Citrus Pest & Disease Prevention Program — While limiting the spread of the Asian citrus psyllid and Huanglongbing are the highest priority for the California citrus industry and the Citrus Pest & Disease Prevention Program, the program continually monitors for a number of threats to the industry and has recently detected sweet orange scab (SOS) in new areas of the state. Additionally, an unofficial Lime Swallowtail Butterfly (LSB) sample was identified from Los Angeles County and several LSB sightings have been uploaded onto the iNaturalist application, including sightings in Los Angeles and San Luis Obispo counties.
Sweet Orange Scab
Sweet Orange Scab
SOS is a cosmetic fungal disease that impacts the marketability of the fruit and effects all citrus, not just oranges. SOS is caused by the fungus Elsinöe australis, which is dispersed by water. You can recognize SOS by the scab-like lesions on fruit, and less frequently on leaves and twigs. SOS can cause premature fruit drop and stunt young nursery trees and new field plantings but has little impact on fruit quality.
A positive detection of SOS was found during a commodity survey on the west side of Riverside County, the fourth detection in California within the last year and a half. To help protect citrus from SOS, growers and packinghouses within five miles from an SOS detection, and packinghouses throughout the state receiving fruit from groves within five miles from an SOS detection, are currently required to follow the below measures:
Sign an SOS compliance agreement with California Department of Food and Agriculture (CDFA).
Disinfect all fruit and field bins.
Collect and appropriately dispose of green waste.
Per the Citrus Pest & Disease Prevention Committee’s direction, CDFA is also reviewing SOS impacts and analyzing the need to establish SOS interior quarantine regulations. Currently the program regulates areas within a five-mile radius from each SOS detection, following the United States Department of Agriculture’s quarantine protocols.
Working hand in hand with growers, CDFA is exploring the rulemaking process to create state interior quarantines, which will avoid a broader statewide quarantine that would be more burdensome to the industry.
Lime Swallowtail Butterfly
There was one unofficial detection of LSB in Los Angeles and several reported sightings in Los Angeles and in San Luis Obispo counties.
LSB in the larval stage eat citrus leaves and have been very damaging to nursery stock in other parts of the world. The larva looks similar to bird guano before maturing into green caterpillars. As butterflies, they are largely black with irregular yellow spots on the outer wings.
The U.S. Food and Drug Administration (FDA) has released a report on its investigation of the Salmonella Enteritidis outbreak in Peaches. The FDA and multiple state and federal partners investigated an outbreak of Salmonella Enteritidis infections that were linked to the consumption of peaches during the summer of 2020. In total, the outbreak caused 101 reported illnesses across 17 states, including 28 hospitalizations. This appears to be the first time a Salmonella outbreak has been linked to peaches.
The FDA conducted this investigation in conjunction with the U.S. Centers for Disease Control and Prevention (CDC), state partners, and Canadian public health officials between August and October 2020. The epidemiological and traceback investigation determined that peaches packed or supplied by a large grower/producer were the likely source of the outbreak. The traceback evidence informed and helped to prioritize two subsequent investigations of peach packing/holding operations and peach orchards in Cutler, Kerman, and Sanger, California. The large grower/producer cooperated with FDA throughout the investigation and is continuing to engage with FDA on the agency’s findings and recommendations.
Investigators conducted over 700 tests on environmental, peach, and peach tree leaf samples. While no test results matched the 2020 outbreak strain, four tests conducted on peach and peach tree leaf samples collected from an orchard adjacent to a poultry operation yielded positives for Salmonella Alachua which were further linked via whole genome sequencing (WGS) to 2019 and 2020 chicken isolates. This finding prompted a follow-up investigation more closely focused on growing areas and a voluntary recall by the firm, preventing the tested, contaminated product from reaching the market. During the follow-up investigation, two tests of peach tree leaf samples collected from orchards adjacent to a cattle feedlot yielded positives for Salmonella Montevideo that were genetically similar via WGS to 2018-2020 beef and cattle isolates.
