Breaking out from the standard red, white and pink varieties, Suntory Flowers introduced a new color and form in mandevilla with Sun Parasol Apricot.
While the flowers are 3.4-4.5 inches large, like Sun Parasol Giant types, the growth habit is significantly different. Instead of being a natural climber, the growth is more pendulous or hanging. Vines get loaded with large buds and blooms.
The plant can still be trained to a trellis or cut back to produce a full bushy plant. But the natural habit is ideal for hanging baskets. Compared to other mandevillas, growth is fast and vigorous with excellent branching to produce a high flower count.
Researchers at the University of Hawaii at Manoa have curbed powdery mildew symptoms in a critically endangered plant via a microbiome transplant. Influenced by human microbiome research, the researchers pureed a wild Hawaiian native plant, Phyllostegia hirsuta, and sprayed the resulting leaf slurry on the leaves of a close relative, the endangered Phyllostegia kaalaensis plant.
The researchers were surprised when they looked closely at the symptom-slashing slurry, because it contained DNA of the same powdery mildew pathogen they were fighting.
“We couldn’t detect any genetic difference between this wild strain of powdery mildew and the one that’s attacking the [plant] — we think it’s the exact same pathogen,” says Dr. Anthony Amend, associate professor of botany at the University of Hawaii at Manoa. Amend conducted the study with Dr. Geoffrey Zahn, a former postdoctoral research associate at UH Manoa who is now an assistant professor at Utah Valley University.
Germs for good
The genus Phyllostegia has only been found on the Hawaiian Islands, according to the study. Out of the 32 recognized species of Phyllostegia, the International Union for the Conservation of Nature lists 14 as critically endangered. This includes P. kaalaensis, which is native to Hawaii’s Waianae Mountains on the island of Oahu, but until recently existed only in two greenhouses — one managed by the State of Hawaii and the other by the U.S. Army.
A variety of factors account for P. kaalaensis’ endangerment, according to Amend. “Disease is one of them, climate change probably has something to do with it, and a lot of their habitats have also been trashed because of developments in Hawaii,” he says. “Range restriction, climate change and disease are probably the one-two-three punch.”
In deciding to introduce beneficial microbes into the plant, the study’s researchers were influenced by a similar discussion about human populations. Amend notes that antimicrobial hand sanitizers and germicidal soaps became popular in the 1990s, but scientists and society have since warmed up to the concept of beneficial germs.
“Kids that are exposed to dogs have a lower prevalence of asthma, for example, and people that are hunter-gatherers have a richer gut flora, and that maybe helps with digestion,” Amend says. “I think we’re probably coming around to some of the same ideas with plants.”
Powdery mildew and the P. plants
The researchers chose to puree the leaves from P. hirsuta because it is a close wild relative of P. kaalaensis and grows in the same range. “The assumption was that it would have a lot of the same fungi — beneficial fungi — growing with it, that Phyllostegia kaalaensis would have,” Amend says.
The researchers chose a healthy P. hirsuta plant, unaware, Amend says, that the powdery mildew pathogen was in the plant. They sterilized the exterior surface of the plant’s leaves, pureed the leaves into a slurry, then inoculated P. kaalaensis’ leaves with the slurry weekly for a total of three weeks, according to the study. The next step was to place a P. kaalaensis leaf infected with powdery mildew in the air intake of P. kaalaensis’ growth chambers.
While researchers lessened powdery mildew in P. kaalaensis using the slurry from the wild P. hirsuta plant, they were unable to achieve the same results using the slurry on a plant relative. “The other part of this story is this sister plant — Phyllostegia mollis — same genus, same issues — this slurry did not work on that plant, for whatever reason,” Amend says. “Same protocols, same methods, same issues, different results.”
Upon reducing powdery mildew symptoms in P. kaalaensis, Amend says the researchers celebrated. “Then we got our data back three months later, and we could actually see what was in that slurry that we had applied,” he says. “It turns out it was full of the powdery mildew.”
Amend theorizes that the powdery mildew in the slurry didn’t cause symptoms because it was part of a larger ecosystem that included a yeast called Pseudozyma aphidis, which produces antagonistic glycolipids and feeds on powdery mildew spores. “Higher P. aphidis abundance was negatively correlated with infection severity,” the study states.
Reintroduction into the wild
A year and a half ago, the healthy P. kaalaensis plants from the study were returned to the Waianae Mountains, and are currently the only plants in the species in the wild, Amend says.
