- Author: Kat Kerlin, UC Davis
Natural habitat maximizes the benefits of birds for farmers, food safety and conservation
A supportive environment can bring out the best in an individual — even for a bird.
After an E.coli outbreak in 2006 devastated the spinach industry, farmers were pressured to remove natural habitat to keep wildlife — and the foodborne pathogens they can sometimes carry — from visiting crops. A study published today from the University of California, Davis, shows that farms with surrounding natural habitat experience the most benefits from birds, including less crop damage and lower food-safety risks.
The study, published in the Journal of Applied Ecology, was conducted at 21 strawberry fields along California's Central Coast. It found that birds were more likely to carry pathogens and eat berries without surrounding natural habitat.
The authors said a better understanding of the interplay of farming practices, the landscape, and the roles birds play in ecosystems can help growers make the most out of wild birds near their fields.
“Bird communities respond to changes in the landscape,” said lead author Elissa Olimpi, a postdoctoral scholar in the UC Davis Department of Wildlife, Fish and Conservation Biology at the time of the study. “As birds shift in response to management, so do the costs and benefits they provide.”
The single most important driver
The study looked at how different farming practices influenced the costs and benefits that wild birds provided on the strawberry farms. The scientists combined nearly 300 bird surveys and the molecular analyses of more than 1,000 fecal samples from 55 bird species to determine which birds ate pests, beneficial insects and crops, and carried foodborne pathogens.
They also ranked birds to see which were more likely to bring benefits or costs to farmlands. Barn swallows, for instance, got a “gold star” in the study, Olimpi said. Their mud nests are commonly seen clinging to the underside of barn eaves, from which they fly out to swoop over fields, foraging on insects.
But rather than resulting in a list of “good” and “bad” birds, the study found that most bird species brought both costs and benefits to farms, depending on how the landscape was managed.
The presence of natural habitat was the single most important driver differentiating a farm where wild birds brought more benefits than harm.
“Nature is messy, and birds are complex,” Olimpi said. “The best we can do is understand how to take advantage of the benefits while reducing the harms. Growers will tell you it's impossible to keep birds off your farm — you can't do that and don't want to from a conservation perspective. So how can we take advantage of the services birds provide?”
Win-wins for birds and farms
The study is one of several publications from UC Davis Professor Daniel Karp's lab highlighting the environmental, agricultural, and food safety impacts of conserving bird habitat around farms. A related study in 2020 found that farms with natural habitat attracted more insect-eating birds — and fewer strawberry-eating birds — so that farmers experience less berry damage on farms with more habitat nearby. Such habitats also bring greater numbers of bird species to the landscape.
“All together, these studies suggest that farming landscapes with natural habitat tend to be good for conservation, farmers, and public health,” said Karp.
Additional co-authors of this study include Karina Garcia and David Gonthier of University of Kentucky, Claire Kremen of UC Berkeley and the University of British Columbia, William E. Snyder of University of Georgia, and Erin Wilson-Rankin of UC Riverside.
The research was funded by the USDA and UC Davis Department of Wildlife, Fish and Conservation Biology.
/h3>/h3>/h2>- Author: Belinda J. Messenger-Sikes
Figuring out what's wrong with your plant takes a little detective work. Plants can look unhealthy for a number of reasons, including diseases, pest insects, or even environmental conditions like sunburn, too much water, not enough water, wind damage, and other issues. Start by examining the plant closely for anything out of place. Knowing what the plant should look like will help you determine if there's a problem. Because some pests attack only specific plants, identifying the type of plant, including the variety or cultivar, narrows down disease possibilities.
Diseases caused by a plant pathogen, like a fungus, will look and act differently than something caused by environmental factors. Note the plant's location in the garden or landscape and compare the symptoms to nearby plants. Disease symptoms will usually develop slowly and unevenly on one type of plant. Damage from environmental issues is more likely to appear quickly and be widespread.
If the plant is growing in a preferred location and receiving the right amount of water and fertilizer, it will be less susceptible to disease and environmental disorders.
To learn more about plant diseases and what might be affecting your plant, find your plant in the UC IPM plant disease index. Not sure if you have a disease or another type of pest? Use the plant problem diagnostic tool to help narrow down what's wrong with your plant. Find out more about plant problems on the UC IPM website.
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- Author: Surendra K. Dara
Strawberry, a high-value specialty crop in California, suffers from several soilborne, fruit, and foliar diseases. Verticillium wilt caused by Verticillium dahliae, Fusarium wilt caused by Fusarium oxysporum f. sp. fragariae, and Macrophomina crown rot or charcoal rot caused by Macrophomina phaseolina are major soilborne diseases that cause significant losses without proper control. Chemical fumigation, crop rotation with broccoli, nutrient and irrigation management to minimize plant stress, and non-chemical soil disinfestation are usual control strategies for these diseases. Botrytis fruit rot or gray mold caused by Botrytis cineaea is a common fruit disease requiring frequent fungicidal applications. Propagules of gray mold fungus survive in the soil and infect flowers and fruits. A study was conducted to evaluate the impact of drip application of various fungicides on improving strawberry health and enhancing fruit yields.