While investigators did not find the outbreak strain, and the strains of Salmonella found during this outbreak were not linked to any clinical illnesses, the investigational findings reinforce the FDA’s concern about the potential impact that adjacent land uses can have on the safety of produce.
The FDA views the implementation of appropriate science- and risk-based measures to reduce the potential for contamination of peaches and other produce as the most effective and practicable means to improve the safety of fresh produce, especially when measures are tailored to the specific practices and conditions on individual farms. The FDA encourages all growers to be cognizant of and assess risks that may be posed by adjacent and nearby land uses, including for the potential impact of dust exposure. The FDA also recognizes the interconnection between people, animals, plants, and their shared environment when it comes to public health outcomes, and we encourage collaboration among various groups in the broader agricultural community (e.g., produce growers, those managing animal operations, state and federal government agencies, and academia) to address this issue.
It has been heart breaking to seeing wheat and alfalfa fields dry up the last few weeks. The recent hot temperatures caused many fields to wither, while placing greater irrigation needs on the few crops being irrigated with well water. It’s the driest year I have experienced in my 10 years in the Klamath Basin!
Several people asked me about strategies moving forward this summer and what yields they can expect from crops with limited irrigation. I do not know all the answers, but I tried to highlight some of my past experiences from research and farming below. Please keep in mind every field situation is unique and one strategy rarely works in all situations. I want to commend the farming community for being resilient in a terrible situation. I also want to thank all those that have spent countless hours trying to improve the water situation today and in the future.
Irrigation tips
Almost all fields started this year with very little residual soil moisture. At IREC, not a drop of water flowed through our tile drains this winter and spring. Darrin and I noticed the first irrigation on many fields did not even refill the soil profile especially when irrigating during strong winds. This made 2021 even more difficult as winter precipitation did not refill the soil profile naturally. As a result, many alfalfa and grain fields are starting to show unusual patterns from drought such as wind strips and tall growth under sprinkler drains. If you can water fields with well water, it is very important to check the sprinkler heads to make sure they are the proper size, check water pressure on the ends of irrigation lines, and make sure your irrigation is providing good coverage. Offset your wheel-lines one roll the next irrigation in fields with wind strips. As many of us are irrigating out of drains, it is important to make sure you have adequate sprinkler pressure. If you do not have adequate pressure, you need to reduce the size of your sprinkler heads and extend the duration of the irrigation set (16 hrs vs 12 hrs) or run less lines.
Many alfalfa producers are in the position to harvest 1st cutting and cannot water for the next couple weeks until the hay is picked up. In this situation, producers should consolidate limited water on their most productive fields. Once an alfalfa field wilts from drought it will typically go dormant. This is good as the alfalfa will likely survive until next year, but it also means the alfalfa is resistant to green-up and grow again in mid-summer. As such, I’d recommend using limited water to irrigate healthy fields instead of trying to stretch it across all fields especially those fields that are already wilted with poor growth going into first cutting.
Potato producers will need to apply long sets to refill the soil profile when the potatoes emerge. Most field have very little residual soil moisture, and it is important to avoid drought stress during vegetation growth and tuber initiation to maximize tuber set and tuber quality. I advise potato growers to check soil moisture frequently throughout the potato rooting zone to make sure water reached the bottom of the hill and is uniform throughout the field.
Most farmers should be done irrigating winter grain, and I see a few producers irrigating spring grain. If you decide to irrigate spring grain, I recommend irrigating the crop fully until you run out of your water allocation instead of trying to space irrigation throughout the summer. Irrigating spring grain fully to meet the crop water demand during tillering and elongation will maximize forage yields, and once wheat and barley fields show signs of drought stress, they will start to head producing low forage and grain yields.
Fertilization tips
Producers that decide to irrigate grain and grass fields should make sure to apply adequate nitrogen. The cost of the fertilizer will easily pay for itself with high forage prices and nitrogen can double grass forage yields compared to leaving fields unfertilized. Granular nitrogen fertilizer applied as a topdress (over the top of the crop) should be watered into the soil with at least an inch of water within a few days of application to prevent volatility losses. Don’t fertilize fields if you do not have adequate water to irrigate crop!
