Spring into the following free webinars from the UC IPM Urban & Community Program! Held every third Thursday from 12:00-1:00pm PDT, these informative webinars will help you identify, prevent, and control pests in and around the home, garden, and landscape!

April 20, 2023: Aphids, Scales, and Mealybugs, Oh My!

Insects such as aphids, certain scales, mealybugs, and others can produce a sticky substance called honeydew that can create a big mess around gardens and landscapes. Learn how to identify, prevent, and control these honeydew-producing insects and their damage to plants. This presentation will be given by Karey Windbiel-Rojas, UC IPM Associate Director for Urban & Community IPM/Area IPM Advisor. Register for this webinar.

A racing pigeon.

May 18, 2023: Birds: Friends or Foes?

Birds are sometimes considered pests around homes, buildings, and in gardens, but they can also help to control other pests. This webinar will cover pest bird biology, identification, monitoring, and common types of damage; in addition to predatory birds and ways to enhance their control of pests. This presentation will be given by Breanna Martinico, Human-Wildlife Interactions Advisor, Napa, Lake, and Solano counties. Register for this webinar.

June 15, 2023: Summertime Household Pests

This webinar will cover identification, prevention, and management of common household pests that can be a problem in the summer months. Dr. Andrew Sutherland, Area Urban IPM Advisor for the San Francisco Bay Area, will present the webinar. Register for this webinar.

July 20, 2023: Natural Enemies & Beneficial Bugs: What are they?

While some insects can be damaging pests, many others are actually useful and keep pest species in check by parasitizing them or preying on them. These beneficial bugs are known as natural enemies and are vital to help keep pests from getting out of control. In this webinar, learn about natural enemies, how to identify them, and how they can help you out in your home and garden. This presentation will be given by Eric Middleton, Area IPM Advisor for San Diego county. Register for this webinar.

Can't make a webinar? Don't worry, all presentations are recorded and posted on the UC IPM YouTube channel! More webinars will be announced in the late summer. Follow us on social media @ucipmurban for the latest IPM content and news.

Webinars from the IPM Institute of North America

From April 10-14, Midwest Grows Green and Green Shield Certified will host Green Shield Week, a series of webinars discussing sustainable landscaping and pest management practices, strategies and policies. The webinars include:

• Monday, April 10^th – Barry Draycott from Tech Terra Environmental discusses how to protect our water resources while maintaining a healthy and resilient lawn. Register for free at bit.ly/GreenLawns23. 
• Tuesday, April 11^th – Bradley Herrick from the University of Wisconsin Madison Arboretum focuses on best management practices, control methods and latest research of jumping worms. Register for $10 at bit.ly/InvasiveJumpingWormsWebinar.
• Thursday, April 13^th– Dr. Doug Richmond from Purdue University's Soil Insect Ecology Laboratory presents a systems approach for integrating cultural, biological and low impact chemical tools to reduce the ecological footprint of managing turf pests. Register for $10 at bit.ly/SustainablePest23.

NEW HLB Detection Response Guide for Growers 

To ensure California citrus growers are well prepared in the event of a potential commercial grove detection of Huanglongbing (HLB), the Citrus Pest and Disease Prevention Program (CPDPP) has developed the  Response Guide for a Confirmed HLB Positive Detection in a Commercial Grove, which details the steps taken by CDFA and actions required of the property or grove owner, as outlined in CDFA's Action Plan and Information for Citrus Growers/Grove Managers.

Additional ACP/HLB Resources

• CDFA Citrus Division website: https://www.cdfa.ca.gov/Citrus/
• General ACP/HLB

oInformation on the state ACP/HLB program including maps, quarantine information, and a signup option for email alerts: citrusinsider.org/

oBiology of ACP and HLB, detection maps and recommendations for monitoring, eradication and management: ucanr.edu/sites/acp/ 

oUC IPM recommendations for ACP insecticides

oWeb-based map to find out how close you are to HLB: ucanr.edu/hlbgrowerapp

oVideo on Best Practices in the Field, available in English and Spanish

oSpanish-only ACP/HLB presentation video presentation and audio-only recording. 

• Research

oUC Ag Experts Talk presentations on management of various citrus pests and diseases are available for viewing here and here on YouTube.

oSummaries of the latest research to combat HLB: ucanr.edu/sites/scienceforcitrushealth/

oScience-based analyses to guide policy decisions, logistics, and operations: www.datoc.us

• Regulatory/Quarantine

oSign up for program updates from the Citrus Pest and Disease Prevention Division at www.cdfa/signup-email-updates.

