Predatory mites: Alternative to toxic insecticides

Strawberry farmers using billions of tiny, blind, predatory mites as successful alternative to toxic insecticides

ABC Rural

 / By Jennifer Nichols

Posted 4h ago4 hours ago

James Hill oversees the breeding of billions of Phytoseiulus persimilis bugs.(Supplied: Bugs for Bugs)

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As concern over chemical use in food production grows and insect species become more resistant to poisons, farmers are turning to nature for solutions to pests that can cripple crop production.

Billions of tiny, blind, predatory mites are being bred, harvested, packed on ice, and posted to strawberry farms in the battle against destructive sap-sucking insects.

James Hill with a cup of persimilis, from the arachnid family.(ABC Rural: Jennifer Nichols)

“We’re producing beneficial insects for farmers to use instead of insecticides,” Bugs for Bugs Donnybrook insectarium manager James Hill said.

“Ninety per cent of farmers in the strawberry industry are using our product.”

Strawberries can now be grown with considerably fewer chemicals.(ABC Rural: Jennifer Nichols)

The battle

Australians love strawberries — 72 per cent of households bought them last financial year and on average we each ate around 2.27 kilograms of the fruit. 

One of the main insect enemies that farmers battle to produce tasty red strawberries is two-spotted mites, a sap-sucking species related to ticks, too tiny to spot with the naked eye.

The two-spotted mite is bred to feed the Phytoseiulus persimilis bugs.(ABC Rural: Jennifer Nichols)

Left unchecked, you can see the damage two-spotted mites can do, sucking the life out of bean leaves in the polytunnels where they are raised as food for the predator mites that are sold to growers.

“If left unchecked the two-spotted mite would just devastate your crop, it would wipe you out,” Queensland Strawberry Growers president Adrian Schultz said.

A line of tiny insects hangs from a sick bean leaf.(ABC Rural: Jennifer Nichols)

The tiny warrior

An eight-legged member of the arachnid family, Phytoseiulus persimilis, is blind.

It hunts down two-spotted mites by touch and scent and can be dropped by drone to decimate populations of two-spotted mites and spider mites.

Phytoseiulus persimilis thrives in humid conditions.(Supplied: Bugs for Bugs)

Just 0.5mm long, persimilis are voracious, specialised predators that breed twice as fast as their prey, can be carried on the wind, and are deployed to protect crops, greenhouses and commercial installations of indoor plants.

Once they have exterminated the pests they turn on their own eggs and larvae, posing no threat to other insects.

Mr Shultz said the insects have become real cost savers for big farms.

https://www.youtube.com/embed/jE8xHOTCfGA?feature=oembedYOUTUBENathan Roy’s drone dropping beneficial bugs.

“In years gone by, we had to rotate different insecticides to control the two-spotted mite and you’d get a higher percentage of pests that were resistant,” he said.

“The advent of the predator mites enabled industry to use considerably less chemicals in controlling pests, now we also have the option of introducing lady beetles into our crops to control aphids.”

Queensland Strawberry Growers Association president Adrian Schultz says the industry has embraced beneficial insects.(ABC Rural: Melanie Groves)

Integrated pest management

Integrated pest management (IPM) is increasingly popular with farmers and uses a range of preventive measures to control pests, including natural predators, parasites, nematodes, and pheromone traps.

“It’s not set and forget, you need to monitor the situation and you’ve got to be aware of the impacts of environmental conditions,” Mr Schultz said.

Paul Jones helped pioneer beneficial insect breeding for horticulture in Australia.(Supplied: Bugs for Bugs)

Changing attitudes

The job satisfaction of helping farmers produce higher quality products with fewer chemicals is why Bugs for Bugs director Paul Jones has been working in integrated pest management for 30 years.

“When we first went out to farmers there was a lot of fear and scepticism about reducing the use of sprays and using beneficial insects to control pests,” the agricultural scientist said.

