This year I had a serious problem with fruit fly larvae in some growing areas. My container trees were flooded and dropped/spoiled lots of fruit as a result, providing a large amount of rotted fruit for FFs reproduce on. I experienced very high losses as a result so hardly any useable fruit from them at all . Inground trees were much less affected, but some still were, likely because of individual circumstances: less than thorough picking and disposal of damaged figs, dense shade canopy providing attractive habitat, and large numbers of FFs migrating from nearby hosts. I spent a great deal of time sampling figs for lavae and monitoring FF activity to better understand the situation. I saw a great deal of both spotted wing drosophila and african fig flies, peaking in September and also associated their numbers with warm/wet/humid conditions.
To be absolutely certain of the species that were causing the problem I placed several (unsplit) affected figs in a jar and allowed the larvae to mature into adults. The fruit flies that hatched were Zaprionus indianus, aka the speedracer fly for the 2 racing stripes that run down its back, which was introduced around the same time as SWD but has received much less attention; so far, aside from figs it only bothers damaged or overripe fruits.
While SWD is highly attracted to unripe figs the skin has an effective defense against it in the form of bleeding latex when stung, this blocks and seals the breathing tube attached to the SWD egg and it is unable to hatch. I have observed SWD and these drops of latex for several years but the figs never contained larvae or spoiled.
The AFF is specialized to figs, adult females lay eggs near the ostiole which hatch and immediately enter ripening figs to begin feeding. When the interior is completely solid/blocked the AFF larvae may be contained to a small area just inside the ostiole. In some cases, where the fig has split, or the ostiole is large and with an open interior; both SWD and AFF adult females themselves crawl in and lay eggs on the flowers. Observation shows that the flowers do not bleed latex when damaged, so figs have no interior defense against SWD.
AFF causes significant losses to commercial fig orchards in Brazil, which developed the idea to apply stickers over the ostioles of figs at the beginning of ripening/swelling to exclude all adults and larvae from entering. It is obviously the most effective way to exclude FF larvae/adults/other insects from entering the figs, and a label or price sticker “gun” should help the job go faster. Spraying may be a less time consuming alternative but also may not provide adequate control in all situations. The sticker, for me, would provide much more confidence than sprays.
Did anyone else have FF larvae in their figs this year? Read anything fruit fly related that is fig specific? Hatch their own? Please share any experience or discussion you want on the topic.
Thanks, it was an easy experiment but still interesting and a little exciting to see what would hatch out. I sort of wish I had kept some alive to test how much cold they could take. Overnight in the freezer seemed to kill all the adults.
One entomologist thinks that AFFs are not cold tolerant at all and die back to southern Florida every winter on the east coast, only to become “aerial plankton” in the spring and be carried north by wind. But a few could survive in houses or urban heat island microclimates further north. And also be transported with shipments of infested fruit. No telling where they would have come from by the time figs are ripening in summer.
I think SWD survive winters here but just take a while to build their population back up. There has been research into predatory species that will hopefully be able to rebalance nature some in the future. Ants are actually a major predator of fruit fly eggs and larvae so they do have at least one redeeming quality I guess.
I can tell them apart pretty easily, AFF is a little bit larger than SWD and the racing stripes are not hard to see if it is sitting still, and other fruit flies don’t seem to be interested in ripening figs. I might use traps to monitor the population though.
This is the first year that I noticed fruit fly maggots in some of my over ripe figs. It came as a very unpleasant surprise.
In past years I could let the fruit hang on the tree and dry with no insect problem, just had to net for birds.
Unfortunately I don’t know what type of fruit fly larvae they were
Getting figs dead ripe will probably be much more difficult in the future. SWD can sting ripe figs, varieties with thick skins might be resistant but will still be vulnerable when the skin cracks. I’d consider picking when ripe, splitting them and using a dehydrator, the flavor is much better IMO because natural slow usually involves some fermentation.
It might be that there are fewer host plants for fruit flies in your area. I went to boot camp at Ft. Jackson and remember it was mostly pine trees.
A total of 1,313 adult flies of the family Drosophilidae (Diptera) was collected. The species identified were African fig fly, Zaprionus indianus Gupta (n = 1,024) (Fig. 1A and 1B), spotted wing drosophila, Drosophila suzukii Matsumura (n = 31) (Fig. 1C and 1D), and vinegar fly, Drosophila melanogaster Meigen (n = 258) (Fig. 1E and 1F). Adults of Z. indianus emerged from ripe and overripe fruits, whereas D. suzukii and D. melanogaster emerged only from overripe fruits, and so are considered secondary or opportunistic…
According to our observations, Z. indianus is a major pest of fig plantations of the area because of the damage it causes to the fruits, and its potential to disrupt commercialization of fig fruit. Drosphila susukii and D. melanogaster, however, were opportunistic insects, probably attracted by the volatiles released by overripe fruits, and may take advantage of free access through the ostiole and damage on the epidermis.
