By Gus Lorenz, Ben Thrash, Nick Bateman, and Glenn Studebaker; University of Arkansas Division of Agriculture Entomologists
A few people have called this past week about finding 4 or 5 small corn earworms per 25 sweeps in blooming soybeans. In this situation the corn earworm virus (Heligen), might be a good option, especially with the low price of soybeans this year. Also, the likelihood of getting reinfested is substantial because of how late this crop is, and the virus may provide control of those later generations. Remember, this virus isn’t like a conventional insecticide. Catch the worms when they are still small (<1/2”). Consult our fact sheet, AG1306, on how to properly use this product.
Link to virus fact sheet: https://www.uaex.edu/publications/pdf/AG1306.pdf
Some folks are also picking up threshold levels stink bugs in blooming beans. The vast majority of the time they are just passing through and will be gone in a week or so. We do not recommend treatment. Remember stink bugs are seed feeders and if no seed are present, they will move to a place where they have some seed to feed on. With that being said, we have been picking up plenty of stink bugs in ditches and cover crops and anticipate them being a problem a little later in the growing season. While we are on the topic of stink bugs, let’s talk about the elephant in the room, redbanded stink bug. Currently, they are being sprayed in Louisiana and numbers are high in areas. They will likely move up into the state later in the year, and we know they did overwinter in southeast AR. Numbers usually begin to increase when Louisiana begins harvest, pushing them farther north and into the state.
We have cotton in the state ranging from just coming out of the ground to about to bloom. In young cotton, colleagues from around the state have been picking up some three cornered alfalfa hopper damage, so keep an eye out for that.
In wild hosts we are finding high numbers of plant bug adults and they are beginning to move into cotton fields. Lots of growers are wanting to use imidacloprid to control the adults – we are not recommending it. We get it, it’s cheap. Just remember that the most expensive application is the one that doesn’t work. Our experience with it has been very poor over the past several years and yes, we have tested it at above labeled rates. It still doesn’t work. “But I have aphids!” Still doesn’t work. Centric works a little bit better and Transform at 1.5 oz would be a much better choice. In fields with nematodes and plant bug numbers around threshold, Vydate is a good option, giving us about 70% control on average. Diamond at 6 oz/a combined with a knockdown product is a good idea where cotton is around the 3rdweek of squaring and plant bug numbers are increasing. One thing we do want to stay away from are the pyrethroids and acephate. Spraying these broad-spectrum products this early in the season kills our beneficials and opens the door for mites and worms. Remember, we just want to keep our square set above 80%. Keeping 100% of fruit on the plant can actually be detrimental to yield.
Speaking of worms, a few are showing up in some conventional cotton around the state, not a lot, but some. We saw an interesting field yesterday where cotton had been planted into a fairly thick stand of weeds. After the grower killed the weeds, bollworms moved over onto the cotton and were eating the terminals and boring into the stems of the plants. Did I mention it was pre-blooming Bollgard II? I understand you have to do what you have to do, just don’t be surprised when it comes back to bite you. (Pictures below)
Nick Bateman and Jarrod Hardke wrote about rice water weevils (RWW) in a blog post on June 7thso I won’t go into too much detail, but RWW numbers continue to be high and in many fields there is a substantial amount of leaf scarring. Most rice in the state is treated with NipsIt or CruiserMaxx, which provides adequate control of RWW as long as the field is flooded in a timely manner. If it takes longer than 28-35 days after planting to get to flood and there is significant leaf scarring, a foliar application within 5-7 days after flood may be needed. Rice treated with Dermacor or Fortenza will not need a foliar application for RWW.
Just a heads up, we are finding huge amounts of rice stink bug in wild hosts this year. So the earliest heading fields will likely be hit hard.
Not a whole lot going on with insects in corn, but a few first generation corn borers are being caught in some areas. In a few weeks (Late June – Early July) the second generation of borers should show up. If you have conventional corn you need to be trapping for southwestern corn borer. Contact your county agent about where to get corn borer traps. Most of our counties are running traps at this time and can tell you if borers are showing up in your county.
Some people are observing stunted and tillered corn along field edges. With all the stink bugs we’ve been seeing, this was likely due to stink bugs being present earlier in the growing season.
Fall armyworms and corn earworms are showing up in corn whorls in some conventional hybrids. It is extremelyrare to see a yield loss from defoliation in whorl stage corn, the exception being if it is extremely late planted. Threshold is 3-5 larvae per whorl.
If you need us don’t hesitate to give us a call.