James HanulaResearch Entomologist
Insects, Diseases, and Invasive Plants (RWU 4552)
USDA Forest Service
SRS Staff Directory Profile
SRS Publications List
- B.S. in Forest Management, Texas A&M University (1978)
- M.S. in Forest Entomology, University of Georgia (1981)
- Ph.D. in Forest Entomology, University of Georgia (1983)
- Assistant Entomologist, Connecticut Agric. Exp. Station (1985-1991)
- Research Entomologist at USDA-FS-SRS (1991-Present)
My research focuses on the functional roles of insects in forest ecosystems and the effects of forest management on them. Recently, I have also worked on invasive insects and plants in southeastern forests.
Pollinators in forests
Pollinators are receiving a lot of attention worldwide due to the decline of honey bees, monarch butterflies, and bumblebees. But that’s only a small fraction of the pollinating insects which includes many species of bees, butterflies, flies, and beetles. Some are better pollinators (for example, bees) than others (beetles) but most pollinators have not been studied well enough to know how important they are. Most studies of pollinators have been conducted on farms because of the importance of pollinators for food production but they also pollinate most of the plants in forests too. Although we know they are important in forests, pollinators in forests have not gotten much attention until recently. We began research on pollinators in forests in 1998 looking at techniques for studying pollinator visitation to rare plants. Since then we have focused on the following:
Effects of prescribed fire and shrub removal on pollinators. Uncontrolled fires are often bad for forests so for a long time people tried to prevent all fire in forests. This resulted in the development of closed canopy forests with lots of shrubs beneath. But we now know that forests, and many of the organisms in them, do better with some fire usually referred to as controlled burning or prescribed fire. As part of the National Fire/Fire Surrogate Project, Tom Waldrop (SRS 4156) set up a long-term study area in the Appalachian Mountains of NC in which he cut shrubs (mountain laurel), prescribed burned, or did both. We then examined the effects of those treatments on pollinators. After two years the combination of cutting shrubs followed by burning resulted in more pollinators and more species of them then other treatments. Burning after cutting shrubs resulted in hotter fires that killed some trees, allowing more sunlight to reach the forest floor and increased cover of small plants on the forest floor (Campbell et al. 2007).
Collaborators: SRS 4156 scientists
Effect of Chinese privet and its removal on plant and pollinator communities. Chinese privet is one of the worst invasive plant species in southeastern forests in terms of acres infested, but its effects on ecosystems are not well known. We used two techniques to remove Chinese privet and then examined plant and pollinator community responses after 2 and 5 years. Both plant and pollinator diversity and abundance increased within 2 years (Hanula et al. 2009, Hanula and Horn 2011a, 2011b) and were still much greater than untreated areas (those still infested with privet) 5 years after privet removal (Hudson et al. 2014a, 2014b). These studies along with others conducted on the plots (Ulyshen et al. 2010, Lobe et al. 2014) demonstrate the long-term, negative effects of an invasive species.
Collaborators: Sandy Creek Nature Center; The State Botanical Garden of Georgia; The University of Georgia’s Warnell School of Forest Resources; Oconee National Forest; Region 8 State and Private Forestry, Forest Health Protection; SRS 4156; the University of Georgia’s Department of Entomology.
Forest Condition and pollinators. Southern forests have changed dramatically in the past 100 years. Most people don’t realize that most of the trees in the South were cut and much of the land was burned frequently afterwards so that few trees could grow. How has the change from cutover, frequently burned land with little or no tree cover, to present day densely planted forests with fire excluded from them, affected pollinators? We selected 7 forest types typical of the southeastern U. S. and monitored bees on them for one growing season. Pollinators were greatest in thinned stands of mature pine that were frequently burned, resulting in little or no shrub cover, or in clearcuts. The fewest were in dense young pine stands. Results indicate that the long-term transition from extensive open, poorly forested land to fully stocked infrequently burned forests may have contributed to declining pollinator abundance.
Collaborators: SRS 4156 scientists
Redbay ambrosia beetle (RAB) and laurel wilt
Laurel wilt (Raffaelea lauricola) has killed millions of redbay (Persea borbonia) trees from North Carolina to the southern tip of Florida. The fungus is spread by redbay ambrosia beetle (Xyleborus glabratus), an insect from Asia. Our studies have focused on the biology of the beetle in the U.S. and on host attraction.
