A few years ago, I acquired a small fragment of orchard, now a suburban garden, which included an old pear tree of medium height growing in lawn with clumps of bluebells and wild flowers beneath. The tree turned out to be the common variety Williams’ Bon Chrétien, and to my dismay, it suffered total crop failure from an infestation of pear midge (Contarinia pyrivora).
Thus began an annual battle which may be instructive or at least amuse. The books indicate that the female midge deposits her eggs in the blossom bud or balloon when it is just opening and the rapidly developing larvae cause the fruitlets to swell, distort, turn black and fall to the ground. The larvae pupate about 5 cms underground and the next generation midges emerge the next spring. The classic advice is to pick and burn all the affected fruit and also cultivate the ground and spray with carbaryl or gamma-HCH which I was reluctant to do.
Determined to find a non chemical solution, I lowered the height of the tree, which enabled me to pick every single fruitlet, hoping to break the cycle. Next year the fruitlets were still virtually all affected and were totally picked again. Over subsequent years various attempts were made to use a barrier sheeting under the tree coupled with fruitlet picking and even fly papers and ultra violet lights but to little avail, although a few pears did mature. I also discovered that some larvae drop to the ground before the affected fruitlet does, so early removal of affected fruitlets is required. It seemed possible that midges were arriving from other nearby gardens. It also appears that Williams’ is very attractive to pear midge so the tree is being partially top grafted over to Comice.
Close observation of the emerging midges at blossom time, they are quite large, like eighth-size crane flies, showed that they emerged just before sunset and formed small mating swarms often in the same airspace between the blossom and the setting sun. They dance from 2 to 5 metres above ground level and can be easily seen against a clear sky. Finding that water jets were ineffective, in desperation I fitted a long PVC bathroom waste pipe to the vacuum cleaner nozzle and found to my astonishment that midge clouds could be very effectively hoovered out of the sky! This continued for several evenings as new midges emerged. Clearly this approach is very time consuming, small-scale and slightly eccentric but it is pleasant to be out with the blossom at sunset whilst knowing the method has zero impact on other pollinating insects.
The improvement in fruit yield was dramatic and I now have so many sound fruit that I am able to thin the crop in line with normal practice. Using garlic spray against scab and feeding the tree has completed the restoration of an attractive and now productive garden pear tree.