“The change has been quite radical, what was once considered a cottage industry for small organic and family farms has now become the backbone for pest management in conventional agriculture.”

https://www.youtube.com/embed/8sEVXfjX3s8?feature=oembedYOUTUBEUsing good bugs to fight bad bugs could be the key to pesticide-free farming

Bugs for Bugs is one of only a handful of commercial suppliers of beneficial insects in Australia.

From insectaries at Donnybrook, Toowoomba and Mundubbera, it sells 12 different species including predatory mites, ladybirds, lacewings, and parasitic wasps.

Home gardeners can also order the insects online.

Bugs for Bugs has expanded its insectaries.(ABC Rural: Jennifer Nichols)

Worldwide, predatory bioagents are being used to target gnats, thrips, caterpillars, scale, mealybugs, aphids, heliothis larvae, loopers, whitefly, and mites in crops including strawberries, raspberries, blackberries, cotton, macadamias, almonds, avocados, citrus, maize, cut flowers and hops.

Parasitic wasps kill fly maggots for the poultry, pig, dairy and feedlot industries, and black soldier fly larvae transform organic waste into compost.

Bugs for Bugs Phytoseiulus persimilis ready to be posted.(ABC Rural: Jennifer Nichols)

At the Donnybrook insectary, billions of persimilis are being harvested from polytunnels for the start of the Queensland winter strawberry season.

Each insect order is weighed and packed on ice to keep the persimilis mites in hibernation during transport.

Deb Hill packs predatory insects on ice and posts them to farmers.(ABC Rural: Jennifer Nichols)

A vermiculite mineral is included to make it easier for farmers to evenly spread the tiny predators on their fields.

“It’s evolved, refining the craft, we’ve got better and better,” Mr Jones said.

“Mainstream chemical companies now collaborate with us to ensure products are less harmful to beneficial insects.”

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Climate change is shifting the zones where plants grow

Climate change is shifting the zones where plants grow – here’s what that could mean for your garden

The Conversation

Published: March 22, 2024 8:34am EDT

Author

1. Matt KassonAssociate Professor of Mycology and Plant Pathology, West Virginia University

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With the arrival of spring in North America, many people are gravitating to the gardening and landscaping section of home improvement stores, where displays are overstocked with eye-catching seed packs and benches are filled with potted annuals and perennials.

But some plants that once thrived in your yard may not flourish there now. To understand why, look to the U.S. Department of Agriculture’s recent update of its plant hardiness zone map, which has long helped gardeners and growers figure out which plants are most likely to thrive in a given location.

The 2023 USDA plant hardiness zone map shows the areas where plants can be expected to grow, based on extreme winter temperatures. Darker shades (purple to blue) denote colder zones, phasing southward into temperate (green) and warm zones (yellow and orange). USDA

Comparing the 2023 map to the previous version from 2012 clearly shows that as climate change warms the Earth, plant hardiness zones are shifting northward. On average, the coldest days of winter in our current climate, based on temperature records from 1991 through 2020, are 5 degrees Fahrenheit (2.8 Celsius) warmer than they were between 1976 and 2005.

In some areas, including the central Appalachians, northern New England and north central Idaho, winter temperatures have warmed by 1.5 hardiness zones – 15 degrees F (8.3 C) – over the same 30-year window. This warming changes the zones in which plants, whether annual or perennial, will ultimately succeed in a climate on the move.

This map shows how plant hardiness zones have shifted northward from the 2012 to the 2023 USDA maps. A half-zone change corresponds to a tan area. Areas in white indicate zones that experienced minimal change. Prism Climate Group, Oregon State University, CC BY-ND

As a plant pathologist, I have devoted my career to understanding and addressing plant health issues. Many stresses not only shorten the lives of plants, but also affect their growth and productivity.

I am also a gardener who has seen firsthand how warming temperatures, pests and disease affect my annual harvest. By understanding climate change impacts on plant communities, you can help your garden reach its full potential in a warming world.