Pest Management tips
2021 is shaping up to be a very bad pest year. We have already witnessed problems with blue aphid and weevils in alfalfa, and I am starting to see armyworms in grain and alfalfa. We had a very high population of seedcorn maggot in onions as all the maggot flies seemed to congregate in the few irrigated fields throughout the basin. Thrip populations are also very high. Onion producers should start scouting for thrips earlier than normal and be ready to start insecticide applications if thrip numbers build on young plants. Potato producers should expect higher than normal pest populations. Aphid populations are high, and many insects will be moving into potato fields after alfalfa and grain harvest. Mites may be more problematic than normal as fields are receiving less overhead irrigation and we have a lot of dust in the air. I hope the dry weather will help reduce foliar crop diseases, but the hot temperatures and stagnant water sources may make my prediction incorrect. Potato and onion farmers need to apply frequent irrigation to keep up with crop water use, so make sure to scout for foliar diseases and try to avoid keeping leaf surfaces wet for extended periods. — By Rob Wilson, UCCE Farm Advisor, ANR Intermountain Research & Extension Center
Sutter County grows between 300 and 800 acres of fresh-market honeydew, mixed melon and cantaloupe each year. The fields vary between furrow and drip irrigation, with many fields in the Sutter Basin only receiving a pre-irrigation.
Because of the rapid growth of melons, they are competitive with weeds and one cultivation may be sufficient to control weed issues. The growing habits of melons reduce the need for herbicides, which is fortunate since the availability of registered and effective herbicides is limited.
Generally, in Sutter County, the field is tilled, pre-irrigated, worked again, and melons are planted into moisture. When weed pressure is high, a hand-hoeing crew comes in and cultivates. Since many of the conventional fields in the northern region receive little water, herbicides may not be as effective since they do not work well without water. If water is available, herbicides like Prefar and Curbit may be used.
Bensulide (Prefar) can be applied before planting and incorporated shallowly or as a preemergent herbicide under sprinkler irrigation. It is used to control small-seeded annual grasses, pigweed and purslane. Remember to always check the label and consider plantback restrictions, especially if following with corn or sorghum. A layby application of ethalfuralin (Curbit) may also be used after thinning when melon plants are young (4-5 leaf stage) to control late germinating weeds.
In 2017, I received a farm call about a grassy weed in a honeydew field that the pest control adviser had never seen in a melon field during his long career. He applied sethoxydim (Poast) twice and the grass (johnsongrass) kept coming back. When grasses are moisture stressed, sethoxydim can be less effective, which makes sense in a melon field receiving little irrigation. — By Amber Vinchesi-Vahl, Area Vegetable Crops Advisor, UCCE Colusa County
Disease-causing bacteria like Escherichia coli O157:H7 and Salmonella enterica could survive sanitization in beef processing facilities. Scientists and collaborators in the United States Department of Agriculture’s (USDA), Agricultural Research Center (ARS) are investigating how this happens while also seeking approaches to solve the problem.
E. coli O157:H7 (a Shiga toxin-producing E. coli) and S. enterica are two disease-causing bacteria (pathogens) associated with foodborne illnesses in the United States. Because these pathogens can make people sick through contaminated food, scientists are researching effective and economical ways to lower risks of cross-contamination at food processing facilities.
In a study, scientists explained the survival behavior of E. coli O157:H7 after exposure to unfavorable conditions such as those created by routine sanitation procedures, and how it varies within beef processing facilities that are following similar sanitizing protocols. “Under certain conditions, pathogens like E. coli O157:H7 and S. enterica would enter into a dormant or “hibernation” stage, forming a thin film that allows it to better survive on hard surfaces such as concrete or steel. This is called a bacterial biofilm, and it cannot be seen with the naked eye,” explained Dr. Rong Wang, Research Microbiologist with U.S. Meat Animal Research Center in Clay Center, NE.