oRegulatory requirements for moving bulk citrus: Information for Citrus Growers

oSummary of regulatory requirements in the event of an HLB detection in commercial citrus: citrusinsider.org/Regulatory-Flyer

oSanta Barbara County Ag Commissioner's Office

Notes on Applying Gibberellic Acid (GA3) to Navel Orange and other Citrus

in the San Joaquin Valley of California

Craig Kallsen, Citrus and Pistachio Farm Advisor, Kern County

Typically, the price of navel oranges drops during the peak of the navel harvest season. When the peak harvest is over, prices often increase for navels that are harvested later. There is no mystery here. The price curve is merely following the law of supply and demand. When supplies are plentiful for most commodities, prices fall. Products containing gibberellic acid (GA3) are registered and available to citrus growers. For many decades growers have been extending the harvest season of navel oranges by application of plant growth regulators (PGRs) such as gibberellic acid to retard navel orange rind maturity in combination with the isopropyl ester of 2,4-D to prevent pre-harvest fruit drop. Citrus fruits, generally, store on the tree much better than in refrigerated facilities. Growers also have the option of replanting mid-season maturing orange orchards with late-maturing navels (and have been doing so). Generally, the late navels do not require application of PGRs such as GA3. However, for those that do not have the luxury of having late-maturing navels in the orchard, PGRs provide an opportunity to take advantage of higher prices that may come with a later harvest. The following “notes” may help the grower in successfully timing and applying PGRs to navel oranges. Always read and follow label directions of any chemical product carefully before using.

Note 1: Dr. Coggins, a former professor at the University of California in Riverside, spent many years researching the use of foliar-applied GA3 to prolong storage of navel oranges on the tree (for more info see: https://www2.ipm.ucanr.edu/agriculture/citrus/Delaying-Fruit-Senescence-with-Gibberellic-Acid-GA3/ ). The late September to mid- October application window, was found to be best time to apply GA3 to navels in the San Joaquin Valley for reducing puff and crease, rind staining, and, generally, for maintaining a more juvenile rind longer. Applying the gibberellic acid two-weeks before the fruit begins to change color from green to orange (called “color break”) remains a handy rule-of-thumb. Color break in mid-season navels (like Washington, Frost Nucellar, Atwood and others) usually occurs about two weeks after color break in the early navels (like Beck and Fukumoto). Dr. Coggin's research showed the GA3 was significantly more effective when a nonionic silicon-based surfactant was included with the spray as an adjuvant. Note that the addition of an effective surfactant can increase the chance and/or severity of significant leaf drop. Always follow the surfactant's label carefully and make note of any cautionary statements regarding phytotoxicity.

Note 2: Treating with an auxin (an isopropyl ester of 2,4-D is registered for this purpose) in November or early December is necessary if fruit is treated with GA3. The auxin prevents fruit from dropping too early. There is no point in delaying the maturation of the rind with GA3 into April or May if the navel is going to drop from the tree in February.

Note 3: Uptake of GA3 by the peel is improved if the spray solution is acidic. A pH of the spray solution of about 4 to 5 is recommended and several acidifying agents and products are available to accomplish this. Zinc sulfate, applied at a rate of 1 lb. of zinc sulfate/100 gallons of spray solution, has been used as an acidifying agent with gibberellic acid, which, also, helps correct zinc deficiency. Obviously, many other acidifying and buffering agents are available. In general, tank mixing other pesticides or nutrient solutions with GA3 should be avoided.

Note 4: Growers have obtained good results with GA3 applications using the labeled rates of GA3 on a weight-of-product-per-acre basis using dilute or concentrated sprays. Whichever option is selected, good spray coverage of the fruit is essential, and all else being equal, better coverage is more likely with higher spray volumes. Most of the beneficial results of GA3 are obtained with about 25 grams (active ingredient) of gibberellic acid per acre.

Note 5: Not uncommonly, a navel grower in Kern County will report a significant drop of fruit and leaves as a result of a GA3 spray. Usually in these cases, GA3 was sprayed within a week or two of a narrow-range oil spray. There appears to be a connection here, but GA3 and oil have been sprayed a few days apart with no observed phytotoxic effects. However, erring on the side of caution suggests avoiding spraying petroleum oils and GA3 within a few weeks of each other. Make sure when applying either GA3 or oil that the trees are not under water stress and that GA3 or oil are not applied to trees that show phytotoxic affects from either a previous oil or other chemical spray. The addition of a spreader adjuvant may increase the risk of leaf drop with gibberellic acid. Monitor soil-water carefully in the fall before gibberellic acid or oil is applied. The temptation is to reduce irrigation too much in response to the first light rains of fall. Often these rains, especially in the southern San Joaquin Valley, will not meet the evapotranspiration requirements of citrus, especially on the hilltops where soils are thin, leaving the trees more susceptible to damage from chemical spray applications.

Note 6: Gibberellic acid works best on blocks of fruit that normally hold well on the tree. Past harvest records can play an important role here. A good strategy is to harvest blocks that are prone to early rind breakdown first and to treat only blocks where the fruit naturally holds longer with GA3. Applying GA3 to an orchard with poor fruit-holding qualities may extend the life of the fruit a few weeks, while applying it to fruit of a good-holding block may give the grower an additional six to eight weeks of tree storage.

