How long does a kudzu bug live? One report showed that female adult kudzu bugs live between 44 and 81 days depending on the temperature. In an ongoing development project I am running, I have found a similar range for average adult longevity. However, there are a few (very very few) bugs who greatly exceed this lifespan. For example, the bug pictured above turned one year old today.
Kudzu bugs were found in southern Prince George’s County yesterday. In Maryland, it can be difficult to find the bugs in June and July. Yesterday, however, we found a cluster of large nymphs and a few adults. This find will help us narrow in our prediction of their phenology, the timing of life stages.
Two kudzu bugs were caught at the end of May in Calvert County. The male and female pair were sunning together on a kudzu leaf. Populations will likely remain low until late summer. If you know of any kudzu patches please let us know.
The kudzu bugs have been spotted this year in Calvert and Prince George’s counties. Numbers are still low (thirty minutes of searching yielded four bugs!) but populations are on the rebound from the cold winter. We have brought back a handful of bugs to the lab to start trying to raise a colony and measure development. Below are pictures of what is going on in the lab.
From Left to Right:
1. Adult bugs mating
The few bugs we have collected have already laid four egg masses in less than two weeks.
2. A typical kudzu bug egg mass
Note the parallel lines and light cream coloring laid on the stem of a kudzu vine.
3. Tiny newly hatched kudzu bugs
They will hang out by the eggs till they have hardened and consumed a small symbiotic packet left by their mother. This packet contains bacteria to help them digest their food.
4. Close up of two newly emerged kudzu bugs
You can see how they easily blend in with kudzu or soybeans with their green color and fuzzy appearance. They are only given away by their red eyes!
Jessica Grant, Alan Leslie, and William Lamp
Background: The kudzu bug life cycle needs to be assessed in Maryland, its northern limit
Since Maryland is currently the northern limit of the kudzu bug’s known range, we monitored populations to develop an understanding of their life stages in the mid-Atlantic region.
During summer and fall of 2014 our goals were:
1. Adopt a standard sampling method
2. Check the persistence of bugs at previously known sites
3. Monitor sites of known kudzu bug populations and expected sites of expansion
4. Determine the number of generations of the bugs in Maryland
1. New standardized sampling method of vine cutting and sweep netting
We adopted a standardized sampling method for kudzu bugs that allowed us to compare densities of eggs, nymphs, and adults across sample sites and times. For sampling we:
1. Collected 10 sections of 0.5m long kudzu vines
2. Swept through the kudzu foliage for a total of 60 seconds
The kudzu vine sections allowed us to count the small and hard to find life stages (that are often not found in other sampling methods) back in the lab. Sweeping made higher areas of the kudzu patch canopy easier to reach, where we often found more of them. Sweeping also allowed us to detect a presence over a large area quickly.
2. Kudzu bugs have persisted at previous sites but have not expanded their distribution in Maryland
During 2014, we resampled all kudzu patches that were positive for kudzu bugs in 2013. 17 of the 18 sites that had kudzu bugs in 2013 still had kudzu bugs in 2014. The one site where kudzu bugs were not detected had a reduced amount of kudzu vines. Thus, the county-level distribution of the kudzu bug in Maryland remains the same as 2013 (Fig. 1).
3. Kudzu bug numbers were low in the summer but increased in early fall
We used the new sampling approach to sample four sites each week through the summer, and every other week in the fall until kudzu leaves senesced. Two of the sites had kudzu bugs in 2013, while the other two did not but we expected the bugs to colonize the sites in 2014. We only found kudzu bugs at the two sites with previous populations. All sites started the summer with low densities but grew quickly by fall. At several of the sites with abundant kudzu bugs, we could easily detect their presence when we first arrived at the site because of their distinctive smell!
Lower population numbers found in the summer may be due to a colder than average winter
ased on sampling in 2013, the sites we visited in June and July in 2014 left an impression of reduced numbers of kudzu bugs compared to 2013. One possible reason for this trend is that the colder than average winter of 2013-14 may have increased mortality of overwintering adults (see temperature patterns in Fig. 2). Fewer surviving adults may have delayed the population growth we expected to see by mid-summer.
4. Two-generations of bugs per season found in Maryland
Patterns in adult abundance indicated there are two generations of kudzu bugs in Maryland. Looking at the life stages of our sampling, particularly August through October, we found:
· August had the highest number of egg masses
· September was dominated by nymphs
· October showed an equal number of nymphs to adults (Fig. 3).
