cranberry fruitworm sprays in blueberry

§ Topsin M Section 18 request for blueberries denied by EPA

§ Manipulating blueberries with Gibberellin

§ Small fruit meeting

Other news

§ Emergency Ag Relief Act

§ Regional reports

§ Weather news

Dealing with frost and fruit crops

With the recent cool weather and frost conditions, growers are concerned about frost damage to their crops. In 2002, the MSU Fruit Area of Expertise team and the Fruit CAT Alert published two special issues about frost at http://www.ipm.msu.edu/fruitfrost02.htm.

Winter injury in sweet cherry

Nikki Rothwell, District horticulturist and Greg Lang, Horticulture

Winter damage has been observed in sweet cherries in the northwest as well as other regions of the state. Growers first noticed this damage because trees had no bloom. The trees look brownish and relatively bare compared to those with a true full bloom. The branches are covered with large reddish buds that feel empty to the touch (Photo 1). When these oversized buds open, there is nothing inside the buds, giving the damaged trees a brown appearance with few visible blossoms (Photo 2). This damage is likely due January 2008 weather when we had temperatures ranges from the mid-40s to single digits in a 12-hour time period. We believe that the injury showing up now in sweet orchards is a result of this mid-winter damage.

The next question is how to manage damaged trees this season to maximize tree health for the future. To begin, growers should assess the level of damage, as this measurement will guide their management decisions for the 2008 season. If growers do indeed have no bloom, a minimal pesticide spray program would save money and time. Sprays for cherry leaf spot are still warranted to maintain healthy leaves for photosynthesis throughout the season. However, with no fruit on the trees, growers will not need to spray for fruit-infesting insects such as plum curculio and cherry fruit fly. Additionally, American brown rot sprays can be limited as there will be no fruit for the Monilinia pathogen to infect. The dilemma is that most orchards are not likely to have a total loss of fruit. Therefore, if a small amount of fruit is present, insecticide and fungicide sprays are still warranted as pest infestation and fungal infection this season can lead to higher insect populations and increased fungal inoculum for 2009. Another potential problem is that certain varieties appear to have been hit harder than others (i.e., Schmidt), and in mixed blocks, growers would have to apply a standard spray program for only the undamaged cultivars in the block; limiting treatment for damaged cultivars may not prove cost and time effective.

Fertilizer recommendations will not vary greatly between orchards with and without damage. However, if nitrogen (N) applications have not yet been made this season, growers could reduce the N at this time. Trees will need some N to for growth, but with no fruit (which contribute greatly to N demand during the growing season) there will be more available N for tree growth. In short, the N that would have been used in fruit growth will go into tree growth. If blocks have no crop, growers could reduce N by 30 to 40 percent. Partial crops should receive the same N level as a full crop. If the crop is extremely light, growers could reduce N a small amount (approximately 10 percent).

In terms of pruning strategies for trees with winter damage observed this spring, no special techniques are required. Vegetative buds will likely have stronger growth because both overwintering reserves and new carbohydrates from current season photosynthesis that would have gone to early fruit formation and development will be used by the vegetative growing points. Stronger vegetative growth often occurs when trees suffer from winter damage compared to spring frost damage. Often only the floral ovary is killed by frost, and the otherwise undamaged flowers still use reserves for the bloom period even if the rudimentary fruit ultimately aborts.

Lastly, trees with few blossoms this year will have strong return bloom in 2009. Trees with few fruits and strong vegetative growth will lead to increased flower production the following year. Growers may want to prune a bit harder in dormancy to prevent overcropping, especially on varieties that have a tendency to set heavy crops (i.e., Ulster or Napoleon) or for cherries that will be used for the fresh market, since the proportion of small-sized fruit increases with heavy croploads.

