Plums are among the most popular plums grown in Germany. When the plum harvest begins in early autumn, many are enthusiastic about it, but the joy is quickly clouded when numerous worms enjoy the fruits. The worms are usually only noticed when the fruit is opened, which often causes disgust and the plums then have to be disposed of. Fighting the worms can work wonders against the infestation.
pest
Which insect is it?
The worms are not worms, but caterpillars of the plum moth, one of the major pests in commercial and domestic fruit growing. Grapholita funebrana is a butterfly, more precisely a moth, which comes from the Tortricidae family, the moths. The species occurs exclusively in the Palearctic and has chosen all species of the genus Prunus as the main food for the caterpillars, but roses and pears are also on the menu. The caterpillars attack the plums with great appetite and once infected, the fruit is usually dead.
The plum moth proceeds as follows when infesting the fruit:
- Plum moths lay eggs on the underside of the fruit
- this happens as soon as night-time temperatures of over 16°C are reached
- a female plum moth lays up to 60 eggs
- around 14 to 21 days later, the first caterpillars hatch and dig into the fruit with their mouthparts
- now they spend a long time in the fruit until they disappear from the fruit again
- by this time, much of the inside of the plums has been eaten away
- the worms are divided into two generations
- the first generation usually appears in early summer
- these ensure that the first fruits fall from the tree and can no longer ripen
- the second generation grows out of the first generation
- this usually presents itself in late summer and autumn, exactly at harvest time
- then they pupate and become moths
Plum moth in plum fruit, Grapholita funebrana
This form of further development ensures that Prunus domestica subsp. domestica for considerable damage, since the moths often appear in large groups and can thus infest an entire group of trees. In the garden there are usually only a small number of trees, which are quickly taken over by the pests and thus destroy a large part of the possible harvest. But you can breathe a sigh of relief, because there are numerous ways you can prevent and combat the infestation of plum moths. Good prevention is particularly effective here.
Plum moth moth, Grapholita funebrana
Tip: The moth Hedya pruniana from the same family is rarely referred to as the plum moth, because the two species look very similar in their characteristics at first glance. However, Hedya pruniana is lighter in color and feeds on other plants including hazel, hawthorn, blackthorn, rose and whitebeam.
Prevent
Prevent plum moths
If you want to prevent infestation by the worms, you must effectively prevent an infestation. Here it must be said that it is not possible to stop all moths, but the majority can be prevented from reproducing. One of the most important actions you can take to develop the larvae can prevent is the search for and removal of the larval nests. As soon as the first small fruits can be seen, you should examine them for conspicuous eggs that are laid on the underside. The eggs look like small, glassy balls that you simply remove from the plums with gloves.
Plum moth caterpillar, Grapholita funebrana
So-called pheromone traps are also available:
1. The pheromone traps are shaped like a small tent that is hung on the tree. It is equipped with glue paper inside and out and has sex attractants whose composition corresponds to that of the female plum moth.
2. Fold and hang one of each of the traps on a plum tree. The folding instructions differ from manufacturer to manufacturer. In the case of large plum trees, several traps are available depending on the size. The males are now attracted by the pheromones and stick to the glued paper in the trap.
3. With the pheromone traps you can stop a large number of males and thereby prevent the fertilization of the females. You should be extremely thorough in doing this, because if you forget a tree, that could be where the infestation is particularly severe.
4. The traps cost around 15 to 20 euros each and they are manufactured by companies such as COMPO or Neudorff.
5. Be aware of the weather when hanging the traps. Strong winds could blow the trap off the tree, so make sure to fasten it securely.
True plum, Prunus domestica
With these two measures you can prevent an infestation by the worms and protect your plums from them. The more thorough you are, the more effective the protection and the better your harvest will be.
Fight
Fight plum moths
Despite prevention, it can happen that a large part of the plums are affected. This is particularly noticeable in very warm years. If this is the case, you need to effectively control the prune moth maggots to save the majority of your harvest. A first measure to the maggots to combat is the careful selection, collection and disposal of infested fruits. The more infested plums you find, the easier it is to fight the worms. You can recognize a possible infestation by feeding holes in the shell. You should also check the previous fallen fruit to prevent the pest from spreading. Then there are the following options to fight the worms.
1. Catch Belt
Caterpillar belts are excellent for preventing caterpillar infestation. Since the first generation of caterpillars fall to the ground after development, they then have to climb the tree again via the trunk to get to the plums. the lanyard for a trunk is something 20 to 40 centimeters long and is placed right around it. This method works easily and quickly and is very inexpensive due to the cost of about 5 euros per meter. Check the girdle in early September to remove any caterpillars trying to get to the fruit via the girdle.
Glue ring on the fruit tree trunk
2. Ichneumon wasps
Ichneumon wasps are also extremely effective against the worms in the plums. for this parasitic wasps of the genus Trichogramma, as these are natural predators of maggots. They are 0.4 millimeters in size, are hardly noticeable and act as parasites on the cycle of the larvae, with the females laying their eggs in the moth's eggs. The larvae of the parasitic wasps destroy the eggs and reduce the population. The parasitic wasps are sold in packs of 3,000 to 6,000 and are simply hung on the tree as cards. The cost is between 10 and 40 euros depending on the quantity desired.
Tip: During cool summers, the moths usually do not form a second generation, which is the ideal case for your harvest. Because the first generation affects only young fruit that is not yet mature, much of the crop yield remains consumable and does not need to be discarded.