General science-technology orientation, specific benefit-risk assessment frame, and public acceptance of gene drive biotechnology.

With limited understanding of most new biotechnologies, how do citizens form their opinion and what factors influence their attitudes about these innovations? In this study, we use gene drive biotechnology in agricultural pest management as an example and theoretically propose that given low levels of knowledge and awareness, citizens' acceptance of, or opposition to, gene drive is significantly shaped by two predisposition factors: individuals' general orientation toward science and technology, and their specific benefit-risk assessment frame. Empirically, we employ data collected from a recent US nationally representative public opinion survey (N = 1220) and conduct statistical analyses to test the hypotheses derived from our theoretical expectations. Our statistical analyses, based on various model specifications and controlling for individual-level covariates and state-fixed effects, show that citizens with a more favorable general orientation toward science and technology are more likely to accept gene drive. Our data analyses also demonstrate that citizens' specific gene drive assessment frame-consisting of a potential benefit dimension and a potential risk dimension, significantly shapes their attitudes as well-specifically, people emphasizing more on the benefit dimension are more likely to accept gene drive, whereas those who place more importance on the risk dimension tend to oppose it. We discuss contributions of our study and make suggestions for future research in the conclusion.

Transcriptomic analysis of the honey bee (Apis mellifera) queen brain reveals that gene expression is affected by pesticide exposure during development.

Honey bees (Apis mellifera) play a pivotal role in agricultural production worldwide, primarily through the provision of pollination services. But despite their importance, honey bee health continues to be threatened by many factors, including parasitization by the mite Varroa destructor, poor queen quality, and pesticide exposure. Accumulation of pesticides in the hive's comb matrix over time inevitably leads to the exposure of developing brood, including queens, to wax contaminated with multiple compounds. Here, we characterized the brain transcriptome of queens that were reared in wax contaminated with pesticides commonly found in commercial beekeeping operations including either (a) a combination of 204,000 ppb of tau-fluvalinate and 91,900 ppb of coumaphos ("FC" group), (b) a combination of 9,800 ppb of chlorpyrifos and 53,700 ppb of chlorothalonil ("CC" group), or (c) 43,000 ppb of amitraz ("A" group). Control queens were reared in pesticide-free wax. Adult queens were allowed to mate naturally before being dissected. RNA isolated from brain tissue from three individuals per treatment group was sequenced using three technical replicates per queen. Using a cutoff log2 fold-change value of 1.5, we identified 247 differentially expressed genes (DEGs) in the FC group, 244 in the CC treatment group, and 668 in the A group, when comparing each group to the control. This is the first study to examine the sublethal effects of pesticides commonly found in wax (particularly amitraz) on the queen's brain transcriptome. Future studies should further explore the relationship between our molecular findings and the queen's behavior and physiology.

Quantifying the impacts of symbiotic interactions between two invasive species: the tawny crazy ant (Nylanderia fulva) tending the sorghum aphid (Melanaphis sorghi).

The establishment of new symbiotic interactions between introduced species may facilitate invasion success. For instance, tawny crazy ant (Nylanderia fulva Mayr) is known to be an opportunistic tender of honeydew producing insects and this ants' symbiotic interactions have exacerbated agricultural damage in some invaded regions of the world. The invasive sorghum aphid (Melanaphis sorghi Theobald) was first reported as a pest in the continental United States-in Texas and Louisiana-as recent as 2013, and tawny crazy ant (TCA) was reported in Texas in the early 2000s. Although these introductions are relatively recent, TCA workers tend sorghum aphids in field and greenhouse settings. This study quantified the tending duration of TCA workers to sorghum aphids and the impact of TCA tending on aphid biomass. For this study aphids were collected from three different host plant species (i.e., sugarcane, Johnson grass, and sorghum) and clone colonies were established. Sorghum is the main economic crop in which these aphids occur, hence we focused our study on the potential impacts of interactions on sorghum. Quantification of invasive ant-aphid interactions, on either stems or leaves of sorghum plants, were conducted in greenhouse conditions. Our results show that although these two invasive insect species do not have a long coevolutionary history, TCA developed a tending interaction with sorghum aphid, and aphids were observed excreting honeydew after being antennated by TCA workers. Interestingly, this relatively recent symbiotic interaction significantly increased overall aphid biomass for aphids that were positioned on stems and collected from Johnson grass. It is recommended to continue monitoring the interaction between TCA and sorghum aphid in field conditions due to its potential to increase aphid populations and sorghum plant damage.

