Midge success!

I think the pear midge spraying experiment was a success - the only fruits affected were the first ones to set on Morettini, before the rest of the blossom had dropped; so far neither this or any other variety has developed any maggot-bloated fruitlets. My aim was to lessen the incidence, rather than eradicate it completely (the affected varieties all require thinning anyway) so I'm very pleased with the result of 'spot' treating.

Pear Midge

Morettini is the most precocious pear, so it is hardly surprising that it is the earliest to show signs of pear midge damage, despite my spraying experiment. This variety actually blooms over a long period relatively, and the very first ones to set ('king' fruitlets) are now clearly affected. I didn't spray until 100 % petal loss, so these first fruits would not have been protected anyway. I suspect the exercise will prove ineffective anway. Picking off distorted fruitlets will be another daily task from now on.

Pests - Pear Midge

Well, the midges are still there in force. At least I think they are as the whole internet does not have a single picture of an adult pear midge to help identify them. However, midge-like insects are floating around the tops of most of my pear trees. And I do mean the tops, I saw none on the shorter cordons or step-overs. It will be interesting to see if there is any correlation between what I think are the adults and the trees/fruit which is eventually affected. At the moment they are most in evidence on Morettini, Bishop's Thumb, Santa Claus, and the cordons of Comice/Rogue red and Devoe.

Pear midge - Morettini

The blossom dropped very suddenly on the Morettini standard, so I decided to try an experimental treatment for pear midgel. This tree was very badly affected last year and is fairly isolated from others, so it should be easier to assess if spraying for adult midges has any effect. Fortunately the wind was low yesterday and as soon as the derris spray hit the foliage a cloud of midges flew up. Unfortunately the same thing happened when I tried spraying again today, suggesting the insecticide isn't really having a deterrent effect. I went back later to see if I could retrieve any dead midges for identification, but the one I found managed to fly out of my grasp. So I'm not holding out much hope for the effectiveness of spraying. I probably should have started a day earlier too, as the midges were clearing active before full petal drop, given the large number that had already arrived.

Morettini: set

After losing such a large percentage of the crop to pear midge, I'm relieved to see there is still a fairly decent crop remaining. I found only one blackened fruitlet that the midge larvae had vacated, though this will still probably result in enough adults to ensure a bad attack again next year. I will hoe underneath regularly as an extra measure.

More Pear Midge

More bad news on pear midge infestation. I got a stepladder to investigate the top of my half-standard Morettini and found an even greater number of infected fruitlets at the top of the tree. This tree did not set any fruit last year as it flowered in January, so the midges that infected it must have travelled a fair distance.

I also found infected fruitlets on Winter Nelis, Sucrée de Montluçon and Fondante d'Automne which showed no outward symptoms other than looking slightly dehydrated (example far left). I would not have detected any on Winter Nelis if I hadn't carried out random checks. Round/conical varieties don't seem to change shape or size as greatly as the pyriform/calabasse types do in reaction to the larvae.

Pear Midge: Further information and links

RHS Leaflet Pear Fruitlet Gall Midge

Some good information here. I haven't found it to be the case that mid-season varieties are unduly affected, two of the earliest to flower (Morettini and Devoe) have been the worst affected this year. There is definitely a marked difference in susceptibility in some varieties, as adjacent cultivars flowering at exactly the same time have remained unaffected. Now that an infestation pattern seems to be emerging, I will probably consider spraying the most susceptible varieties next year, as pear midge can eventually result in significant losses. Whether spot treatment of affected varieties only will be effective in reducing adult midge numbers remains to be seen.

GQT

The usual un-informed musings from the team. It much easier to control the maggots BEFORE they emerge and crawl off into the environment (see below for further reasons why leaving the maggots in situ to cause maximum damage isn't a good idea). I see no evidence that it is a self-limiting problem; in my experience it tends to increase in severity over time particularly where control is lax or difficult.

Which? leaflet

Excellent information here (particularly re. the mobility of the larvae in the environment). Very interesting to read that the presence of infected fruitlets can have a negative effect on the development of the unaffected percentage of the crop; I've certainly found this to be the case on my in-laws' Conference which invariably loses the whole crop by June. Most plant Galls are triggered by chemicals secreted by the infecting larvae, which deliberately encourages abnormal excess growth. Yet another reason to exercise vigilance and remove all affected fruitlets as early as possible. 

Re. 'biological controls' I have to say that poultry don't appear to have much effect on mopping up midge grubs, or any other pests for that matter; the last place my hens ever want to scratch around is in the vegetable garden or under fruit trees.

Another instance of Pear midge

Another example, this time on Morettini which shows how variable the presentation of the problem can be. The fruitlets don't swell up but develop a bumpy, irregular appearance. Normal ones have an even red flush, but affected fruitlets show an uneven colour. On some, the stem-end has started to become a little flaccid too. The infestation on this tree is particularly bad, probably about 25% of the crop. The entry hole is visible on this one.

Regarding prevention, removing ALL infected fruitlets asap is the only effective control in my opinion. Books will suggest cultivation of soil under trees as a way to control the problem. All my pear trees are grown in soil that is cultivated and whilst this might have been one reason the problem has been slow to develop here, it hasn't prevented it from increasing in incidence. I've dismissed spraying as an option as it is unpractical to do all the trees, at least for the time being. 

It should be possible to find and identify a large number of affected fruits on cordon-grown pears. The problem is that because there is so much variability in the way the grubs affect the appearance of the fruit they infect, it can be easy to miss on a variety that hasn't suffered before. It's also a bit demoralising to cut open slightly bumpy fruits only to find that they are unaffected and lose yet more fruit. So far there has been a fairly predictable pattern to the infection: Comic, Conference and Devoe had single fruits affected sporadically over the cordons (usually the earliest central fruits in the cluster); Morettini has whole spurs affected, and this was also the case with Fondante d'Automne a couple of seasons back. This year I have only found one fruitlet affected on the latter, no doubt I have missed some. 

In contrast, my in-laws 15 year old Conference has had the entire crop affected for several years now, every single fruit turning black and dropping by the end of May, even the few not affected by midge larvae.

Pear Midge

The first casualties of the season. This is a very good example of a fruitlet infected with pear midge. The variety is conference, and there is a very clear difference between the rounded shape of the affected fruit and the pyriform shape of the others. Also, there is a clear entry wound in the form of a small, darkened dot, though this isn't always easy to find when culling potentially affected fruitlets.

Cutting open reveals a wriggling mass of the grubs.

Midge hasn't been too much of a problem here to date. Only certain varieties seem to be affected, though whether this is due to a particular susceptibility or just that these happen to be at the right stage for the midge's cycle is unclear.