Cold Weather Effects on Insect Populations?

In my mind, the past winter was similar to last, with some colder than average conditions. Below is a repeat of an article last year discussing how winter weather affects insect populations. I added some comments, scoring my predictions.

Hey, let’s face it. The reason we have more kinds of bugs in the South is because we have a warmer environment. However, not all insect pests are equally affected. Some are very tolerant of cold weather while others take a hit during a hard winter. Below are some examples.

1) Boll weevil: I know this one is eradicated in the Mid South, but this pest is one reason this question arises so much. Most people recall that boll weevils are sensitive to winter kill, and populations would be substantially reduced the year following a harsh winter.

2) Tarnished plant bug: Sorry, they can tolerate very cold winter, and this species actually occurs well into Canada. Don’t expect much in way of a winter kill, but a cold winter can definitely delay the weedy hosts that support early plant bug populations. How this affects populations that will occur in cotton is much less predictable. We had a average or higher plant bug populations in 2014. I expect the same for 2015. Our recent sampling indicates overwintering adults are currently feeding and laying eggs on weedy hosts.

3) Southern green stink bug: This species does not like the cold and rarely occurs in Tennessee except late season and/or after 2-3 consecutive mild winters. We will certainly see reduced populations across much of the South this year. I don’t expect to see one in Tennessee! Expect the same this year.

4) Green and brown stink bugs: They don’t mind the cold too bad and populations persist well north of Tennessee. They tend to have fewer problems with stink bugs in the Midwest because they have fewer generations and less time for populations to build to economic levels. I’m not expecting much winter impact in Tennessee. Stink bug populations were typical in 2014. This will be similar in 2015.

5) Brown marmorated stink bug: An invasive pest from Asia, this species is well established in Pennsylvania, Virginia, Delaware and other surrounding states. It is also well established in the Knoxville and Nashville area. It is invading from the north and appears to do well in the cold. Indeed, hot summers may negatively affect the spread of this pest in the South. This one continues it’s slow spread. I’m not so sure about the hot weather prediction, but this critter seems to prefer urban environments and areas with more woods than crops. It’s doing well in east Tennessee and the Nashville area. 

6) Kudzu bug: Another Asian invasive that does not appear too sensitive to cold weather. We will find out more this year. However, both kudzu bug and brown marmorated stink bugs like to overwinter in homes and other structures, so we know some will make it through the winter. Based on its distribution in its native home range, this pest should make it just about anywhere kudzu is common in the South. However, the kick off to seeing the first generation will occur later as you move northward. I expect there is a place where only one generation (as opposed to two) occurs each year.  This could be a help, but we don’t know where that line is yet. It looks like this pest is more susceptible to winter temperatures than originally thought. We had some winter set back in 2014, and I expect similar help in 2015. It will eventually spread across West Tennessee, especially after we have a warm winter, and then we will be dealing with Kudzu bugs more consistently. I’m sure the winter in 2014 set them back in the Knoxville area, where they have been well established for a couple of years, but there were enough of survivors to cause issues for homeowners and require treatments in some soybean fields.

7) Southwestern corn borer: The hard winter should give us some help here. Cold definitely hurts this critter. Thus, it rarely gets much further north than Kentucky and southern Illinois. I expect reduced problems in Tennessee during 2014.  I expect the same … reduced populations but enough survivors to still some potential problems in non-Bt corn fields.

8) European corn borer: This corn borer does just find in both northern and southern geographies. It has a history of being a major pest in the upper Corn Belt.  Expect little effects from winter, but this one is not normally a major problem in most of Tennessee.

9) Threecornered alfalfa hopper: Tennessee is about this insect’s upper limit, and I’ve seen slow starts for this pest following previous cold winters. Expect the same for 2014, but populations may still rebound enough to be a problem in wheat beans. Populations started slow last year, and I expect them same in 2015.