Now, Amend and his colleagues are inoculating plants with mycorrhizae in addition to leaf slurries. They are providing both leaf fungi to knock back powdery mildew, and root fungi to let the plants extract water and nutrients from the soil. These “super plants,” as the researchers call them, will soon be returned to the wild.
As researchers perform more experiments, Amend says, growers should not go spraying their plants with powdery mildew. But they should follow this advice from Amend: “Don’t think of all microbes as germs — some of them are also our friends.”
The devastating Thomas Fire, a more than month-long blaze that ravaged Southern California, was finally extinguished in mid-January. According to the California Department of Forestry and Fire Protection, the Thomas Fire was the largest wildfire in the state’s history, destroying 273,400 acres. The lengthy duration and intensity of the fire resulted in more than $170 million in damages just in Ventura County, according to the Ventura County Star. Hundreds of thousands of people, residents and tourists alike, have been impacted by the Thomas Fire. Lauris Rose, owner of Cal-Orchid in Santa Barbara, felt the impact first-hand, and said it was a “once-in-a-generation disaster.” The havoc the Thomas Fire wreaked on residents and businesses in the area will not soon be forgotten.
In this month's cover story, Chris Manning takes a look at how the Thomas Fire affected growers in Southern California, and how they're moving forward.
Josh Henry is currently a graduate student at North Carolina State University, although some may recognize him as a Cultivate’17 floriculture tour guide. Below, he answers three questions about his internship, why he decided to go into research and more.
Greenhouse Management: What about the American Floral Endowment internship you did as an undergraduate in 2014 appealed to you, and how do you think it helped set you up for the work you are doing now?
Josh Henry: I learned a lot at that internship [at Smith’s Gardens, in Aurora, Ore.]. What I really appreciated about it was the ability to learn about all of the different aspects of the greenhouse industry, and not just the growing side of it, but maintenance, human resources and all of that. I got to see some of the different problems that are faced in each segment of the greenhouse industry, and that was a really good experience. It’s only helped find ways to fix and think about some of the different problems facing different areas of production.
GM: Why did you decide to pursue a career at a university instead of going to work for a commercial greenhouse operation?
JH: I originally loved the idea of being a grower, and I’ve always been very passionate about the growing aspect. However, as an undergrad, I found that I really loved doing research and felt that I would be better served working closely with growers, but trying to find solutions to the issues that we face with things like plant nutrition. I feel like that’s a good way to apply my knowledge and help growers with the problems they have.
GM: What are some projects you have worked on, or are about to, that you are excited about for what they could do for growers?
JH: Most of my research over the past two years has been on the phosphorus fertilization of bedding plants, and I’m pretty much done with those experiments now and am in the process of publishing all of that research. It’s been a really rewarding experience, and I find that getting the information out to growers is really useful. [Phosphorus nutrition] is such a basic thing, but there are a lot of misconceptions by growers and within the industry, so it’s really good to help clear up some of those misconceptions.
The relationship between insects & plant viruses
2018 Pest Control Supplement - Virus-carrying Insects
Learn how insect pests in greenhouse-grown crops vector plant viruses.
Insect pests of greenhouse-grown horticultural crops (ornamentals and vegetables) cause direct damage to plants; however, a number of insect pests can also cause indirect damage. Indirect damage is primarily associated with the ability of certain insect pests to serve as vectors of plant viruses that are transmitted to crops. Insect pests that serve as vectors (organisms capable of transmitting a virus from one plant to another) and consequently can transmit plant viruses include: aphids, thrips (western flower thrips), whiteflies, mealybugs, and leafhoppers.
Insects obtain a virus or viral particles when feeding on infected plants. They transmit plant viruses during the feeding process. The virus is secreted, along with saliva, into a new host plant and transmission occurs. Sucking insects such as aphids can carry plant viruses in their mouthparts or stylets (referred to as non-persistent transmission) or virus particles can accumulate inside their body, and be introduced into a plant during feeding (referred to as persistent or circulative transmission). The primary insect vectors affiliated with greenhouse production systems are aphids, whiteflies, and western flower thrips (Frankliniella occidentalis).
