Maggoty apples?

For those of you who came on the winter 'fruit care' day in February, you may remember mention of Codling moths. These insects are responsible for the maggots found in apples, and are a real pain to home fruit growers. 2009 was a very bad year for this pest. Now is time to think about controlling them.

First a bit of biology: Adult moths start flying in May when evenings are warm, and the females lay their eggs on flowers/young fruit. The eggs hatch and the maggots burrow their way into the young fruit. However, the first time you will notice them being a problem is later in June when a hole appears and brown 'frass' starts bubbling out of the apple. This is the maggot finding its way out (not an insect trying to find its way in !). By this time it is too late to do anything. So you have to act early, that is now, as you are reading this!

Back to May: the first thing you can do (whether you are organic or not) is to purchase a codling moth trap. This comprises a weather proof plastic tunnel you hang near your apples trees (one will be enough for an allotment plot). Inside is a piece of sticky card, and in the middle of the sticky trap you place a pheromone lure. This emits a chemical which attracts male moths which fly into the trap and get stuck. This will reduce the pressure of moths on your fruit trees, but remember it is the female which lays the eggs, so the female is still free to go about her business. There are a few brands which market traps, for instances 'Agralan' and 'Growing Success' found in most garden centres and usual internet suppliers. Plums also suffer from a plum maggot and sticky traps and lures can also be purchased, to use in the same way.

Really, the trap is there so you can count the number of moths, and gauge the best time to treat the trees. Because you cannot see the moths or the eggs, counting the moths trapped is the only guide you have as to what is going on. When you count more than 15 moths per week, infestation is high and you should spray a week later. Timing is crucial - you are trying to kill the grubs as they are hatching, not the adult moths.

So what to treat with? Well, you can leave it to nature and if you encourage a lot of birds on your plot, some will eat the insects and their eggs. If you are growing organically you can try a spray based on garlic extract - a typical example can be found at www.npk.ltd.uk/garlic.htm. There is not a lot of strong evidence to support its efficacy, but some commercial growers are using garlic sprays. The main problem with garlic is that it is not very persistent so timing is even more critical. If you are not organic, the conventional treatment for home and garden use is based on products containing bifenthrin such as 'Bayer Sprayday Greenfly Killer Plus'. With this product apples can be treated up to three times per season (if you really need to). Guidance will vary with other products. Read the label carefully.

Hopefully these notes will give you a good crop of fruit in 2010, and avoid the frustration of apples going rotten in store next autumn and winter.

Richard Weightman