The sweat pea plant does suffer from some pests, the most common being the Greenfly. These insects suck the sap out of the plants and reduce the growth and can spread incurable diseases. Another pest being the Pollen Beatle which are small, shiny black beatles which eat the pollen and disfigure the flowers. Other pests include Caterpillars and Thrips.
Another problem that is not necessarily a disease is Mildew, this is a white powdery coating that covers the leaves and slows down growth. A disease called Mosaic is spread by greenfly which causes the leaves to turn yellow, new shoots become distorted and flowering stops.