Larry,

I rarely see thrips here, but the speckled-looking damage in the first photo does look like thrip damage. The only two kinds of thrips I know of that attack onions are western flower thrips and onion thrips. If you have garlic, watch those as well because the thrips will attack them too.

Usually the thrips will attack onions that are hot, dry and stressed, so be sure (don't throw things at me for saying this) to keep their soil moist. Also, if the onions are lacking in nitrogen that seems to draw thrips to them. Remember that onions are heavy feeders that need nitrogen-rich soil or regular feedings.

One thing I am wondering about your onions in particular is this: we know that you sometimes get rain in very high amounts, and we know that waterlogged roots cannot absorb nutrients properly until the waterlogging ceases. Whenthat has happened at my house in the past, I can tell the plants in waterlogged soil stop taking up nutrients via their root system because their color fades from the normal healthy green to a pale green that may have a yellowish tint. That sort of nutritional deficiency can make the onions more attractive to thrips. The only way I know of to combat that is to foliar feed the onion foliage with a water-soluable fertilizer high in nitrogen. Since the roots couldn't take up the nitrogen in waterlogged soil, you'd want to spray a light mist of high nitrogen water soluable fertilizer on the foliage in the hope that the leaves would absorb enough nitrogen to help them be less stressed and less attractive to thrips.

You also could spray your onions with any pesticide labeled for use with thrips. Since I try to garden organically as much as possible, I'd likely use a product containing Spinosad. or maybe neem. I might use insecticial soap early in the season when the temperatures are still below 90 degrees. I am not sure what synthetic pesticide is labeled for thrips, but I'm sure you'd have plenty of choices.

If you have beneficial insects like green lacewings or minute pirate bugs around, they'll help control the thrips.

Thrips reproduce very quickly, so it is important to nip the thrip infestation in the bud as soon as you notice it and before they can reproduce many new generations. The can reproduce incredibly quickly, and the females can reproduce without the assistance of the males. Hmmm. That makes you wonder why there are any male thrips, doesn't it, if they aren't necessary?

That's about all I know about thrips.

Oh, one more thing. You can distract thrips from hitting the onions so hard by having diverse plantings around them....other veggies, herbs and flowers. However, grow grains away from your onions. Thrips seem worse in onions grown near fields of grain, so if you plant your onions near a winter cover crop of cereal rye or any other grain, I'd cut that stuff down before I planted onions.

Hope this helps,

Dawn

Dawn. thanks. I try to hold off on the insecticide as much as possible, but will use it if I feel it is needed.

This area is in the north garden and it has been too wet to work all this year. I have been waiting on my soil test to get back before I do anything, but I will feed nitrogen because I an sure the plants can use it. I dont have to worry about P & K because I will be running high in that area. I will also add some mulch later because I read that would help draw the predators.

My garlic is in the first row of the third picture. It looks worst than the onions. Matter of fact the garlic was the reason I checked the onions. I certainly did not expect to see any insect damage because it has been so cold.

I did not grow a cover crop this year so I wont have to be concerned about the thrips and rye, but I had planned on growing corn in the area just east of the onion crop.

Thanks again, I will get some nitrogen the next time I go to town.

Larry

Larry,

I know the garlic looks bad, but I don't know what is causing it. It could be the soil is too wet, or very cold weather has nipped back the plants at bit, or maybe you have thrips on them too. It does look like you can see speckled spots or stippling on the garlic foliage similar to what is on the onions.

I love garlic because it is so easy to grow----as long as the ground doesn't waterlog and make it rot, you cannot kill it. If you look at the garlic and it seems to have the same problem as the onions, then the solution would be the same.

I know that the color of the onions and garlic in your photo are not as good as what I usually see in your garden, but I am sure that's because it is too cold for the plants to take up enough nitrogen to be really green. Neither my onions or garlic are as green as I'd like either, but so far they are not showing any thrip damage.

As soon as we have a few warmer days and nights, nitrogen uptake should improve and the onion and garlic plants should green up more. I don't usually see it warm enough here for that to happen until April. As long as your ground stays very wet, it cannot happen either.

I tried walking in my garden today. It was not a pretty sight....it still is mud city in there.

Dawn

heres an article on onion thrips.

The following article, by Professor A.M. Shelton of Cornell University, appeared in the March 2007 issue of Onion World and is reprinted by permission.
Onion Thrips
Scientific Name:
Thrips tabaci
Geographic Distribution:
Worldwide. Found in most areas where onions are grown.
Identification
Immature: White to pale yellow in color, onion thrips in the immature stage are very small, usually 0.5 to 1.2 mm in length. These thrips have elongated, elliptical and slender bodies with dark colored eyes that are easy to see. Unlike adults, immatures do not have wings and, hence, cannot fly.
Pupae: This is the intermediate stage between the immature and adult stages. Thrips pupae are pale yellow to brown in color and have short antennae and wing buds that are visible but nonfunctional.
Eggs: White or yellow in color, eggs are microscopic and are difficult to see without the aid of a microscope. Females typically insert the eggs, one by one, into the plant tissue. Adults prefer to lay their eggs in leaf, cotyledon or flower tissues.
Adults: Adults are about 2 mm in length and have fully developed wings that are fringed with long hairs. When at rest, the wings are folded along the back of the insect. Adults are pale yellow to dark brown in color.

Host
Preferred hosts are onions, garlic and other related plants. Onion Thrips also attack various crops including cabbage, cotton, celery, tomatoes, beans, cucumber and pineapple. Thrips can be found on almost any cultivated and weedy plants.

Biology and Ecology
Typical life cycle is 14 to 30 days, however, when temperatures are over 90˚ F, the life cycle can be as short as 10 or 11 days. Adults may live up to 20 days. Thrips do not need to mate for reproduction. Females that do not mate will produce only female offspring. Each female can produce up to 80 eggs. It is important to remember that a single thrips can produce a substantial population within a very short time.

Damage
Thrips can cause considerable economic damage. They begin feeding by piercing and rasping the leaf surface with their mouth parts to release the liquids from the plant cells. Later, they suck up plant contents. Thrips prefer to feed on the young plant tissue on the newest emerged leaves, so scouting for thrips should begin there. When the leaf grows, the previous damage produced by the thrips enlarges, leaving silvery patches or streaks on the leaves. Small black fecal matter is also commonly seen on the leaves. When damage is severe, these small patches can occupy much of the surface of the leaf and the plant cannot adequately photosynthesize. The plant loses more water than normal through the damaged tissue and plant pathogens can easily penetrate the injured plant. In severe attacks, the whole plant can turn white or silver and leaves can wither. In injured plants, bulb size is reduced. Thrips may also serve as vectors of some viruses such as Iris Yellow Spot Virus and other plant diseases, including the fungus, purple blotch (Alternaria porri).

Control
Onion thrips populations and damage are most severe during hot, dry weather. The reasons are that rainfall is normally a major mortality factor and more generations are produced in hot weather. The main method of control is the use of insecticides, but populations of thrips in some areas have developed resistance to some insecticides, especially pyrethroids. Best control results are obtained with an integrated strategy that includes making sure transplants are free from thrips, plots are planted away from infested areas, culls and volunteers are removed from the field (since they can serve as a source of infestation), and the plants are not stressed by other factors such as poor irrigation. Because of the occurrence of insecticide resistance in some regions, check with your local extension service to determine which insecticides might be useful in your area. It is best to rotate classes (i.e. different modes of action) of insecticides every two weeks to slow the development of resistance to any single class. Before using insecticides, use the economic threshold for onions in your particular area as a guide for when to treat. Modify the general treatment guidelines based on the weather, cultivar and market value of the crop. Special attention needs to be observed when the weather is hot and dry since thrips populations can explode. Due to growing insecticide resistance problems around the world, it is very important to use insecticides as little as possible in an IPM program.

Robert, thanks, that is very helpful.

Larry

I have thrips here every year. At least for the last 5-6. Although in some years the infestation has been heavy usually I don't see that they affect the size of the bulbs much. Mine are usually very well fed and that might make the difference. The problem I have is the thrips carry diseases that wipe out my tomatoes. One reason I'm considering not planting onions this year. My garlic looks good but haven't grown as much as the last few years although planted earlier. I feel a lot of that is due to the although not cold overall cool weather. No signs of the trees budding here yet. By this time last year some were. One thing I find interesting is that you are seeing some damage on your garlic. I have never seen any damage on my garlic. In fact I use the concentrated spray to control them on my onions. Jay