A major concern is that biofilms allow harmful bacteria to better survive on hard surfaces at the facility, potentially contaminating food, and making consumers sick. Interestingly, studies show that these pathogens do not survive on their own! After comparing samples from different facilities that follow similar cleaning measures but experiencing different levels of pathogens, scientists learned that multiple species of bacteria found in the processing plant environment of each location could either enhance or reduce a pathogen’s chance of surviving sanitizing procedures. They do this by forming a biofilm community (mixed biofilm structure).
“We look at the unique communities of environmental bacteria that collaborate or compete with pathogens at each location. The collaboration may lead to high pathogen prevalence at certain locations, but strong competition may inhibit pathogen survival at other places. Since many of these environmental bacteria are not harmful to humans or animals, if we can identify the specific species that inhibit pathogen biofilm formation, we can use them as probiotics (preventive measures) against disease-causing bacteria.”
Meanwhile, a couple of studies published in the Journal of Food Protection from this research group show that multi-component sanitizers, a novel multifaceted approach using combinations of various sanitizing reagents and treatments could inactivate biofilms formed by E. coli O157:H7 and S. enterica more effectively, reducing the chances of the pathogen surviving cleaning practices at beef processing facilities.
More research is needed to understand the interaction of multiple species of bacteria present in different processing plant environments and how they vary from one facility to another—reflecting different locations, temperatures, and other factors. Can we develop a more environmentally friendly and cost-effective approach against pathogens in food processing facilities?
“We understand how crucial it is for the food industry to have measures that will effectively prevent the formation of these biofilms and reduce the risk of food contamination and protecting public health,” said Wang.
The Agricultural Research Service is the U.S. Department of Agriculture’s chief scientific in-house research agency. Daily, ARS focuses on solutions to agricultural problems affecting America. Each dollar invested in agricultural research results in $17 of economic impact.
Scientists from the Agricultural Research Service (ARS) are working to understand how something can be equally effective as both a government-approved food additive and as a pesticide.
Methyl benzoate is a naturally occurring compound produced by plants. The U.S. Food and Drug Administration long ago approved methyl benzoate for human use; its fruity and floral aroma makes it a staple in perfumes and cosmetics and as a food additive. Nature employs it to attract pollinators.
From left, research chemist Aijun Zhang, postdoctoral Nick Larson, and intern Lauryn Brooks demonstrated research into methyl benzoate uses as a pesticide in an ARS poster day demonstration.
Zhang’s research has focused on methyl benzoate’s utility as a pesticide for human protection and crop protection. So far, Zhang has documented that the compound will kill or repel many insects in various stages of development, including mosquitoes, bed bugs, fire ants, ticks, flies, moths, and the brown marmorated stink bug. Perhaps most important, however, is its ability to repel and kill the spotted wing drosophila fly (SWD). “SWD is the most significant invasive insect pest of soft-skinned fruit crops in the USA,” Zhang said.
Since SWD was first detected in California a little over a decade ago, the fly has become a key pest in blueberries, blackberries, raspberries, strawberries, and cherries. These crops have a combined annual value of over $5.8 billion, and farmers lose about $718 million annually to SWD damage.
Farmers fight SWD with synthetic insecticides, but at prices up to $1,200 per acre, that method is expensive. It is costly in other ways, too, Zhang said; the synthetic insecticide is harmful to the environment, contributes to pesticide resistance, and may be harmful to humans.
Because methyl benzoate is an environmentally friendly, bio-based compound, Zhang thinks it has great potential to be used by people for human protection as an alternative to synthetic pesticides. It also costs much less than synthetic pesticide treatments.
According to Zhang, methyl benzoate shares the same “chemical skeleton” as DEET, the gold standard in arthropod repellency, a detail that is leading future research efforts.
“Understanding the structure-activity relationship will allow researchers to modify the chemical structure of the methyl benzoate molecule to develop pesticides that are more efficient at controlling arthropod pests,” he said. — By Scott Elliott, USDA-ARS Office of Communications.
Almond experts say there is only one proven way to know when hull split begins: inspect your trees from the top down, starting in the southwest corner of the canopy.