Aphids can transmit more than 300 plant viruses to many greenhouse-grown plants. For example, the green peach aphid, Myzus persicae, which is a common aphid species that feeds on many greenhouse-grown crops, can transmit over 100 plant viruses including bean yellow mosaic virus, carnation mottle virus, and cucumber mosaic virus. The green peach aphid transmits these viruses in a non-persistent manner, in which the viruses are stylet-borne and do not enter the hemolymph (fluid similar to blood that circulates inside the body of insects). In general, for most viruses associated with greenhouse-grown crops, aphids can transmit plant viruses almost immediately after feeding on infected plants. However, these aphids with non-persistent transmission lose the ability to vector a virus after a few minutes or hours after acquisition. As such, aphids associated with non-persistent transmission must reacquire viral particles in order to continue transmitting a virus.
Whiteflies can acquire a virus as nymphs or adults in about an hour after feeding on an infected plant. Once a virus is acquired, whiteflies remain vectors for the remainder of their life (for adults, up to 45 days). The sweet potato whitefly (Bemisia tabaci) is known to transmit more than 100 plant viruses including ageratum yellow vein virus and tomato yellow leaf curl virus. Whiteflies can transmit viruses in a persistent or circulative manner.
Adult western flower thrips can transmit viruses such as the tospoviruses, impatiens necrotic spot virus and tomato spotted wilt virus, during their lifespan (up to 35 days) with the virus replicating within the body of the western flower thrips. Western flower thrips acquire viruses as first or second instar larvae, although first instar larvae are more efficient in acquiring a virus. The virus is then transmitted by either second instar larvae or adults during feeding. Western flower thrips acquire a virus through their mouthparts when feeding on infected plants. The virus initially infects the gut where the virus replicates (makes copies of itself). Then, the virus accumulates in the gut tissue and spreads internally within the thrips’ body. The virus must reach the salivary glands in the mouthparts for transmission to occur. During the feeding process, the virus, along with saliva, enters the new host plant, resulting in transmission. To transmit a virus, western flower thrips larvae must feed on infected plants or weeds for 15 to 30 minutes. Then, the virus incubates inside the thrips’ body for four to 10 days before transmission to plants can occur.
Adults are unable to acquire and transmit a virus because the salivary glands of adults do not become infected with the virus. Although the virus may replicate or multiply inside the body of an adult western flower thrips, transovarial transmission does not occur, which means that the virus is not passed on to the offspring. Therefore, each new generation of thrips needs to feed on a new infected plant.
The primary insect vectors affiliated with greenhouse production systems are aphids, whiteflies and western flower thrips (Frankliniella occidentalis).
Management of virus vectors
Because aphids, western flower thrips, and whitefly females have a high reproductive capacity, management strategies need to be implemented early in the production cycle to maintain populations below damaging levels and to avoid transmission of viruses. Preventing infective vectors from transmitting viruses to susceptible plants involves sanitation, exclusion, and applying insecticides. Sanitation primarily entails weed removal, which is important in alleviating problems with insects that vector viruses. Remove weeds from inside and outside the greenhouse, as many broadleaf weeds can serve as a refuge or reservoir for the viruses transmitted by aphids, western flower thrips, and whiteflies. For instance, weeds that are known to harbor impatiens necrotic spot virus include: wood sorrel (Oxalis sp.), chickweed (Stellaria media), bittercress (Barbarea vulgaris), prostrate spurge (Euphorbia supina), and jewelweed (Impatiens capensis). Furthermore, old stock plants or “pet plants” maintained in greenhouses may serve as reservoirs for viruses.
Physical exclusion by means of installing insect screening, with a mesh or pore size of 150 µm, over greenhouse openings (vents or side-walls) will restrict the movement of flying insects such as adult aphids, western flower thrips and whiteflies into the greenhouse. Due to the low tolerance level for insects that transmit viruses, extensive applications of insecticides are conducted. Moreover, mortality must be high because any insect vectors that survive can continually spread viruses. However, this can lead to insecticide resistance — and this is important, as aphids, western flower thrips, and whiteflies are three major insect pests that are widely known to develop resistance to insecticides. When using insecticides to suppress populations of these insect pests, always rotate insecticides with different modes of action within a generation (two to three weeks, although this varies depending on temperature) before switching to another mode of action. This will mitigate the possibility of developing resistance.
Raymond is a professor and extension specialist in horticultural entomology/plant protection in the Department of Entomology at Kansas State University. His research and extension program involves plant protection in greenhouses, nurseries, landscapes, conservatories and vegetables and fruits. firstname.lastname@example.org or 785-532-4750
The author acknowledges Dr. Ann Chase and Margery Daughtrey (plant pathologists) for providing feedback and ensuring that the information associated with viruses is accurate.