Thus, since there is a second peak of adults beginning in October we can extrapolate that there are most likely two generations of kudzu bugs in Maryland (Fig. 4). Furthermore, kudzu bugs may have a shifted emergence and population growth towards later in the season than is found in the Southeast as suggested by our findings of mixed life stages persisting into the late fall.
Continued research into understanding kudzu bug cold tolerance and development could aid in Maryland pest predictions
Overall, our observations during 2014 have confirmed that the kudzu bug can survive colder than average winters in Maryland, although its abundance may be reduced during spring and the first half of the summer. We plan to continue to monitor kudzu bug populations during 2015 with the goal of being able to predict the abundance, distribution, and timing of development for egg laying in the spring. Kudzu bugs have the potential to expand throughout Maryland and become a pest on soybeans. Knowing their cold tolerance and development will aid us in pest management plans.
Last year, we tracked the arrival of the invasive kudzu bug to Maryland kudzu patches and soybean fields. We found populations of the bug across all of the southern counties west of the Chesapeake, and two counties on the Eastern Shore. For the summer of 2014, we have been tracking populations found last summer and monitoring any spread northward. We have been sampling patches of kudzu vines along the border of the 2013 range of the insect across Prince George's, Montgomery, and Howard Counties. Our goal for this summer is to determine the timing of the kudzu bug life cycle in Maryland, including measuring generation times and changes in population size and demographics. We have conducted our sampling since April, and have so far only recovered one adult kudzu bug from sites that had kudzu bug populations last year. No eggs or nymphs have been found, indicating that many of the local populations of kudzu bugs may not have persisted through the harsh winter of 2013/14.
Or sampling methods at each site include using clear sticky traps over white pvc tubes, sweeping vegetation with an insect net, and collecting sections of vines to return to the lab. The sticky traps are left for a week to continuously monitor for adults, which are attracted to white surfaces, and would get stuck to the trap. Sweeping with the insect net is an efficient way to sample large portions of the kudzu patch for mobile adults, which tend to fall off of kudzu vines when disturbed, and would be caught in the net. The sections of vine that are returned to the lab are screened visually for smaller nymphs and egg masses, that may be overlooked in the field. So far all of our sampling trips except one have returned with no insects recovered from kudzu patches that had large, reproducing populations of kudzu bugs at the end of the summer of 2013.
So far our surveys suggest that winter weather was too harsh for most of the kudzu bugs in Maryland, due in part to extreme cold temperatures from the polar vortex that was experienced in January. Kudzu bugs are far from being eradicated in the state however, as extra surveys outside of our repeated, weekly collections have found at least one population of kudzu bugs surviving and reproducing on kudzu vines in Talbot County, near St. Michaels.
Our surveys of kudzu vines will continue through the remainder of the summer, despite extremely low numbers. There is still the possibility for insects to re-colonize kudzu patches from nearby sources before the end of the season, and the onset of senescence in kudzu vines. We will continue to report updates on kudzu bug populations through our surveys. We could also use your help to widen our surveys for the insect around the state, as we do not have the capacity to cover the entire state this summer with our sampling efforts. If you find kudzu bugs in kudzu vines or soybean fields around you, please report them here to our website. Your reports will help us to track this invasive pest through Maryland, and help to prepare for the possibility of a rebound in its population in the future.
Kudzu bugs have now been reported from two more Maryland counties. Adults and nymphs have been documented on kudzu vines growing near the Chesapeake and Ohio Canal in Montgomery County. This continues the pattern of spread for the insect in kudzu vines among counties west of the Chesapeake Bay. Two adult kudzu bugs have also been collected from a soybean field in Dorchester County on the Eastern Shore. This is the first record of the insect on the Maryland portion of the Delmarva Peninsula, although it has already been found in the Delaware and Virginia portions. This is also the first record of the insect collected from soybean plants in Maryland. Searches for this insect will continue throughout the state to determine the extent to which kudzu bugs infest soybeans.
Over the past month we have found existing populations of kudzu bugs to be reproducing and increasing in size on kudzu vines. At sites where we had previously found only scattered adults, there are now greater populations of all life stages, including eggs and nymphs. Adult kudzu bugs are also apparently on the move, and have been detected in northern Prince George's County near Greenbelt. We have yet to detect the insects making the leap across any borders to establish in any new counties in Maryland.