The importance of knowing precisely when hull split occurs is critical because it signals the proper timing for treatments to control navel orangeworm (NOW) and, as appropriate, hull rot. Whether growers use a ladder, climb atop a pruning tower or lop off a few high branches with extension pruners, the goal is to understand what’s happening in the top of the tree, where nuts mature at a faster rate.
Simply looking up into a tree’s canopy from the orchard floor is a sure fire way to miss the advent of hull split. When hulls split, a scent is released into the air, attracting female NOW moths to lay their eggs on the suture of the splitting hull. As the hull splits, fungal spores also can enter and spawn hull rot infections.
Missing the beginning of hull split and allowing NOW or pathogens to gain a toehold in an orchard can wreck a grower’s entire season and reduce the value of the crop, costing growers in returns if nuts are rejected after harvest.
Summer split invites unwanted guests
Growers can determine if hull split has occurred – and if it’s time to spray – if, when they squeeze the end of the hull, the entire suture opens up, exposing the shell within. Almond hulls split as the fruit ripens, and timing varies based on weather conditions and variety. For instance, the variety Nonpareil typically splits in early- to- mid-July, earlier than some other varieties.
However, it’s at the stage before this, when the hull is split in a deep “V,” that susceptibility to NOW and wound pathogens that cause hull rot (Rhizopus, Aspergillus, and Monilinia) increase, making it vitally important that growers actively monitor their trees.
Vice President of Member Services for Blue Diamond Growers Mel Machado advises growers to look for blank nuts – those without a kernel inside – as those hulls are the first to split, several days ahead of the “sound” nuts (those with a full kernel).
Mel Machado, Blue Diamond Growers
“The blanks are like the warning shot, signaling the start of hull split,” he said. “When full hull split does occur, the nuts at the top of the canopy will open up first.”
Experts say growers should pay attention to trees on the edge of their orchards as they often ripen more quickly. Growers should also closely monitor the upper and outer portions of the canopy, particularly the southwest quadrant of the orchard block where the hot afternoon sun aids in the splitting and drying process.
“Better to be too early than too late”
Hull split applications should be made no later than at 1% hull split. This is the most effective time to spray for NOW as it often coincides with initiation of the second NOW flight.1
Once growers identify hull split in their orchard, their next step should be to initiate timely treatment. Experts warn that waiting too long to begin spraying will cost growers, as will performing a poor spray job.
Machado advised, “It’s better to be a bit on the early side than late” when spraying. Once hull split begins, he recommended the entire orchard be sprayed in five days or less. “If it takes 10 or 15 days, that’s too long,” he said.
Planning ahead – especially for smaller growers who rely on custom applicators – is essential.
“Watch your fields closely and be in contact with your operator early on,” Machado advised.
In larger orchards, Machado advises growers consider starting with aerial sprays, recognizing that ground-based sprays don’t always provide complete coverage at the tops of the trees.
“We’re seeing growers effectively incorporate aerial applications into their treatment programs for the first application in order to cover the acreage in a timely manner,” Machado said.
The best time to spray is early in the morning or at dusk.
“Do not spray in the heat of the day – your application will evaporate into thin air and you won’t get the material where it needs to go. That’s a waste of time and money, as you’re not only wasting spray material but you also won’t achieve the coverage necessary to combat crop damage,” Machado said.
Finally, growers should ensure their ground-based sprayers are properly calibrated, the nozzles are unplugged and that air flow isn’t restricted. Once it’s time to spray, growers should remind applicators to drive no more than two mph through orchards to ensure optimum coverage and to drive down each row to ensure the trees are equally covered.
“There are some guys who spray every other row, and that’s not a good idea,” Machado said. “There are two sides to the tree; you need to spray both of them.”
