By Ronnie Barentine
After two seasons of relatively heavy and late thrips pressure in Georgia, it is understandable that growers are asking questions about thrips management options for 2015. The most common questions involve the use of imidacloprid (Admire Pro or a generic formulation) as a liquid in-furrow at plant. Here are a few options for growers in 2015 and some points to remember as decisions are being made:
1. Phorate (Thimet 20G) in furrow – Thimet has been around for a long time, and we have years (decades really) of data that show Thimet does a good job of reducing thrips injury and that it can also reduce the incidence of tomato spotted wilt virus. Thimet is an organophosphate insecticide, and as with all pesticides, read and follow label instructions. Some phytotoxicity (aka “Thimet burn”) is commonly observed when Thimet is applied to peanut, but this injury has not been associated with lost productivity.
2. Thiamethoxam (CruiserMaxx Peanut) seed treatment – Thiamethoxam is the active ingredient in CruiserMaxx Peanut seed treatment. In some research trials and grower fields in 2013 and 2014 we saw elevated thrips damage on CruiserMaxx treated peanut where pest pressure was high. Growers should be aware that thimethoxam on the seed is not expected to give control of thrips beyond 21 days after planting. This can lead to problems when thrips migrations occur later than normal. We do not recommend an automatic foliar insecticide application at 21 days after planting, but we highly recommend that growers scout their fields for the presence of immature thrips around 15 days after planting. Thiamethoxam does not reduce the risk of tomato spotted wilt in peanut.
3. Imidacloprid (Admire Pro, Velum Total, various generics) liquid in-furrow – Imidacloprid applied as a liquid in the furrow at planting has given good control of thrips in trials at UGA and other Southeastern universities in recent years. Imidacloprid has been shown to be compatible with most liquid inoculants and fungicides (not all combinations of products have been tested). Like thiamethoxam, imidacloprid will not reduce the risk of tomato spotted wilt in peanut. Growers should note of the product formulation they plan to use as rates vary by formulation. Applying a 2F product at a 4F product rate will result in significantly less active ingredient than the label recommendation. Velum Total contains both imidacloprid and an active ingredient (Fluopyram) targeting nematodes. Growers who want to use imidacloprid for thrips but who do not have a nematode problem do not need to invest in the additional AI, but should choose a stand alone imidacloprid product (e.g. Admire Pro).
4. Acephate (Orthene) foliar spray – Orthene will still kill thrips, and we use it regularly in GA when at-plant insecticides “run out of steam”. The problem associated with leaving off an at-plant application in favor of a foliar spray alone is timing. This approach requires careful scouting (something that is much less common on our peanut acreage than it should be) and the ability to get into the field on short notice to make an application. Given the hectic schedule of most growers in the spring and the potential for unfavorable weather, being able to cover large acreage with a foliar application is a gamble most growers should avoid.
No matter what thrips management tactic is chosen, scouting is still a good idea. Nothing provides 100% control 100% of the time, and the only way to know if a problem is developing is to monitor fields regularly. Price of inputs will be an important factor in decision making in 2015. We need to be sure not to cut labeled rates in an effort to save money…reduced rates will likely lead to reduced efficacy and can ultimately cost more in supplemental treatments and/or lost productivity. Another thing to consider is that peanuts planted before 10 May are at an increased risk for tomato spotted wilt virus; none of the insecticides registered for thips control in peanut will reduce the risk of the disease except Thimet.