- Author: Ben Faber
Dogs can detect agricultural diseases early
Study shows dogs can sniff out laurel wilt-infected avocado trees well in advance
A study out of Florida International University evaluates the use of scent-discriminating canines for the detection of laurel wilt-affected wood from avocado trees. Julian Mendel, Kenneth G. Furton, and DeEtta Mills have ferreted out a possible solution to a serious issue in one corner of the horticultural industry, and then ascertained the extent to which this solution is effective.
The results of this study are presented in their article "An Evaluation of Scent-discriminating Canines for Rapid Response to Agricultural Diseases" published in the latest issue of HortTechnology.
Laurel wilt disease has resulted in the death of more than 300 million laurel trees in the United States alone. One affected plant is the commercially important avocado tree, the second-largest tree crop in Florida behind citrus. This disease has had a devastating effect on the industry in South Florida in past harvest seasons, and two larger avocado industries in Mexico and California are naturally worried that this disease, if it hits their crops, could spread fast enough to destroy their seasons.
Once affected by laurel wilt disease, trees succumb soon after infection. Once external symptoms are evident, this disease is very difficult to control and contain as the pathogen can spread to adjacent trees via root grafting. Until now, there has been no viable, cost-effective method of early diagnosis and treatment.
Laurel wilt is the consequence of an invasive species--the redbay ambrosia beetle--originally from Asia, which was inadvertently introduced into the United States in untreated wooden packing material.
But as with so many ailments, early detection can be instrumental in deterring a widespread infection. The use of scent-discriminating dogs has shown to offer the avocado industry legitimate signs of hope in their fight against the spread of such a profit-crusher throughout their groves.
Three dogs were trained and studied for their ability to detect the early presence of laurel wilt by scent. At present, canines are extensively used in law enforcement and forensics in the location of missing persons, explosives, drugs, weapons, and ammunition. More directly applicable, dogs have demonstrated the ability to detect invasive species of spotted knapweed, brown tree snakes, desert tortoises, and various cancers.
The highly sensitive canine olfactory system is capable of detecting odor concentrations at exceedingly minute 1 to 2 parts per trillion. The authors believe it likely, with properly directed training, that these dogs could use their natural talents to service the protective needs of the potentially ailing avocado industry.
During the course of the study, 229 trials were performed, and only 12 of those yielded false alerts. It was observed that dogs are indeed capable of high levels of relevant performance, even in harsh weather conditions such as high heat and humidity. The study provided proof that dogs can detect agricultural diseases such as laurel wilt and can be a powerful management tool if the disease is caught in its earliest stages.
About the valuable service provided by these dogs, Mills adds, "It is the best 'technology' so far that can detect a diseased tree before external symptoms are visible. The old saying that 'dogs are man's best friend' reaches far beyond a personal bond with their handler and trainer. It is depicted in their excitement every day as they deploy to the groves. Man's best friend may even help save an industry."
The complete article is available on the ASHS HortTechnology electronic journal web site: http://horttech.
Also a great article on dog-sniffing bee hives for foul brood. Go DOGS!
Image:
Cobra, a 3-year-old Belgian Malinois, is trained to detect laurel wilt-diseased trees before the visible symptoms are seen. She and two other Dutch Shepherd canines detect asymptomatic, but infected trees. Once a diseased tree is identified, these "agri-dogs" will sit, indicating a positive alert.
/h1>- Author: Ben Faber
There is a wild world in those avocado orchards. A study was done locally of some of the carnivores besides humans that show up there.
Carnivore Use of Avocado Orchards Across and Agricultural-Wildland Gradient
Wide-ranging species cannot persist in reserves alone. Consequently, there is growing interest in the conservation value of agricultural lands that separate or buffer natural areas. The value of agricultural lands for wildlife habitat and connectivity varies as a function of the crop type and landscape context, and quantifying these differences will improve our ability to manage these lands more effectively for animals. In southern California, many species are present in avocado orchards, including mammalian carnivores. We examined occupancy of avocado orchards by mammalian carnivores across agricultural-wildland gradients in southern California with motion-activated cameras. More carnivore species were detected with cameras in orchards than in wildland sites, and for bobcats and gray foxes, orchards were associated with higher occupancy rates. Our results demonstrate that agricultural lands have potential to contribute to conservation by providing habitat or facilitating landscape connectivity.
Read on:
http://www.avocadosource.com/journals/plos_one/nogeiretheresa2013.pdf
- Author: Ben Faber
A recent study by Joey Mayorquin and team shows a promising chemical response in sycamore trees infected with Fusarium Dieback. This holds hope for the pest/disease complex in avocado, as well.
Chemical Management of Invasive Shot Hole Borer and Fusarium Dieback in California Sycamore (Platanus racemosa) in Southern California
Fusarium dieback (FD) is a new vascular disease of hardwood trees caused by Fusariumspp. and other associated fungal species which are vectored by two recently introduced and highly invasive species of ambrosia beetle (Euwallacea spp. nr. fornicatus). One of these ambrosia beetles is known as the polyphagous shot hole borer (PSHB) and the other as the Kuroshio shot hole borer (KSHB). Together with the fungi that they vector, this pest–disease complex is known as the shot hole borer–Fusarium dieback (SHB-FD) complex. Mitigation of this pest–disease complex currently relies on tree removal; however, this practice is expensive and impractical given the wide host range and rapid advancement of the beetles throughout hardwoods in southern California. This study reports on the assessment of various pesticides for use in the management of SHB-FD. In vitro screening of 13 fungicides revealed that pyraclostrobin, trifloxystrobin, and azoxystrobin generally have lower effective concentration that reduces 50% of mycelial growth (EC50) values across all fungal symbionts of PSHB and KSHB; metconazole was found to have lower EC50 values for Fusarium spp. and Paracremonium pembeum. Triadimefon and fluxapyroxad were not capable of inhibiting any fungal symbiont at the concentrations tested. A 1-year field study showed that two insecticides, emamectin benzoate alone and in combination with propiconazole, and bifenthrin, could significantly reduce SHB attacks. Two injected fungicides (tebuconazole and a combination of carbendazim and debacarb) and one spray fungicide (metconazole) could also significantly reduce SHB attacks. Bioassays designed to assess fungicide retention 1 year postapplication revealed that six of the seven fungicides exhibited some level of inhibition in vitro and all thiabendazole-treated trees sampled exhibiting inhibition. This study has identified several pesticides which can be implemented as part of an integrated pest management strategy to reduce SHB infestation in low to moderately infested landscape California sycamore trees and potentially other landscape trees currently affected by SHB-FD.