Hotter summers, warmer winters

There’s no question that the temperature trend is upward. From 2014 through 2023, the world experienced the 10 hottest summers ever recorded in 174 years of climate data. Just a few months of sweltering, unrelenting heat can significantly affect plant health, especially cool-season garden crops like broccoli, carrots, radishes and kale.

Radishes are cool-season garden crops that cannot withstand the hottest days of summer. Matt Kasson, CC BY-ND

Winters are also warming, and this matters for plants. The USDA defines plant hardiness zones based on the coldest average annual temperature in winter at a given location. Each zone represents a 10-degree F range, with zones numbered from 1 (coldest) to 13 (warmest). Zones are divided into 5-degree F half zones, which are lettered “a” (northern) or “b” (southern).

For example, the coldest hardiness zone in the lower 48 states on the new map, 3a, covers small pockets in the northernmost parts of Minnesota and has winter extreme temperatures of -40 F to -35 F. The warmest zone, 11b, is in Key West, Florida, where the coldest annual lows range from 45 F to 50 F.

On the 2012 map, northern Minnesota had a much more extensive and continuous zone 3a. North Dakota also had areas designated in this same zone, but those regions now have shifted completely into Canada. Zone 10b once covered the southern tip of mainland Florida, including Miami and Fort Lauderdale, but has now been pushed northward by a rapidly encroaching zone 11a.

Many people buy seeds or seedlings without thinking about hardiness zones, planting dates or disease risks. But when plants have to contend with temperature shifts, heat stress and disease, they will eventually struggle to survive in areas where they once thrived.

Successful gardening is still possible, though. Here are some things to consider before you plant:

Annuals versus perennials

Hardiness zones matter far less for annual plants, which germinate, flower and die in a single growing season, than for perennial plants that last for several years. Annuals typically avoid the lethal winter temperatures that define plant hardiness zones.

In fact, most annual seed packs don’t even list the plants’ hardiness zones. Instead, they provide sowing date guidelines by geographic region. It’s still important to follow those dates, which help ensure that frost-tender crops are not planted too early and that cool-season crops are not harvested too late in the year.

California poppies are typically grown as annuals in cool areas, but can survive for several years in hardiness zones 8-10. The Marmot/Flickr, CC BY

User-friendly perennials have broad hardiness zones

Many perennials can grow across wide temperature ranges. For example, hardy fig and hardy kiwifruit grow well in zones 4-8, an area that includes most of the Northeast, Midwest and Plains states. Raspberries are hardy in zones 3-9, and blackberries are hardy in zones 5-9. This eliminates a lot of guesswork for most gardeners, since a majority of U.S. states are dominated by two or more of these zones.

Nevertheless, it’s important to pay attention to plant tags to avoid selecting a variety or cultivar with a restricted hardiness zone over another with greater flexibility. Also, pay attention to instructions about proper sun exposure and planting dates after the last frost in your area.

Fruit trees are sensitive to temperature fluctuations

Fruit trees have two parts, the rootstock and the scion wood, that are grafted together to form a single tree. Rootstocks, which consist mainly of a root system, determine the tree’s size, timing of flowering and tolerance of soil-dwelling pests and pathogens. Scion wood, which supports the flowers and fruit, determines the fruit variety.

Most commercially available fruit trees can tolerate a wide range of hardiness zones. However, stone fruits like peaches, plums and cherries are more sensitive to temperature fluctuations within those zones – particularly abrupt swings in winter temperatures that create unpredictable freeze-thaw events.

Following planting instructions carefully can maximize plants’ chances of success. Matt Kasson, CC BY-ND

These seesaw weather episodes affect all types of fruit trees, but stone fruits appear to be more susceptible, possibly because they flower earlier in spring, have fewer hardy rootstock options, or have bark characteristics that make them more vulnerable to winter injury.

Perennial plants’ hardiness increases through the seasons in a process called hardening off, which conditions them for harsher temperatures, moisture loss in sun and wind, and full sun exposure. But a too-sudden autumn temperature drop can cause plants to die back in winter, an event known as winter kill. Similarly, a sudden spring temperature spike can lead to premature flowering and subsequent frost kill.