RAB biology: We investigated the biology of RAB to determine peak flight periods, emergence from individual galleries over time, and relative attraction of potential hosts (Hanula et al. 2008, Mayfield and Hanula 2012, Maner et al. 2013a, 2013b, 2014). A 5-yr population monitoring study showed the beetle persisted in areas where all mature host trees were already dead when the study started. Studies of RAB in small stems demonstrated they can use them for producing young but only a few make it. These results suggest RAB populations may do poorly but be able to persist long-term in areas by using small diameter redbay saplings (Maner et al. 2014).
Collaborators: USFS Forest Health Protection R8; University of Georgia, Department of Entomology; SRS 4552 scientists.
Host attraction: We demonstrated redbay trees produce odors that attract RAB and found that extracts from manuka shrubs (native to New Zealand) and Brazilian walnut trees (Phoebe porosa) were as attractive to RAB as redbay wood (Hanula and Sullivan 2008). Other studies showed that an extract from a type of pepper seed (cubeb oil) was as attractive as manuka oil and lures manufactured with it lasted longer than manuka oil lures (Hanula et al. 2013). We also tested trap designs and demonstrated that the number of beetles captured in traps indicated the numbers of RAB in an area (Hanula et al. 2011).
Collaborators: USFS Forest Health Protection Region 8, SRS 4552 scientists
Kudzu bug: Kudzu bug (Megacopta cribraria) was first discovered in 2009 near Atlanta, GA but it is from Asia. Unlike many insects that accidentally arrive in the U.S. and become pests, this one may benefit forestry by suppressing kudzu growth. We studied the biology of kudzu bug and how it might affect native forest legumes (Zhang et al. 2012), its attraction to different colored traps (Horn and Hanula 2011), and its impact on kudzu over a 5-yr period. Our results indicate kudzu bug is unlikely to affect other native plants, and it slows the growth of kudzu giving other plants an opportunity to grow. A recently discovered parasitic wasp that attacks kudzu bug eggs has the potential to undo these beneficial effects.
Collaborators: Univ. of Ga., Dept. of Entomol.
Biological control of Chinese privet
Over the past ten years we have been working on developing biological controls for Chinese privet in cooperation with scientists in China. Exploration in China resulted in two candidates, a flea beetle and a lace bug. Tests in China showed the flea beetle was host specific (Zhang et al. 2008) and effective (Zhang et al. 2009) but further testing with U.S. natives showed it was not host specific enough. On the other hand, the lace bug looks promising (Zhang et al. 2011, Zhang et al. 2013) and a petition for its release has been submitted.
Collaborators: Chinese Acad. of Sci.; Univ. of Ga, Dept. of Entomol.; FS, FHP, FHTET; Manaaki Whenua Landcare Research, New Zealand.
Hemlock Woolly Adelgid
Hemlock trees are under assault from an exotic insect, the hemlock woolly adelgid, which literally sucks the life out of them. Millions of hemlock trees have died as a result. We teamed with scientists at the University of Georgia to investigate control tactic for this insect. Biological control (use of one insect to control another) is one of the most promising options but in the Southern Appalachians hemlocks die so quickly the predator beetles being released don’t have enough time for their populations to grow. We wanted to see if we could prolong tree health with insecticides plus fertilizer but still allow some adelgids to survive on the trees for the predators to eat (Joseph et al. 2011). We did this by applying low doses of the insecticide to trees with or without fertilizer. The 25% rate of insecticide was too high and killed all the adelgids but the 10% rate allowed sufficient numbers of adelgids for predators to eat. In addition, the fertilizer increased the number of eggs produced by the adelgid, providing more food for the predators. Later studies showed that trees receiving the 25% rate harbored as many predators as untreated trees 7 years after treatment, but they had better tree health suggesting the trees will produce predators longer (Mayfield et al. 2014).
We also investigated insecticides for adelgid control (Joseph et al. 2011a), the effects of fertilization on tree resistance to adelgids (Joseph et al. 2011b), and how adelgids are distributed throughout a tree (Joseph et al. 2011c).
Collaborators: Univ. of Ga., Dept. of Entomol.
Red-cockaded Woodpecker Prey
The red-cockaded woodpecker (RCW) is an endangered species mostly found on public lands like national forests, military bases and state parks because they contain forests that the birds can still live in. Unlike most woodpeckers, RCW find their food on live trees, so managing forests to provide adequate food is important. To help managers understand how forest conditions affect the insects and other arthropod (spiders, centipedes, etc.) RCW feed on, we studied what they eat, where it comes from, and how forest conditions like tree age, tree species, tree size, number of trees per acre, and time since the last prescribed burn affect the insects they depend on.
