Tag Archives: sooty blotch

June 6, 2017 Volume XIII No. 4

Fruit Bud Stages

In the Durham area on June 5th, McIntosh and Cortland apples both had some fruit at 3/4 inch size. Peaches: fruit size 3/4 inch. Blueberries: bloom almost over. Raspberries: bloom. Grapes had flower buds visible, shoots up to 18 inches long.

Apple Scab

The primary apple scab season is over for much of the southern part of New Hampshire. If you are using the NEWA system data from a site close to you, it should predict the end relatively  accurately, provided that you had correctly entered the apple scab biofix (date when 50% of McIntosh buds are at green tip). The primary season ends with the next daytime rain, after all the spores have matured. Ten days after the end of primary season is an excellent time to do a final assessment (we often call it indexing) to see how well you did at managing the primary phase of the disease. All the lesions resulting from ascospore infection should be visible by that time. If you find no or very few lesions, you can relax scab management for the remainder of the season, and focus on bitter rot, flyspeck, sooty blotch and others. If you find a significant number of scab lesions, you may wish to make two back-to-back captan treatments to “burn out” those spore-producing lesions.

As a test, on June 2nd I looked at the NEWA data for Ossipee, and used April 14th as the date of green tip. That is two days later than we observed at the UNH Kingman farm in Madbury, and was my best guess for Ossipee. The model then predicted that all ascospores were mature June 1st, and primary season would end with the next daytime rain after June 1st.

Flyspeck and Sooty blotch of Apple

These “summer diseases” are caused by fungi that grow on the surface of the fruit, and on stems of LOTS of other hosts, including brambles, maples, wild apples & relatives. When the fungi grow on the surface of apples, they create cosmetic blemishes that lower the value of the fruit. So, many growers think about how to manage these fungi. They grow very slowly. The number of hours of leaf wetness after petal fall (I’ll abbreviate that & call it HLWAPF) is a critical measurement in managing the disease. Basically, we need 270 HLWAPF (if you are using old-style leaf wetness equipment) or 200 HLWAPF (of you are using the latest equipment) for each cycle of the fungus to grow and produce spores. We want to apply a fungicide that works on summer diseases at least once every cycle. In the early part of the year, we are usually focusing on apple scab, and often the fungicides we use also control summer diseases. We have the NEWA system to help monitor the weather. If you turn on your computer and visit the NEWA page for the weather station closest to you, it will predict where we are in the Sooty blotch/flyspeck cycle. First, it asks you to confirm the petal fall date for that site. For Durham/Madbury, petal fall on McIntosh was May 21-22. The model said that on June 2nd, we had accumulated 132 hours of leaf wetness after petal fall. If you enter when your last fungicide was, the model will predict the risk level you have for summer diseases. By the way, fungicides that are really effective on summer diseases include materials like Cabrio, Dithane, Flint, Manzate, Inspire, Penncozeb, Polyram, Pristine, Sovran and Topsin-M. Remember to rotate fungicides between activity groups, to reduce the risk of the fungi becoming resistant to the fungicides.

Summer diseases show up especially on varieties that are light, such as golden delicious and gingergold. The growth is less obvious on dark red fruit. A low incidence of these is probably not a problem on pick-your-own blocks.

Got Cherries and Peaches?

I haven’t said anything about cherries this year, because things were so busy on the other fruits we grow. Brown rot can be a serious problem on cherries and peaches, and we have two phases where we focus attention. One is the blossom and shoot phase, mostly passed now. The second phase is attacking the fruit. Fruit become very susceptible as they begin to ripen. A second risk factor (especially for cherries) is splitting and cracking. This opens up infection routes for the fungus to attack. Bird attack also threatens when the fruit turn color. Are your bird protection methods ready?  The time will arrive before you know it.

San Jose Scale   

If you have a block of apples with SJS in them, you’ll probably want to consider making an insecticide application for the crawlers. The timing is important, and we use degree days to predict when the crawlers emerge. The NEWA system doesn’t currently include an SJS model, but it will compute degree days for you. You have to feed it information. It will need to know what base temperature you’re using [50F for SJS]. It will need to know the starting date (“biofix”). That’s when you captured your first SJS male in a sticky trap. Don’t use those traps?  Then substitute the full bloom date. We expect SJS crawlers to appear 310DD after full bloom. Usually that is in mid to late June.

Plum Curculio Time

Plum curculio attack is heaviest from the time apples are 6mm in size, through the next 3 weeks or so. PC is abundant enough and active enough to reduce your apple crop by 75 to 100%, if you do nothing to control it. The early injury (see my photo) looks like tiny c-shaped scars. Soon, the eggs laid in those scars hatch, the larvae bore through the fruit, and the affected fruit usually drop to the ground.

