Hi Jonathan – I am a landscape designer having a run-in with thrips! I installed a hedge of dodonaea shrubs several months ago. My client recently called me to check on the hedge – I was horrified to see the condition they were in and shocked that they hadn’t called me months early as there was obviously a problem. All 20 dodonaeas need to be removed and I will replace them with podocarpus gracilior . My question to you is: Should I treat the soil and area before installing the new plant material? How can I prevent the problem from returning? Any help you can give my on the subject will be greatly appreciated. Many Thanks – J.
I don’t think there will be much to gain from treating the soil right now so hold off for now. However, I strongly suspect there is a nearby infestation that might need to dealt with and I suggest you do a good inspection prior to the install. If you read our THRIP CONTROL ARTICLE, you’ll learn this pest will thrive on a wide range of plants. If you can find other nearby shrubs infested, I would recommend dealing with them first before you replant. New plantings are particularly vulnerable to aggressive thrips and they’ll take full advantage. To hold off any such attack, you’ll need to find where the current problem is located and treat it accordingly.
I fully expect you will find them on some other plants in your clients yard. If that comes to be, treat with the TALSTAR and SPREADER STICKER. I also recommend hitting the soil in these areas with the CYFLUTHRIN GRANULES. After monitoring the infestation for a week or so, you should see the population dwindle and disappear. At that point you can proceed as you desire and no soil treatments should be done if this happens now or this fall.
Now if you can’t find thrips on your clients property but suspect they could be coming from a neighboring property, treatment options might be limited. If this proves to be the case, you may want to proceed with the replanting of the dodonaea’s but just be sure and let the client know they’ll have to spray every 1-2 months if they wish to keep the plants protected. Unfortunately, I’m afraid if you cannot treat and reduce a neighboring problem, thrips will naturally forage onto the clients property and plants left unprotected will suffer. This fall treating the soil with granules would be smart but treating this area now won’t help much whether you replant or not.
Here are direct links to the information and products listed above:
Thrip Control Article: http://www.bugspray.com/article/thrips.html
Spreader Sticker: http://www.bugspray.com/catalog/products/page1317.html
Cyfluthrin Granules: http://www.bugspray.com/catalog/products/page1321.html