Optimizing insecticide sprays for plum curculio

John Wise, Nikki Rothwell, David Epstein, Larry Gut and Mark Whalon, Entomology

The plum curculio (PC) is an important early season pest on pome and stone fruits. There is an array of insecticides available for control of the PC, but their performance characteristics vary greatly compared to our traditional broad-spectrum chemistries. These conventional insecticides, such as organophosphates and pyrethroids, work primarily as lethal contact poisons on PC adults in the tree canopy. Avaunt, a newly registered insecticide on cherry, as well as pome fruits, also works primarily by lethal activity, but ingestion is the important means for delivering the poison. Neonicotinoids are highly lethal to PC for the first several days after application, but as these systemic compounds move into plant tissue, they protect fruit from PC injury via their oviposition (egg-laying) deterrence and anti-feedant modes of activity. Neonicotinoids and OP’s can also be used as rescue treatments because they have a curative action that can kill eggs and larvae that are already present in the fruit. For organic growers, Surround WP can reduce PC injury to fruit if applied to attain a heavy coating on the tree canopy; this kaolin clay product works as a PC repellent. The following table is designed to summarize several key variables that can help growers determine how to optimize the performance of various insecticides for integrated pest management (IPM) programs.

Table 1. Insecticidal modes of activity on plum curculio life stages.

Compound trade name	Chemical class	Activity on adult PC	Activity on PC larvae or eggs in fruit
Guthion, Imidan	Organophosphates	Lethal via contact	curative
Asana, Warrior, Danitol, Baythroid	Pyrethroids	Lethal via contact, Repellent	none
Avaunt	Oxadiazine	Lethal via ingestion	minimal curative on larvae in cherries
Actara, Assail, Calypso	Neonicotinoids	Lethal, Oviposition deterrent, Antifeedant	curative
Surround	Particle film	Repellent	none

Optimal timing and order selection of insecticides for PC management is based on matching the performance characteristics of each chemistry (Table 1) with PC life-cycle development and tree phenology (Table 2). Because organophosphates and pyrethroid insecticides are contact poisons, they can be used as early as petal fall to knock beetles out of the tree canopy. However, we do caution the use of pyrethroids to as they are toxic to mite predators. Because PC adults are feeding on tree parts during bloom and petal fall, we recommend Avaunt be used at this petal fall timing. The performance of neonicotinoids is optimized when sprays are made after fruit set (pome fruits) or suck-split (stone fruits), so that fruit and foliage are both covered. Surround will not work unless tree is completely covered, so multiple sprays are needed on the tree prior to PC oviposition activity. If PC infestation occurs and a rescue treatment is needed, organophosphates and neonicotinoids can provide curative action up to two weeks after PC infestation, although in some cases dead cadavers can still be found in fruit (Figure 1). Please make sure to read the footnotes in Table 2 to help with the proper order of insecticides.

Table 2. Labeled control materials for plum curculio

Compounds²	Crop	Rate	Crop Stage and Initial Control Timing (DD₅₀)
Guthion 50W	Pome fruit Cherries	2 lb 2 lb	Petal fall (approx. 250 DD) Petal fall (approx. 175 DD)
Imidan 70W	Pome fruit Stone fruit	3 lb 2½ lb	Petal fall (approx. 250 DD) Petal fall (approx. 175 DD)
Actara 25WG	Pome fruit Stone fruit	4½ oz 4½ oz	Petal fall + 3-5 days (approx. 300 DD) Shuck-off (approx. 250 DD)
Calypso 480SC	Pome fruit	4 oz	Petal fall + 3-5 days (approx. 300 DD)
Assail 30SG	Pome fruit Stone fruit	8 oz	Petal fall + 3-5 days (approx. 300 DD) Shuck-off (approx. 250 DD)
Clutch 50WDG	Pome fruit	3 oz	Petal fall + 3-5 days (approx. 300 DD)
Avaunt 30WG	Pome fruit ¹ Stone fruit ¹	5 oz	Petal fall (approx. 250 DD) Petal fall (approx. 175 DD)
Surround WP (Not Recommended For Cherries)	Pome & Stone Fruits	Usually 16 lb by First Cover	Multiple applications starting before bloom to achieve complete coverage
Pyrethroids	Pome fruit Stone fruit	- -	Petal fall (approx. 250 DD) Petal fall (approx. 175 DD)
Rimon (targeting codling moth)	Pome fruits	20-40 oz/ acre	200-250 DD

¹Avaunt should be used first when in a program combination with a neonicotinoid. Avaunt’s lethal activity on PC is enhanced with adult injestion. Neonicotinoids are antifeedants, which if applied first may reduce Avaunt’s primary mode of activity.

