This is a condition and not a disease (see photo at right).
Bud drop usually happens at the start of the flowering period and is mainly caused by variation in temperature (hot days and cold nights). The buds turn yellow/green and fall off when touched.
There is not a lot that you can do about bud drop, you just have to wait until the weather settles and the nights get warmer. Do not feed plants until the buds start to set and flower. You can get this problem more than once in a season.
Bud drop can also be caused by watering with a cold hosepipe - use water that has stood for 24 hours if possible. Leave as much growth on as possible, including tendrils, until it passes.
These are the little black beetles that get inside the 'keel' of the flower and come out onto your window when brought into the house.
Again, there is not a lot that you can do about these beetles, as they are coming from fields of Oil Seed Rape (they are sometimes called The Rape Beetle). You might try placing the cut flowers in a shed or garage with a window overnight, and the majority of the beetles will come out onto the window. You may also try placing a yellow bucket of water amongst the plants in the garden, which will attract a lot of the beetles out; they will fall into the water and drown.
Yellow leaves on the bottom of the plant
Leaves starting to go yellow on the bottom of the plant is usually caused by over-watering, or by watering from a cold hosepipe. It can also be caused by the compost being used being too rich and burning the roots of the plants. This is very common in containers with too many plants.
Sweet Peas grown in containers need to be planted with at least 10" around each plant and in a container that is as deep as possible. They are very hungy and thirsty, and if grown too close to each other will be fighting over any goodness in the container.
This is the white powder that is seen on the plants (see photo at right). This can be kept at bay by spraying the plants with a product called 'Systhane' which is available from most good garden centres. We spray in anticipation from early June, and continue once a month for the rest of the flowering season. Dry conditions and lack of air circulation (plants too close together) can cause this problem. Dry conditions can be sorted by watering the foliage regularly.
Germination and Growing
For advice on germinating and growing Sweet Peas, please read our 'How to Grow Sweet Peas' page.