Burgeoning Apple Maggot Issues

Intense pressure from apple maggot fly (AMF) once again this year was made all the worse by having a relatively light crop. Some management changes are in order as warmer temps make possible a prolonged infestation period.

Susceptible Varieties?
Minnesota genetics are at the heart of Honeycrisp susceptibility to apple maggot fly. (Which in truth may be the Malinda apple from Vermont used in the Minnesota breeding program.) That's my observation anyway, seeing's as what happens to Chestnut Crab, Frostbite, Sweet Sixteen, and the like. I had multiple AMF traps in Honeycrisp on G.30 and got slammed again this season. I am curious to hear what others experience where certain varieties are mucked but others ride through relatively unscathed to harvest. Higher acid apples like Erwin Bauer appear relatively immune. Heirlooms like Bethel also seemed to be less attractive. Not much we can do in this regard other than note those varieties that need particular attention.

Trap Dynamics
Sticky ball traps are only fully effective on the front end, prior to the actual apples coming closer to size and emitting volatile ripening odors. Ron Prokopy reported these flies only see out about three feet so those volatiles pay a big role in trap draw (even more so than color). It would be good to figure out a baiting attractant that can be renewed from year to year.

Late Season Maneuvers
Another factor in burgeoning AMF numbers is maggots apparently "parachute" to the ground from later varieties as I rarely find the actual maggot in infested varieties like Spy and Melrose that basically hang on the tree despite obvious ruin. Picking up early drops twice a week is no longer a complete defense in these much warmer falls where AMF perpetuates.

Nutrition
Let's especially examine this canard. I tell certain people that I'm being slammed by AMF and then get told that obviously there's a nutritional factor amiss. I'm open on this score but doubtful given the special attention given to full spectrum nutrition in this holistic orchard. It's worth noting this advice comes from folks who aren't fruit growers. High insect pressure driven by the reproductive urge strikes regardless of good theories.

What to Do
I have three things in mind. Parasitic nematodes applied beneath the dripline in spring to defuse overwhelming AMF emergence come August should capture those late end-run-arounds as well as earlier season misses. Use of a homegrown bait attractant (using spinosad) to attract immature flies on the front end -- or one can purchase GF-120 Naturalyte Fruit Fly Bait. This approach gets applied to underside of leaves to attract immature flies in the first ten days or so after emergence. Note: AMF emerges over as much as two-month window. Lastly, weekly "spot sprays" of spinosad on more susceptible varieties once sticky ball traps are not as quick to the draw. Visualize the fly's journey, hopping from fruitlet to fruitlet . . . which means eggs are indeed laid hither and thither before the female finds the trap. The upshot here is more money to spend, more to do!

Lost Nation Orchard
Zone 4b in New Hampshire

Thank you for these thoughts on AMF! We too had the heaviest damage (almost 100% infested) on Honeycrisp this season, even with 2 sticky ball traps in the tree. Other nearby trees, which also had 2 traps each had close to zero maggots. These were Tsuguru, Karmijn d Sonnaville, Enterprise and William's Pride. I am wondering if I put the traps out too late, the apples were about quarter sized. We pick up ALL drops and keep the orchard floor as clean as possible. Drops and culls are fed to our sheep. I'm assuming, maybe incorrectly, that the maggots cannot survive the multiple stomachs of ruminants.

We had a very large population of swallowtail butterflies this season and many got caught in the red maggot traps. I will try the nematodes this year. Possibly strive for weekly spinosad on the Honeycrisp? Even though most of our fruit is sold for hard cider, we press 40-50 gallons of juice for ourselves and I have an aversion to drinking crushed maggots. I look forward to more discussion on these nasty bugs!

VistaRidge orchard, Quilcene, WA zone 8a est. 2012
235 Cider and heritage apple trees, 72 varieties,

Apparently, we're the only growers in this discussion forum dealing with AMF, Karen. From New Hampshire to Washington, no less! So goes the pace of mutual learning by sharing approaches and varietal observations.

You can use a couple yellow sticky cards impregnated with ammonium (which mimics bird poop) to know when the first immature flies show up on your scene. That's the appropriate time to get out whatever variant of the AMF sticky ball trap you use. I'd venture to say Honeycrisp is bigger than quarter-size at that point, leastways here with East Coast AMF. First sticky ball traps here typically go up about the third week of July.