²For a complete list of insecticides registered and/or recommended for PC control, see the 2008 MSU Fruit Management Guide (MSUE bulletin E-154).

Timing cranberry fruitworm sprays in blueberry

Rufus Isaacs, Carlos Garcia-Salaza, and John Wise, Entomology

Cranberry fruitworm is one of the key insect pests of blueberry in Michigan, infesting the crop during and after bloom. Moths usually start flying during bloom, and this year is no exception. The first male moths have been trapped in the past few days in southern Van Buren County, coinciding with peak Jersey flowering.

Egglaying by this species often begins as soon as petals have fallen off young fruit. Larvae hatching from the eggs bore into the berries and feed inside, eventually webbing multiple fruit together. The aim of managing this pest is to minimize the number of larvae that bore into the fruit, but timing sprays for fruitworms has been challenging in some years. Recent research by MSU entomologists provides insight into when to protect berries from fruitworm infestation, using degree days to understand the stage of development of this pest. Using degree days to refine your spray timings is expected to improve the effectiveness of your insect management program. Implementing degree-day based management for cranberry fruitworm requires the following:

A) Monitoring traps to detect size and timing of moth activity.

B) A method to track insect development.

Monitoring traps

We recommend the sturdy large plastic delta trap to monitor for fruitworms, because these withstand rain and keep irrigation intact, plus they can be used for multiple years. Place 1-2 traps per field near historical fruitworm hot spots or near deciduous woods. Place the trap baited with a lure containing the fruitworm sex pheromone in the top third of the bush. Traps should be in place by the start of ‘Bluecrop’ bloom, and checked twice each week until moths are trapped. Regular checking will allow you to detect the first sustained catch of moths (biofix), the peak of moth activity, and how long moths are active. The first sustained catch, or biofix, is set when one or more moths are trapped in consecutive trap visits. This is the start point for counting degree days to time the first spray for cranberry fruitworm.

Degree-day based development of cranberry fruitworm

Over the past four years, we have carefully monitored cranberry fruitworm development in west Michigan blueberry farms. This has revealed some patterns in the timing of their development based on growing degree days. These are shown in Table 1, using degree days accumulated above 50^oF. The monitoring traps are used to set biofix, and the timing of the first spray should be aimed at the eggs or young larvae when they are first hatching, which our study predicts to start 85 degree days after biofix. This often occurs during bloom, so if a pesticide is warranted, use only bee safe insecticides. This includes Dipel, Javelin and other B.t. containing insecticides, or the insect growth regulator insecticides Confirm and Intrepid. Follow label directions regarding bee safety. A follow-up spray may be needed with the timing of this depending on the residual control provided by the first spray, the amount of new petal-fall since the first application, whether bees are still in the field, amount of rain, etc.

2007 small plot trial results

Last year, we conducted a spray trial to test the performance of sprays timed at different numbers of degree days after biofix. Confirm was applied at 100, 200 or 300 degree days after biofix with a follow-up spray seven days after the first in each treatment. This was compared to a Guthion application immediately after bloom with another 14 days later. The results (Figure 1) show the value of making an application close to the timing that coincides with the emergence of larvae from eggs if a Confirm application is being made during bloom (100 degree days after biofix).

Keeping track of degree days

The simplest method used to estimate the number of degree-days for one day is called the averaging method:

[(max temp. + min temp.)/2]-developmental threshold = DD

For example, suppose on May 13 in Grand Junction, Michigan, maximum daily temperature and minimum daily temperatures were 75° and 45°F. Using 50° F for the lower development threshold for cranberry fruitworm, degree days accumulated would be:

(75 + 45)/2 - 50 = 10 DD.

