John F Tooker

Pennsylvania State University | Penn State · Department of Entomology

Background Preventative pesticide seed treatments (hereafter preventative pest management or PPM) are common corn and soybean treatments, and often include both fungicides and neonicotinoid insecticides. While PPM is intended to protect crops from soil-borne pathogens and early season insect pests, these seed treatments may have detrimental effects...

Environmental cues that predict increased risk of herbivory can prime plant defenses; however, few studies have explored how such cues elicit broader plant responses, including potential effects on plant growth and other resource allocations that may affect tolerance to herbivore damage. We exposed goldenrod plants (Solidago altissima) to varying c...

Endophytic insects, including gall insects and leaf miners, are prominent in both natural and agricultural plant communities. We catalog the endophytic insect fauna in North America that are known to associate with rosinweeds (Silphium L., Heliantheae, Asteraceae). We provide details on host plant species, brief descriptions of insect associations,...

Cryptic species present challenges across many subdisciplines of biology. Not all “cryptic” species, however, are truly cryptic; many are simply underexplored morphologically. We examined this idea for the Antistrophus rufus species complex, which previously contained three species thought to be morphologically cryptic. To determine whether the A....

Context There is great interest in land management practices for pollinators; however, a quantitative comparison of landscape and local effects on bee communities is necessary to determine if adding small habitat patches can increase bee abundance or species richness. The value of increasing floral abundance at a site is undoubtedly influenced by t...

Within the last four decades, widespread transition to no‐till corn (Zea mays L.) and soybean [Glycine max (L.) Merr.] production in Pennsylvania has improved soil conservation and soil quality but can result in residue and pest management challenges. To effectively manage residue in no‐till cropping systems, some growers have adopted vertical till...

Interactions between plants and herbivores are central in most ecosystems, but their strength is highly variable. The amount of variability within a system is thought to influence most aspects of plant-herbivore biology, from ecological stability to plant defense evolution. Our understanding of what influences variability, however, is limited by sp...

Many herbivorous insect species are capable of hijacking plant development to induce novel plant organs called galls. In most groups of galling insects, the insect organs and molecular signals involved in gall induction are poorly understood. We focused on gall wasps (Hymenoptera:Cynipidae), the second largest clade of gall inducers (~1,400 spp.),...

Abscisic acid (ABA) is an isoprenoid-derived plant signaling molecule involved in a wide variety of plant processes, including facets of growth and development as well as responses to abiotic and biotic stress. ABA had previously been reported in a wide variety of animals, including insects and humans. We used high-performance liquid chromatography...

The morphology of insect-induced galls contributes to defences of the gall-inducing insect species against its natural enemies. In terms of gall chemistry, the only defensive compounds thus far identified in galls are tannins that accumulate in many galls, preventing damage by herbivores. Intrigued by the fruit-like appearance of the translucent oa...

Slugs are cryptic terrestrial pests that target a wide range of crops and are especially damaging to seedlings. Management of these invertebrates mostly relies on synthetic chemistry. These molecules can be efficient against slugs and snails but can be toxic to other organisms (e.g., dogs) and harmful to the environment (e.g., leaching into surface...

In addition to directly inducing physical and chemical defenses, herbivory experienced by plants in one generation can influence the expression of defensive traits in offspring. Plant defense phenotypes can be compromised by inbreeding, and there is some evidence that such adverse effects can extend to the transgenerational expression of induced re...

Mineral nutrients, such as zinc (Zn), are critical for plant growth; however, the effect of Zn on insect herbivory is poorly characterized. Because Zn deficiency may compromise plant physiology while high levels of zinc may be directly toxic to herbivores, we predicted lepidopteran herbivores would perform best on plants deficient in Zn or those wi...

No-till farming is a conservation agriculture practice employed on over 100 million acres of farmland in the United States. This practice provides benefits ranging from erosion control to pest suppression but can also facilitate outbreaks of novel pests. In the Mid-Atlantic, USA, where no-till production is widely adopted to help maintain the healt...

Context There is great interest in land management practices for pollinators; however, a quantitative comparison of landscape and local effects on bee communities is necessary to determine if adding small habitat patches can increase bee abundance or species richness. The value of increasing floral abundance at a site is undoubtedly influenced by t...

Growing evidence suggests that conservation agricultural practices, like no‐till and cover crops, help protect annual crops from insect pests by supporting populations of resident arthropod predators. While adoption of conservation practices is growing, most field crop producers are also using more insecticides, including neonicotinoid seed coating...

