Rosy apple aphid

Fig. 5.26. Life cycle of rosy apple aphid Dysaphis plantaginea).

The reproduction rate of the rosy apple aphid is enormously high, and so it can cause very great damage. Apart from the distinctive rolling of the leaves, the fruits are also damaged hy the sucking of the aphids. The fruits stay small and deformed and do not drop. 

This damage to the fruit can occur during or shortly after flowering. The shoots are rolled up (curled tail shoots). Shoots attacked hy rosy apple aphids do not usually develop flower huds. 

Fig. 5.27. Rosy apple aphid severely affected shoot.

ENEMIES. Aphids have many enemies, hut in the case of the rosy apple aphid they are not effective enough, especially in spring. The most important enemies are ... 

These beneficials have a disadvantage relative to the rosy apple aphid they can only reproduce very slowly in cold spring weather. 

When the rosy apple aphid subsequently starts to produce nests, from June onwards, the conditions for development of the beneficials are better and they are able to keep the aphid populations in check. The beneficials thus play a significant role mainly in summer, but for the reasons just explained they are less important in the spring. 

INSPECTION AND DAMAGE THRESHOED. Because of the rapid reproduction rate and the enormous damage that the rosy apple aphid can cause, the damage threshold is very low. 

In the event of rosy apple aphid infestation occurring during spring or summer, the shoots should be cut off and removed from the orchard if more than 5% of shoots are affected. Spraying should be carried out after that. 

A reduction in winter egg laying by rosy apple aphids can be observed in orchards which lose their leaves quickly because of early termination of shoot growth in autumn. 

ENEMIES. The rosy leaf-curling aphid has the same enemies as the rosy apple aphid. In the case of the rosy leaf-curling aphid, however, the enemies are much more effective, as the rosy leaf-curling aphid does not have the same reproductive potential. 

As far as possible, control measures should not be applied immediately, in order to give beneficials (predators and parasites) the possibility of self-regulation. Because the rosy leaf-curling aphid has a large number of enemies, this is easier than in the case of the rosy apple aphid. 

Although Siegler and Popence, (1925) are responsible for the early lively interest in the toxicity of the fatty acid derivatives containing a 12-carbon chain, the ccnnon use of coconut oil is only in part due to their suggestions (38). It should be noted that coconut oil is the most important and widely used oil in the soap industry. Ihe principal pests treated were aE ids rosy and green apple af ids bean aphids black chrysanthemum, etc. 

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