Thanks for sharing. SWD is not a problem in upstate SC yet but friends in GA and other places near us are getting slammed by them. I have seen a few fruit flies and fungus gnats in years past but nothing too major. Our biggest fig pests are yellow jackets, bald face hornets, European hornets, various wasps, ambrosia beetles, and stink bugs.
Hope it stays that way for you guys, @firstname.lastname@example.org SWD is getting much more attention and research so there might be releases of biocontrols/natural predators before long that will help control them. The AFF not so much, figs are a minor crop so the best we could hope for is some overlap with any predators they release for SWD control.
Is that the brown marmorated stink bug? They used to be really bad here but have declined in the past 5 years. I read kudzu bugs are on their way here now, have you ever had trouble with them on anything?
We have trouble with the brown marmorated stink bug and the leaf footed stink bug. The only time I’ve seen kudzu bugs was while doing a job in Hickory NC they was all over the side of an apartment complex up there.
Thank you for sharing Brent. All this time I thought it was SWD when in actuality it is AFF. I will be picking up every leaf around the figs this year + not missing a single blackberry/raspberry/strawberry.
I also have an old cherry tree on the property… blanking on the name, but I discovered this year that drops loads of cherries that attracts all kinds of fruit flies. Gonna get as many of those up that I can with maybe the leaf blower?
I was surprised that the vinegar fly was even more common than SWD in overripe figs, although they look so similar I’ve probably just been mistaking any I see for SWD.
I’m not really sure if it is a good thing or a bad thing that AFF is the problem. Selecting thick skinned varieties that would have been resistant to SWD stings might have been easier than finding types that AFF does not bother. With AFF the things that could give resistance might not be as reliable… Ostiole size can vary, as well as the inside being solid or open. Dripping honey or having resin in the eye should stop them, but that can also vary and might not happen early enough in the ripening process to prevent them getting in anyway. At least putting stickers on the ostiole when there are AFF around is not hard.
I read about rotting fig leaves being attractive to SWD and bet they are to AFF as well, something to think about since I usually just toss green prunings on the lawn to get mowed when thinning in July.
I have an idea but not sure if this will work. Tie a ripe banana to the electric bugs zapper with the purple light. The ripe banana will attract them to the bugs zapper and hopefully this will reduce their population during fig harvest season.
More research. Reported in Maui and Oahu in 2017, and France (during winter, yikes!) in 2016. It is still unclear whether it has or will adapt to cold winters. I didn’t see them until late in the season last year, and not yet this year.
In the grape world we’ve found that SWD is a minor concern, even on thin skinned varieties, regular ol’ melanogaster is by far the main spreader/intensifier of sour rot. They need an opening or weakened skin which birds, wasps, and botrytis provide for them.
I have posted not too long about Fruit flies if this was a local problem where I live because we have so many. But didn’t knew if they have them in all the other estates as well?
I’m guessing that they are in most of other places, estates but probably not as bad as others like here.
I wanted to pick this chat back up and see if anyone has some solutions. My Violette de Bourdeaux figs had a large crop this year, but due to heavy rains, a lot of them started splitting early. I was initially picking them early and letting them ripen, but their flavor fresh has been ok, but not great. They are fine cooked. With the heavy drop, there’s been a huge fruit fly problem. The ostiole of the fig has fruit flies crawling into it, even before they are ripe. I attached a picture. If I pick them early and leave them out to ripen on the counter, there are tiny maggots inside. By the time the fig splits open even a little on the tree, it’s covered in them. I’ve captured quite a few in bags, and I’ve fairly certain they are vinegar flies, not the AFF or SWD mentioned previously, but I’ll defer someone with a more experienced eye.
My solution has been to add some split figs back on the tree dusted with BT, as well as making a vinegar trap in a milk jug below. So far, the jug has caught one slug, results are yet to be seen with the BT figs but fruit flies have been congregating around them.
Is the open ostiole of VdB a problem? We were able to leave some ripen last year (less rain during that time) and they were delicious. I also don’t recall fruit flies being an issue. What are other solutions that people have tried?