Pests are moving north too

Plants aren’t the only organisms constrained by temperature. With milder winters, southern insect pests and plant pathogens are expanding their ranges northward.

One example is Southern blight, a stem and root rot disease that affects 500 plant species and is caused by a fungus, Agroathelia rolfsii. It’s often thought of as affecting hot Southern gardens, but has become more commonplace recently in the Northeast U.S. on tomatoes, pumpkins and squash, and other crops, including apples in Pennsylvania.

Southern blight (small round fungal structures) at the base of a tomato plant. Purdue University, CC BY-ND

Other plant pathogens may take advantage of milder winter temperatures, which leads to prolonged saturation of soils instead of freezing. Both plants and microbes are less active when soil is frozen, but in wet soil, microbes have an opportunity to colonize dormant perennial plant roots, leading to more disease.

It can be challenging to accept that climate change is stressing some of your garden favorites, but there are thousands of varieties of plants to suit both your interests and your hardiness zone. Growing plants is an opportunity to admire their flexibility and the features that enable many of them to thrive in a world of change.

• Agriculture
• Climate change
• Soil
• Crops
• Insects
• Plants
• Fungi
• Extreme weather
• Horticulture
• Seasons
• Gardening
• US Department of Agriculture
• Fruit growing

Before you go…

Information is flying at us from all directions. And it can be overwhelming. Wouldn’t it be easier if you could get trusted science information in one place? That place is The Conversation. As an editor here, I am fortunate to work with scientists and researchers who explain their latest research. And each week, our team sends an email that brings together the best of our coverage of science, technology and environment.

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Vivian Lam

Associate Health and Biomedicine Editor

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That sharp, green smell of freshly cut grass? It’s a plant’s cry for help – and it may work as a less toxic pesticide for farmers’

Saturday, 03 February 2024 08:23:00

PestNet

Grahame Jackson posted a new submission ‘That sharp, green smell of freshly cut grass? It’s a plant’s cry for help – and it may work as a less toxic pesticide for farmers’

Submission

That sharp, green smell of freshly cut grass? It’s a plant’s cry for help – and it may work as a less toxic pesticide for farmers

The Conversation

Have you ever wondered about that sharp, green note that hits your nose when you mow the lawn or cut flower stems? Those are green leaf volatiles, or GLVs: easily evaporated oils that plants use to communicate with other plants and defend themselves against herbivores or pathogens like bacteria or fungi.

Almost every green plant can quickly synthesize and release GLVs when attacked, both directly warding off attackers as well as indirectly attracting predators of herbivores like insects and priming the plant’s other defense mechanisms. Researchers know that GLVs play an important role in protecting plants, but how they work remains unclear.

I am a biochemistry researcher, and through a collaboration between the Wang Lab and Stratmann Lab of the University of South Carolina, my colleagues and I study how plant cells deploy green leaf volatiles. In our recently published research, we identified the potential signaling pathways GLVs use to induce defense responses in tomato cells. Our ultimate goal is to figure out ways to use GLVs to control agricultural pests for cleaner farming.

Read on: https://theconversation.com/that-sharp-green-smell-of-freshly-cut-grass-its-a-plants-cry-for-help-and-it-may-work-as-a-less-toxic-pesticide-for-farmers-204673

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Plant warfare: The crucial function of Nrc proteins in tomato defense mechanisms

by Boyce Thompson Institute

Credit: CC0 Public Domain

In the fascinating world of plant biology, a study recently featured on the cover of The Plant Journal has been turning heads. The research delves into the intricate defense mechanisms of tomatoes against the notorious bacterial pathogen Pseudomonas syringae pv. tomato (Pst). It’s a classic tale of nature’s arms race: As pathogens evolve to outsmart plant defenses, plants counter with more sophisticated immune responses.

