Answer: I'm not sure what might be going on with your glads. Especially if they turn white and then fall over dead. Doesn't sound good, does it! Gladioli are relatively free of insect pests. The most troublesome pest is the gladiolus thrips. This insect is very small and seldom seen as it feeds in hidden places. It does considerable damage, especially to the flowers. It works on the buds before they emerge from the sheaths and causes malformed and spotted flowers. Thrips may overwinter on the corms. Aphids, grasshoppers and cucumber beetles are other insect pests that may cause damage to flowers or foliage.
There are many different disease organisms that attack the corms and stems of the gladiolus. Collectively, they might best be called corm and stem rots. Most are active during storage and develop with improper curing and storage. Before corms are planted in the spring, they should be carefully inspected. Pull back some of the husk to examine the inner surface and eliminate all corms that are infected. Although infected bulbs may grow if planted, growth is generally weak and stem rots often develop later to cause death. One of the best control measures against these rots is immediate removal and destruction of bulbs or plants that show disease.
Roses can shrivel if the weather is hot and windy. They might also shrivel up if you've sprayed insecticides with an oil base. The oil can cook the leaves and flowers in the summer sunshine. Deep watering once or twice a week is all they need so I don't think they are shrivelling because of lack of water, especially if you amended the soil with organic matter prior to planting. Maybe the best approach is to clip off affected leaves and flowers of your plants, place them in sealable plastic bags and take them to your local Master Gardener Clinic, cooperative extension or well staffed nursery for onsite help. It's really difficult for me to try to diagnose a problem without actually being able to examine each plant. Wish I could offer more help!
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