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Figure 4. Susceptibility of various fig cultivars to limb dieback pathogen Neoscytalidium dimidiatum. Dr. Themis Michailides sampling symptomatic fig trees. Continued from Page 26 Figure 5. Effect of stress factors (mallet wounding and sunburn) and treatment with white wash affecting the severity of limb dieback of fig. Limb and branch samples from the majority of these orchards had 60% to 100% Neoscytalidium, while three had 7% to 11%, and two 26% to 32%. In 12 of these orchards, a second pathogen, Phomopsis spp., was isolated along with Neoscytalidium in the first year of the survey. Phomopsis sinarencis has been reported in California causing an epidemic on Kadota figs back in 1935 and in other countries as an important fig canker pathogen. By the third year of this survey, less Phomopsis was isolated, and, very recently, almost none was isolated, probably because the very susceptible Kadota variety is rarely now planted in California. Phomopsis is known as a pathogen fungus associated with canker diseases in many other crops around the world, but more investigations are needed to figure out its role in fig limb dieback. Differences in Susceptibility To determine if there were any differences in susceptibility to the limb dieback pathogen, we inoculated six cultivars directly in the field. We found that three months after inoculations, the cultivars Kadota, Black Mission and Sierra developed twice as long canker size than the cultivars Brown Turkey, Calimyrna and Conadria (Figure 4). Growers also reported that they see the problem to be more severe in Black Mission than other cultivars. Inoculations of six cultivars showed that Neoscytalidium is a plant pathogen that likes high temperatures. For instance, it cannot grow below 50 degrees F; its optimum temperature for growth is 90 to 95 degrees F, and it can even grow at 104 degrees F to some extent. Therefore, this fungus likes hot summer temperatures and prefers to infect sunburned branches and pruning wounds. Figure 6. Effect of Surround® spray on the severity of limb dieback of fig. In experiments, we inoculated shoots of fig of different ages, including current growth (green) shoots, one-year, two-year and threeyear-old shoots, by wounding and inoculating with either a mycelial plug or a spore suspension. Interestingly, the three-year-old shoots 28 Progressive Crop Consultant March / April 2021
developed almost three-fold larger cankers than the cankers on current and the one-year-old shoots. This suggests that larger cuts in the field during pruning seem to be more susceptible to infection than cuts made in current or one-yearold shoots. Also, inoculations done in May, June and July resulted in larger cankers than those done from August to November. ‘ NAVEL ORANGEWORM MONITORING SYSTEMS When we compared infection on pruning wounds done in winter vs. those done in summer, pruning wounds in the summer developed almost threefold larger cankers than those done during winter months. Therefore, it is recommended that pruning of figs should be done in winter when pruning wounds seem to be less susceptible. Figs can be protected from infections of the branch wilt pathogen if shoots are painted with whitewash to protect them from sunburn. Applying Surround® on shoots also protected the shoots from infection, and this is recommended to become a routine practice by fig growers. Figure 5 shows results of inoculation experiments done following various treatments in the field and artificial inoculation with the pathogen. NEW! Multi-Gender Attractant System: PHEROCON ® NOW PPO-HR L 2 + NOW 2 L Lures PHEROCON 1CD QUICK-CHANGE Trap + Female Attractant System: PHEROCON ® IV NOW PHEROCON IV NOW Egg Trap Male Attractant System: PHEROCON ® NOW L 2 Lure PHEROCON VI Delta Trap NEW! Predator Detection System: PHEROCON ® PREDATOR Trap PHEROCON PREDATOR Trap Although wounding by only mallet or only sunburn resulted in larger canker than the non-inoculated, un-wounded/ un-treated shoots, the shoots that were damaged by mallet wounding and sunburn at the same time resulted in the longest cankers. White wash or spraying with Surround protected the shoots even after wounding with mallets and inoculation (Figure 5 and 6, see page 28). Therefore, pruning that exposes the shoots to sunburn and or any other type of wounding should be avoided, and spraying with Surround will help protect the fig shoots from the limb dieback pathogen. The authors thank the California Fig Institute for funding this research and a number of fig growers who allowed us to sample their orchards. Comments about this article? We want to hear from you. Feel free to email us at article@jcsmarketinginc.com — Brad Higbee, Field R&D Mgr, Trécé, Inc INCORPORAT ED INSECT PHEROMONE & KAIROMONE SYSTEMS Your Edge – And Ours – Is Knowledge. trece.com ® Brad’s Monitoring Program LEARN MORE © 2021, Trécé Inc., Adair, OK USA • TRECE, PHEROCON and CIDETRAK are registered trademarks of Trece, Inc., Adair, OK USA • TRE-1870, 12/20 March / April 2021 www.progressivecrop.com 29
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Page 5 and 6: Figure 1. Integration of universal
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Page 9 and 10: Average Yield (lb/ac, 12% protein)
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Page 15 and 16: Pythium pathogens form thick-walled
Page 17 and 18: NAVEL ORANGEWORM MANAGEMENT discolo
Page 19 and 20: (Left) Spotted-wing drosophila adul
Page 21 and 22: decreased the number of larvae in f
Page 24 and 25: New Findings on Limb Dieback of Fig
Page 26 and 27: Figure 3. Left, pycnidia protruding
Page 30 and 31: Enhancing Diamondback Moth Manageme
Page 32 and 33: Continued from Page 31 study (Figur
Page 34 and 35: Diamondback moth larva and adult (p
Page 36 and 37: Vegetable Growers Express Impressio
Page 38: Continued from Page 37 Responses Re
Page 41 and 42: References Biofertilizers Market Si
Page 43 and 44: Go boldly into every battle. Includ
Page 45 and 46: everything at fall pre-plant with P
Page 47 and 48: Apply less, expect more? There’s

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