Blueberries: Mummyberry Disease and Fruitworms 

We had really good conditions for primary mummyberry infection this year. The risk of infecting the tiny green berries continues, and can be reduced by fungicide application. When bloom ends is the time to consider an insecticide for cherry fruitworm and cranberry fruitworm, both of which attack blueberries. Many plantings can go without this treatment, but some sites are prone to repeated attack. Both fruitworms are tiny caterpillars that bore inside the fruit. There are other caterpillars that eat the leaves, but most of them occur a little later in the year… usually July or August. One exception (on lowbush fields) is blueberry spanworm, which is feeding now.

Strawberry Clipper in Blackberries

I covered this tiny weevil in the last issue, and pointed out that it was attacking Strawberries and Raspberries. Blackberries are in perfect stage for attack as I write this, and the process is the same. The weevils hit the unopened flower buds. Damage is typically worst at the edges of a bed, especially bordering woods.

 Slime Mold  —  Yuck – In Strawberries

 We have had so much cool, wet weather this year, I’m anticipating that we will see a significant amount of slime mold this year. I hope it will get drier and I’ll be wrong. But in case that’s not correct, I’ll show a photo. Strawberry fields seem especially good places to find slim mold. Maybe it is our use of mulch that helps keep the soil at the right temperature and moisture for slime mold. Whatever it is, slime mold doesn’t actually attack the plant… it just grows over it. Typically it appears as blackish stubble growing on a nice, healthy green plant. It changes/moves quickly. Customers do not like it, and the best advice I can give is to assure them that it is not dangerous, and there’s not much we can do to avoid it.

Alan T. Eaton
Extension Specialist
Integrated Pest Management

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August 25, 2015 Volume XI No. 7

Apple Summer Diseases

 Apple Maggot

All varieties of apple are vulnerable to attack by apple maggot, but my fruit evaluations over the years have pointed to a pattern where some varieties get more damage than others. This could be in part because of preferences of the females laying the eggs. But it could also be affected by growers’ pattern of insecticide use… not using traps to discover when the flies are active, stopping spraying too soon, beginning too late. So, keeping those factors in mind, here’s my data from 1996 to 2005. In that period, I examined 119,500 apples. These are visual examinations. No fruit were sliced open to search for tunnels.

Variety                        incidence of AM blemishes

McIntosh                   18 of 50,740 fruit (0.035%)

Cortland                    33 of 29,000 fruit (0.114%)

Delicious                   27 of 12,430 fruit (0.217%)

Idared                        4 of 420 fruit        (0.952%)

Northern Spy            3 of 670 fruit        (0.448%)

Gingergold                1 of 320 fruit        (0.312%)

Gravenstein              1 of 340 fruit        (0.294%)

Empire                       7 of 5,040 fruit     (0.139%)

Macoun: 0 of 7,830 fruit. Paulared: 0 of 2,600 fruit. Gala: 0 of 2,650 fruit. Mutsu: 0 of 1,560 fruit. Honeycrisp: 0 of 1,010 fruit. Plus other varieties in small amounts…

The mix of varieties we grow has changed, and now I see more Gala, Mutsu, Honeycrisp, Fuji, Gingergold, Zestar, Akane and other varieties. But for what it’s worth, this is the pattern I’ve seen. Note that McIntosh, the variety that has the largest acreage here, has among the lowest apple maggot damage rates. Cortland has a damage incidence three times higher than McIntosh, and Delicious has an incidence 6 times higher.


White Apple Leafhoppers

We have two generations of white apple leafhoppers per year, and the adults of the second generation fly in September. The nymphs and adults both drop brown poop on whatever is below them, like your fruit, or the insect trap in the photo. When we get a light rain, heavily decorated fruit appear to be dripping in yellow droplets…not too appetizing. The leafhoppers feed on the foliage, creating white stippling. But many growers feel the most annoying problem is bothering pickers by flying in their faces. So some growers elect to apply an insecticide if leafhopper numbers get high. You can do that, but a better course of action (next year) is to monitor the first generation of leafhoppers (shortly after petal fall) and treat then if the population crosses the threshold.


Vegetable Insect & SWD Trapping Data

So far this year, sweet corn insect catches have been pretty low, but you can see the details yourself at the IPM Trapping & Monitoring page of our website.

Spotted Wing Drosophila

The catches Aug 1st to 7th were mostly 0-4 per trap, with a couple sites having 30. The week of Aug 2nd to 9th had a similar pattern, with catches up to 42 in a trap, especially in woods edge and in raspberries or plums. The week of Aug 9th to 15th had the same pattern with some catches as high as 60! But again, Most traps still have low numbers.

In Sullivan and Grafton counties, SWD catches are still very low, typically zero to 3 per trap per week. This is the same pattern we have seen since SWD arrived… the areas with cooler temperatures have slower buildup and lower numbers. Overall, New Hampshire catches so far seem lower than last year, but they should continue to build. You can view our trap catches on the IPM Trapping & Monitoring page of UNH Cooperative Extension’s website. When you reach the SWD data, click on the town that is of interest to you, and various weeks will appear under that town. Select the week of interest, then click on the “submit” button. The data will then be displayed for that site & week.

