Biological Controls Have a Place in Fruit Production
Integrating biological products into pest and disease control can be a challenging endeavor for growers, many of whom are reluctant to try something new.
However, presenters at the tree fruit and small fruit breakout sessions of the recently held Biocontrols USA East 2018 Conference & Expo in Rochester, NY, said there is a place for these newer biological products coming out, even in conventional programs.
Chris Becker, Research Scientist with BAAR Scientific LLC, says until about two years ago, the general consensus among growers were that biocontrols are less effective than conventional products. But, Becker says growers need to consider the level of pest and disease pressure before writing off biological products.
“A lot of products under low pest pressure can be quite effective,” he says.
Becker says that any crop can be susceptible to disease and pests, “the best thing you can do is know your pests.”
Kerik Cox, Associate Professor of Plant Pathology at Cornell University says it’s most important for growers to understand that biocontrols for fire blight are effective, even as troubling a disease as fire blight can be especially for Eastern U.S. growers. The approach to application may need to change compared to conventional antibiotics
“It’s easy to make any product fail,” he says. “It just takes time to learn how to use them.”
As growers have moved away from larger semi-dwarf plantings, the trees are not as equipped to handle fire blight strikes. And, as growers feed young plantings nutrients to get the trees to fill canopies and reach the top wire quickly, that exacerbates the pathogen’s presence.
“It loves free nitrogen and nutrients,” Cox says as he pointed to a presentation slide, “here’s a high-density orchard of fire blight.”
Growers need to take the management technique of pruning out strikes and protecting trees early in the season. Applications of products like Blossom Protect (Westbridge Agricultural Products) at 80% bloom will help protect against blossom blight.
“If you manage blossom blight, you’ll get good protection against shoot blight,” he says.
Cox says the best biological products for early season protection are induced systemic resistance (ISR) and systemic acquired resistance (SAR) products. Applications should be made every 10 to 14 days until terminal bud set.
An Integrated Approach
Tom Heeman, Field and Strategic Projects Manager of Heeman Greenhouses and Strawberry Farm in London, ON, Canada, says his family’s move to biocontrols was in part a response to consumer demand for environmentally friendly products. Heeman has moved to hedgerows and bioinsectaries with beneficial boosting plants.
“We wanted to put the best foot forward for our consumers,” he says. “Kill what you want and not what you don’t.”
For Heeman, using biological products is like looking at the farm as an ecosystem, and integrating biocontrols is a way to keep the ecosystem in balance. Flare-ups in pests and diseases rarely happen.
“In horticulture, they don’t accumulate overnight, they tend to trickle in,” he says.
Heeman has been using biocontrols for five years, and the motivation was to provide a unique, safe, and environmentally friendly experience for consumers who visit his family’s farm. Heeman approaches the seasonal pests in incremental treatment windows. He also followed advice from Professor of Horticulture of Clemson University Guido Schnabel’s spray recommendations for to help improve timing and reduce the number of sprays as well as prevent disease and pest resistance.
“In my mind, biopesticides and biofungicides help break that up,” he says.
Heeman says that a couple of sprays he’s used in the past for anthracnose are starting to fail, and this is where biological products can give him a leg up. But, in order to effectively evaluate biological products, data on their effectiveness is vital to making good product choices. Overall, integrating biological products is just “the switch in the mindset of not using systemic insecticides and not going to the nuclear option.”
Heather Leach, Penn State University Extension Associate, kicked off the fruit sessions with a talk on spotted lanternfly (SLF), a new invasive pest found in Pennsylvania in 2014. Leach’s presentation was timely as SLF was recently found in the Finger Lakes, and her presentation served as part introduction to SLF and part discussion of its future in the states. SLF can feed on nearly 70 different crops from fruit to ornamental. However, Tree of Heaven is its preferred host.
“Spotted lanternfly is absolutely a grape pest,” Leach says. “They are super easy to kill, but the population increases every 3to-5 days.”
This population renewal makes it more difficult to completely eliminate the pest. Direct feeding causes vine death or stress. SLF also secrete honeydew, which causes sooty mold. Stressed vines often do not flower the following year.
“The idea of eradication is unlikely,” Leach says, indicating conventional pesticides in a Tree of Heaven trap-and-kill method also could be a solution. But, what makes that more difficult is how widespread Tree of Heaven is across the Eastern part of the U.S., and how quickly populations can regenerate.
Studies are looking at conventional sprays first, but there also is an increased focus on biological controls for SLF, including two parasitoid wasps that could be a targeted control for SLF. There also is increased interest in microbial control agents for SLF that look promising. One showed 70% to 80% mortality. But, the research on parasitoid wasps and microbial control agents is early.
One grower in the audience spoke about the challenges the juice grape industry would have with the cost of SLF control versus the winegrape growers.
For now, though Leach says the focus is to “use what we’ve got against spotted lanternfly and limit its spread.”
Following along the theme of invasive pests, Peter Jentsch, Senior Research Associate in Cornell University’s Department of Entomology, discussed the progress made on research for biological controls of brown marmorated stink bug (BMSB).
What’s most alarming about BMSB feeding on apples is “it changes the flavor,” of the fruit.
Jentsch has looked at pheromone netting as an attract and kill, mainly for homeowners. He says when lights were included with the netting, they were getting 300 to 500 BMSB per trap.
Residual chemistries are ineffective for BMSB, Jentsch says. Stink bugs stand on legs and their abdomen does not come in contact with fruit. They also probe with proboscis, a straw-like tube, to feed. Which also limits the pest’s exposure to fruit sprayed with chemistries.
Jentsch says to integrate biocontrol options, measurements of effectiveness need to change. Instead of measuring how effective a pesticide is by insect death, it’s more important to look at fruit damage. Bifenthrin is the most effective pyrethroid. But, with pyrethroids, it’s impossible to apply the products close to harvest.
“You can’t make a traditional IPM decision based on its presence in fruit,” he says.
However, in comparing pyrethroids, biological pesticides, and untreated controls, Venerate (Marrone Bio Innovations) showed promising results. After seven days, there was no feeding, and it has a 0-day PHI.
Jentsch also is on a team of researchers looking at Trissolcus japoinicus, a samurai wasp, which oviposits into eggs of BMSB. Larva feed on nymphs. This parasitoid wasp, originally from Asia, but found in the U.S., has a fit in bringing BMSB into an ecological balance.
“[BMBS] entered into an ecology that is not prepared for BMSB,” he says.
Philip Fanning, an Entomology Research Associate with Michigan State University, says biopesticides have a good fit in controls of spotted wing drosophila (SWD) as they conserve natural enemies of pests. Another important factor in the move toward biopesticides for SWD are maximum residue levels – or MRLs. Fanning says 41% of export destinations have lower MRLs that the U.S.
“Biopesticides could give us the potential to meet those MRLS,” he says.
A new spider venom product, Spear-T (Vestaron) has no MRL; and when paired with adjuvants, had nearly 100% mortality. It was just labeled for field use and state registrations are pending.
Grandevo (Marrone Bio Innovations) interrupts SWD’s feeding behavior and reproduction and the product can be tank mixed with Imidan (Gowan USA) in a conventional spray program.
“Biopesticides do have a place in our conventional management,” he says. But, it’s crucial for growers to use the highest label rate for maximum effectiveness when it comes to biological products.
“Growers want to use 30 to 40 gallons an acre,” he says, when he will use 50 gallons per acre.