Genes drive organisms and slippery slopes.

The bioethical debate about using gene drives to alter or eradicate wild populations has focused mostly on issues concerning short-term risk assessment and management, governance and oversight, and public and community engagement, but has not examined big-picture- 'where is this going?'-questions in great depth. In other areas of bioethical controversy, big-picture questions often enter the public forum via slippery slope arguments. Given the incredible potential of gene drive organisms to alter the Earth's biota, it is somewhat surprising that slippery slope arguments have not played a more prominent role in ethical and policy debates about these emerging technologies. In this article, we examine a type of slippery slope argument against using gene drives to alter or suppress wild pest populations and consider whether it has a role to play in ethical and policy debates. Although we conclude that this argument does not provide compelling reasons for banning the use of gene drives in wild pest populations, we believe that it still has value as a morally instructive cautionary narrative that can motivate scientists, ethicists, and members of the public to think more clearly about appropriate vs. inappropriate uses of gene drive technologies, the long-term and cumulative and emergent risks of using gene drives in wild populations, and steps that can be taken to manage these risks, such as protecting wilderness areas where people can enjoy life forms that have not been genetically engineered.

Improving Natural Enemy Selection in Biological Control through Greater Attention to Chemical Ecology and Host-Associated Differentiation of Target Arthropod Pests.

Host-associated differentiation (HAD) refers to cases in which genetically distinct populations of a species (e.g., herbivores or natural enemies) preferentially reproduce or feed on different host species. In agroecosystems, HAD often results in unique strains or biotypes of pest species, each attacking different species of crops. However, HAD is not restricted to pest populations, and may cascade to the third trophic level, affecting host selection by natural enemies, and ultimately leading to HAD within natural enemy species. Natural enemy HAD may affect the outcomes of biological control efforts, whether classical, conservation, or augmentative. Here, we explore the potential effects of pest and natural enemy HAD on biological control in agroecosystems, with emphases on current knowledge gaps and implications of HAD for selection of biological control agents. Additionally, given the importance of semiochemicals in mediating interactions between trophic levels, we emphasize the role of chemical ecology in interactions between pests and natural enemies, and suggest areas of consideration for biological control. Overall, we aim to jump-start a conversation concerning the relevance of HAD in biological control by reviewing currently available information on natural enemy HAD, identifying challenges to incorporating HAD considerations into biological control efforts, and proposing future research directions on natural enemy selection and HAD.

Stakeholder Views on Engagement, Trust, Performance, and Risk Considerations About Use of Gene Drive Technology in Agricultural Pest Management.

Gene drive is an experimental technique that may make it possible to alter the genetic traits of whole populations of a species through the genetic modification of a relatively small number of individuals. This technology is sufficiently new that literature on the understanding and views of stakeholders and the public regarding the use of gene drive organisms in agricultural pest management is just beginning to emerge. Our team conducted a 2-pronged engagement process with Texas gene drive agricultural stakeholders to ascertain their values, beliefs, and preferences about the efficacy, safety, and risk management considerations of gene drive technology as a potential tool for agricultural pest management. We found that a majority of stakeholders support gene drive research and its potential use for managing agricultural pests. Our work with stakeholders confirms both their willingness to be engaged and the importance they place on stakeholder and public engagement regarding these issues, as well as the need to address these issues before use of gene drive as a pest management mechanism will be accepted and trusted.

Aphelinus nigritus Howard (Hymenoptera: Aphelinidae) Preference for Sorghum Aphid, Melanaphis sorghi (Theobald, 1904) (Hemiptera: Aphididae), Honeydew Is Stronger in Johnson Grass, Sorghum halepense, Than in Grain Sorghum, Sorghum bicolor.

