Griffin Greenhouse Supplies recently hosted a virtual expo featuring a wide variety of educational sessions. George Grant, Griffin’s technical specialist manager, presented about the current hot topics in insect control, mite control and plant growth regulators.
Grant emphasized that “starting clean is essential for staying clean.” All surfaces, materials and plants should be sanitized before continuing.
Grant spoke about multiple pests that are present in the greenhouse industry, including mealybugs, aphids, thrips and mites. Mealybugs are growing in pressure across the country and are “one of the most difficult pests to control,” he said. They like to hide in small spaces throughout the plants and containers and are pretty resistant to many pesticides due to their protective coatings.
Aphids continue to be a common pest year to year as they “attack almost every sort of species we grow.” Grant said, “Although there are several pest species we run into that are not considered a major issue, these are one of them, and they will not go away on their own.”
Aphids reproduce asexually and can clone themselves at an incredibly fast rate. They leave behind a bright-white skin cast when they molt, “which is a dead giveaway aphids are present.”
Thrips are another common pest that attack newly-developing and older plant growth. They scrape away at a leaf’s surface, causing discoloration and scarring. As the foliage expands, the scarring leads to a malformed leaf or flower. These scars can also cause the leaf tissue to rip open as it grows, leaving open holes in the leaves.
There were two mites Grant discussed: broad mites and spider mites. Broad mites are much smaller than spider mites – they cannot be seen by the naked eye – and they’re very good at hiding. They target new growth and continue to be a major issue for a select number of species.
Broad mites inject a toxin into foliage, leading to malformation. The foliage grows into a dark-green, leathery texture with the sides of their leaves curling in. By the time this damage is noticed, growers generally already have an infestation.
Spider mites are still relatively small but can be observed by the naked eye. They have been repeatedly hit with a wide variety of chemicals and pesticides throughout the years, so they are “incredibly resistant” throughout the country. They reproduce quickly, and it doesn’t take a lot of them to create a lot of damage, according to Grant.
Throughout the years, there has been a considerable decrease in the use of neonicotinoids due to social, environmental and legislative pressures. There are two insecticides that are gaining popularity in the industry that may be the “new neonics” – Mainspring® and Kontos®. Mainspring is meant to be used as a protectant when the plant is clean, not a knockdown when the plant is infested. It is taken up by the plant through its roots, remains effective for up to eight weeks and is plant safe. Kontos “takes a very long time to get up in the plant,” Grant said – anywhere from two to three weeks. It remains effective for up to seven weeks, and is the “only miticide that can be drenched.” Mainspring and Kontos can be used to control many pests.
Broad mites are best controlled when using a translaminar systemic miticide, allowing the spray to absorb from the top of the leaf to the underside of the tissue where the mites are hiding. (Translaminar materials move only short distances, not through the entire plant.)
Besides using insecticides and miticides, growers also apply predatory mites to control spider mite infestations, and use sticky tape in the greenhouse to trap flying insects.
On another topic, Grant said plant growth regulators (PGRs) are “incredibly powerful tools” that can be used in a “variety of different ways.” It’s important to read the product labels, as each PGR varies in how it’s applied, where it’s absorbed, how effective it is in slowing down growth, how long it’s effective and more.
He recommended applying PGRs in the morning or in the evening when the temperature and humidity are ideal, and to avoid applying when plants are under stress. Sumagic® is a common PGR that can be used on edible crops like tomatoes, peppers and eggplants, as well as some flowers. Florel® and Bonzi® can be used on flowers like fuchsia, geranium, verbena, petunia, and Calibrachoa.
Insecticides, miticides and other control methods cannot be used the same way in all situations. Some pests may be resistant to them, and some plants may be damaged if they’re used.
Griffin Greenhouse Supplies provides a wide variety of online resources to help growers identify and problem solve issues in their greenhouses. Grant highlighted how “Griffin is the only single-source supplier for horticultural needs that provides a free technical support team.”
Visit griffins.com to view all of their GGSPro resources, including technical reference guides and pocket guides.
by Kelsi Devolve