Machado reinforced that hullsplit sprays offer the final chance to manage NOW populations before harvest. Still, these applications are only part of a coordinated, year-round, integrated pest management plan to combat NOW that also must include winter sanitation and mating disruption, both of which are performed earlier in the crop year. — By the Almond Board of California
The Organic Center — Soil fumigants that fight soil-borne diseases and ensure crop production continue to be banned to protect the health and safety of rural communities. Organic farmers and conventional farmers who can no longer use these chemical tools need effective alternatives to protect their yields. A recent study published in the journal Agronomy(link is external) demonstrates that a non-chemical alternative can be effective and affordable if farmers receive a high enough price for their crops. Until 2016, Methyl Bromide had been used in California for decades as a soil fumigant to disinfest soils of devastating diseases before planting high-value crops such as strawberries. Methyl Bromide was never permitted for use in organic farming, and its recent ban due to public health safety concerns also left conventional farmers without an important disease control tool. The ban has prompted much research into alternatives to chemical soil fumigants such as steam, solarization, and anaerobic soil disinfestation (ASD) using rice bran or mustard seed meal. While many studies are optimizing the effectiveness of these strategies, a missing key component is the consideration of the economic cost of these alternatives. This study took a comprehensive approach, and measured the effectiveness and affordability of two alternative management strategies to chemical soil disinfestation for strawberries produced under conventional and organic management.
The results show that organic-approved methods of soil disinfestation (steam and steam plus mustard seed meal) resulted in better yields compared to the control for both conventional and organic systems. And when the cost of treatment is considered, along with yield and crop value, organic far out-competes conventional management. In this study, organic yields were greater than conventional, which helped better cover the high cost of soil treatment. The higher price premium earned for organic strawberries even further enhanced the affordability of the soil treatment for organic management. This study shows that a non-chemical method of managing devastating soil diseases is effective and affordable, but only if the farmer receives a high enough price to cover the added expense. This study brings up an important consideration: when we ask farmers to use practices that benefit not just their own production, but also their surrounding environment which improves public and environmental health of rural communities, it’s clear that the farmers need financial assistance to make the safer choice.
Nematodes normally get a bad reputation. Yes, some of these miniscule creatures can cause harm in plants and animals. But little is known about the non-parasitic nematodes, which have many beneficial roles. Ashley Shaw from the University of Oregon explores this topic in this Soils Matter blog:
It might be hard to believe, but you may never have seen the most abundant animal on Earth: soil nematodes! They represent eighty percent of animal life by number and live in nearly every habitat. They are hard-working and important organisms.
Soil-dwelling nematodes, which I research, are tiny – usually between 1/500th to 1/20th of an inch! (But there is a nematode that lives inside sperm whales that is nearly thirty feet long.)
Indeed, some of the best-known nematodes are parasites. There are different nematode parasites of plants and animals. That means they live in or on the plant or animal, cannot survive without them, and sometimes kill their host (and then move on). But many more nematodes are free-living. In soils, nematodes live in water films that surround soil particles. Both plant root parasitic and free-living nematodes play an important role in plant health and plant feedback to soil carbon.
Photo of a predatory nematode. Predatory nematodes attack and devour other nematodes. Through their feeding, they keep populations of plant parasites and microbial feeding nematodes in check, optimizing plant growth (Credit: Ashley Shaw).
An incredible variety of soil nematodes exist at all levels of the soil food web. At the base of the food web, some feed on plants and algae, others graze on microbes (bacteria and fungi). At higher levels in the food web, nematodes that are predators and omnivores eat other invertebrates, protists, and even other nematodes. In some cases, “predatory” nematodes are the “good guys,” keeping populations of parasitic nematodes in check.
This food web is important to plant health and soil carbon storage. For example, by feeding on bacteria and fungi, microbial grazing nematodes help return nitrogen to the soil through their waste. This makes the nitrogen available again for plant use, improving plant growth.
Nematodes bring other species into the soil food web, too. Some bacteria survive the nematode gut and are deposited along with nematodes’ waste products. Still more hitch a ride on the outside of nematodes’ bodies. As nematodes move around in soil, they deposit bacteria in new places, spreading them around. The bacteria can contribute to and speed the process of decomposition, returning carbon to the soil for storage.
But most good things have a limit: at very high populations, nematodes that feed on bacteria and fungi can reduce their populations. This can lead to lower decomposition and nutrient turnover rates by bacteria and fungi, even lowering plant growth.