How aphid parasitoids of recent invasive species interact with their hosts can affect the feasibility of biological control. In this study, we focus on a recent invasive pest of US grain sorghum, Sorghum bicolor, the sorghum aphid (SA), Melanaphis sorghi. Understanding this pest's ecology in the grain sorghum agroecosystem is critical to develop effective control strategies. As parasitoids often use aphid honeydew as a sugar resource, and honeydew is known to mediate parasitoid-aphid interactions, we investigated the ability of SA honeydew to retain the parasitoid Aphelinus nigritus. Since SAs in the US have multiple plant hosts, and host-plant diet can modulate parasitoid retention (a major component in host foraging), we measured SA honeydew sugar, organic acid, and amino acid profiles, then assessed via retention time A. nigritus preference for honeydew produced on grain sorghum or Johnson grass, Sorghum halepense. Compared to a water control, A. nigritus spent more time on SA honeydew produced on either host plant. Despite similar honeydew profiles from both plant species, A. nigritus preferred honeydew produced on Johnson grass. Our results suggest the potential for SA honeydew to facilitate augmentation strategies aimed at maintaining A. nigritus on Johnson grass to suppress SAs before grain sorghum is planted.

Morphometric and molecular discrimination of the sugarcane aphid, Melanaphis sacchari, (Zehntner, 1897) and the sorghum aphid Melanaphis sorghi (Theobald, 1904).

Melanaphis sacchari (Zehntner, 1897) and Melanaphis sorghi (Theobald, 1904) are major worldwide crop pests causing direct feeding damage on sorghum and transmitting viruses to sugarcane. It is common in the scientific literature to consider these two species as synonyms, referred to as the 'sugarcane aphid', although no formal study has validated this synonymy. In this study, based on the comparison of samples collected from their whole distribution area, we use both morphometric and molecular data to better characterize the discrimination between M. sacchari and M. sorghi. An unsupervised multivariate analysis of morphometric data clearly confirmed the separation of the two species. The best discriminating characters separating these species were length of the antenna processus terminalis relative to length of hind tibia, siphunculus or cauda. However, those criteria sometimes do not allow an unambiguous identification. Bayesian clustering based on microsatellite data delimited two clusters, which corresponded to the morphological species separation. The DNA sequencing of three nuclear and three mitochondrial regions revealed slight divergence between species. In particular, the COI barcode region proved to be uninformative for species separation because one haplotype is shared by both species. In contrast, one SNP located on the nuclear EF1-α gene was diagnostic for species separation. Based on morphological and molecular evidence, the invasive genotype damaging to sorghum in the US, Mexico and the Caribbean since 2013 is found to be M. sorghi.

Research on Integrated Management for Cattle Fever Ticks and Bovine Babesiosis in the United States and Mexico: Current Status and Opportunities for Binational Coordination.

Bovine babesiosis is a reportable transboundary animal disease caused by Babesia bovis and Babesiabigemina in the Americas where these apicomplexan protozoa are transmitted by the invasive cattle fever ticks Rhipicephalus (Boophilus) microplus and Rhipicephalus(Boophilus) annulatus. In countries like Mexico where cattle fever ticks remain endemic, bovine babesiosis is detrimental to cattle health and results in a significant economic cost to the livestock industry. These cattle disease vectors continue to threaten the U.S. cattle industry despite their elimination through efforts of the Cattle Fever Tick Eradication Program. Mexico and the U.S. share a common interest in managing cattle fever ticks through their economically important binational cattle trade. Here, we report the outcomes of a meeting where stakeholders from Mexico and the U.S. representing the livestock and pharmaceutical industry, regulatory agencies, and research institutions gathered to discuss research and knowledge gaps requiring attention to advance progressive management strategies for bovine babesiosis and cattle fever ticks. Research recommendations and other actionable activities reflect commitment among meeting participants to seize opportunities for collaborative efforts. Addressing these research gaps is expected to yield scientific knowledge benefitting the interdependent livestock industries of Mexico and the U.S. through its translation into enhanced biosecurity against the economic and animal health impacts of bovine babesiosis and cattle fever ticks.

A comparative evaluation of northern and southern Ixodes scapularis questing height and hiding behaviour in the USA.

Ticks display a distinct type of host-seeking behaviour called questing. It has been proposed that the questing behaviour of Ixodes scapularis explains the geographic variation in Lyme disease (LD) risk in the eastern USA because the northern population has been shown to quest more often than the southern population. The height at which questing occurs is variable and this study aimed to characterize questing height for I. scapularis. Ticks were collected from a northern and southern state (i.e. Maryland and Texas) and bioassays were conducted. We report that nymphs from Texas quested at lower heights compared to nymphs from Maryland. In addition, only Texas nymphs exhibited a behaviour we call 'hiding behaviour'. These results may reflect the different composition of hosts between these two areas as the south has a higher abundance of lizards. In contrast, there was no significant difference in questing height between Maryland adults and Texas adults which was to be expected since adults are feeding on white-tailed deer in both locations. If all southern I. scapularis nymphs are questing at lower heights, this might make them less likely to come into contact with humans and this may be contributing to the geographical difference in LD prevalence.