- RCW Food: If nestling RCW’s could speak they might say, “Cockroaches again Mom?!”, because over 50% of their diets consists of wood cockroaches common to forests throughout the south (Horn and Hanula 2002). We developed special cameras placed near nest cavities in trees to record what adults brought back to their young (Hanula and Franzreb 1995). We recorded over 10,000 nest visits of RCW with food in forests from the coast of South Carolina to old growth forest in South Georgia and the answer was the same, “Yes, cockroaches.”, but with a variety of other items thrown in including spiders, caterpillars, ants, scorpions, centipedes, and even blueberries at one forest (Hanula and Franzreb 1995, Hanula et al. 2000, Hanula and Engstrom 2000, Hanula and Horn 2004).
- Source of RCW Food: Where do all those cockroaches and other food items come from? Do they live on live trees all the time or do they move around the forest a lot? We answered that question by using special traps (Hanula and New 1996) to catch insect climbing up trees. On half of the trees we put barriers to keep insects and other arthropods from climbing up. We found that most of the food available on live trees climbs onto them from the ground (Hanula and Franzreb 1998), so the tree may be the dinner plate but the food is coming from somewhere else in the forest.
- Where Do Wood Cockroaches Live: If RCW eat lots of wood cockroaches they collect from live trees but the roaches don’t spend all their time on live trees – where do they live the rest of the time? We studied the common cockroaches in a typical forest and found they live in dead trees a lot of the time. They seem to especially like standing dead trees (Horn and Hanula 2002, 2008; Hanula et al. 2006). Even though RCW don’t spend a lot of time looking for food on dead trees their major food spends at least part of their life in them.
- Effects of Forest Management on RCW Food Availability: Forest managers make lots of decision about the forests they manage like what species of tree to plant, how long to let it grow, how often do they need to be thinned, and should the forest be burned and how often. We wanted to know how these decisions affect arthropods available for RCW. For example, something like prescribed burning should have a big effect since RCW prey spend time on the ground and in dead wood, but it had surprisingly little effect (New and Hanula 1998). On the other hand, what species of pine tree occurs in the forest has a major effect because longleaf pine has very large, overlapping bark scales that provide lots of places to hide for roaches and other arthropods (Horn and Hanula 2002). We also found that the oldest or largest trees weren’t necessary better but young, small trees weren’t the best either (Hanula et al. 2000). Also, fewer trees per acre didn’t result in more prey concentrated on them. Our results show that forest managers have a lot of flexibility in the types of forest conditions they provide in the foraging areas of these endangered woodpeckers.
Effects of Fire on Arthropods
- Long-term Winter Burning Effects: Burning the forest should be bad for insects, spiders, and other arthropods that live on the forest floor and burning every year for 40 years should be worse – right? Well, that’s true for some species but others like it hot. In fact, no matter what group we looked at (spiders, ground beetles, ants, etc.) some species were more common in forest plots that were burned every year for 40 years than in plots only burned every 4 years or not at all during that period, while others had the reverse response to prescribed burning (Hanula et al. 2000). These results show that prescribed fires result in increased numbers of some species and decreases in others.
- Does Fire Increase Bark Beetle Attacks on Pine Trees?: A common question associated with prescribed burning is – does it result in increased risk of bark beetle attack? Pine bark beetles are insects that can attack and kill trees, but many simply attack trees recently killed by other causes like lightning. After a fire it is difficult to know if the fire killed the trees and bark beetles took advantage of the dead trees for food, or if the fire weakened the trees and the bark beetles killed them. We examined pine tree mortality following a wildfire in Florida (Hanula et al. 2002) and prescribed burning in Alabama (Campbell et al. 2008). In both cases trees died but we concluded that the fire killed the trees not bark beetles. In the Florida fire, so many trees died that many were never attacked either because the fire was so hot it made the trees unsuitable for food or not enough bark beetles were available to attack them all. In the Alabama study fewer trees died and many were attacked by bark beetles but the attacks were “dry” with no resin. Also, just as many trees died in unburned forest plots as in burned plots suggesting that fire doesn’t predispose trees to bark beetle attack.
Dead Wood in Forests
Dead wood or dead trees are an incredibly important part of forests (e.g., Grove and Hanula 2006, McMinn and Crossley 1996). Some estimates suggest that as many as 20% of all the organisms in a forest use dead wood some time during their life as food, shelter or both. We examined how dead wood in southern forests affects the abundance and diversity of arthropods in the same forests. We examined a variety of factors such as species of wood, age of the wood, type of forest, and position of the dead wood (standing dead tree or log on the ground). All had an effect but the responses were often species specific (Ulyshen et al. 2011, 2012, Ulyshen and Hanula 2010a, 2010b). We also examined what happens when you remove or add dead wood to a forest (Ulyshen and Hanula 2009a, 2009b).