I have yet to snag butterflies on these traps but can understand how that's not happy. Maybe more precise AMF (slightly delayed) timing will help.

Entrust has a 7 to 10 day residual. I might make two apps at peak pressure on Honeycrisp based on that. I want to stress to limit these applications by grouping -- early/midseason/late varieties -- as ripening volatiles will shift which apples are on the AMF radar as summer proceeds. I pretty much know here this means around August 1 for the first app on Honeycrisp and early varieties, followed by a second app around August 10 for Honeycrisp and problematic late varieties. Keep in mind to correlate those dates according to tracking AMF emergence via those yellow sticky cards. Immature flies require10 or so days before oviposition commences.

Otherwise you gotta appreciate that fresh juice with high protein content!

Lost Nation Orchard
Zone 4b in New Hampshire

Nope, you two are definitely not alone. This year was our worst ever for AMF, though last year was a close second. High soil moisture both years...

Thank you both for the ideas and observations. Some from our end:

1. We definitely do notice varietal preferences, though timing of ripening also plays a role in attractiveness of course. Yes, AMF adores Honeycrisp. Ours were pretty thoroughly infested, so with also having frost-ringing on that particular variety, we ended up not even harvesting a large amount of our Honeycrisp this year. Painful.

2. Interestingly, our earliest apple which tends to coincide with AMF emergence, Lodi, had almost no damage this year. Usually it is our early trap tree, but the flies left them alone in 2018 for some reason. No ideas as to why.

3. Many of our heirlooms with russeted and/or thicker skin were also untouched; I've noticed this in most years, actually. Perhaps the ripening time of Honeycrisp, plus red color, plus thin skin equals AMF treat? Two heirlooms they DO seem to like are Pink Pearl and Calville Blanc...both of which have pale yellow skin. So go figure.

3. We also saw flies later than ever into the season. While picking in Mid-October, we spotted one. Very discouraging.

4. We do catch butterflies sometimes on our red ball traps (mainly Swallowtail and Monarch), though not as many as the year we tried using red solo cups instead of the red balls. This is one of the reasons we ended that experiment (which had been recommended as a money saving measure by a scientist at Michigan State), though I can also anecdotally report that the cups did not catch flies as well as the balls.

I am interested in trying baited traps next year as our non-baited trap-out (red ball in every tree on perimeter, multiple traps in center of blocks, many traps in large trees like the Lodi and Duchess that ripen early and are attractive), though catching hundreds of flies, has not been sufficient to control our crazy population the past two seasons. The nematode application is also intriguing, though the cost of doing this orchard-wide would probably be prohibitive for us. Perhaps just under the Honeycrisp...?

Door Creek Orchard
Zone 5a in Wisconsin

Three points, Liz. No, actually, four . . . Karen and I are glad to include the upper Midwest in the AMF matrix! Which obviously is a real thing in your bioregion despite such kidding.

Lodi with no AMF issues in 2018 tells me this is a case of delayed emergence. Thus why I look to the yellow sticky card test for zeroing in on actual timing at the start of the AMF season each year. In theory, somewhat drier ground in early to mid July would be a plausible explanation for an emergence delay. Growers need to recognize variables from season to season has real import.

More than a few have stated concerns about baited traps possibly drawing in more than a share for of adult flies. Let's seriously consider this. Ron Prokopy and team showed that adults migrate a mere hundred yards in the face of the moment, and this as defined exclusively by volatile attraction. Not all that far when you think about it, eh?. Does it really matter if the lure drives further momentum from outside the orchard given this relatively small reach? I think the key is to beat varietal impetus . . . and thus the emphasis on timing on sticky ball trap placeout after known emergence.

Nematodes have relevance within that hundred yard flight radius. You only have AMF emergence under Honeycrisp if you didn't pick up all drops twice a week. But later varieties subject to the "parachute option" will contribute to the following year's pressure, and often in a big unexpected way. Check out Arbico Organic's nematode options at farm scale here. It's actually far more affordable than the spinosad card from our friends at Dow Agro Science. [Pure sarcasm alert, for any who don't yet know me.)

This conversation is definitely on the rise!

Lost Nation Orchard
Zone 4b in New Hampshire

Thanks, Michael. The nematodes look great - no specific species is listed on their site for AMF, though I see they list a combo (Sc, Sf, Hb) for "Fruit Trees". Sr is listed for PC. What species (or combo) are you thinking?