Corn Stunt Disease: An Ideal Insect-Microbial-Plant Pathosystem for Comprehensive Studies of Vector-Borne Plant Diseases of Corn.

Over 700 plant diseases identified as vector-borne negatively impact plant health and food security globally. The pest control of vector-borne diseases in agricultural settings is in urgent need of more effective tools. Ongoing research in genetics, molecular biology, physiology, and vector behavior has begun to unravel new insights into the transmission of phytopathogens by their insect vectors. However, the intricate mechanisms involved in phytopathogen transmission for certain pathosystems warrant further investigation. In this review, we propose the corn stunt pathosystem (Zea mays-Spiroplasma kunkelii-Dalbulus maidis) as an ideal model for dissecting the molecular determinants and mechanisms underpinning the persistent transmission of a mollicute by its specialist insect vector to an economically important monocotyledonous crop. Corn stunt is the most important disease of corn in the Americas and the Caribbean, where it causes the severe stunting of corn plants and can result in up to 100% yield loss. A comprehensive study of the corn stunt disease system will pave the way for the discovery of novel molecular targets for genetic pest control targeting either the insect vector or the phytopathogen.

Prevalence of protozoan parasites in small and medium mammals in Texas, USA.

Wildlife interaction with humans increases the risk of potentially infected ticks seeking an opportunistic blood meal and consequently leading to zoonotic transmission. In the United States, human babesiosis is a tick-borne zoonosis most commonly caused by the intraerythrocytic protozoan parasite, Babesia microti. The presence of Babesia microti and other species of Babesia within Texas has not been well characterized, and the molecular prevalence of these pathogens within wildlife species is largely unknown. Small (e.g. rodents) and medium sized mammalian species (e.g. racoons) represent potential reservoirs for specific species of Babesia, though this relationship has not been thoroughly evaluated within Texas. This study aimed to characterize the molecular prevalence of Babesia species within small and medium sized mammals at two sites in East Texas with an emphasis on detection of pathogen presence in these two contrasting wild mammal groups at these sites. To that end, a total of 480 wild mammals representing eight genera were trapped, sampled, and screened for Babesia species using the TickPath layerplex qPCR assay. Two sites were selected for animal collection, including The Big Thicket National Preserve and Gus Engeling Wildlife Management Area. Molecular analysis revealed the prevalence of various Babesia and Hepathozoon species at 0.09% each, and Sarcocystis at 0.06% . Continued molecular prevalence surveys of tick-borne pathogens in Texas wild mammals will be needed to provide novel information as to which species of Babesia are most prevalent and identify specific wildlife species as pathogen reservoirs.

Did maize domestication and early spread mediate the population genetics of corn leafhopper?

Investigating how crop domestication and early farming mediated crop attributes, distributions, and interactions with antagonists may shed light on today's agricultural pest problems. Crop domestication generally involved artificial selection for traits desirable to early farmers, for example, increased productivity or yield, and enhanced qualities, though invariably it altered the interactions between crops and insects, and expanded the geographical ranges of crops. Thus, some studies suggest that with crop domestication and spread, insect populations on wild crop ancestors gave rise to pestiferous insect populations on crops. Here, we addressed whether the emergence of corn leafhopper (Dalbulus maidis) as an agricultural pest may be associated with domestication and early spread of maize (Zea mays mays). We used AFLP markers and mitochondrial COI sequences to assess population genetic structuring and haplotype relationships among corn leafhopper samples from maize and its wild relative Zea diploperennis from multiple locations in Mexico and Argentina. We uncovered seven corn leafhopper haplotypes contained within two haplogroups, one haplogroup containing haplotypes associated with maize and the other containing haplotypes associated with Z. diploperennis in a mountainous habitat. Within the first haplogroup, one haplotype was predominant across Mexican locations, and another across Argentinean locations; both were considered pestiferous. We suggested that the divergence times of the maize-associated haplogroup and of the "pestiferous" haplotypes are correlated with the chronology of maize spread following its domestication. Overall, our results support a hypothesis positing that maize domestication favored corn leafhopper genotypes preadapted for exploiting maize so that they became pestiferous, and that with the geographical expansion of maize farming, corn leafhopper colonized Z. diploperennis, a host exclusive to secluded habitats that serves as a refuge for archaic corn leafhopper genotypic diversity. Broadly, our results help explain the extents to which crop domestication and early spread may have mediated the emergence of today's agricultural pests.

