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Pecky Rice and Stink Bug Damage: Are They the Same Thing?
Author: Gus Lorenz, Extension Entomologist

Last week, I had a consultant call me to say that samples had been pulled in several fields and reports from the samples indicated that the rice was estimated to be at 2.9% peck. The field has been sprayed twice for stink bug and scouting records indicate that populations have been kept below threshold the entire season. This situation begs the question, “Are pecky rice and stink bug damage the same thing?”

There is a lot of literature out there that tells us pecky rice is associated with stink bugs certainly but also with several fungi and bacterial diseases. I guess anything that causes a spot to appear on a rice kernel could be the causal agent for peck. So while most of us associate pecky rice solely with stink bugs, this is not entirely accurate.According to the literature there are at least 5 or 6 different fungi (probably more) that can also cause this condition on rice.  We all know the growing conditions this crop has gone through, and the rice agronomists tell me that last year’s crop experienced “heat damage,” so if we had it last year, I have to assume we have it this year.  I’ll say right up front, I don’t know a whole lot about the agronomics/physiology aspect of rice. I do know that by and large the growers and consultants I’ve visited with have done an excellent job of handling this stink bug situation we were dealt with this year. The stink bug situation on the earliest heading fields was as bad as many of us have seen. However, as time went on the populations moderated. Also, remember that in the first two weeks, we treat stink bugs to maintain yield potential, not to reduce peck. It’s the third and fourth week of heading that we treat for stink bugs to control pecky rice. During that time, on all the rice I am aware of, we were able to maintain populations below threshold with well-timed applications. I won’t even guess how many phone calls we’ve taken on stink bugs this year…I’ll just say that I think I’ve talked to growers and consultants representing the majority of the acreage in this state, at least it seems like it.

Pecky rice

Pecky rice - Photo courtesy of LSU AgCenter

Obviously, there are many concerns here, and the biggest is the rice crop and how these environmental conditions will impact the yield, quality, and ultimately the rice growers’ profitability. Secondly, if “peck” is a problem with this crop, as growers and industry understand, there is more at hand here than stink bugs. Growers may want to blame consultants for pecky rice discounts thinking stink bugs were the problem, when in reality, it was environmental and other factors the consultant has no control over. Finally, we don’t want to get overly aggressive on controlling stink bugs. Spraying too much leads to too many problems: reducing profitability for the grower, insecticide resistance, secondary insect problems, etc. We have been aggressive this year with the reductions in percentage peck allowed from 5% to 2.9%, and most growers and consultants felt the need to be proactive and treat as soon as stink bug numbers got close to thresholds. This is understandable to a degree, but like everything else, you can go too far with anything.

With all that being said, we still aren’t out of the woods with stink bugs. Many fields are just now heading and some aren’t even heading yet. We have to continue to scout closely. The stink bugs have transitioned from hitting fields at early heading and have moved to fields in the last two weeks of heading. Remember, rice stink bugs are seed feeders and they will prefer feeding on seed that is formed. Also remember that in the second two weeks of heading, our threshold goes to one per sweep or 10 stink bugs per 10 sweeps. The decision now becomes when to terminate insecticide applications. Consider how much of the panicle on the average in a field is still soft dough and how many stink bugs you have to help you determine whether or not the field will require an insecticide application. The pyrethroids continue to provide excellent control, but we need more options in the future if rice stink bugs continue to be a problem. Word of warning: These late-maturing fields will be a real challenge to keep stink bugs below threshold levels. Keep scouting.

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