Wasp Control on PYO Farms

Stinging wasps can be a threat to both customers and farm workers. Late summer and early Fall seems to be the time of year when the threat is greatest. The wasp colonies are at their largest size then, and sometimes frost starts limiting food options for wasps. I suspect that might help switch them into a more aggressive pattern, but I really don’t know. I do know that it is better to deal with the problem relatively early, if you can. We have 11 pretty aggressive species in New Hampshire, including 9 species of yellow jackets, plus bald-faced hornet and giant European hornet. We also have species that are much less aggressive, like brown paper wasps. Frequently the less aggressive ones pose so low a risk, they can be left alone.

Please remember two things. 1) If you are allergic to bee/wasp stings, do not attempt to eliminate a nest yourself. Have someone else do it. 2) During the daytime, mark the position of a nest you want to eliminate. Then return at least 1 hour after dark, to treat it. Why at night? All of the workers should be back in the nest then.

Consider buying a can of wasp and hornet JET spray. Jet is not a brand… it means the stuff is designed to shoot a solid stream of product, often up to 10 feet or more. I would not bother to try the canned sprays that create a fine mist. .Approach the nest gently, quietly. Aim directly into the opening. This might mean positioning the spray can a bit below an aerial nest. I use a red light to help me see what is going on. After hitting the opening for several seconds, stop and walk away. Stay away until the next day. If you still see wasps flying in or out, re-treat the next night.

Large aerial nests are fairly easy to find by their size. Nests inside walls or in the ground are much harder to spot. To find them, I look for insects flying into or out of a hole. I do one additional thing when treating a ground nest. In addition to the flashlight and spray can, I bring along about a quart of damp sand. As soon as I have stopped spraying, I dump the sand over the entrance tunnel. That helps seal in the toxicant and prevent wasps from escaping.

One contributor to the problem may be a bit hard for you to control: wasps are attracted to dropped fruit and spilled sugary things (like cider). Removing drops is often impractical, but it works. Here is a link to my publication on controlling wasps.


Flyspeck and Sooty Blotch of Apple: As of August 17th in Durham, we have accumulated 295 hours of leaf wetness since the end of the first 270 hour cycle. So that means the second cycle ended on August 12th and spores started getting released. As of Tuesday morning Aug 18th we are 25 hours into the 3rd cycle of flyspeck. Remember to check the days to harvest if you apply a flyspeck fungicide. Manzate, Dithane, Polyram and Penncozeb have a 77days to harvest interval! Sovran has a 30 day interval, while others have 14, 1 or zero.

Alan T. Eaton

Extension Specialist

Integrated Pest Management

July 22, 2015 Volume XI No. 6

Apple Summer Diseases

Flyspeck and sooty blotch we refer to as “summer” diseases of apple. The number of hours of leaf wetness after petal fall (we abbreviate this HLWAPF) is a critical factor in growth of the fungi that cause the diseases. Each cycle of the fungus requires 270 HLWAPF to complete (200 hours if you are using modern leaf wetness equipment). At UNH, we were relying on equipment that has repeatedly failed at critical times this spring. So it wasn’t until July 8 that we discovered the first 270hr cycle had been completed (in Durham) on June 28th. That means spores from the numerous alternate hosts (maple trees, raspberry and blackberry, etc) released spores starting then, and now we are in the second cycle, where those fungi are trying to grow on apples. As of July 20th, we [in Durham] had accumulated 137 hours of wetness in this second cycle. Some sites have a history of summer disease problems, probably because they have lots of nearby hosts providing spores.

Brown Rot on Peaches

Peach fruit become really susceptible to brown rot as they mature and begin to ripen. If we have warm, wet weather, that helps still more. Anything you can do to reduce mechanical injury to the fruit will help reduce the problem, and refrigerating fruit will help too. The 2015 New England Tree Fruit Management Guide lists fungicide options. Note that they vary widely in days-to-harvest… from zero to 14 days!  Yesterday I saw some nectarines that were heavily attacked by the fungus.

Fire Blight

Driving home from a tree fruit meeting in Alexandria, Cheryl Smith noted severe fireblight damage on roadside apples in a churchyard in Alexandria. Scattered strikes have been seen as far north as Lisbon this year.


Apple Maggot

Some orchards have trapped several apple maggots by now, and others still have none. That is normal. There is great variability in the population (and timing) from site to site. Right now, I would expect early varieties (Gravenstein, Early Bird, Lodi, Vista Bella) to be most at risk.


