Eric R. Gallandt

University of Maine | UM · School of Food and Agriculture

Weeds are a major challenge for organic farmers, yet we know little about the factors influencing organic farmers' weed management decisions. We hypothesized that farmers and scientist 'experts' differ in fundamental areas of knowledge and perceptions regarding weeds and weed management. Moreover, these differences prevent effective communication,...

Cultivation remains the foundation of weed management in organic farming. Low and variable efficacy, increasingly unpredictable weather, cost, and perceived harm to soil quality inspire organic farmers, to varying degrees, to learn and implement ecologically based management practices. Crop rotation and cover cropping are system-level practices fre...

Because herbicide and cultivation efficacy is generally density independent, seedling density following these weed control practices will be proportional to the density of germinable seeds in the seedbank. Most farmers would therefore benefit from management practices that reduce seed inputs, increase seed losses, and reduce the probability that re...

We reviewed the timing of the peak rate of emergence for 15 problematic weed species as well as ways to use this knowledge to improve control. Much of the previous literature modeled emergence based on growing-degree-days. For these models, we input average temperature data from several zones of Northeast USA. Within species, model-predicted peak e...

Increasing atmospheric carbon dioxide concentrations [CO2] and climate change are impacting farming worldwide. Ecological weed management (EWM) principles, including use of diverse tactics already employed by many farmers, may assist in adapting to and mitigating climate change. We systematically reviewed the literature on EWM and climate change an...

The long-term success of weed management programs requires that all crops in a rotation receive satisfactory weed control. Band sowing with inter-band hoeing has been proposed as an innovative weed management strategy for grain crops. In the band sowing system, crops are sown in a broadcast pattern within a band of some chosen width (here we select...

Stale seedbeds are commonly used by organic vegetable farmers to reduce in-season weed density. The primary purpose of this study was to evaluate the efficacy of soil solarization (clear plastic) with subsequent flaming for stale seedbed preparation. A secondary objective was to compare the efficacy of solarization with tarping (black plastic). Sol...

Soil solarization using clear plastic is a promising weed management strategy for organic farms in the Northeast USA. Based on grower concerns that the practice might negatively affect beneficial soil microbiota, we conducted experiments to measure the effects of 2 and 4 weeks of solarization in a field and a closed greenhouse. Soil microbial commu...

Weeds remain the foremost production challenge for organic small grain farmers in the Northeastern United States. Instead of sowing crops in narrow, single-line rows, band-sowing offers a more uniform spatial arrangement of the crop, maximizing interspecific while reducing intraspecific competition. Weeds in the inter-band zone are controlled by cu...

Weed management strategies likely provide trade-offs in economic implications. Farmers may prioritize weed control during the “critical period” of the crop and ignore subsequent weeds; they may focus on the long term by eliminating additions to the weed seedbank with a “zero seed rain” approach; or they may suppress weed emergence with polyethylene...

Tillage is a foundational management practice in many cropping systems to manage weed seedbanks and reduce reliance on herbicides for weed management. Tillage alters established weed communities but can also stimulate weed seed germination and emergence. Hence, viewed within a community assembly framework tillage is a strong assembly filter that ca...

Organic vegetable farmers execute weed management using many overall philosophies, including focusing management during the early-season critical period, managing the weed seedbank with a ‘zero seed rain’ strategy, or physically suppressing weeds with plastic or natural mulches. While these strategies vary in their ecological and economic implicati...

Previous research has demonstrated that the season in which soil is tilled (spring versus fall) can strongly influence weed community assembly and subsequent species composition and abundance in annual cropping systems. Despite this understanding, it is unknown whether finer-scale, within-season variation in the timing of tillage has similar impact...

Weed management strategies differ in their ability to control weeds, and often have unique agroecological implications. To provide growers with an improved sense of trade-offs between weed control and ecological effects, we implemented several prominent organic weed management strategies in yellow onion in 2014 and 2015. Strategies included cultiva...

The effect of tillage timing on weed community assembly was assessed at four locations in the Northeastern United States by tilling the soil every two weeks from April to September and quantifying the emerged weed community six weeks after each tillage event. Variance partitioning analysis was used to test the relative importance of tillage timing...

The northern New England region includes the states of Vermont, New Hampshire, and Maine and encompasses a large degree of climate and edaphic variation across a relatively small spatial area, making it ideal for studying climate change impacts on agricultural weed communities. We sampled weed seedbanks and measured soil physical and chemical chara...

Tillage is a foundational management practice in many cropping systems. Although effective at reducing weed populations and preparing a crop seedbed, tillage and cultivation can also dramatically alter weed community composition. We examined the impact of soil tillage timing on weed community structure at four sites across the northeastern United S...

Intrarow cultivation efficacy is often low and highly variable. As the mechanisms affecting weed mortality likely vary by tool, several companies have developed cultivators with the ability to use several different intrarow tools at once. We evaluated the potential for such ‘stacking’ of cultivation tools to increase efficacy. We used different seq...

Non-chemical weed management covers all management practices that influence weeds except herbicides. This chapter summarises the major achievements in European research, as well as work undertaken in North America. Research groups from both continents have interacted strongly on the topic over the years and shared common interests on the developmen...

Postdispersal weed seed predation is a significant source of weed mortality in agroecosystems. The magnitude of seed predation, however, is variable. Understanding the relative importance of factors driving variability in seed predation rates will increase the potential utility of seed predation to farmers. We conducted landscape-scale field experi...

Two broad aims drive weed science research: improved management and improved understanding of weed biology and ecology. In recent years, agricultural weed research addressing these two aims has effectively split into separate subdisciplines despite repeated calls for greater integration. Although some excellent work is being done, agricultural weed...

Background/Question/Methods Weed management remains a high priority for organic farmers, whose fields generally have higher weed density and species diversity than those of their conventional counterparts. However, we know little about the factors influencing weed management decisions by organic farmers. Through a series of interviews, we explore...

Weed management remains a high priority for organic farmers, whose fields generally have higher weed density and species diversity than those of their conventional counterparts. We explored whether variability in farmer knowledge and perceptions of weeds and weed management practices were predictive of variability in on-farm weed, seedbanks on 23 o...

Background/Question/Methods Weed communities on organic farms vary widely in density and diversity from their conventionally managed counterparts, but only a handful of studies report weed seedbank data from organic farms. We will present a detailed comparison of weed seedbanks on 91 organic farms from four distinct regions: northern New England,...

Background/Question/Methods Post-dispersal seed predation can reduce arable weed seedbanks, providing a desirable ecosystem service to farmers. Seed predation can be substantial, but the magnitude of seed predation is highly variable. To help farmers maximize benefits received from seed predators, we must understand sources driving this variabili...

Although we know that alterations in crop density, crop spatial pattern and inclusion of more selective weed control can improve weed suppression for organic growers, it is unknown whether these result in changes to the weed seedbank that increase cropping system profitability over time. Data collected from field trials conducted in 2009 and 2010 i...

Background/Question/Methods Organic agriculture is a rapidly increasing sector globally, and serves as a broad systems-based approach to conserving both biodiversity and ecosystem functions while providing healthy food. Although weed management is a major challenge for organic farmers, we know little about why farmers do or do not decide to use e...

Effective in-season weed management options are limited for organic cereal farmers. Two alternatives to current farmer practices are improving efficacy of physical weed control through use of interrow cultivation or increasing the competitive ability of the crop through elevated seeding rates and more uniform spatial planting patterns. It is unknow...

Cereals are among the most competitive of crops, but under organic management, weeds remain the foremost production problem. Understanding the ecology of both weeds and cereals is paramount to developing non-chemical strategies that limit yield loss due to weeds whilst suppressing weed growth and weed seed deposition. Key mechanisms for weed manage...

Harpalus rufipes, a member of the Carabidae, is the most common granivorous invertebrate in Maine agroecosystems. While previous research demonstrated a positive correlation between H. rufipes activity-density and weed seed predation, little is known about the behaviour of this seed predator. We conducted mesocosm experiments to examine seed burial...

Future advancements in crop production will rely on increased understanding of ecological principles that control interactions among cropping system components. Our interest in linking soil quality and weed management derives from the belief that greater understanding of key processes and properties that define soil-weed relationships will lead to...

Kolb LN, Gallandt ER & Molloy T (2010). Improving weed management in organic spring barley: physical weed control vs. interspecific competition. Weed Research 50, 597–605. Few options exist for effectively managing weeds in organic spring cereals. Establishing a competitive crop through increased seeding rate provides improved weed suppression, but...

Kruidhof HM, Gallandt ER, Haramoto ER & Bastiaans L (2011). Selective weed suppression by cover crop residues: effects of seed mass and timing of species’ sensitivity. Weed Research 51 , 177–186. Summary Laboratory bioassays have shown that large‐seeded species better tolerate cover crop residue–mediated stress than small‐seeded species. This prov...

Mirsky SB, Gallandt ER, Mortensen DA, Curran WS & Shumway DL (2010). Reducing the germinable weed seedbank with soil disturbance and cover crops. Weed Research50, 341–352. Ecologically based weed management relies heavily on a greater integration of cultural and mechanical control tactics than conventional weed management. As such, management outco...

Postdispersal seed predation by ground beetles may be an important form of biological weed control. Field experiments conducted in 2002 and 2003 determined invertebrate seed predators' ability to detect and remove seeds from different experimental substrates. Predation of wild mustard and common lambsquarters was greater when seeds were presented o...

Cover crop systems were investigated in 2004 and 2005 for their effects on the activity-density (a function of movement and density) of a promising group of weed biocontrol organisms, the ground beetles collectively known as carabids, with particular emphasis on a beneficial carabid species Harpalus rufipes DeGeer. Marked H. rufipes released into p...

The rapid expansion of the plant bioeconomy is creating strong economic incentives to distribute novel plant material, including transgenic cultivars, exotic species, and species that were formerly constrained to small geographical areas, at large geographical scales. Such introductions carry with them the risk of invasive spread of the introduced...

Considerable discussion has occurred among the weed science community regarding the potential benefits and limitations of integrated approaches to crop and pest management. This discussion also needs to occur in our weed science classrooms, where students from a wide range of academic disciplines are trained in the fundamentals of weed ecology and...

Distance-based redundancy analysis (db-RDA), a recently developed ordination technique useful for both multivariate hypothesis testing and data interpretation, was used to evaluate treatment effects on weed communities in a long-term study of alternative potato cropping systems. The experiment consisted of a factorial arrangement of three pest mana...

The benefits of cover crops in cropping systems have long been recognized. Legumes have historically been used lo provide biologically fixed nitrogen to cash crops, and it has been shown that soil erosion can be slowed significantly with even minimal amounts of soil cover during vulnerable times of year. The role of cover crops in North American fa...

Competition from weeds is the most important of all biological factors that reduce agricultural crop yield. This occurs primarily because weeds use resources that would otherwise be available to the crop. The magnitude of yield loss is affected by numerous agronomic and environmental factors, most importantly, weed density and time of emergence rel...

Ground beetles are well known as beneficial organisms in agroecosystems, contributing to the predation of a wide range of animal pests and weed seeds. Tillage has generally been shown to have a negative effect on ground beetles, but it is not known whether this is because of direct mortality or the result of indirect losses resulting from dispersal...

Assessing learning outcomes in general education is increasingly important to accrediting bodies. A fertile area of assessment is measuring changes in student attitudes/values in response to general education. University of Maine faculty experimented with such an attitude assessment. The results reveal interesting questions about general education...

Assessing learning outcomes in general education is increasingly important to accrediting bodies. A fertile area of assessment is measuring changes in student attitudes/values in response to general education. University of Maine faculty experimented with such an attitude assessment. The results reveal interesting questions about general education...

Seed predators may significantly reduce the weed seedbank. In Maine, one ground beetle species, Harpalus rufipes DeGeer, can consume 90% of the epigeous seeds of certain weeds. H. rufipes is the predominant carabid seed predator in Maine agricultural systems. The mechanisms by which H. rufipes can be promoted are not well understood. Two weed manag...

Contrasting cover-cropping systems were compared to determine whether fundamental differences in cover-cropping strategies affect weed seed predators and resulting seed predation. We conducted typical “feeding” trials in which 25 seeds of each of six weed species, including velvetleaf, wild mustard, yellow foxtail, common lambsquarters, redroot pig...

Cover crops offer many benefits for farmers seeking to reduce their reliance on external inputs. These include maintaining and improving soil quality, preventing erosion and, in some cases, allelopathic weed control. Allelopathic potential has been well documented for cover crops such as cereal rye (Secale cereale L.), hairy vetch (Vicia villosa Ro...

No-tillage offers potential for improved soil quality, reduced erosion, and equal or increased crop yields. We hypothesized that, compared with conservation tillage (CT), no-tillage (NT) offers conditions more conducive to microbial decay of weed seed. In NT systems seed remain at or near the soil surface where crop residues, moisture, and lack of...

Weed management in industrial agroecosystems continues to rely heavily on the use of herbicides to minimize weed densities within a given crop growth period. Despite widespread contamination of surface and ground waters, human health concerns, and increasing incidence of herbicide resistance that have emerged over the past twenty years, and increas...

Using a soil bioassay technique, seedling growth and incidence of disease of wild mustard (Brassica kaber) and sweet corn (Zea mays) were assessed in soil from field plots that received either of two treatments: incorporated red clover (Trifolium pratense) residue plus application of compost (`amended soil'), or application of ammonium nitrate fert...

Cultivar mixtures have been suggested as a means to achieve increased crop productivity. By choosing cultivars that complement each other for performance of important traits, mixtures could be formulated to meet specific production requirements. The objective of this study was to evaluate the performance of wheat mixtures and their pure line compon...

To manage jointed goatgrass (Aegilops cylindrical, growers need an action threshold decision aid to assist them in deciding when to rotate to a spring crop instead of growing winter wheat (Triticum aestivum). A study was conducted in Washington from 1992 to 1995 to predict winter wheat yield loss based on a jointed goatgrass population in the previ...

Previous studies have suggested that phenolics from legume green manures may contribute to weed control through allelopathy. The objective was to determine if red clover (Trifolium pratense L.) residue amended field soils expressed phytotoxicity to a weed species, wild mustard (Sinapisarvensis L.). Field plots involving incorporation treatments of...

Future advancements in crop production will rely on increased understanding of ecological principles that control interactions among cropping system components. Our interest in linking soil quality and weed management derives from the belief that greater understanding of key processes and properties that define soil-weed relationships will lead to...

Potato acreage and total production in Maine have declined steadily since the 1960s. In 1991, a University of Maine research team established a large-scale, long-term, comparative study of three factors that form the foundation of productive potato cropping systems: soil management, pest management, and variety choice. This study, the Potato Ecosys...

Results from the 'Potato Ecosystem Project,' a cropping systems study in northern Maine, were used to test the hypothesis that greater reliance on organic nutrient sources and less reliance on synthetic fertilizer sources can benefit weed management efforts. 'Atlantic' potato was grown in a 2-yr rotation within a factorial arrangement of three pest...

The bulletin reports on the first four years of the Maine Potato Ecosystem Project, a long-term, multidisciplinary study of alternative crop management strategies. The study site is a 15-acre tract on the northern boundary of the University of Maine's Aroostook Farm in Presque Isle, Maine, divided into 96 main plots that are grouped into four block...

Proteins extracted from suspension-cultured soybean (Glycine max (L.) Merr. Corsoy 79) cells contained O- and N-glucosyltransferases (GTs; EC 2.4.1) that catalyzed glucosylation of several xenobiotic compounds including (a) the hydroxylated herbicide metabolites 6-hydroxybentazone (B-6-OH), 8-hydroxybentazone and 5-hydroxydiclofop (b) the herbicide...

Typescript. Thesis (M.S.)--Montana State University, 1988. Vita. Includes bibliographical references (leaves 77-82).