With a simple maximum - minimum thermometer, daily degree day accumulation can be tallied after biofix until the target spray timing of 85 degree days are reached.

Degree days are also tallied electronically by MSU’s Enviroweather program, with the reports available online at www.enviroweather.msu.edu. This system has weather stations across Michigan, and provides a daily summary of degree day totals and also predicted degree days for each weather station. This can allow growers and consultants to look at when the target degree day accumulation is expected to be reached, helping to plan sprays ahead of time.

If you have not used degree days in your pest management program before, there are some useful resources online to explain them. One is at: www.ipm.ucdavis.edu/WEATHER/ddconcepts.html. Your local MSU Extension educator will also be able to help with how to monitor degree days on your farm, or how to access information from the nearest weather station.

A short note on cherry fruitworm

There is no degree day model for this pest in blueberries, but we have been trapping this insect in the past few weeks. In fields that have experienced infestation in past years, and where moths have been trapped this spring already, protection of the young fruit should be considered as petal fall starts to expose the fruit to egglaying.

Table 1. Events in the development of cranberry fruitworm, predicted by growing degree days, base 50^oF

Event±	Degree-days (since March 1)	Degree-days from Biofix
First male	375±20	0
First eggs	460± 20	85± 20

Topsin M Section 18 request for blueberries denied by EPA

Annemiek Schilder, Plant Pathology

After seven years of granting emergency exemptions for the use of the fungicide Topsin M (thiophanate methyl) as a replacement for Benlate (benomyl) in blueberries in Michigan, the Environmental Protection Agency (EPA) has not granted our emergency exemption request for the 2008 season. Of the Topsin M Section 18s originally issued to multiple states for blueberries, the only remaining applicant in 2007 and 2008 was Michigan, indicating that growers in other states had found alternatives among the currently registered products.

The reason for the denial of the Topsin M Section 18 request this year was the need for a strong emergency rationale and avoided loss picture in light of the registration of a number of new fungicides directly labeled for the diseases of concern. This made it very hard to argue that this year's request could meet even the minimum requirements for significant economic loss (i.e., 20 percent yield or gross revenue loss, or 50 percent net operating revenue loss). The EPA did listen to our concerns for maintaining a resistance management program for the future, but to reasonably narrow the emergency exemption program to "urgent and non-routine" situations, the Section 18 program is geared only to cases of demonstrated fungicide resistance that result in significant economic losses. In addition, new data regarding the toxicological status of Topsin M did not favor this product in its review by the EPA. It is my understanding that if and when an emergency situation does develop, the EPA will reconsider our request.

Since we cannot use Topsin M this year, and its fate regarding full registration for blueberries is unclear, we need to consider alternative fungicide options. Michigan blueberry growers have done very well in rotating different fungicide chemistries, which is important for fungicide resistance management. Topsin M has a different chemistry from all other fungicides in our arsenal. Therefore, we have to be careful to not overuse the remaining fungicides since both the strobilurins and sterol inhibitors are at risk of resistance development in target fungi.

Good alternatives for control of Phomopsis and mummy berry are Pristine (pyraclostrobin + boscalid), Indar (fenbuconazole) and Orbit (propiconazole), whereas Bravo (chlorothalonil), Ziram (ziram), and Captan (captan) have moderate efficacy as protectants. It is important to remember that Indar and Orbit belong to the same chemical class (sterol inhibitors) and have a 30-day PHI. Serenade (Bacillus subtilis) is also an option for mummy berry control. Alternatives for control of anthracnose fruit rot are Abound (azoxystrobin), Cabrio (pyraclostrobin), Pristine, Switch (cyprodinil and fludioxonil), Bravo, Captan, Captevate (captan + fenhexamid), and Ziram. Botrytis blossom blight is controlled well by Captevate, Elevate (fenhexamid), Switch, and Pristine. Table 1 lists various fungicides and their efficacy against blueberry diseases.

Table 1. Effectiveness of fungicides for blueberry disease control.