We pick up all drops in July and August, but by the time we hit Honeycrisp we don't have the time or man power to pick up drops. Just too darn swamped. Our sheep do great clean up on drops but not til later in the season and not on the block with Honeycrisp. So I definitely think an application of nematodes is warranted.

I've definitely heard the warning about baited traps, but I agree with you that since it is such small distance the outside flies could be pulled from, I'm willing to take the risk.

As a side note, we used to monitor emergence with baited yellow cards, but found that we got the same results by using the red balls in our earliest varieties. However after this year's unexpected results (with the unscathed Lodi vs everything else), maybe we will try them again in 2019.

Door Creek Orchard
Zone 5a in Wisconsin

Report from up-North...
Here I didn't notice any sort of increase in maggot - if anything there were actually much less than average.
My Honeycrisp tree was in an off year, but the few apples were rather nice, I didn't notice any bug in them.

I don't do anything special here, other than picking the drops and maintaining the orchard floor rather clean. But I do pick the drops very often during the season.
As many of you already know, I don't sell apples - I mostly make cider out of them. But I do notice it when there are lots of maggots and it seems to me that the more it goes, and the less maggots there are. Can't explain why...

And Karen was worried about drinking crushed maggots... There is no reason to worry - I have noticed that maggots remain intact inside the pulp after pressing...
Claude

Jolicoeur Orchard
Zone 4 in Quebec

Claude Jolicoeur Wrote:
-------------------------------------------------------
> Report from up-North...

> As many of you already know, I don't sell apples -
> I mostly make cider out of them. But I do notice
> it when there are lots of maggots and it seems to
> me that the more it goes, and the less maggots
> there are. Can't explain why...
>
> And Karen was worried about drinking crushed
> maggots... There is no reason to worry - I have
> noticed that maggots remain intact inside the pulp
> after pressing...
> Claude

Hi Claude, that is interesting! Most of our apples are sold for hard cider. They don't want Honeycrisp and I do for eating! They keep so well for so long in our uncontrolled outside storage, they are still wonderfully crisp now, more than 2 months past harvest. We press about 50 gallons of juice for drinking, frozen, not fermented. I just can't get past the idea of drinking maggots that may have been cut up by the chopper. We had excess Honeycrisp this year and before pressing, I cut them open. 99% saturated with tunnels. The sheep were happy to eat them. Ugh.

I find it so interesting that we found zero maggots in Williams Pride this year. It had a lot last year and is right next to HC tree. Enterprise had some last year too, and this year, a huge crop that we are still eating and not a maggot to be found. It is also adjacent to HC tree. Belle d Boskoop, which has a thick russet skin and is mostly yellow/green has been infested in the past, but it was an off year for them here, no fruit. I plan to try the nematodes on susceptible trees, and will hang yellow trap cards early to learn the timing better for our orchard. We had a very dry summer, all the way through October. But our trees are irrigated so dry ground may not be a factor in the life cycle here.

Regarding Spinosad, I tend to be very conservative with it, using only when a big surge of bugs happens, such as a big leaf roller problem a few years ago. Our surrounding forest was invaded by tent caterpillars this year, I'm betting I will be breaking out Spinosad for that next summer. Maybe the timing will coincide with AMF hatch!

VistaRidge orchard, Quilcene, WA zone 8a est. 2012
235 Cider and heritage apple trees, 72 varieties,

Liz, I'll go with the Triple Threat package (three species) from Arbico as I don't really know the full range of depth of AMF pupae. This spring application might equally be valid for European Apple Sawfly, provided it's a few weeks prior to bloom. One question I've always had as regards parasitic nematodes is if effectiveness will be higher at the larval (entry) stage or equally good to go once the pupae phase has begun? This would be a legitimate discussion in its own right if anyone wants to carry on with nematode nuance.

Claude, I will agree with the notion of "intact maggot" if pomace is less than finely ground. As in downright chunky, and this is why hand cranking cider makers are surely good to go. But introduce more effective grinding via electric motors and planer blades -- or finer grinding teeth as in your case -- and I have a hard time believing AMF larvae are not "juiced" to the same degree as individual apple cells.You win awards for your excellent cider, mon ami, and we all have our special secrets, no?

As for the rest of you, varietal observations regarding AMF are rock'n'roll territory . . . help make this forum alive by boldly sharing where you've never gone before!

Lost Nation Orchard
Zone 4b in New Hampshire