When you reach a cumulative average of 1 apple maggot fly per trap, it is time to apply an insecticide. If you use odor-baited traps, the threshold is an average of 5 to 10 per trap. (the big spread in range is one reason I don’t add odor lures for this species). Then, for the next 7-12 days, discount any AMF’s you happen to catch. If I’m using Sevin, I do this for 7 days, since the residue is shorter lived than that from the pyrethroid insecticides, or Guthion, Imidan. If I’m using the labeled rate of a pyrethroid insecticide (Warrior, for example), I discount for 12 to 14 days, since those insecticides have long residual action. When it is time to start harvesting a block, I move the traps to later-maturing trees. At the end of the season, I remove the traps, put them in heavy plastic bags (keeps dirt & dust out) and store them until next July.

Spotted Wing Drosophila

One point to remember regards a key alternate host: pokeweed. The fruit are excellent habitat for SWD larvae. If you grow fruit that are vulnerable to SWD, it is important to destroy pokeweed before it produces fruit. I’ve included a photo as a reminder.


We caught our first SWD on June 23rd, a bit of a surprise that early. One was tapped in Essex Co, MA at about the same time. Finally we trapped another fly on July 8th, then at another site the next day. These numbers are really low, but should rise. In your plantings, I recommend considering an insecticide application if both 1) your crop is ripe and 2) you have trapped one or more SWD’s on your farm this year.

Details on traps, baits, how to hang, etc are on the SWD page.  The 2015 pesticide options are there as well, thanks to Mary Concklin of University of Connecticut Cooperative Extension. If you click on the trapping data link on our SWD page, you can view our trapping results, though with a slight delay. If you monitor traps yourself, you won’t have that delay.

There’s Still Time Left: Tree Fruit Leaf Tissue Testing for Nutrient Analysis

For tree fruit, leaf sampling for nutrient analysis should be done in late July through early August. The forms have the specific instructions, which can be found on the Problem Diagnosis and Testing page of UNHCE’s website.  Look near the bottom of the page, under “Additional Testing Services”. You can also download the form here.

Vegetable Insect & SWD Trapping Data

Those sweet corn growers who looked at the trapping data for the week of July 6-11 saw that we detected low numbers of corn earworms then. That is a bit earlier than we expect this pest, and is another example of the value of monitoring with traps. Sometimes you detect surprises! Numbers were not very high, but any sweet corn in fresh silk at that time was vulnerable to attack. Because of a delay getting help here on campus, we had just started setting sweet corn traps in the seacoast… but caught three earworms in the one trap we had set, in Derry. It may be that this flight was heavier along the coast, as compared to inland.

If you grow sweet corn, chrysanthemums, peppers, squash or pumpkins, and want to see the current year’s trapping data for corn borers or other insects, point your browser to our IPM Trapping and Monitoring page. Once on that page, you’ll see that one of the options is to view the current data, and it will show you how many insects were captured in traps at various sites. You could look at several weeks of data, if you wish. To help protect privacy, we don’t include farm names on the site, just the town names. On the vegetable insect trapping data pages, you’ll see that on the far right side it says “No Spray Recommended” after each entry. That’s because we want to keep the spray recommendations private as well. Look at the very bottom of the page as well. There you’ll see the threshold information, to help you decide what to do when a particular number of earworms or other insects are caught. The data is ready for you to examine any time you wish, for sweet corn & squash trapping. As I finalize this on July 21st, we have caught a few fall armyworms… not too many yet.

Summer Caterpillars

On apples, we see two large caterpillars regularly, in summer. Both can completely strip leaves off a limb or two, or even the whole tree. Both are highly recognizable. Cecropia moth is one of our native silkworms, and the larvae are light green with a series of colored spiny knobs. They can get HUGE.

parasitized cecropia 202trrotated

The second species is called redhumped caterpillar, and you can see why from the photo. This species is gregarious; you almost never have just one. The female lays eggs in masses, while cecropia moths lay their eggs singly.


In blueberries, we often see two very closely related species, yellow-necked caterpillar and its look-alike, Drexel’s datana. Like red-humped caterpillar, they are gregarious species, and a bush might get largely stripped of leaves if you don’t keep checking.


All of these species can be controlled (if that’s necessary) by either chemicals or Bacillus thuringiensis sprays. Since most of our blueberries are sold on a pick-your-own basis, and the caterpillars occur during picking season, many blueberry growers avoid using the chemical sprays. Some growers spray nothing, and when customers mention finding the caterpillars, the grower points to it as proof that he/she doesn’t spray.

Fruit-Related Events:

There are many events that might be of interest on our events calendar. Among them are:

Tuesday, July 28, 2015. Sprayer Calibration & Vegetable Twilight Meeting, Moulton Farm, Quarry Rd, Meredith. The sprayer calibration workshop is 3 to 4:30PM; Veg meeting will be 5:00 to 7PM

Alan T. Eaton
Extension Specialist
Integrated Pest Management