We have sampled a total of 30 different kudzu patches across eight counties in Maryland. Most of the sites are roadside patches of vines, but a couple are off the main roads in parks, neighborhoods, and agricultural fields. The northernmost sites we have sampled include patches of kudzu vines in Howard and Baltimore Counties around the Triadelphia Reservoir and Catonsville. Other patches have been spotted off of busy highways, such as I-495, I-270, and I-95, but these sites are generally unsafe to be sampled and have been left alone. We have yet to find any patches of kudzu to sample in counties on the mid and lower Eastern Shore of Maryland but we are still searching.
The next, ongoing phase of this summer's project is to monitor whether the kudzu bug moves into crops like soybeans before overwintering. For this stage of the project, we are monitoring plots of edible soybean plants (edamame) on research farms across the state. Edible soybeans are vegetable crops that produce a soft, green bean, while the soybeans conventionally grown in Maryland produce a harder seed used as feed for livestock and for vegetable oil production. Edible soybeans are thought to be more attractive to the kudzu bug than conventional soybeans grown as field crops. So far we have not detected any stages of the insect on the edible soybeans or other soybean plants grown on research farms. Through the remainder of the summer, we will expand the scope of our sampling to include fields outside of the Maryland research farms. Our sampling efforts will be combined with those of other research teams investigating the abundance of another invader, the brown marmorated stink bug (Halyomorpha halys) in soybean fields across Maryland.
By the end of the summer, we expect to have documented the distribution of this new invasive species within the state of Maryland, and to make predictions for the impact this insect will have on Maryland's agriculture in the future. The ongoing surveys of kudzu vine patches will help to monitor the spread of the insect from southern counties into more northern areas. As a perennial vine, these patches will be around again next year, and knowledge of the locations of these sites will allow more effective monitoring of the spread of the insect. Our surveys of soybean fields will help to determine whether this insect poses a serious threat to Maryland agriculture, and whether Maryland farmers will need to look out for this insect in future seasons.
Our surveys of roadside kudzu patches this summer have the invasive kudzu bug showing up in two more southern Maryland counties. Two kudzu patches off of route 5 were found to have adult kudzu bugs; one in St. Mary's County, and the other in Charles County. This brings the total to five Maryland counties confirmed to have kudzu bugs present. We also suspect that the kudzu bug has made it to some of the counties on Maryland's Eastern Shore, since the insect has been reported in the Delaware and Virginia portions of the Delmarva peninsula.
Of course the invasion of the kudzu bug into Maryland was expected to occur this year, as a part of the northward dispersal from it's introduced range in the south. The real question for kudzu bug in Maryland is how large of a population our climate can support. Currently the numbers of insects we are finding in kudzu patches is very low compared to the more sever infestations in the south. This may be because the insect is still becoming established, and numbers will increase for future summers, but we do not yet have the data to determine what those numbers might look like. Another factor is the amount of kudzu. Although the vine is present in Maryland, it's distribution is not nearly as widespread as it is in the south. However, more research will have to be done to see if the insect can develop on other closely related plant species that occur in Maryland.
As news of this new invasive insect reaches farmers, there will be growing concern about what this will mean for their crops. In the south, the insect completes an entire second generation on soybean plants, which can cause major crop loss if left untreated. However, for Maryland, we don't know if we will get a huge second generation because of the difference in climate. So far this summer we have focused on sampling kudzu vines since that is the primary host, and our primary goal was simply to detect the insect. For the rest of the summer we will also be scouting soybean fields to see if the insect moves into field crops, and at what numbers. So the potential is there for this insect to be a pest of economic concern in the future, but more research is definitely needed to figure out how bad it might be.
This spring and summer we have been combing over Maryland's back roads and scenic byways in search of stands of kudzu vines (Pueraria montana), which are the preferred host of the invasive kudzu bug (Megacopta cribraria ). We have been focusing our search in southern counties and counties that border Virginia. After scouting for kudzu bug in Howard, Montgomery, Prince George's, St. Mary's, and Calvert Counties, adult kudzu bugs have been found on roadside kudzu patches in Anne Arundel, Calvert, and Prince George's Counties. These are the first reported sightings of this introduced insect species for the state of Maryland, and marks the new northernmost sighting of the insect along the path of its invasion from the south. In 2012, the closest reports of kudzu bug were from Goochland County, Virginia, but the insect has since been spotted in four new Virginia counties, including Culpeper and Frederick.
Adult bugs were found actively flying around the patch of vines, and two egg masses were found on the undersides of leaves. The egg masses were collected and returned to the lab, where they were positively identified as eggs from the kudzu bug. No nymphs have been found.