Fungicide	Mummy berry		Phomopsis twig blight and canker	Fusicoc-cum canker	Alter-naria fruit rot	Anthrac-nose fruit rot	Botrytis blight and fruit rot	Phytoph-thora Root Rot
Fungicide	Shoot	Fruit	Phomopsis twig blight and canker	Fusicoc-cum canker	Alter-naria fruit rot	Anthrac-nose fruit rot	Botrytis blight and fruit rot	Phytoph-thora Root Rot
Abound	+ / ++	+ / ++	++	?	++	++++	+	?
Aliette	0	0	+++	?	+++	+++	?	+++
Topsin M + Captan or	++	++	+++	+++	+	+++	+++	0
Ziram	+ / ++	+ / ++	++++	?	++	+++	+++	0
Bravo	++	+	+++	+++	+	+++	++	0
Cabrio	+ / ++	+ / ++	+++	?	++	++++	+	?
Captan	+	+ / ++	++	+	+	++ / +++	+	0
Captevate	++	++	++	?	?	++	++++	0
Elevate	+	+	+	?	0	0	+++	0
Indar	+++	+++	++++	?	+	0	?	0
Lime sulfur	++ / +++	+	++*	?	?	+ / ++	+	0
Orbit	+++	++	++++	?	?	0	?	0
Pristine	++	+++	+++	?	+++	++++	++++	?
Rovral	0	0	0	0	0	0	++++	0
Ridomil	0	0	0	0	0	0	0	++++
Serenade	++ / +++	++ / +++	+ / ++	?	?	0	?	?
Sulforix	+++	++	?	?	?	+	?	?
Switch	+	++	+ / ++	?	++++	+++	++++	?
Ziram (3 Ib)	++	+	++	++	+*	++	+	0
Ziram (4 Ib)	++	++	+++	++ / +++	++*	+++	++	0

0 = not effective, + = poor, ++= fair, +++ = good, ++++ = excellent, ? = not known. Ratings are based on published information and observations in Michigan and other states.

Manipulating blueberries with Gibberellin

Eric Hanson, Horticulture

Some athletes have been consumed by scandal for taking hormones or other substances to improve their performance. Plants also produce hormones or plant growth regulators that can potentially be used to improve their performance as well. Gibberellins are one group of plant growth regulators that are also synthesized and sold as commercial products (ProGibb, ProVide). In blueberries, gibberellins can increase fruit set or decrease flower numbers, depending on when they are applied.

When bees are numerous and weather is warm and calm, 80-95 percent of blueberry flowers may set fruit. However, cold, rainy weather during bloom restricts honey bee activity and pollination, resulting in lower fruit set and often reduced berry size. Flowers that are not pollinated within three to five days after opening are unlikely to set fruit. After normal pollination, berry growth is dependent on the production of gibberellin and perhaps other growth promoters in the ovary tissues and viable seeds. If flowers are not pollinated, they abort. If only a few ovules are fertilized, the fruit may set, but not contain enough seeds to grow to full size.

When pollination is limited by poor weather, gibberellin (GA) sometimes improves percentage set and berry size. Several GA products (ProGibb, GibGro) are labeled for highbush blueberries. GA may result in retention of some seedless (parthenocarpic) fruit that normally drop, and increases the size of berries with low seed numbers. GA can be applied in a single spray during bloom (80 gram active ingredient per acre) or two 40 g sprays, one during bloom and the second 10-14 days later. Higher spray volumes (40 to 100 gallons per acre) may improve coverage and effects. Slow-drying conditions also increase absorption. Also make sure your spray water pH is not above 7.5.

Since GA is costly, it is important to know when it will help. If weather has been favorable for bee activity and the white corollas fall easily from the bushes, pollination is probably adequate. Keep in mind that blueberries can bloom over a long time, and often only a few days on good conditions are enough for adequate pollination. Consistently cold, rainy or windy weather through bloom causes pollination problems. If the corollas hang on bushes longer than usual and turn red or purple before eventually dropping, pollination may have been inadequate. The corollas of pollinated flowers drop readily while still white. Varieties with fruit set problems (Jersey, Coville, Earliblue, Berkeley, Blueray) are most likely to benefit from GA. Jersey, for example, is relatively unattractive to honeybees, and berry numbers and size are often limited by inadequate pollination. GA does not always provide a benefit and effects can be subtle. Make sure to leave non-treated check rows to tell if your money was well spent.