Note 7: Sometime fruit does not grow as quickly as a grower would like, and a block that was scheduled for an early or mid-season harvest may be rescheduled for a late season harvest. Gibberellic acid applications can still delay harvest (although not for as long a period of time) if treated later than October. Do not apply GA3 to fruit that is in the process of changing color. A permanently two-tone fruit may result. If fruit is in the process of changing color, wait until the fruit has turned completely orange and then apply the gibberellic acid. Check the label for application timing. Gibberellic acid can negatively affect next year's crop if applied too late.

Note 8: Gibberellic acid and an isopropyl ester of 2,4-D can also be applied to some other citrus fruit with useful results. Read and follow the labels carefully before applying the commercially available PGRs. Label directions include crop registrations, uses, timings, rates, cautions and other necessary information that will vary with citrus variety. Puff and crease and rind staining of Minneola tangelo, lemons, and some mandarins may be reduced and fruit storage on the tree may be extended by the use of these growth regulators. The timing of application is similar to that of navels in most cases.

Note 9: Late harvested navel varieties have been readily available to citrus growers in California now for over four decades. Late maturing navels are not as likely to require the addition of gibberellic acid and 2,4-D to produce high-quality fruit late in the season. Growers wishing to compete in the late-navel market are encouraged to plant one of the many late navel varieties.

Mycorrhizae means fungus (myco) root (rhizae). These root-associated fungi predate the evolution of terrestrial plants, and the partnership with mycorrhizal fungi facilitated the establishment of plant on earth. Mycorrhizae form symbiotic associations with more than 70% of land plants across a broad range of terrestrial ecosystems. Plants supplies mycorrhizae with photo-assimilated carbon in exchange for nutrients and water. This is the definition of a perfect relationship whereby the two sides support each other and have a personal interest at maintaining their counterpart well-being for survival. Once mycorrhizae colonize the host plant, its mycelium can grow over large distances to neighboring plants connecting them together by a common network. This extension of the root network allows plants to acquire water and nutrients (especially nitrogen and phosphorus) far beyond its root zone, rendering plants more resilient to drought and nutrient deficiency. The ability of mycorrhizae to form this underground web also enables the connected plant to communicate with each other through chemical signals and exchange water and nutrients. For example, in forest ecosystems, saplings rely on nutrients and carbon supply from older trees sent through the mycorrhizal network. This underground mycorrhizal web has also great physical properties because they improve the soil structure by forming stable soil aggregates thereby limiting erosion and leaching of nutrients.

Several studies have highlighted the instrumental role of these beneficial fungi in several cropping systems, including tree crops. In citrus for instance, they have been shown to delay diseases caused by soilborne pathogens such as Fusarium and Phytophthora. We also think that these fungi play a key role in the citrus Huanglongbing (HLB) pathosystem by protecting trees from suffering root loss. Results from our recent survey in Florida showed that healthy trees were more frequently associated with a biodiverse mycorrhizal population whereas declining trees rarely formed a symbiotic association with mycorrhizae and were frequently infected with Phytophthora and Fusarium. We think that tree decline is due not just to HLB infection in the aerial portions of the tree but also to large sectors of the root community shifting toward microbes that engage in pathogenic and saprophytic relationships with the host.

If you are a grower, how do you ensure that trees in your orchard have mycorrhizae? Well, this is where the challenge resides because the intricate relationship between the fungus and its host is not easy to replicate on command in the field. Several commercial products are available to use but it is unclear how efficient exogenous applications of mycorrhiza inocula are. Nurseries have increasingly used commercial inoculum, and data showed that it is a great way to improve productivity for some annual plants (see figure). But science is still lacking to evaluate if the symbiotic relationship can last for trees after planting and how it translates to the orchard life with respect to tree performance and longevity. An efficient way to foster relationship between plants and mycorrhizae is to adopt mycorrhizae-friendly practices. In general, low input agriculture systems that rely on soil fertility and microbial activity are conducive to mycorrhizae. One of our recent studies compared organic and conventional farming practices in California citrus orchards and showed that the former has much higher mycorrhizae biodiversity and more frequent association with trees than the later. Mycorrhizae are sensitive to conventional agrochemicals. Foliar fungicide application runoffs and glyphosate treatments have been shown to negatively affect these fungi. Similarly, high input of inorganic nitrogen and phosphorous are detrimental to mycorrhizae. In general, practices that increase organic matter in soils (compost, manure), planting of cover crops, low to moderate dose of N and P organic fertilizers and avoidance of soil disturbance (tillage) favor mycorrhizae establishment and biodiversity. Yet, a lot more needs to be accomplished before we can fully exploit this powerful underground resource.