Plant parasitic nematodes attack roots using a piercing tool in their mouth. This “stylet” punctures plant cells so it can suck its carbon-rich juices. Some nematodes release chemicals that cause lesions or tumor-like growths on roots. They drain the plant’s strength above- and belowground.
In small populations, plant parasitic nematodes can stimulate root growth, but in high numbers they destroy roots, stunt aboveground growth, and cause disease. Lower plant growth (of both roots and shoots) leads to lower return of organic material to soil and eventually, lower soil carbon.
While the nematode species responsible for plant diseases have received a lot of attention, far less is known about the non-parasitic part of the soil nematode community, which plays mostly beneficial roles in soil. Ensuring a balance between beneficial and plant parasitic nematode groups is important for plant health and its contributions to soil carbon.
Generally, plant-root parasitic nematodes harm plant growth and microbial-feeding nematodes improve it, but other nematodes are also important. For example, predatory nematodes play an important role in regulating populations of plant-parasitic and microbial-feeding nematodes. Through their feeding, they keep populations of plant parasites and microbial feeding nematodes in check, optimizing plant growth.
However, predatory nematodes are also highly sensitive to environmental changes. Their populations often decline with soil disturbances such as pesticide use, fertilization, tilling, or soil compaction. Situations where soil is heavily managed often leads to very low predator populations and higher populations of harmful groups. Predators are also sensitive to changes in rain and temperature, which can also cause an imbalance toward harmful groups.
Shaw is studying compost additions to rangelands to determine the effects on soil carbon and plant growth. Compost also changes the soil food web – including the numbers and diversity of nematodes.
My current research is examining how active land management practices can help boost beneficial nematode groups in soil by improving soil habitat. We are studying compost additions to rangelands and whether they can improve soil carbon storage and plant growth.
Compost directly provides nutrients and increases soil water retention, improving plant growth. Compost is also changing the soil food web in ways not seen in some of the other treatments in our study plots. We think that the soil organic matter in the compost improves soil habitat for predators, supporting the long and complex soil food webs with abundant predatory nematodes that help keep root parasitic nematode populations in check. The result is that plant disease and root parasitism has declined, leading to greater plant growth and root carbon inputs under compost treatments, which benefits soil carbon storage.
Photo: After collecting soil samples, Shaw and her research group inspect nematodes by extracting them into water and examining them in a dish using a microscope. Shown: a diverse grouping of nematodes (longer, worm-like structures) along with a tardigrade and some small soil debris that made it through the extraction process. Credit: Ashley Shaw
The Soil Science Society of America (SSSA) is a progressive, international scientific society that fosters the transfer of knowledge and practices to sustain global soils. Based in Madison, WI, SSSA is the professional home for 6,000+ members dedicated to advancing the field of soil science. It provides information about soils in relation to crop production, environmental quality, ecosystem sustainability, bioremediation, waste management, recycling, and wise land use.
What Nobel Prize-winning Economics Research Tells Us About ACP and HLB Management in California
As you have likely heard many times, coordinating management measures for the Asian citrus psyllid (ACP) and Huanglongbing (HLB) over a larger scale than individual properties is key to achieving effective control and limiting the spread of the disease. Coordination is important in terms of surveying for HLB-positive trees and removing them from the ground as soon as possible, applying insecticide treatments at the same time for multiple citrus groves within a Psyllid Management Area (PMA) or a Pest Control District (PCD), complying with quarantine measures for the movement of bulk citrus, using certified budwood and sharing information with neighbors.
But this coordination comes at a cost, and some individuals may be tempted to skip the costs of treating within the recommended window for ACP, correctly tarping their trucks, or even investing some time to convince their neighbors about the importance of these measures. Yet, if everyone skipped these costs and relied on the efforts of others, the ability of the citrus industry to combat HLB would be greatly reduced, leading to a higher risk of HLB spread in California.
This temptation to free-ride on the efforts of others exists in the management of many natural resources, such as groundwater, fisheries or forests. In 2009, social scientist Elinor Ostrom received the Nobel Prize for Economics for studying how societies organized themselves to manage these types of resources and avoid the problem of free-riding. Throughout her career, she studied many different cases of this problem in different parts of the world, and she identified eight principles that were associated with sustained collective action. Interestingly, most of these principles are present in the strategy for HLB management in California, as shown in the table below.
