Plants in retail yards may be showing signs of nutrient deficiency as well as botrytis blight and possibly root rots.
Clean plants by shaking hanging baskets over a trash barrel to dislodge spent flowers. It is also a good time to check the root health of plants. Healthy roots will be firm and fill out the pot. Decaying flowers and plants give off ethylene which will contribute to premature loss of foliage and flowers or premature flower death of nearby plants, so removed dead and decaying plant material. Plants sensitive to ethylene include geraniums, salvia and snapdragons.
Tospovirus is a genus that includes Tomato Spotted Wilt Virus (TSWV) and Impatiens Necrotic Spot Virus (INSV). Western flower thrips is the predominant insect vector. Thrips acquire the disease as a first instar larvae as they feed on virus-infected plants (including infected weeds showing few, if any symptoms). Once mature, the winged adult thrips are primarily responsible for viral spread. An infected thrips is able to transmit tospoviruses to at least one plant per day until its death. Adults do not transmit the virus to their young.
Impatiens Downy Mildew was found in greenhouses in Michigan. Earlier this spring, growers in three nearby states reported outbreaks of downy mildew on impatiens in their greenhouses. In the last two weeks, downy mildew on impatiens has been confirmed in Michigan greenhouses spanning four counties. In each case, the disease was widespread within the greenhouse and the losses were nearly 100 percent. The diseased plants were disposed of immediately and were not purchased by consumers.
Iron deficiency has been observed on petunias, calibrachoa, thunbergia, scaevola and vinca (myrtle). Symptoms appear as interveinal chlorosis, normally starting at the shoot tips, but often they occur throughout the entire plant. Sometimes the leaves of some Fe deficient plants turn almost white. Preventing Fe deficiency can be accomplished by controlling pH and using an iron chelate fertilizer. In addition to pH, cold media (cold roots) or poor root development will affect uptake of iron.
Shore flies (Scatella stagnalis) are often mistaken for fungus gnats because both are small, dark colored flies found in moist environments in the greenhouse. Both adult and shore fly larvae primarily feed on algae and are found in areas where algae are growing. While shore flies do not feed directly on plants, adult flies deposit unsightly black fly specks on foliage. Shore flies may also carry Pythium oospores in their midgut and excrete them in their droppings.