The study is based on research conducted by scientists in Dr. Greg Martin’s lab at the Boyce Thompson Institute (BTI). Central to the study are proteins called Nucleotide-binding leucine-rich repeat receptors (NLRs), the plant equivalent of immune system warriors. They recognize and respond to pathogen attacks, triggering a series of defense mechanisms. Among these are the helper NLRs, Nrc2 and Nrc3, which work in concert with the tomato NLR Prf and its partner kinase, Pto, in a well-orchestrated defense against Pst.

The groundbreaking aspect of this research lies in its exploration of the roles of Nrc2 and Nrc3. Using CRISPR technology, the scientists created tomato mutant plants lacking these NLRs. While these mutants appeared normal under typical conditions, they exhibited increased susceptibility to Pst, similar to plants lacking the Prf protein.

“This finding was pivotal, highlighting the indispensable role of Nrc2 and Nrc3 in the tomato immune response,” noted Dr. Ning Zhang, a post-doctoral researcher at BTI and first author of the study.

One of the most intriguing outcomes of the research is understanding how Nrc2 and Nrc3 fit into the overall defense system. They seem to act upstream in the signaling cascade that leads to programmed cell death—a critical component of the plant’s immune response. This places them as essential intermediaries of the complex network of plant immunity.

The attention to Zhang’s research is a validation of its significance. “I’m thrilled that our discoveries on the workings of helper NLRs received prominent coverage in The Plant Journal,” she remarked. “Our work sheds light on how plants defend themselves—a topic of immense importance in agriculture.”

In essence, the research by Zhang and colleagues isn’t just a story of scientific discovery; it’s a roadmap for future innovations in crop resilience. “By unraveling the roles of helper NLRs like Nrc2 and Nrc3, we are a step closer to developing crops that can better withstand the challenges posed by pathogens, helping ensure food security and agricultural sustainability,” said Zhang.

More information: Ning Zhang et al, Helper NLRs Nrc2 and Nrc3 act codependently with Prf/Pto and activate MAPK signaling to induce immunity in tomato, The Plant Journal (2023). DOI: 10.1111/tpj.16502

Journal information: The Plant Journal 

Provided by Boyce Thompson Institute 

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Two plant immune branches more intimately connected than previously believed

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Plant defensive responses to insect eggs are inducible by general egg-associated elicitors

Monday, 15 January 2024 05:44:09

Grahame Jackson posted a new submission ‘Plant defensive responses to insect eggs are inducible by general egg-associated elicitors ‘

Submission

Plant defensive responses to insect eggs are inducible by general egg-associated elicitors

Nature

Vivien Lortzing, Georgios Valsamakis, Friederike Jantzen, Janik Hundacker, Luis R. Paniagua Voirol, Fabian Schumacher, Burkhard Kleuser & Monika Hilker  Scientific Reports volume 14, Article number: 1076 (2024) 

Egg deposition by herbivorous insects is well known to elicit defensive plant responses. Our study aimed to elucidate the insect and plant species specificity of these responses. To study the insect species specificity, we treated Arabidopsis thaliana with egg extracts and egg-associated secretions of a sawfly (Diprion pini), a beetle (Xanthogaleruca luteola) and a butterfly (Pieris brassicae). All egg extracts elicited salicylic acid (SA) accumulation in the plant, and all secretions induced expression of plant genes known to be responsive to the butterfly eggs, among them Pathogenesis-Related (PR) genes. All secretions contained phosphatidylcholine derivatives, known elicitors of SA accumulation and PR gene expression in Arabidopsis. The sawfly egg extract did not induce plant camalexin levels, while the other extracts did. Our studies on the plant species specificity revealed that Solanum dulcamara and Ulmus minor responded with SA accumulation and cell death to P. brassicae eggs, i.e. responses also known for A. thaliana. However, the butterfly eggs induced neoplasms only in S. dulcamara. Our results provide evidence for general, phosphatidylcholine-based, egg-associated elicitors of plant responses and for conserved plant core responses to eggs, but also point to plant and insect species-specific traits in plant–insect egg interactions.

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