Over-watered Plants: Stunted plants may be a sign of over-watering. Plants can be easily over-watered during overcast, cloudy weather, when plants with different water needs are grouped together or by an inexperienced waterer. Over-watering deprives roots of oxygen and increases susceptibility to root diseases such as Pythium and also leads to algae growth and infestations of fungus gnats and shore flies. Check roots regularly for signs of over-watering by gently removing plants from their containers.
Cloudy, rainy weather, cool nights and greenhouses full of plants provide an ideal environment for Botrytis. Botrytis symptoms may include leaf spots, flower blights, bud rots, stem cankers, and stem and crown rots and can be mistaken for other causes.
Watch for aphids including the foxglove and green peach aphids. Foxglove aphids tend to feed first on the underside of the lowermost leaves and then migrate to the flowers. Because foxglove aphids reproduce faster at 50˚ to 60˚ F than at 77˚ F, they are more of a problem if your crops are grown cool. Foxglove aphids also tend to drop off of the plant and cause more leaf distortion than the other types of aphids. Green peach aphids blend in and you will often see signs of aphid activity (white shed skins, curled growth) before seeing the actual aphids.
Calibrachoas are susceptible to several diseases and nutrient disorders during production. Here is a list of common problems to watch for and prevent this growing season.
Most thrips in greenhouse are females. Adult females may live for approximately 30 to 45 days and lay from 2-10 eggs per day which are inserted into plant tissue. The first two larval stages remain protected in the tender young growth. After the 2nd instar larvae stops feeding, it migrates to the base of the plants and enters the growing medium to pupate. Adults emerge in two to five days, depending upon temperature. Thrips development occurs between 50˚F and 90˚F. They can survive cooler temperatures than 50˚F; however, there is no development at that temperature.