Ants disperse oak galls of some cynipid wasp species similarly to how they disperse seeds with elaiosomes. We conducted choice assays in field and laboratory settings with ant-dispersed seeds and wasp-induced galls found in ant nests and found that seed-dispersing ants retrieve these galls as they do myrmecochorous seeds. We also conducted manipula...

Honeydew is the sugar-rich excretion of phloem-feeding hemipteran insects such as aphids, mealybugs, whiteflies, and psyllids, and can be a main carbohydrate source for beneficial insects in some ecosystems. Recent research has revealed that water-soluble, systemic insecticides contaminate honeydew excreted by hemipterans that feed on plants treate...

Because the diet of many herbivorous insects is restricted to closely related taxa with similar chemistry, intercropping with diverse plant communities may reduce both pest populations and reliance on chemical pesticides in agroecosystems. We tested whether the effectiveness of intercropping against herbivorous insects depends on the phylogenetic r...

This datasheet on Halyomorpha halys covers Identity, Overview, Distribution, Dispersal, Hosts/Species Affected, Diagnosis, Biology & Ecology, Environmental Requirements, Natural Enemies, Impacts, Prevention/Control, Further Information.

Background Previous research suggests that fireflies (Coleoptera: Lampyridae) are susceptible to commonly used insecticides. In the United States, there has been a rapid and widespread adoption of neonicotinoid insecticides, predominantly used as seed coatings on large-acreage crops like corn, soy, and cotton. Neonicotinoid insecticides are persist...

Field crop growers in the United States have adopted prophylactic pest management strategies to control sporadic crop pests that are spatially and temporally difficult to predict. While evidence shows these preventative management practices, specifically pesticidal seed treatments, can be important in regions with predictable pest pressures, employ...

Pterostichus melanarius (Illiger, 1798) is a Palearctic generalist predator native to Europe. It was unintentionally introduced to North America at least twice in the mid 1920s and has since become widespread in Canada and the United States. Although P. melanarius is a valuable natural enemy in many different agricultural systems, we are not aware...

The push for sustainable intensification requires development of alternative strategies for managing crop production that improve yields while maintaining or enhancing environmental services. We propose that intraspecific mixtures potentially exploit landscape ecosystem services to help suppress pests, impede disease spread, and ultimately improve...

Neonicotinoids from insecticidal seed coatings can contaminate soil in treated fields and adjacent areas, posing a potential risk to nontarget organisms and ecological function. To determine if cover crops can mitigate neonicotinoid contamination in treated and adjacent areas, we measured neonicotinoid concentrations for three years in no-till corn...

Polycultures, mixtures of different crop species in the same field, may provide both production and ecological benefits. Silage production in annual cropping systems may incorporate polycultures and take advantage of species’ niche partitioning, potentially stabilizing yield variation due to abiotic stress. Using maize (Zea mays L.) silage as the b...

Increased use of neonicotinoid‐coated crop seeds introduces greater amounts of insecticides into the environment, where they are vulnerable to transport. To understand the transport of neonicotinoids from agricultural fields, we planted maize (Zea mays L.) seeds coated with thiamethoxam in lysimeter plots in central Pennsylvania. Over the next year...

During the Green Revolution, older classes of insecticides contributed to biodiversity loss by decreasing insect populations and bioaccumulating across food webs. Introduction of Integrated Pest Management (IPM) improved stewardship of insecticides and promised fewer non-target effects. IPM adoption has waned in recent decades, and popularity of ne...

A diverse array of organisms induce plants to form galls. This phenomenon is one of the most striking instances of convergent evolution, yet the underlying mechanism is only well understood in gall-inducing microbes. To determine if gall induction by insects is associated with bacterial symbiosis, we used 16S rRNA gene sequencing to examine the mic...

Eurosta solidaginis males produce large amounts of putative sex pheromone compared to other insect species; however, neither the site of pheromone production nor the release mechanism has been characterized. We compared E. solidaginis males and females, focusing on sexually dimorphic structures that are known to be involved in pheromone production...

Wild bees, like many other taxa, are threatened by land‐use and climate change, which, in turn, jeopardizes pollination of crops and wild plants. Understanding how land‐use and climate factors interact is critical to predicting and managing pollinator populations and ensuring adequate pollination services, but most studies have evaluated either lan...

Insecticides use in field crops has grown increasingly prophylactic, which poses a potentially unnecessary risk to arthropod decomposers. These decomposers — including millipedes (Diplopoda), soil mites (Acari, mostly Oribatida), and Collembola — act as alternative prey for generalist predators, facilitate crop-residue breakdown, and can influence...

