How to control the most common pests in the spring greenhouse

by Steve Wagner
“The pesticide label is the law,” said Rick Yates, “and there’s no wiggle room there.” Yates, who is the GGSPro technical services manager for Griffin Greenhouse Supplies, has been providing technical support for greenhouse and nursery growers for nearly a quarter century. “It is also important to remember that pesticide labels change often. Just because you’ve been using a product for years, if you get a new container in, take time to read the label to make sure it hasn’t changed.” With that caveat out of the way, Yates discussed Altus, from Bayer, saying he thinks it will be a breakthrough product. Similar to some nicotinoid products, it has a very distinct difference. “If you are an MOA (Mode of Action) wonk,” he said, “you know that nicotinoids are Group 4-A. Nicotines are 4-B. When XXpire came out, one of its active ingredients was a 4-C. Altus is a 4-D. It is not considered a neo-nic, which is important to some of you out there.”
Most major greenhouse pests and spider mites are controlled by Altus. Aphids and whiteflies are very susceptible to it, but it isn’t so good against thrips. “It also does a very good job against the very pesticide-resistant [Q-Biotype] whitefly,” said Yates. And when Yates says Altus is xylem mobile “what we mean is that in the vascular system of the plant, xylem carries the fluids up through the plant. A pesticide that is xylem mobile will continue to move up into the new foliage for a period of time.” And what that means is it extends your control. Usually, insecticides and fungicides lose their grip when new growth coming out of the growing tips is no longer protected. It can be applied as a drench or spray.
Aphids could well be the most ubiquitous pest in greenhouses. They feed on almost every plant part. They are found underground in roots. They also attack bulbs, shoots, stems, leaves and flower buds. “They have a very wide host range,” Yates maintains. “It might be easier to give you a list of plants that we haven’t seen aphids on. I’ve even heard of aphids on cactus.” Aphids are vectors of many plant viruses. Yates notes, “aphids secrete what we call honeydew — a very nice way of saying that they slightly reprocess the plant sugars on the way through themselves, leaving a sugary messy deposit on the other side. Ants use…that sugary frass. Ants will actually colonize aphids, move them around to better places to feed and defend them from bio-controls. Aphids and ants work in cahoots sometimes, though not for our benefit.” One effective aphid strategy would be use of long lasting drenches for aphid prone crops and hanging baskets right before they get hung up.
Fungus gnats and shore flies are often thought of as pests which are the same insofar as remedies are concerned, but there are fundamental differences in controlling them. Fungus gnats are weak fliers. If disturbed, they tend to hop to the next plant. They have long antennae, long legs, wispy and weak, whereas shore flies look like miniature houseflies with short legs, short antennae, and are very strong fliers. “When you see the adult fungus gnat,” said Yates, “that’s just the tip of the iceberg. Most of their life cycle is in the soil, so if you see one, you’ll know where they are.” Similarities in these two pests show adult fungus gnats and shore flies do not feed on plants. Their job description is to live for about seven to 10 days, lay eggs, and die. They don’t even eat. “Larvae of the fungus gnat are well known to feed on plant roots and other plant parts, which is not the case with shore flies.” Shore flies are semi-aquatic, like mosquitoes.
Asia originated many things like chilli thrips. “Though they’ve really only established themselves in the gulf coast region — Texas to Florida — they are showing up all through the U.S. and even in Canada,” said Yates. Chilli thrips tend to feed on tender foliage and growing tips of plants. Often thrips damage is confused with broad mites. The good news on control is as of right now, they are very susceptible to all the pesticides we typically use for Western Flower thrips, but also Rycar and Conserve. “We have seen so much broad mite damage the past few years, I can understand how you would be easily confused if confronted with the two.”

2017-06-02T13:24:46-05:00June 2, 2017|Grower East, Grower Midwest, Grower West|0 Comments

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