Insect swarm before sunset

Question: Can you identify the prst that swarmed me and all on my roofdeck today, about an hour before sunset (~ 7:40 pm). Teeny-tiny flying insects. I don't think they were white flies. Do aphids swarm? Lace wings? They decended on all of the plants. My neighbor, two buildings over, experienced the same. First photo is a portulaca flower that opened a few hours earlier in the day. These blooms are maybe 1/2" max. 2nd pic shows when these insects landed. They covered the bloom. 3rd pic shows the insects on cherry tomato plant. I've seen aphids, but NEVER swarming behavior like this. What to do? How to treat?Thank you

responder: Answered by the Home and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied June 06, 2023, 12:02 PM EDT
response: The pictured insects appear to be thrips (adults, with wings, as juvenile thrips can jump but not fly). Thrips feed on plant juices similar to sap-sucking insects like aphids, but in a slightly different way. When they are behaving as a plant pest, they can cause some foliage damage but not extensive enough to warrant treatment. In this case, they instead appear to be congregating for other reasons (perhaps drawn to the intense flower color as they also do visit flowers...sticky traps for pest insects tend to be bright yellow or blue), but we aren't certain why. Although thrips can bite people, it's not something they seek us out for (in other words, it tends to happen when they land on us by accident after jumping around, not because they feed on us like a mosquito), so don't need management for that reason. Still, a number of thrips species pupate (the stage between the juvenile and adult) in the soil, so if this plant is in a pot, and if that container's soil has been re-used for a couple years or more, maybe their populations have just reached this level of abundance over time. In that case, we'd recommend replacing the soil, either now (and just carefully replanting the Portulaca) or this coming winter between growing seasons. For now, we do not recommend using an insecticide as thrips are hard to manage well using them, plus the use of such products may risk harming other organisms, including visitors to the Portulaca flowers. If they congregate again, you could try plucking the flowers hosting the "party" while wearing gardening gloves and just tossing them into a compost pile or the trash, as this might reduce their numbers if they don't disperse immediately from the disturbance.  Miri

responder: The Question Asker Replied June 06, 2023, 6:04 PM EDT
response: Dear Miri,   Thank you for your response. I think I may have brought them home from the local Ace garden shop. Now thinking about it, I was there just about sunset about 10 days ago. I remember seeing teeny-tiny bugs swarming in the rays of the sun, but just figured it was what bugs do and I was noticing them only because the suns rays were highlighting them.    I just checked my roofdeck plants/pots. These bugs are on EVERY SINGLE PLANT AND FLOWER. There must be a million of them - I am not exaggerating. And yes, when I've been up there, a few land on me and I can feel the bite.   So it seems these invaders never left and live here now. Which means they are replucating and laying eggs or whatever in the soil and that this is the new norm for my garden?? Do thrips have a habit of swarming at sunset?   Ugh! Gardening can be so frustrating!! A few pics of the "party in the petunia". But they are in the dipladenia, the tomatoes, the marigolds...everything!   I was up on the deck before I read your email. I was spraying them with Safer brand 3-in-1 spray. It was killing them on contact.  Our gardens typically get hit by aphids, so I always have that and Neem Oil spray on hand. I never spray when the bees are around (early morning this time of year for my garden - then, as more flowers bloom, it becomes an all-day thing for the bees) and I thought the  residue of "potassium salts of fatty acids" insecticides were fine for pollinators, no?   Thank you Maureen

responder: The Question Asker Replied June 06, 2023, 7:35 PM EDT
response: An additional question. Can you identify the eggs/larvae on the back of this Hollyhock leaf? Found this leaf on one of my young plants May 29.    Thank you!

responder: Answered by the Home and Garden Information Center (HGIC), University of Maryland Extension. For timely gardening information and tips, subscribe to our Maryland Grows blog and quarterly newsletter. Follow us on Facebook, Instagram, and YouTube. Replied June 07, 2023, 5:00 PM EDT
response: Hello Maureen,  The insects on the back of the hollyhock leaf appear to be aphids, one of the most ubiquitous of insect garden pests. They rarely need control and can be squished, blasted-off with a strong spray of water, or if absolutely necessary, treated with either horticultural oil or insecticidal soap. Note that no pesticide should be applied during temperatures above 85 degrees, so depending on weather conditions plus how hot it might get up on the roof, keep this in mind so treatments can be done in the evening or during a cooler break in the weather. Always follow label instructions and re-treat as directed since aphids breed quite quickly and one application won't be enough. Plenty of beneficial insects consume aphids, though, so usually they can be ignored and populations will wane on their own.  Predatory thrips species do exist, which look fairly indistinguishable from plant-feeding thrips, though we suspect you would not be finding nearly this many if that's what they were. On the flip side, though, having this many of most plant-feeding thrips would almost certainly be resulting in heavy plant damage, which we're not seeing. That said, these might be flower thrips (despite this name, other thrips species can also visit flowers) and if so, they tend to not damage foliage. Perhaps they're getting enough nutrition from the pollen in the flowers, in which case they're not as big of a concern aside from the nuisance of potential exploratory bites if they accidentally land on someone after being disturbed into jumping off the plant.  Treatment with a topical insecticide like insecticidal soap or horticultural oil (neem being one type) can work to knock-down a population but requires regular re-treatment (as per label instructions). It should be low-risk to bees and other pollinators as long as they are not present while spray residues are wet. Once dried, usually these ingredients are not hazardous to them or other insects (including the pest).  Miri