Karol
May i thank you for all the great information that you have been giving us on here. I had never thought about wasps before in that way. now i have a bit of a different question/problem. where i work i have a big compost heap where i have put some very ripe fruit, over the past few weeks i have noticed there is more and more wasp activity on it. now this is not a problem for bees as i dont have any there yet, next year maybe, but it is in school grounds.
Management of compost heaps requires a little understanding of wasp feeding behaviour. The dietary requirements of 'wasps' is predicated almost entirely on their life cycle. Adult wasps have mouth parts that only allow for 'liquid' feeding and much like bees, this liquid sustinance has to be high in carbohydrates because wasp flight consumes a vast amount of energy. Queen wasps coming out of hibernation get this from nectar and are therefore pollinators of flowers in the early spring. Wasp grubs on the other hand require protein to grow. Adult wasps therefore hunt other insects (and scavenge for carrion) to feed their grubs. The exoskeleton of insects is made from chitin (n-acetylglucosamine) which is a complex sugar. The grubs 'digest' this chitin and convert it into simple sugars which they re-feed back to their adult wasps. Wasp nests mature when they release their sexual progeny afterwhich the resident queen stops laying eggs which means there are no grubs left to feed the adult wasps. It is at this point that wasps apparently change their feeding behaviour and 'visibly' come after sweet foods;- invariably fruit, honey in hives and whatever sweet foods we adorn our alfresco dining experience with. Importantly, wasps were here before humans and in nature they have evolved to co-exist symbiotically with fruit trees. In attacking fruit, wasps don't 'eat' the fruit. Their mouth parts don't allow it. Instead they gouge the fruit with their mandibles to release the juice which they drink. The flesh of the fruit falls to the ground to fertilize the ground ready for the fruit seeds. So wasps (in nature) play an important part in fruit tree procreation. I tend to regard wasps as nature's gardener. They pollinate fruit trees in spring, then keep the trees free from insect pests, then harvest the fruit. I wonder at the marvels of nature (and greatly respect wasps as an incredibly important insect and natural asset).
Now, back to compost heaps. Compost heaps provide ideal hunting grounds for wasps because of the high volume of insects that gather there. These hunting wasps (i.e. during colony founding and colony growth phases of the wasp life cycle) aren't so noticeable because they are constantly flitting back to their nests and therefore rarely swarm feed at the heap. (You might be surprised to know that an average wasp nest will eradicate between 4 to 5 metric tonnes of insect pests in a year!). There's very little that can or should be done to stop wasps hunting at compost heaps because in reality this isn't a problem.
Later on when wasps convert to sweet feeding after nest maturation, compost heaps become a problem when, as in your case, fruit is put on them. As I've already mentioned, wasps swarm feed around sweet foods (which is a defensive strategy employed by wasps competing with other wasp colonies). Wasps also programme feed. In other words, they will keep returning to the same food source until it is consumed to the exclusion of other food sources within the vicinity. This presents you with a problem. Given that the wasps have already found the fruit in the compost heap, they will ignore your traps. If you then use low efficiency traps (dome traps, oak stump traps, pop bottle traps and jam jar traps etc) you will merely attract more wasps to the traps without dealing with those wasps already at the compost heap which will merrily continue ignoring your traps. So you will get the worst of both worlds. My advice is quite simple. Don't use traps in this situation because they are not warranted. Instead, you have to break the programmed sweet feeding behaviour of the wasps visiting the compost heap. How do you do that? Simple, cover the fruit with more 'non-sweet' compost. Once covered, the wasps won't be able to get to the fruit which will stop swarm feeding and end of problem. A little bit of sweat but a cheaper and more effective solution.
Best wishes,
Karol