Due to a lack of participation in coordinated mitigation tactics – the free-rider problem – a similar HLB-management program in Florida was not as effective in keeping HLB at bay. But California has so far been more successful in achieving collective action than other infected areas like Florida, and as is seeing more success in preventing the spread of ACP and HLB, including keeping HLB out of commercial groves.
To continue to stay a step ahead of HLB, it is crucial that California’s citrus industry and residents remain vigilant and engage in coordinated management efforts and follow best practices and regulatory requirements.
Although Ostrom’s principles do not offer a universal solution to all free-riding problems, they can be useful to guide our efforts as we continue to work together to face the threat of HLB.
More information on her research, which was recently published in Food Security Journal, can be found on https://doi.org/10.1007/s12571-020-01133-9— By Sara Garcia Figuera, Citrus Pest & Disease Prevention Program
Design Principle (Ostrom, 1990)
HLB Management in California
1. Clearly defined boundaries: the boundaries define who is responsible for the collective effort and over what area, reducing the cost of monitoring behavior.
PMAs
PCDs
2A. Congruence between rules and local conditions: the rules that are established for the management and maintenance of a resource are aligned with the predominant social norms, culture and agro-ecological conditions in a community.
Rules defined by the citrus industry through Citrus Pest and Disease Prevention Committee (CPDPC) in collaboration with County Agricultural Commissioners (CACs) and California Department of Food and Agriculture (CDFA)
Some pre-existing PCDs
Quarantine zones and rules defined by local conditions (citrus production, ACP populations and/or climatic suitability)
2B. Congruence between appropriation and provision rules: correspondence between the rules governing contributions to the maintenance of the resource system, and the rules governing withdrawal of resources from the system.
Insecticide treatments for ACP funded by individual growers.
Other assessments based on production volume (CPDPP) or acreage (PCD)
3. Collective-choice arrangements: if local users who directly interact with one another can define the rules that regulate the day-to-day decisions about the use of a shared resource, they will be in a better position to incorporate local knowledge.
AWM organized locally through PCDs or PMAs
CPDPC establishes rules in collaboration with CDFA
4A. Monitoring users: a community needs to be able to identify users that do not comply with rules; otherwise there can be no credible commitment. Monitoring should be undertaken by the resource users, better than by external authorities.
Seasonal reports of areas treated for ACP
Packinghouse inspections of grate cleaning or spray & harvest
4B. Monitoring the resource: assesses the extent to which the collective effort is being achieved.
ACP monitoring by CDFA, CACs, Citrus Research Board (CRB) and pest control advisors (PCAs) hired by growers
5. Graduated sanctions: Although sanctioning prevents an excessive violation of community rules, sanctions should be graduated based on the severity and/or repetition of violations to ensure proportionality. And they should be imposed by the resource users or officials accountable to them, to maintain community cohesion.
If less than 90% of the acreage is treated in a PMA or PCD, it will not qualify for the residential buffer treatment
When there is a violation of the tarping requirement, a notice of violation is sent before further sanctions
6. Conflict-resolution mechanisms: Low-cost conflict resolution prevents the cost of conflict from outweighing the benefits of successful collective action.
Task Force meetings and other public meetings have been used for addressing conflicts
7. Minimal recognition of rights to organize:Local institutions are more effective when higher levels of government allow users to self-organize in ways that reflect local social and ecological contexts.
CPDPC
PCDs
Grower leader in PMAs
8. Nested enterprises: refers to the importance of connecting smaller social systems that manage different parts of a larger resource system to facilitate cross-scale coordination.
Statewide program coordinated at the regional, county and local level
Nematodes normally get a bad reputation. Yes, some of these miniscule creatures can cause harm in plants and animals. But little is known about the non-parasitic nematodes, which have many beneficial roles. Ashley Shaw from the University of Oregon explores this topic in this Soils Matter blog:
