Having trouble with thrips? Ask an expert – OregonLive

Were well into gardening season and you might have some questions. For answers, turn to Ask an Expert, an online question-and-answer tool from Oregon State Universitys Extension Service. OSU Extension faculty and Master Gardeners reply to queries within two business days, usually less. To ask a question, simply go to the OSU Extension website, type it in, and include the county where you live. Here are some questions asked by other gardeners. Whats yours?

Q: For a couple of years now, I get a couple of nice blooms from my dahlia at the beginning of the season. And then, on the other buds, they dry out and die before they open, like something is eating it inside.

A: That certainly looks like thrip damage. The eggs are deposited (tiny, tiny ones) on the buds and they eat the inside of the flower, turning it brown and it dies.

Thrips come around in late spring and summer so timing is about right. There are a number of things you can do to not only stop the buds from dying but disrupt the life cycle of thrips.

This may be the western flower thrip, tiny 1/20th of an inch long, they are yellow or brown and very hard to see even as adults.

The larva eat the developing flower petals and by the time the flower starts to open, the larva are gone.

Thrips like dry weather (which we have in abundance this year). Water thoroughly weekly down at least 2 inches and mist frequently.I dont usually recommend this but you can put a sprinkler on the plant to keep it moist.If the weather were anything but hot and windy, I would not recommend this as it is a great way to grow mold, but thats in our wet, foggy and cool weather with rainy periods.

No matter if the plant is in a pot or in the ground, keep the lawn mowed down or any weeds out of the area. Thrips will overwinter on these plants.

Spinosad is a spray that can be used and may penetrate down to the petals in a bud.Itwill kill the thrips.Spray all sides of the plant. Also, 100% pure Neem oil (found online) will kill them.You can alternate, but follow the directions carefully.Both are considered organic sprays and can be used on food plants as well.Getting the population down will help keep the new buds healthy.

Another pest, the broad or cyclamen mite also likes the dahlia buds but they usually attack in wet cool weather. In that case, you would spray with Neem. If the buds are slightly ready to open you can gently open a small area of thebud and spray a little of the Neem inside.Neem is a plant-based oil that helps with fungus as well as pests. Both of the sprays will kill ALL insects so do not spray on open blossoms or near bees and other pollinators.

Neem oil is usually effective for about 24 to 36 hours on the petals.Other flower pests will eat them and die.The bees are interested only in the pollen but it is almost impossible to spray a flower without getting the pollen.

You can also use yellow and/or blue sticky paper. You can find it online.Thrips seem to be attracted to blue sticky paper more than the yellow, but I use both.Another pest that eats dahlias like crazy are the striped and spotted cucumber beetles.They are attracted to the yellow color.

Neem oil likes to gel, so if that happens, put the spray bottle in warm water. It will liquify quickly.Always shake the bottle before spraying to make sure the oil is mixed with the water.

Here is a link about the life cycle of a thrip for your review. Sheryl Casteen, OSU Extension Master Gardener

Fallen pine treeOSU Extension Service

Q: A pine tree fell on my property. It separated where the trunk meets the root structure. Half of the core at the base is black. How do I analyze the standing pines to see if they are impacted? Is there a treatment available to eliminate this fungus? Washington County

A: That is a difficult question as diagnosis of root disease/rot in tree roots is notoriously difficult.In this case it appears that the tree was wounded, and the fungus came in to the tree causing the rot.One way to investigate the other trees is to check for wounding/callus tissue at the base of the tree.

If root disease is an issue for the other trees, it will likely show up in the crown.Trees with root disease tend to have thin foliage (not full crowns),yellowing foliage, maybetop dieback and lots of smaller-than-normal cones (stress crop) in the crown also. If your trees look healthy, they may be OK.Sometimes, the crown will look fine yet the tree somehow compensates, so it is not always for sure.

If the trees are a hazard, ie. if they are big enough to hurt someone, you should invite an arborist to check them out. David Shaw, OSU Extension forestry specialist

Winter squash can take 50-55 days to fruit set. File photo. (Gus Chan / The Plain Dealer) The Plain Dealer

Q: I planted five sweet meat pumpkins in May and for the last few weeks I have only seen male flowers. Should I be worried or are the female flowers coming soon? Im concerned that I wont have enough time for a pumpkin to mature before the weather turns cold. Marion County

A: Generally, it takes about 50 to 55 days after fruit set until harvest for winter squash. Some varieties take a little bit longer.So, there is still time to get harvestable fruit by end of September or early October if the plant starts producing flowers soon. Im guessing that the heatwave interrupted the normal flowering and now the plant has to catch up. So, cross your fingers anddont give up hope yet. Brooke Edmunds, OSU Extension horticulturist

Wood chip mulch would be an easier choice then most plants under a maple tree. Jamie Hale/The Oregonian

Q: Do you have any suggestions for low-growing, easy-care ground cover under a maple tree? Multnomah County

A: Maple tree ground covers are tricky because maples shed their leaves, which need to be raked up. Not raking will often kill a ground cover and raking over it becomes tricky without damaging the plant you have chosen.

A wood chip mulch is sometimes the easiest solution to the ground cover problem, especially for older trees with lots of leaves. It breaks down to give the tree more nutrients and keeps the roots moist and cooler than bare soil. You can get arborist chips for free in most areas.

Then there is the shade problem. You will want a plant that can tolerate shade but doesnt compete too much with the trees roots. Also, some maples actively discourage other plants from growing in their root areas (allelopathic) so not just any plant will work.

Some ideas include sweet woodruff, hostas, ferns, bleeding heart, rhododendron, wild geranium, violets, trillium and hardy cyclamen. Dont add soil to the area or you risk smothering your tree roots. Also realize that birds will add their own seeds to whatever you plant, so keeping the area weed free will be necessary to keep the tree healthy.

I guess that puts me back to the arborists chips. Rhonda Frick-Wright, OSU Extension Master Gardener

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Having trouble with thrips? Ask an expert - OregonLive