Searching for the Immature Stages of Ixodes scapularis (Acari: Ixodidae) in Leaf Litter and Soil in Texas.

The standard tick collection methods of flagging and dragging are successful for collecting all stages of the blacklegged tick, Ixodes scapularis (Say) (Acari: Ixodidae), in the northern United States. However, for unknown reasons, these methods are unsuccessful for collecting the immature stages of I. scapularis in the southern United States. Thus, a different collection strategy was employed to search for the immature stages of I. scapularis in the southern state of Texas. Monthly sampling of three types of microhabitats potentially harboring ticks was conducted for 17 mo at the Big Thicket National Preserve. Samples of leaf litter, topsoil, and subsoil were placed within Berlese funnels to determine if the immature stages of I. scapularis are residing in these layers. No ticks were found in any of the 600 substrate samples examined. Along nearby trail edges in the same area, 656 adult I. scapularis (an average of 22.6 per 1,000 m2), as well as 268 immatures of other species (i.e., Amblyomma americanum (Linnaeaus) (Acari: Ixodidae) and Dermacentor variabilis (Say) (Acari: Ixodidae)) were collected using flagging and dragging. These results suggest that unlike speculations from previous studies in the southern United States, the immature stages of I. scapularis may not be residing in the leaf litter and soil layers in Texas. We hypothesize that they may be residing in their host's nests and burrows. Perhaps I. scapularis in the south is exhibiting a stage specific mixed host-seeking strategy by residing in nests and burrows as immatures, contributing to the geographical difference in Lyme disease prevalence between the northern and southern United States.

Agriculture sows pests: how crop domestication, host shifts, and agricultural intensification can create insect pests from herbivores.

We argue that agriculture as practiced creates pests. We use three examples (Corn leafhopper, Dalbulus maidis; Western corn rootworm, Diabrotica virgifera virgifera; Cotton fleahopper, Pseudatomoscelis seriatus) to illustrate: firstly, how since its origins, agriculture has proven conducive to transforming selected herbivores into pests, particularly through crop domestication and spread, and agricultural intensification, and; secondly, that the herbivores that became pests were among those hosted by crop wild relatives or associates, and were pre-adapted either as whole species or component subpopulations. Two of our examples, Corn leafhopper and Western corn rootworm, illustrate how following a host shift to a domesticated host, emergent pests 'hopped' onto crops and rode expansion waves to spread far beyond the geographic ranges of their wild hosts. Western corn rootworm exemplifies how an herbivore-tolerant crop was left vulnerable when it was bred for yield and protected with insecticides. Cotton fleahopper illustrates how removing preferred wild host plants from landscapes and replacing them with crops, allows herbivores with flexible host preferences to reach pest-level populations. We conclude by arguing that in the new geological epoch we face, the Anthropocene, we can improve agriculture by looking to our past to identify and avoid missteps of early and recent farmers.

Invasion of sorghum in the Americas by a new sugarcane aphid (Melanaphis sacchari) superclone.

In the United States (US), the sugarcane aphid (SCA) Melanaphis sacchari (Zehnter) (Hemiptera: Aphididae) was introduced in the 1970s, however at that time it was only considered a pest of sugarcane. In 2013, a massive outbreak of M. sacchari occured on sorghum, resulting in significant economic damage to sorghum grown in North America including the US, Mexico, and Puerto Rico. The aim of the present study was to determine if the SCA pest emergence in American sorghum resulted from the introduction of new genotypes. To this end we used microsatellite markers and COI sequencing to compare the genetic diversity of SCA populations collected in the Americas after the 2013 SCA outbreak on sorghum (during 2013-2017) to older samples collected before the pest outbreak (during 2007-2009). Our results show that the SCA outbreak in the Americas and the Caribbean observed since 2013 belong to populations exhibiting low genetic diversity and consisting of a dominant clonal lineage, MLL-F, which colonizes Sorghum spp. and sugarcane. The comparison of MLL-F specimens collected post-2013 with specimens collected in Louisiana in 2007 revealed that both populations are genetically distinct, according to COI sequencing and microsatellite data analyses. Our result suggest that MLL-F is a new invasive genotype introduced into the Americas that has spread rapidly across sorghum growing regions in the US, Mexico, Honduras and the Caribbean. The origin of this introduction is either Africa or Asia, with Asia being the most probable source.

Instar- and host-associated differentiation of bacterial communities in the Mediterranean fruit fly Ceratitis capitata.

Microorganisms are acknowledged for their role in shaping insects' evolution, life history and ecology. Previous studies have shown that microbial communities harbored within insects vary through ontogenetic development and among insects feeding on different host-plant species. In this study, we characterized the bacterial microbiota of the highly polyphagous Mediterranean fruit fly, Ceratitis capitata (Diptera: Tephritidae), at different instars and when feeding on different host-plant species. Our results show that the bacterial microbiota hosted within the Mediterranean fruit fly differs among instars and host-plant species. Most of the bacteria harbored by the Mediterranean fruit fly belong to the phylum Proteobacteria, including genera of Alphaproteobacteria such as Acetobacter and Gluconobacter; Betaprotobacteria such as Burkholderia and Gammaproteobacteria such as Pseudomonas.

TRANSLATING ECOLOGY, PHYSIOLOGY, BIOCHEMISTRY, AND POPULATION GENETICS RESEARCH TO MEET THE CHALLENGE OF TICK AND TICK-BORNE DISEASES IN NORTH AMERICA.

Emerging and re-emerging tick-borne diseases threaten public health and the wellbeing of domestic animals and wildlife globally. The adoption of an evolutionary ecology framework aimed to diminish the impact of tick-borne diseases needs to be part of strategies to protect human and animal populations. We present a review of current knowledge on the adaptation of ticks to their environment, and the impact that global change could have on their geographic distribution in North America. Environmental pressures will affect tick population genetics by selecting genotypes able to withstand new and changing environments and by altering the connectivity and isolation of several tick populations. Research in these areas is particularly lacking in the southern United States and most of Mexico with knowledge gaps on the ecology of these diseases, including a void in the identity of reservoir hosts for several tick-borne pathogens. Additionally, the way in which anthropogenic changes to landscapes may influence tick-borne disease ecology remains to be fully understood. Enhanced knowledge in these areas is needed in order to implement effective and sustainable integrated tick management strategies. We propose to refocus ecology studies with emphasis on metacommunity-based approaches to enable a holistic perspective addressing whole pathogen and host assemblages. Network analyses could be used to develop mechanistic models involving multihost-pathogen communities. An increase in our understanding of the ecology of tick-borne diseases across their geographic distribution will aid in the design of effective area-wide tick control strategies aimed to diminish the burden of pathogens transmitted by ticks.

Redbanded Stink Bug (Hemiptera: Pentatomidae) Infestation and Occurrence of Delayed Maturity in Soybean.

Studies done in Brazilian soybean, Glycine max (L.) Merril, in the 1970s suggested the redbanded stink bug, Piezodorus guildinii (Westwood), is principally responsible for delayed maturity in this crop. This stink bug species has recently emerged as a serious pest of soybean in the southern United States, where little is known about its association with the occurrence of delayed maturity disorder. Also, the mechanism behind stink bug-induced soybean delayed maturity remains unknown. It is believed that stink bug feeding during pod development stages results in reduced pod-seed load, causing alteration of source-sink ratio and eventually delayed maturity. To determine the P. guildinii threshold triggering delayed maturity in soybean, experiments were conducted with varying levels of P. guildinii infestation (0, 2, 4, and 8 adults per 0.3 m) during the R4 to R5 soybean growth stages. In addition, to determine if soybean delayed maturity is exclusively because of reduced pod load, experiments with different levels of mechanical pod removal (0, 25, 50, and 75%) were conducted on field-grown soybeans. P. guildinii densities up to 4 adults per 0.3 m did not trigger occurrence of delayed maturity. However, a density of 8 adults per 0.3 m produced a significant increase in the number of green leaves retained on plants at maturity (i.e., delayed maturity). There was no effect of mechanical pod removal on green leaf retention. The lack of a significant positive correlation between mechanical pod removal and green leaf retention indicates the involvement of mechanism(s) other than reduced pod load in the occurrence of soybean delayed maturity.