Methodology
This study was conducted in an experimental strawberry field at the Shafter Research Station during 2019-2020. Cultivar San Andreas was planted on 28 October 2019. No pre-plant fertilizer application was made in this non-fumigated field which had Fusarium wilt, Macrophomina crown rot, and Botrytis fruit rot in the previous year's strawberry planting. Each treatment was applied to a 300' long bed with single drip tape in the center and two rows of strawberry plants. Sprinkler irrigation was provided immediately after planting along with drip irrigation, which was provided one or more times weekly as needed for the rest of the experimental period. Each bed was divided into six 30' long plots, representing replications, with an 18' buffer in between. Between 6 November 2019 and 9 May 2020, 1.88 qt of 20-10-0 (a combination of 32-0-0 urea ammonium nitrate and 10-34-0 ammonium phosphate) and 1.32 qt of potassium thiosulfate was applied 20 times at weekly intervals through fertigation. Treatments were applied either as a transplant dip or through the drip system using a Dosatron fertilizer injector (model D14MZ2). The following treatments were evaluated in this study:
i) Untreated control: Neither transplants nor the planted crop was treated with any fungicides.
ii) Abound transplant dip: Transplants were dipped in 7 fl oz of Abound (azoxystrobin) fungicide in 100 gal of water for 4 min immediately prior to planting. Transplant dip in a fungicide is practiced by several growers to protect the crop from fungal diseases.
iii) Rhyme: Applied Rhyme (flutriafol) at 7 fl oz/ac immediately after and 30, 60, and 90 days after planting through the drip system.
iv) Velum Prime with Switch: Applied Velum Prime (fluopyram) at 6.5 fl oz/ac 14 and 28 days after planting followed by Switch 62.5 WG (cyprodinil + fludioxinil) at 14 oz/ac 42 days after planting through the drip system.
v) Rhyme with Switch: Four applications of Rhyme at 7 fl oz/ac were made 14, 28, 56, and 70 days after planting with a single application of Switch 62.5 WG 42 days after planting through the drip system.
Parameters observed during the study included leaf chlorophyll and leaf nitrogen (with chlorophyll meter) in February and May; fruit sugar (with refractometer) in May; fruit firmness (with penetrometer) in April and May; severity of gray mold (caused by Botrytis cinereae) twice in March and once in May, and other fruit diseases (mucor fruit rot caused by Mucor spp. and Rhizopus fruit rot caused by Rhizopus spp.) once in May 3 and 5 days after harvest (on a scale of 0 to 4 where 0=no infection; 1=1-25%, 2=26-50%, 3=51-75% and 4=76-100% fungal growth); and fruit yield per plant from 11 weekly harvests between 11 March and 14 May 2020. Leaf chlorophyll and nitrogen data for the Abound dip treatment were not collected in February. Data were analyzed using analysis of variance in Statistix software and significant means were separated using the Least Significant Difference test.
Results and Discussion
Leaf chlorophyll content was significantly higher in plants that received drip application of fungicides compared to untreated plants in February while leaf nitrogen content was significantly higher in the same treatments during the May observation. There were no differences in fruit sugar or average fruit firmness among the treatments.
The average gray mold severity from three harvest dates was low and did not statistically differ among the treatments. However, the severity of other diseases was significantly different among various treatments with the lowest rating in Abound transplant dip on both 3 and 5 days after harvest and only 3 days after harvest in plants that received four applications of Rhyme. Unlike the previous year, visible symptoms of the soilborne diseases were not seen during the study period to evaluate the impact of the treatments. However, there were significant differences among treatments for the marketable fruit yield. The highest marketable yield was observed in the treatment that received Rhyme and Switch followed by Velum Prime and Switch and Rhyme alone. The lowest fruit yield was observed in Abound dip treatment. Unmarketable fruit (deformed or diseased) yield was similar among the treatments. Compared to the untreated control, Abound dip resulted in 16% less marketable yield and such a negative impact from transplant dip in fungicides has been seen in other studies (Dara and Peck, 2017 and 2018; Dara, 2020). Marketable fruit yield was 4-28% higher where fungicides were applied to the soil.
Although visible symptoms of soilborne diseases were absent during the study, periodic drip application of the fungicides probably suppressed the fungal inocula and associated stress and might have contributed to increased yields. The direct impact of fungicide treatments on soilborne pathogens was, however, not clear in this study due to the lack of disease symptoms. Considering the cost of chemical fumigation or soil disinfestation and the environmental impact of chemical fumigation, treating the soil with fungicides can be an economical option if they are effective. While this study presents some preliminary data, additional studies in non-fumigated fields in the presence of pathogens are necessary to consider soil fungicide treatment as a control option.