10) Fall armyworm, beet armyworm, soybean looper, and velvetbean caterpillar: These pests typically do not make it through the winters in the U.S., except for extremely southern areas where it does not freeze. Our infestations originate from migratory moths in places like Southern Florida, Puerto Rico, Mexico, South Texas and South America. Thus, mid-southern temperatures do not predict much about the occurrence of these critters. Fall armyworms were awful last year. Enough said!

11) Green cloverworm, yellowstriped armyworm, corn earworm: These are native species with a broad distribution. I do not expected a predictable, negative effect from our hard winter. The corn earworm (i.e., bollworm) may have a little trouble making it through this last Tennessee winter, but it is a very capable migrator. How well it fares on spring hosts to our south probably will have a bigger effect. No change!

12) Fire ants: Yeah, the winter should knock these guys back a good bit in Tennessee. Down but not out! Their distribution will likely continue to ebb and flow northward depending upon how harsh or mild the previous winters have been. No change!

13) Twospotted spider mite: Nah, they will do fine despite the cold winter. I doubt winter had much to do with it … more likley the cool and wet summer … but spider mites were a relatively rare problem in 2014.

14) Japanese beetles: First found in the Northeast (New York, etc.) about 100 years ago. They have been moving our way ever since. Enough said! 2014 did not slow them down!

15) Sugarcane aphid: I’m adding this insect to the list. This new, invasive pest of sorghum rapidly expanded its range across the South in 2014. It made its first appearance in the southern counties of West Tennessee in late July. We THINK this pest will overwinter only in areas where hard freezes are uncommon (i.e., southern areas of the Gulf Coast States). This species has proven it can spread rapidly, but following a relatively cold winter, I’m expecting sugarcane aphids will be a little delayed starting in Tennessee. Expect worse problems than in 2014 but mostly in later planted sorghum. Sorghum growers in the middle and eastern parts of the state will likely get a taste now that sugarcane aphids spread to Alabama, Georgia, South Carolina, and Florida in 2014.

We know less about the survival of the many important beneficial insects that help control insect pests. But bad effects on important beneficial insects favors a rapid build-up of pest populations. So there is some give and take here. Because most insect and mite pests have a high capability to reproduce, they can overcome initially low populations if conditions are favorable during the first generation after winter breaks. In my business, we call this job security!

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7 thoughts on “Cold Weather Effects on Insect Populations?

    1. Matthew – good question and I haven’t studied it, but I know they have similar problems with slugs in Ohio and other places in the Midwest. That doesn’t suggest winter is a big deal to slugs. I’ll do a little research but I’m not optimistic.

      Just a quick check and it looks like the common species we encounter are a problem in Illinois, Indiana, Ohio and other Midwestern states. I doubt our winter will affect their survival much. However, it could delay the growth of some of their spring hosts, so population won’t build as quickly before planting.

  1. I have picked my cotton fields for 2015. Would it help TPB management if I sprayed the vegetation around these fields to kill the wild hosts?

    1. Good question. Managing alternate hosts around fields is a recommended component of managing plant bugs. For example, we would not recommend mowing alternate hosts around cotton field when adults are present. We’ve done some testing of spraying herbicide around field margins at this time of year or sooner. The idea is to convert the border to grasses, not bare dirt. There are few herbicides labeled. We used Strike 3. The spray worked, but there are a few points to consider. It was much less efficient in areas with small fields. The cost per acre and ability to get around the perimeters is much lower in delta type environments than in patchy hill type areas. Also, we had a situation where I think we had the opposite effect. We sprayed field margins in Lauderdale county, but because of the threat of flooding, the fields themselves were burn downed very late. The plant bugs built up within the fields, and the bugs had nothing but crop to go too once it was planted. So this has to be paired with a good in-field weed management. Finally, I don’t think there will near as much benefit when acres are low unless you also spray margins of non-cotton field. You really need to do this in an area, not just for isolated cotton fields. Honestly, I probably wouldn’t recommend this except in ares where a fair number of cotton field are clumped together.

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