Jim Stewart, Ag IPM Consultants, Inc., provides weekly counts of olive fruit flies (OFF) trapped in Tulare County, CA.  Trap catches were relatively high April 1-April 8, 2016, which was the first trapping interval of the season.  Traps maintained in Tonyville, Woodlake, and S. Exeter exhibited the highest trap catches of all locations monitored.   Female OFF were less prevalent in traps than males, presumably because males are actively searching for females that arrive to lay eggs in fruit.  In the San Joaquin Valley, damaging levels of infestation can occur within six days of oviposition, as the eggs quickly hatch into tunneling larvae that feed inside the fruit. 

High temperatures can have a rapid and dramatic effect on OFF populations, especially when daytime temperatures reach 95° F.  Successive days at and above this temperature causes substantial mortality of OFF adults, as well as developing larvae and eggs inside the fruit.  Also at and above this temperature, egg-laying drops off dramatically by surviving females.  For these reasons the pest tends to be more abundant in cooler California climates, such as the Sacramento Valley and along the Pacific coast. 

Inland OFF populations generally decline during the summer and resurge as temperatures cool down in the fall.  When olives reach about 10 mm in length, typically around pit hardening stage in early July, the fruit are mature enough to promote larval growth and development. Until pit hardening, OFF larvae are unable to survive in the fruit. Olive shotberries are typically not appealing for oviposition, as they are too small to support developing larvae.  Intermittent and well-timed heatwave events, such as those experienced lately in the southern San Joaquin Valley, could benefit growers battling the fly as the race to harvest approaches. 

Longevity and survival of adult female OFF increases in orchards where water and sugar sources are available.  For example, flood-irrigated orchards may be more conducive to OFF survival than orchards on microsprinklers. Similarly, orchards with heavy black scale infestation may promote OFF survival because the sugar in honeydew secretions provides a food source for the OFF.  Thus, management of water and sugar in an orchard helps to manage OFF populations.  For more information on management of OFF, visit the UC IPM Online website:  http://www.ipm.ucdavis.edu/PMG/r583301311.html

Reviewed by:  Marshall Johnson

Although over-irrigation may seem like an unlikely diagnosis after an extended drought, the foliar chlorosis observed in Tulare County walnut blocks in late May and early June are identical to  symptomology in research blocks maintained wetter than baseline (Figure 1).  In research plots, foliar chlorosis occurs within just days of an excessive irrigation event. Note that the yellowing associated with overwatering affects all of the leaves on a shoot down to the nuts (i.e. neoformed leaves that were formed in the current season). In contrast, newly emerging leaves may initially appear yellow; however, they gradually turn to green three or four leaves back from the growing tip. Over-irrigated walnut trees in research plots also have a tendency to drop one of two nut doubles, resulting in lower overall nut retention in the canopy.  When this situation is occurring, you can grasp a number of pairs of double nuts on the tree and one of each pair will often come loose with almost no force. These nuts will exhibit blackening while still on the tree (Figure 2) and squirt water vigorously when cut.   Anaerobic conditions in the root zone may cause root rot which may lead to overall tree decline and mortality.

For more information on this topic, please visit the June 2016 In a Nutshell newsletter.

The Master Gardeners in both Tulare and Fresno Counties hosted a lecture on cultivation of olives in the home landscapes.  The program elaborated on the history of olive cultivation and trade with an emphasis of the role of olives in California history. Additionally, Master Gardeners learned the floral biology and plant physiological factors affecting annual crop loads, as well as the strategies for maintaining fruitless trees in the home landscape.  Groups were presented with information on choosing the appropriate variety of olive for multiple curing styles, as well as the flavor profiles associated with varietal oils. Unique pruning and tree design strategies, such as the olive “poodle” or the olive bonsai, were also discussed with respect to managing fruitless olives in the home landscape.

The recent elucidation of the center of origin of olives and history of dissemination of the plant and plant products was discussed.

Attendees learned of varietal selection for numerous home olive curing styles.

On April 29, 2016, the 2^nd grade classes at Centennial Elementary in Bakersfield, CA engaged UCCE farm advisor, Elizabeth Fichtner, in a program designed to highlight the importance of science and technology in agricultural productivity in the southern San Joaquin Valley.  Local grower cooperators hosting on-farm trials conducted by UCCE researchers facilitated the collaboration between UCCE and the elementary school.  Approximately 75 students from the classes of Mrs. King, Mrs. Maybee, and Mrs. Lopez attended the program.  

Elizabeth Fichtner explains the importance of dams in agricultural productivity to 2^nd graders at Centennial Elementary School.