Recent work indicates that GA may have the opposite effect of inhibiting blueberry flower bud formation. ProGibb has been commercially used to limit flowering on sour cherry for some time. Inhibiting blueberry flowering would be of great value in establishing new plants. We now recommend pruning or stripping off flower buds during the first two growing seasons to encourage vegetative growth and greater fruiting in subsequent years. This is particularly useful on more precocious varieties like Elliott. Manual flower bud removal is not always accomplished because it is very time consuming.

In earlier work on potted blueberries, we observed only a slight inhibition of flowering when plants were treated with ProGibb in June or July, when we guessed flower initiation was occuring. However, Brent Black at Utah State University recently reported that flower initiation on ‘Bluecrop’ was reduced by nearly 90 percent by treating plants in August or September with ProVide (GA₄₊₇). This suggested that flower bud initiation or differentiation occurs later in the season. In 2006 through 2007, we tested ProVide and ProGibb on the late varieties ‘Elliott’, ‘Liberty,’ ‘Aurora.’ Timings ranged from early July to mid-October. The only timing that reduced flower bud numbers was the middle timing (August 27 plus September 3), but reductions were small. No differences between the two GA products were observed.

These results do not clarify the important question of when blueberry flower bud initiation and differentiation occurs. If we knew this, we could better time sprays for best results. Additional work is underway that will hopefully assist us in developing a useful treatment to reduce flowering on young bushes.

Small fruit meeting

Blueberry twilight IPM meeting

Topic: Green fruit meeting

Ottawa County, Carini Farms

For more information, please contact: Paul Jenkins (jenki123@msu.edu), Rufus Isaacs (isaacsr@msu.edu) or Annemiek Schilder (schilder@msu.edu).

Emergency Ag Relief Act

Vera Bitsch, Agriculture, Food and Resource Economics

The Senate Appropriations Committee approved legislation sponsored by Senators Feinstein (D-Calif.) and Larry Craig (R-Idaho) that would provide relief to the agricultural employers and farmworkers on May 15. The legislation was attached to the Iraq supplemental spending bill. Different from the stalled AgJOBS legistlation EARA, this is emergency legislation with a five year sunset and does not provide a path to citizenship or a green card. However, it would grant temporary immigration status to farm wokers who continue to work in agriculture at least 100 days per year. It would also modify the H-2A guest worker program.

The bill is supported by many agricultural employer organizations (e.g., American Farm Bureau), agricultural labor advocates and farmworker organizations (e.g., United Farm Workers).
More information is available at http://feinstein.senate.gov/public/index.cfm?FuseAction=NewsRoom.PressReleases&ContentRecord_id=ee2d9ac8-ebdb-0a1c-48c1-484dfc65e9d9

If you or your clientele would like to support or oppose this legislation, it is paramount to act quickly.

Regional reports

1 – Southwest

Mark Longstroth
Bill Shane

Weather

Last week’s temperatures were cool with highs in the 60s and lows near 40. There were scattered frosts with lows near freezing on Thursday, May 15th and Monday, May 19th. Little damage was reported. Rain showers fell in the area Wednesday, May 14th and Saturday, May 17th. Rainfall totals were generally light (about a tenth of an inch). Soil moisture levels are good, but light soils are beginning to dry out. We expect continued cool weather this week until the weekend when we should see temperatures climb into the upper 70’s. There is little chance of rain this week. We need to be aware of the danger of frosts when we get clear, calm conditions. There is a chance of warm rain next Monday or Tuesday. Our GDD totals have fallen back to levels not seen since the late 1990’s.

Southwest Michigan growing degree day totals March 1 through May 18				Grapes, from April 1
Location	GDD 42	GDD 45	GDD 50	GDD 50
SWMREC: