How to Manage Plant Pests and Diseases in Your Home Garden
By Matt Kasson, Brian Lovett and Carolee Bull
Home gardening is having a boom year across the U.S. Whether they're growing their own food in response to pandemic shortages or just looking for a diversion, numerous aspiring gardeners have constructed their first raised beds, and seeds are flying off suppliers' shelves. Now that gardens are largely planted, much of the work for the next several months revolves around keeping them healthy.
Contrary to the Biblical adage, we do not necessarily reap what we sow. As researchers specializing in plant pathology and entomology, we have devoted our careers to understanding and managing plant pests and pathogens. We are also gardeners with varying levels of experience and have seen firsthand the damage these insects and disease-causing agents can inflict.
Plant health is essential for seeing your garden succeed all the way to harvest. The United Nations General Assembly has declared 2020 as the International Year of Plant Health to help bring needed attention to pests and diseases that threaten global food production.
Thousands of pests and pathogens are known to target commercial crops, but a few usual suspects are routinely responsible for havoc in gardens across the U.S. Although each organism's preferences vary, a few common tactics can help you detect them and protect your plants.
Start With Prevention
Just as preventive steps like maintaining a balanced diet help keep humans healthy, home growers can take many actions to help their gardens thrive.
One key step is assessing soil fertility – the ability of soil to sustain plant growth – which can vary widely depending on your location and soil type. Low soil fertility limits food production and predisposes plants to disease and pests. University extension soil testing labs can help evaluate the quality of garden soil and identify nutrient deficiencies and acidic soils, often at no charge.
Using weed barrier landscape cloth for planting rows and mulching between rows is an effective way to suppress weeds. Matt Kasson, CC BY-ND
Suppressing weeds, either through mulching or weeding by hand each week, increases air flow and reduces humidity around garden plants, making it harder for pests and pathogens to thrive. Weed control ensures that nutrients are available for the plants you want to grow.
Proper spacing between plants is also important. Crowding can contribute to disease and pest outbreaks, so check and follow recommendations on seed packs or online as you add and move plants throughout the season. You can always cull plants after they come up to help with spacing. In small gardens, fewer plants that are properly supported can produce a bigger harvest than many overcrowded plants.
And then there's the weather. Frost, hail, drought and flooding all pose unique risks to plants. Inconsistent rainfall can kill thirsty plants more quickly than infertile soils. Both too little and too much water will stress plants and can make them more vulnerable to severe pest and pathogen outbreaks.
A general rule of thumb is to follow a consistent daily watering regimen – preferably first thing in the morning – and to avoid over-watering, which can encourage root pathogens in soil.
Common plant pathogens include viruses, bacteria, nematodes, oomycetes and fungi. All of these microorganisms, especially at an early stage of infection, are too small to see. But when they proliferate, they cause changes in plants that we can recognize.
Unlike insects, which move around on six legs or on wings through the air, pathogens can move unseen and unchecked from leaf to leaf on the wind, through the soil or in droplets of water. Some microbes have even formed intimate relationships with insects and use them as vehicles to move from plant to plant, which makes these pathogens even more challenging to manage. Unfortunately, by the time some pathogens make their presence known, the damage is already done.
We recently conducted a Twitter poll of gardeners nationwide to find out which culprits plagued their gardens. People named aphids, squash vine borers, squash bugs and flea beetles as the most problematic insect pests. Their most troublesome pathogens included powdery mildew, tomato bacterial wilt and cucurbit downy mildew.
To manage such perennial challenges, the first step is to spend time closely looking at your plants. Do you notice any insects consistently hanging around, or molds colonizing leaves or other plant parts? How about symptoms such as blight, stunting, or leaves that are yellowing, browning or wilting?
This white fungal growth is an early sign of powdery mildew on a leaf of susceptible summer squash. Matt Kasson, CC BY-ND
There are countless resources online for keen-eyed and curious gardeners looking to identify and manage pests and diseases. Try uploading a photo to the iNaturalist app or a Facebook gardeners group that can offer a community-sourced ID. Plant disease clinics in your state will also diagnose plant damage from diseases and pests for free or at low cost.
Once you've identified a problem serious enough to intervene, the land grant extension system can provide solutions. Extension programs at land grant schools like West Virginia University and Penn State University offer critical information on agriculture and management of pests and diseases in multiple languages for commercial and home growers.
Their resources include information on safe and proper use of pesticides as part of integrated pest management strategies. This approach employs pesticides in a targeted way along with non-chemical control methods and cultural practices, such as choosing native plants. Our professional societies, including the American Phytopathological Society, also offer a compendium series to help users diagnose and treat pests and diseases.
Sow seed for fall transplants of broccoli, kale, turnip, and cauliflower in flats or containers by the 3rd to 4th w… https://t.co/i3chrkKCj0— Montgomery County Master Gardeners - Maryland (@Montgomery County Master Gardeners - Maryland)1593540775.0
Those who are serious about learning and sharing their experience with others may want to consider Master Gardener programs, which train and certify community members on the latest evidence-based gardening techniques, tailored to their growing area. Master Gardeners pay it forward by training new Master Gardeners and answering questions for any gardener.
Plant pests are a daily reminder that gardens do not exist in a vacuum, and gardeners shouldn't struggle alone either. Joining the gardening community takes attentiveness and time, but we believe the investment required to become an active member of your local gardening community is well worth it. With experience, the nervous tightrope act of keeping pests at bay and food on the table becomes a delicate dance that can help us appreciate where our food comes from – and ultimately, our place in the global ecosystem.
Matt Kasson is an Associate Professor of Plant Pathology and Mycology, West Virginia University.
Brian Lovett is a Postdoctoral Researcher in Mycology, West Virginia University.
Carolee Bull is a Professor of Plant Pathology and Systematic Bacteriology, Pennsylvania State University.
Disclosure statement: Matt Kasson receives funding from USDA and The Ohrstrom Foundation. Carolee Bull receives funding from the USDA and from the mushroom industry, and matching funds from seed companies for her research projects. Brian Lovett does not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.
Reposted with permission from The Conversation.
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By Tara Lohan
Warming temperatures on land and in the water are already forcing many species to seek out more hospitable environments. Atlantic mackerel are swimming farther north; mountain-dwelling pikas are moving upslope; some migratory birds are altering the timing of their flights.
Numerous studies have tracked these shifting ranges, looked at the importance of wildlife corridors to protect these migrations, and identified climate refugia where some species may find a safer climatic haven.
"There's a huge amount of scientific literature about where species will have to move as the climate warms," says U.C. Berkeley biogeographer Matthew Kling. "But there hasn't been much work in terms of actually thinking about how they're going to get there — at least not when it comes to wind-dispersed plants."
Kling and David Ackerly, professor and dean of the College of Natural Resources at U.C. Berkeley, have taken a stab at filling this knowledge gap. Their recent study, published in Nature Climate Change, looks at the vulnerability of wind-dispersed species to climate change.
It's an important field of research, because while a fish can more easily swim toward colder waters, a tree may find its wind-blown seeds landing in places and conditions where they're not adapted to grow.
Kling is careful to point out that the researchers weren't asking how climate change was going to change wind; other research suggests there likely won't be big shifts in global wind patterns.
Instead the study involved exploring those wind patterns — including direction, speed and variability — across the globe. The wind data was then integrated with data on climate variation to build models trying to predict vulnerability patterns showing where wind may either help or hinder biodiversity from responding to climate change.
One of the study's findings was that wind-dispersed or wind-pollinated trees in the tropics and on the windward sides of mountain ranges are more likely to be vulnerable, since the wind isn't likely to move those dispersers in the right direction for a climate-friendly environment.
The researchers also looked specifically at lodgepole pines, a species that's both wind-dispersed and wind-pollinated.
They found that populations of lodgepole pines that already grow along the warmer and drier edges of the species' current range could very well be under threat due to rising temperatures and related climate alterations.
"As temperature increases, we need to think about how the genes that are evolved to tolerate drought and heat are going to get to the portions of the species' range that are going to be getting drier and hotter," says Kling. "So that's what we were able to take a stab at predicting and estimating with these wind models — which populations are mostly likely to receive those beneficial genes in the future."
That's important, he says, because wind-dispersed species like pines, willows and poplars are often keystone species whole ecosystems depend upon — especially in temperate and boreal forests.
And there are even more plants that rely on pollen dispersal by wind.
"That's going to be important for moving genes from the warmer parts of a species' range to the cooler parts of the species' range," he says. "This is not just about species' ranges shifting, but also genetic changes within species."
Kling says this line of research is just beginning, and much more needs to be done to test these models in the field. But there could be important conservation-related benefits to that work.
"All these species and genes need to migrate long distances and we can be thinking more about habitat connectivity and the vulnerability of these systems," he says.
The more we learn, the more we may be able to do to help species adapt.
"The idea is that there will be some landscapes where the wind is likely to help these systems naturally adapt to climate change without much intervention, and other places where land managers might really need to intervene," he says. "That could involve using assisted migration or assisted gene flow to actually get in there, moving seeds or planting trees to help them keep up with rapid climate change."
Tara Lohan is deputy editor of The Revelator and has worked for more than a decade as a digital editor and environmental journalist focused on the intersections of energy, water and climate. Her work has been published by The Nation, American Prospect, High Country News, Grist, Pacific Standard and others. She is the editor of two books on the global water crisis. http://twitter.com/TaraLohan
Reposted with permission from The Revelator.
The last Ice Age eliminated some giant mammals, like the woolly rhino. Conventional thinking initially attributed their extinction to hunting. While overhunting may have contributed, a new study pinpointed a different reason for the woolly rhinos' extinction: climate change.
The last of the woolly rhinos went extinct in Siberia nearly 14,000 years ago, just when the Earth's climate began changing from its frozen conditions to something warmer, wetter and less favorable to the large land mammal. DNA tests conducted by scientists on 14 well-preserved rhinos point to rapid warming as the culprit, CNN reported.
"Humans are well known to alter their environment and so the assumption is that if it was a large animal it would have been useful to people as food and that must have caused its demise," says Edana Lord, a graduate student at the Center for Paleogenetics in Stockholm, Sweden, and co-first author of the paper, Smithsonian Magazine reported. "But our findings highlight the role of rapid climate change in the woolly rhino's extinction."
The study, published in Current Biology, notes that the rhino population stayed fairly consistent for tens of thousands of years until 18,500 years ago. That means that people and rhinos lived together in Northern Siberia for roughly 13,000 years before rhinos went extinct, Science News reported.
The findings are an ominous harbinger for large species during the current climate crisis. As EcoWatch reported, nearly 1,000 species are expected to go extinct within the next 100 years due to their inability to adapt to a rapidly changing climate. Tigers, eagles and rhinos are especially vulnerable.
The difference between now and the phenomenon 14,000 years ago is that human activity is directly responsible for the current climate crisis.
To figure out the cause of the woolly rhinos' extinction, scientists examined DNA from different rhinos across Siberia. The tissue, bone and hair samples allowed them to deduce the population size and diversity for tens of thousands of years prior to extinction, CNN reported.
Researchers spent years exploring the Siberian permafrost to find enough samples. Then they had to look for pristine genetic material, Smithsonian Magazine reported.
It turns out the wooly rhinos actually thrived as they lived alongside humans.
"It was initially thought that humans appeared in northeastern Siberia fourteen or fifteen thousand years ago, around when the woolly rhinoceros went extinct. But recently, there have been several discoveries of much older human occupation sites, the most famous of which is around thirty thousand years old," senior author Love Dalén, a professor of evolutionary genetics at the Center for Paleogenetics, said in a press release.
"This paper shows that woolly rhino coexisted with people for millennia without any significant impact on their population," Grant Zazula, a paleontologist for Canada's Yukon territory and Simon Fraser University who was not involved in the research, told Smithsonian Magazine. "Then all of a sudden the climate changed and they went extinct."
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Transitioning to renewable energy can help reduce global warming, and Jennie Stephens of Northeastern University says it can also drive social change.
For example, she says that locally owned businesses can lead the local clean energy economy and create new jobs in underserved communities.
"We really need to think about … connecting climate and energy with other issues that people wake up every day really worried about," she says, "whether it be jobs, housing, transportation, health and well-being."
To maximize that potential, she says the energy sector must have more women and people of color in positions of influence. Research shows that leadership in the solar industry, for example, is currently dominated by white men.
"I think that a more inclusive, diverse leadership is essential to be able to effectively make these connections," Stephens says. "Diversity is not just about who people are and their identity, but the ideas and the priorities and the approaches and the lens that they bring to the world."
So she says by elevating diverse voices, organizations can better connect the climate benefits of clean energy with social and economic transformation.
Reposted with permission from Yale Climate Connections.