For most of the last two decades, insect pest management in key grain and oilseed crops has relied heavily on an insurance-based approach. This approach mandates a suite of management tactics prior to planting and in the absence of pest data. Because there is little flexibility for using these tactics individually, most producers have adopted this...

Because it keeps land in production, conservation programs that focus on in-field habitat manipulations may help farmers better support predators than by building predator habitat around fields. We investigated two in-field habitat manipulations that benefit producers and soil quality: fertilizing with dry-stack cow manure and planting a wheat cove...

Herbivorous feeding inside plant tissues, or endophagy, is a common lifestyle across Insecta, and occurs in insect taxa that bore, roll, tie, mine, gall, or otherwise modify plant tissues so that the tissues surround the insects while they are feeding. Some researchers have developed hypotheses to explain the adaptive significance of certain endoph...

The striped cucumber beetle, Acalymma vittatum (Fabricius), is an important pest of cucurbit production in the eastern United States, where most commercial producers rely on insecticides to control this pest species. Biological control provides an alternative to insecticide use, but for A. vittatum, top-down control has not been well developed. In...

Halyomorpha halys (Stål), the brown marmorated stink bug, is an invasive and highly polyphagous insect that has caused serious economic injury to specialty and row crops in the United States and Europe. Here, we evaluated the effects of marking adult and nymphal H. halys with four different colors of fluorescent powder (Blaze Orange, Corona Pink, H...

With documented global declines in insects, including wild bees, there has been increasing interest in developing and expanding insect monitoring programs. Our objective here was to organize, validate, and share an analysis-ready version of one of the few existing long-term monitoring datasets for wild bees in the United States. Since 1999, the Nat...

Tall goldenrod plants Solidago altissima appear to eavesdrop on the communication of a specialist gall‐inducing fly Eurosta solidaginis by detecting the volatile emissions of male flies and priming anti‐herbivore defences. However, the effects of defence priming on fly fitness have not previously been demonstrated, despite some evidence that female...

In the United States, current crop production often favors simplified rotations of maize and soybeans in conjunction with a heavy reliance on synthetic inputs that consequently degrade environmental health and increase production costs, without necessarily improving yields. While often stigmatized as underperforming compared to conventional systems...

Mounting evidence suggests that increasing within-species (or genotypic) crop diversity by planting mixtures of cultivars is a promising tactic for managing herbivorous pests. The soybean aphid (Aphis glycines Matsumura) is an invasive species that has forced growers to increase use of insecticides across the Midwestern United States. There is a cl...

Pollinator nutritional ecology provides insights into plant–pollinator interactions, coevolution, and the restoration of declining pollinator populations. Bees obtain their protein and lipid nutrient intake from pollen, which is essential for larval growth and development as well as adult health and reproduction. Our previous research revealed that...

Cytokinins (CKs) are a class of compounds that have long been thought to be exclusively plant growth regulators. Interestingly, some species of phytopathogenic bacteria and fungi have been shown to, and gall-inducing insects have been hypothesized to, produce CKs and use them to manipulate their host plants. We used high performance liquid chromato...

Frequent and intensive tillage can have negative effects on soil, including increasing risk of erosion, oxidizing organic matter, and disrupting life cycles of soil organisms. Even though tillage can negatively affect soil, this practice is still used across much of the world to prepare fields for planting and to manage pests. Farmers who have adop...

Disturbances associated with agricultural intensification reduce our ability to achieve sustainable crop production. These disturbances stem from crop-management tactics and can leave crop fields more vulnerable to insect outbreaks, in part because natural-enemy communities often tend to be more susceptible to disturbance than herbivorous pests. Re...

Neonicotinoid seed treatments are frequently used in cotton (Gossypium hirsutum L. [Malvales: Malvaceae]) production to provide protection against early-season herbivory. However, there is little known about how these applications affect extrafloral nectar (EFN), an important food resource for arthropod natural enemies. Using enzyme-linked immunoso...

1. Spatial synchrony, the tendency for temporal population fluctuations to be correlated across multiple locations at regional scales, is common and contributes to the severity of outbreaks and epidemics, but is little studied in agricultural pests. 2. This study analysed spatial synchrony from 1974 to 2008 in 16 lepidopteran agricultural pests in...

Many farmers use manure as an alternative to inorganic fertilizer. Previous research has shown that manure can decrease plant susceptibility to herbivores, but the mechanisms remain unclear. To determine how manure affects herbivore performance in a greenhouse setting, we fertilized corn with stacked cow manure or an equivalent amount of NPK fertil...

