California Fruit and Vegetable

Tag: USDA-ARS Office of Communications

  • Transplanted Bees Help Blueberry Fields Flourish

    Pollinating bees are in decline, and those that remain may not be up to the task of pollinating all the crops needed to feed the nation. To help keep food on the table, researchers are looking to native wild bees to take up the slack, especially for blueberries and other fruit crops.

    “Honeybees are considered a universal crop pollinator worldwide, but their populations are in trouble, and they do not always pollinate certain crop plants efficiently,” said Blair Sampson, entomologist with the Agricultural Research Service’s Southern Horticultural Research Laboratory in Poplarville, MS. “Therefore, we [are turning] to wild native bees that share a much longer ecological history with our native North American crops.”

    Some of these native bees can be managed like the honeybee, which means beekeepers and farmers can relocate colonies from their home regions for deployment to where crops are blooming. Native bees are very docile when being handled and they take care of themselves with little need for human involvement. Sampson is studying such a native bee, the chimney bee (also known as the miner bee).

    Male chimney bee resting on a cluster of southern highbush blueberry flowers. (Photo by Blair Sampson, ARS)

    Chimney bees are turning out to be an important find for blueberry growers.

    In addition to the problem of declining populations, honeybees have difficulty pollinating blueberries due to their relatively short tongue and preference for other plants. Another wild bee, the southeastern blueberry bee, is an abundant and efficient specialist pollinator of blueberries throughout the Gulf Coast states. Unfortunately, many growers in lower-lying areas lack these bees or have too few of them in their fields. These blueberry bees cannot be managed, but the chimney bee, a close relative, can be actively managed and moved in to fill the pollinator void.

    While chimney bees are not yet commercially available, relocating them is fairly simple, Sampson said. Gathering chimney bee cocoons from nests in the soil that sticks to the roots of fallen trees or roadside clay outcrops requires careful excavation and skilled handlers, but nesting material can simply be sun-dried clay-rich mud gathered locally. Further, there is no need for specialized tools and costs are minimal.

    Chimney bees must be shipped while in a dormant state, then gently warmed to complete their development and emerge from their cocoons. Further, water and additional nesting material should be available to help them thrive.

    “These bees do not produce enough honey for us, just enough for themselves, hence, chimney bees’ principal role would be as fruit pollinators,” Sampson explained. “However, the chimney bee does show certain qualities that highlight their ideal candidacy for commercial management: they are flower generalists with a strong homing instinct, and hence will nest in the same location for many years. They also nest in dense aggregations and remain gentle around people near their nest sites.”

    Sampson said that adult chimney bees resemble small, fast-flying bumble bee workers, yet they nest and behave very differently.

    The bees get their name from their horizontal tubular nests that resemble tiny mine shafts in clay, which they harden into “adobe” with the help of water they collect. As they dig deeper into a clay bank, they use this excess clay to fashion a downward facing tube or “chimney” hanging off the nest entrance.

    Locating and relocating chimney bee nests is fairly easy, because they’re easy to find after construction projects or natural weather events disturb the land and give bees easy access to fresh-turned clay. After finding the nests, Sampson gathers earthen cocoons and moves them to where they are tested or released as fruit pollinators.

    “Since pollinator habitat is continually declining due to increasing urbanization and crop cultivation, managing wild native bees, such as chimney bees, can help conserve vital natural resources and help farmers increase their yields,” Sampson said. “And, for fruit, nuts, and vegetable crops, native bees will be an essential component for optimizing crop production per acre of land, which is vital for maintaining a stable global food supply.” – By Scott Elliott, USDA-ARS Office of Communications

  • Filling in the Blanks About Rose Stem Girdler in Caneberries

    Berry farmers are all too familiar with the rose stem girdler (RSG), an invasive insect from Eurasia that came to North America over a hundred years ago. They know that the copper-colored beetle has migrated to the Pacific Northwest. They know it attacks caneberries — blackberries and raspberries — sometimes ravaging up to 90% of a crop and forcing farmers to replant fields.

    What they may not know is when or where it will strike or how to contain it.

    Now, however, researchers at Washington State University (WSU) may be on the verge of providing a breakthrough by developing a coordinated approach to control RSG; an approach known as integrated pest management. The project was funded by the Northwest Center for Small Fruit Research, , an  Agricultural Research Service-led consortium, to gather information about RSG and then develop tools that growers could employ against it.

    According to Justin O’Dea, a WSU regional agriculture specialist, one such tool is a pest emergence model that will help farmers precisely time their insecticide sprays to be most effective. The model helps predict when RSG, which overwinter as larvae inside the stems of berry plants, emerge into the outside world as adult beetles.

    A major concern with controlling RSG is the insect’s innate unpredictability, O’Dea said.

    “Damage from this pest is commonly intermittent and variable, which blindsides berry growers when infestations flare,” he said. “This can lead to growers making ineffective, pre-emptive sprays to try and make sure they are not blindsided again.”