Acknowledgments: Thanks to FMC for funding this study and Marjan Heidarian Dehkordi and Tamas Zold for their technical assistance.
References
Dara, S. K. 2020. Improving strawberry yields with biostimulants and nutrient supplements: a 2019-2020 study. UCANR eJournal of Entomology and Biologicals. https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=43631
Dara, S. K. and D. Peck. 2017. Evaluating beneficial microbe-based products for their impact on strawberry plant growth, health, and fruit yield. UCANR eJournal of Entomology and Biologicals. https://ucanr.edu/blogs/blogcore/postdetail.cfm?postnum=25122
Dara, S. K. and D. Peck. 2018. Evaluation of additive, soil amendment, and biostimulant products in Santa Maria strawberry. CAPCA Adviser, 21 (5): 44-50.
Invasive species are non-native plants, animals, or pathogens that can cause economic or environmental harm. This year, we will be spotlighting several different invasive species that are established in California to raise awareness and help reduce their spread. Stay tuned—we will be showcasing a different invasive species each day and where you can find more information.
Want to learn more about California Invasive Species Action Week? Check out the full schedule of events on their website.
- Author: Konrad Mathesius
- Co-author: Sarah Light
Septoria leaf blotch (also known as septoria tritici blotch, STB) is caused by the fungal pathogen Mycosphaerella graminicola. It is one of the primary diseases in wheat and one that was seen in several locations around the central and southern Sacramento Valley last winter. Growers that observed STB (or other) outbreaks in their wheat last winter should consider management strategies to reduce the severity of outbreaks this coming winter.
100% control of the pathogen is impossible due to the nature of how the pathogen reproduces itself. Infection takes place in two separate stages during the growing season:
1) the initial infection stage, known as the primary infection and
2) the epidemic stage, known as the secondary infection. Primary infection occurs via ascospores, which are windblown spores that can travel long distances. After primary infection occurs, the pathogen will produce pycnidiospores (which look like small black dots on wheat leaves and are visible with a hand lens). Pycnidiospores will exude jelly-like masses packed with conidia when they come in contact with rain or moisture. The conidia are water-dispersed, and will spread throughout the canopy with dew or rain. This is how the infection will continue to spread during the growing season.
The risk of yield loss is greatest when the flag leaf is affected. There are fungicides that can be applied, but they are often not economical, and applications should only be made between tillering and heading. It is too late to control the pathogen this season. But because local (and not just airborne) inoculum has been shown to increase infection rates in the subsequent season, growers have several options to reduce carryover of and infection by M. graminicola inoculum into the next season.
2) Control alternative hosts and volunteer wheat. Because the pathogen is genetically specialized in grasses, and wheat in particular, control of volunteers and certain species of weeds (including bentgrass, common bent, soft brome, soft cheat, barren brome, tall fescue, annual bluegrass, and Kentucky bluegrass) is an important consideration for growers who may be facing higher than average inoculum loads next season. Pay close attention to early flushes of grass species in edges and control volunteer wheat in neighboring fields with in-season herbicide applications can break the link between two seasons and reduce local sources of inoculum.
4) Crop rotation and Controlling Volunteers. Although M. graminicola is an airborne pathogen, several studies indicate some success in suppressing outbreaks by reducing local inoculum loads. As with many soil-borne diseases, crop rotation is an important part of keeping disease levels low. This is because inoculum levels decrease every year without a susceptible host. A 2-year rotation between wheat crops is long enough to reduce M. graminicola inoculum. Broadleaf crops are ideal because grass-specific herbicides can be used to control volunteers. If broadleaf crops are not an option, other grasses can be used because the pathogen is specialized for wheat; the only setback in this case is the fact that grass herbicides targeting wheat volunteers tend to damage other grasses to some extent as well. In either case, volunteer wheat must be controlled for this strategy to work.
5) Seed and foliar fungicidal treatments: STB is not a seedborne disease, but studies have shown that certain fungicidal seed treatments can reduce and delay infections significantly. One study showed that the formation of epidemic-inducing pycnidiospores was reduced by 5 months when triazole fungicide seed treatments were used. Propiconazole is the only major triazole that has been shown to reduce STB and is labeled for wheat in California (trade names: bumper, tide). Foliar treatments, while effective when applied at certain times in the year, are rarely economically justifiable, but seed treatments may offer a more favorable cost:benefit ratio in terms of disease suppression.
Even after wheat has dried out, some pathogens can still be identified by the overwintering structures left on plant material. Growers should feel free to contact their local farm advisors if they are looking for help in identifying signs or symptoms of pathogens in their wheat to make management decisions for the next season.
Primary Reference:
Suffert, F., I. Sache, C. Lannou. (2011). Early Stages of Septoria Tritici Blotch Epidemics of Winter Wheat; Build-up Overseasoning, and Release of Primary Inoculum. Plant Pathology(60), 166-177. doi:10.1111/j.1365-3059.2010.02369.x