No‐till farmers who want more from their cover crops (CCs) are delaying CC termination until the main crop is planted. Delaying termination can help dry wet soils and reduce erosion. This process is referred to as planting green (PG). We hypothesized that PG would (i) dry soil at main crop planting, but conserve soil moisture later in the growing s...

Insect herbivory induces plant defense responses that are often modulated by components in insect saliva, oral secretions or regurgitant, frass, or oviposition fluids. These secretions contain proteins and small molecules that act as elicitors or effectors of plant defenses. Several non-protein elicitors have been identified from insect oral secret...

Background By sensing environmental cues indicative of pathogens or herbivores, plants can “prime” appropriate defenses and deploy faster, stronger responses to subsequent attack. Such priming presumably entails costs—else the primed state should be constitutively expressed—yet those costs remain poorly documented, in part due to a lack of studies...

Despite many efforts to sustain parasitoid populations in agroecosystems to help control pests, relatively little is known about parasitoid-flower interactions and how dependent each partner is on the other. There are few comprehensive, species-specific, community-level observations of parasitoid-flower interactions. Observing flower visitation by...

In the goldenrod Solidago altissima, most stems are erect, but “ducking” genotypes bend the tip of the apical stem downward for much of the growing season, and this morphology protects against at least two gall-forming herbivore species. Despite this advantage to defense, ducking remains a rare strategy in goldenrod, yet the costs that prevent duck...

Chemical cues are essential for many ecological interactions. Previous studies of chemically mediated multitrophic interactions have typically focused on responses to cues from plants or herbivores above‐ground. It is increasingly clear, however, that below‐ground cues and those produced by organisms at higher trophic levels also have ecological im...

[This corrects the article DOI: 10.3389/fpls.2018.00792.].

Lablab bean (Lablab purpureus) is a popular vegetable crop in Bangladesh, but farmers growing this crop experience significant losses to insect pests despite heavy reliance on conventional insecticides. We conducted field studies to improve pest management in lablab bean by testing biorational insecticides as alternatives to conventional insecticid...

Aphids have long been recognized as good phytochemists. They are small sap-feeding plant herbivores with complex life cycles that can involve cyclical parthenogenesis and seasonal host plant alternation, and most are plant specialists. Aphids have distinctive traits for identifying and exploiting their host plants, including the expression of polyp...

Few studies have examined the combined effect of multiple parasites on host fitness. Previous work in the Cucurbita pepo pathosystem indicates that infection with Zucchini yellow mosaic virus (ZYMV) reduces exposure to a second insect-vectored parasite (Erwinia tracheiphila). In this study, we performed two large-scale field experiments employing w...

Proportion of susceptible plants infected with powdery mildew in mid-August declines as the number of weeks for increasing weeks with zucchini yellow mosaic virus increases. Point size scales with number of plants that were virus infected for a given number of weeks.

Regression analysis for the impact of weeks infected with powdery mildew on the proportion of staminate (β = -0.0245, SE β = 0.0078, R2 = 1.72%, P = 0.002) and pistillate flowers (β = -0.07, SE β = 0.0121, R2 = 5.96%, P = 0.000) produced after first incidence of powdery mildew for 2014 field season. Dotted lines represent 95% confidence intervals.

Severity of powdery mildew on plants from each maternal family for each scoring date during the (A) 2013 and (B) 2014 field seasons. Different letters indicate significant differences between families at the P < 0.05 level.

Percent of susceptible and transgenic plants infected with Zucchini yellow mosaic virus (ZYMV) and the percent of non-inoculated susceptible and transgenic plants infected with Powdery Mildew in both the ZYMV inoculated and not inoculated fields at each time point during the (A) 2013 field season and (B) 2014 field season.

Percent of plants for each treatment type that showed powdery mildew at early and mid-time points during the greenhouse experiment.

Schematic Representation of a 2013 Inoculated Field consisting of 15 rows and 12 columns of plants spaced evenly over a 0.4 ha plot, 180 total plants. Each box lists the type of plant (Wild type = X, non-transgenic backcross 9 = BC, transgenic backcross 9 = BCT) and the family to which it belongs (I2, J5, OZ, D2, or J3). Boxes shaded in red indicat...

Severity of powdery mildew symptoms for each maternal family included in the greenhouse experiment. Different letters indicate significant differences between groups at the P < 0.05 level.

Population dynamic responses to global change have varied widely among taxa. Most studies of population dynamics of insect pests focus on one or a few species, leaving open the question of whether changes in outbreak patterns are species-specific or reveal predictable responses to global change, and what factors explain differences among population...