    The recent discovery of a natural predator of RSG — a parasitoid wasp known as Baryscapus rugglesi – is also now in the integrated pest management toolkit, although its efficacy is not yet fully known. Parasitic wasps lay their eggs inside other insect species, killing the host insect in the process. As a result, these wasps are used extensively, worldwide, to control pest insect populations in agriculture.

    An adult rose stem girdler beetle feeds on a blackberry leaf. (Photo by Justin O’Dea, Washington State University)

    “We know now that we have a parasitoid of RSG [in the Pacific Northwest] and have observed periods where RSG appears to decline inexplicably,” O’Dea said. “This phenomena of RSG pest pressure decline may be at least partly due to parasitism. If so, perhaps parasitoids will eventually lead to RSG becoming less of an important threat to caneberries in the Pacific Northwest, but only time and further research will be able to confirm that.”

    In the meantime, or at least until late spring when the emergence model predicts RSG adulthood, O’Dea said there is something that farmers can do to help prevent infestation: prune. This step is important because, after hatching, RSG larvae burrow into the canes where they feed on water, nutrients, and sugars moving through the plant’s vascular system. The larvae will eventually bore into the middle (the pith) of the cane.

    Thoroughly pruning out all canes that show symptoms of RSG damage (cane swelling, wilting, or breakage) can be done at any point before the pest emerges. The damaged canes should be removed from the field and burned.

    “This strategy [is] part of an effective integrated pest management program,” O’Dea said. “Research in Utah found this method to be about 80% effective. When combined with insecticides, RSG control could be as high as 98%.”

    Successful development of an integrated pest management program for RSG means that growers will have a better chance at minimizing the need for insecticide applications, O’Dea said. That equates to reduced time, energy, and money spent on ineffective and unnecessary insecticide applications, as well as reduced risk to pollinators and other inadvertent impacts to the environment.

    “Based on historical records of how RSG has played out in other regions of the country and our own observations, I’m cautiously hopeful that it will become a limited threat in the long run,” O’Dea said. — By Scott Elliott and Jan Suszkiw, USDA-ARS Office of Communications

  • ARS Team Fights Blueberry Virus to Help Growers Keep Fruit on the Shelves

    In the United States, blueberries are the second-most produced berry, and their popularity has grown exponentially in less than 30 years – up from 45,000 tons grown in the 1990s to 339,000 tons in 2019. ARS researchers are working hard to help farmers keep up with consumer demand.

    Researchers at the Horticultural Crops Production and Genetic Improvement Research (HPCGIR) Unit in Corvallis, OR, are developing new cultivars of not just blueberry, but also blackberry, red raspberry, black raspberry, and strawberry to meet the needs of western growers.

    “In blueberry, we focus on improving the shelf life of fruit so that it reaches consumers with consistently better texture and flavor,” said Claire Luby, plant geneticist with HCPGIR. “This also means developing new types of blueberries that are easier to harvest using mechanical harvesting equipment.”

    Blueberries are notorious for being difficult to harvest with machinery because they bruise so easily.

    Perhaps a larger challenge for Luby and her colleagues is developing a cultivar that is resistant to a disease known to be a scourge of the berry: blueberry shock virus.

    “We’re studying diverse blueberry plants to understand the genetic basis for blueberry shock virus, which can significantly impact yields for farmers,” she said. “Our hope is to use the insights from this project to develop new cultivars that are resistant, or at least more tolerant to, the disease.”

    Blueberry shock virus has caused annual crop losses of 34-90% in the Pacific Northwest.

    “The fruits that we focus on in this project are some of the most consumed fruits in the United States and contribute important nutritional benefits to consumers,” Luby said. The fruits are also economically important to the region, with Washington and Oregon being the nation’s top two producers.

    According to Luby, researchers combine traditional plant breeding with genomics to find the right genetic mix for their disease-resistant cultivars.

    Their plant breeding programs use traditional techniques of taking pollen from one plant and using it to pollinate a different plant with complementary characteristics. They then determine if the progeny of these crosses have the new characteristics that meet the goals of the breeding programs. In general, these techniques have been used in one form or another by people trying to improve agricultural crops for millennia.

    “Where the genomics piece comes in is to try to improve the accuracy and speed of the plant breeding process,” Luby explained. “We are now able to obtain a lot more genetic information about the plants and we can use that information to potentially predict whether an offspring of a given cross might have the characteristics we are looking for before we plant it out in the field. This is important because it can increase the speed of the plant breeding process.”

    Traditional blueberry breeding can take more than 20 years from the time an initial cross is made to when a consumer might eat from a resulting cultivar.

    “Our goals are to develop blueberries that require fewer chemical inputs to fight disease, which can be better for both the environment and for growers’ bottom lines,” Luby said. – By Scott Elliott, USDA-ARS Office of Communications