https://apsjournals.apsnet.org/doi/abs/10.1094/PDIS-10-17-1569-RE
- Author: Tunyalee Martin
UC ANR Integrated Pest Management Program
A sugar volcano is one symptom that shows your avocado tree might be infected with Fusarium dieback, a fungi spread by a beetle called the shothole borer. But what you might see if your tree is being attacked by shothole borer, varies among the different kinds of tree hosts. The symptoms—staining, sugary exudate, gumming and beetle frass—are often noticed before the tiny beetles (1.5–2.5 mm) are found.
As its name suggests, these beetles bore into trees. Near or beneath the symptoms, you might notice the beetle's entry and exit holes into the tree. The female tunnels into trees forming galleries, where she lays her eggs. Once grown, the sibling beetles mate with each other so that females leaving the tree to start their own galleries are already pregnant. Males do not fly and stay in the host tree.
Shothole borers have a special structure in their mouth where they carry two or three kinds of their own novel symbiotic fungi. Shothole borers grow these fungi in their tree galleries. It's these fungi that cause Fusarium dieback disease, which interrupts the transportation of water and nutrients in the host tree. Advanced fungal infections will eventually lead to branch dieback.
Early detection of infestations and removal of the infested branches will help reduce beetle numbers and therefore, also reduce the spread of the fungus.
- Chip infested wood onsite to a size of one inch or smaller. If the branch is too large to chip, solarize them under a clear tarp for several months
- Avoid movement of infested firewood and chipping material out of infested area
Avocado is one tree host. Shothole borers successfully lay eggs and grow fungi in many tree hosts, with some of these trees susceptible to the Fusarium dieback disease. For more information about tree host species, where the shothole borer is in California, and what symptoms look like in other tree hosts, visit the UC Riverside Eskalen Lab website.
Californians can help in the fight against invasive species by learning and participating during California Invasive Species Action Week, June 2–10.
During the week, spend your lunch with us learning the latest about invasive tree killing pests, aquatic nasties like quagga mussels and nutria, and how the invasive weed/wildfire cycle is altering our ecosystems! http://ucanr.edu/sites/invasivelunch/
Content in this post taken from the UC IPM Avocado Pest Management Guidelines. Faber BA, Willen CA, Eskalen A, Morse JG, Hanson B, Hoddle MS. Revised continuously. UC IPM Pest Management Guidelines Avocado. UC ANR Publication 3436. Oakland, CA.
And more about Shot Hole Borers
http://ucanr.edu/sites/pshb/
- Author: Ben Faber
A recent call about the poor control of marestail (horseweed, Conyza canadensis) to glyphosate (Roundup®) wasn't surprising, but that paraquat didnt do the trick was. It turns out that there is multiple resistance to the materials. If horseweed is resistant to glyphosate it is possibly going to be resistant to paraguat which also means that hairy fleabane which has glyphosate resistance could also show resistance to paraquat. A recent study reports on the increased Conyza resistance to paraquat (Distribution of Conyza sp. in Orchards of California and Response to Glyphosate and Paraquat, Moretti et al, https://doi.org/10.1614/WS-D-15-00174.1):
Resistance to glyphosate in hairy fleabane and horseweed is a problem in orchards and vineyards in California. Population genetic analyses suggest that glyphosate resistance evolved multiple times in both species, but it is unknown if resistance to other herbicides is also present. Two approaches of research were undertaken to further evaluate herbicide resistance in Conyza sp. in the perennial crop systems of California. In the initial study, the distribution of Conyza sp. in the Central Valley, using a semistructured field survey, was coupled with evaluation of the presence and level of glyphosate resistance in plants grown from field-collected seed. In a subsequent study, single-seed descendants representing distinct genetic groups were self-pollinated in the greenhouse and these accessions were evaluated for response to glyphosate and paraquat. Conyza sp. were commonly found throughout the Central Valley and glyphosate-resistant individuals were confirmed in all field collections of both species. The level of glyphosate resistance among field collections varied from 5- to 21-fold compared with 50% glyphosate resistance (GR50) of the susceptible, with exception of one region with a GR50 similar to the susceptible. When self-pollinated accessions from different genetic groups were screened, the level of glyphosate resistance, on the basis of GR50 values, ranged from 1.7- to 42.5-fold in hairy fleabane, and 5.9- to 40.3-fold in horseweed. Three accessions of hairy fleabane from different genetic groups were also resistant to paraquat (40.1- to 352.5-fold). One glyphosate-resistant horseweed accession was resistant to paraquat (322.8-fold), which is the first confirmed case in California. All paraquat-resistant accessions of Conyza sp. identified so far have also been resistant to glyphosate, probably because glyphosate resistance is already widespread in the state. Because glyphosate and paraquat resistances are found across a wide geographical range and in accessions from distinct genetic groups, multiple resistant Conyza sp. likely developed independently several times in California.