UCCE Ventura County- Blogs

Rodents Coming Out of the Hills

There have been a number of calls about damage to citrus tree trunks.  Lemon is especially delicious, it seems. As the hills have dried and we haven't had much fall rain, rodents who like to eat the green part just below the bark of the trees are looking for stuff to eat and they've decided trees are good enough.  It's possible to tell what animal is doing the damage based on the position in the tree where the damage is happening.

Gopher girdling damage is usually belowground.  Vole damage usually starts at ground level and will extend up to maybe 6-8 inches aboveground.  Occasionally, vole girdling damage will extend an inch or two belowground, as well.  Mouse (such as deer mice), roof rat and ground squirrel damage can occur anywhere on the tree.  Rabbit damage can occur from ground level up to perhaps 2-3 feet aboveground (although damage above 1.5 feet aboveground is fairly uncommon) depending on if the damage is from cottontails or jackrabbits (jackrabbits reach higher on the tree).

As soon as they find more tasty things to eat as the hillsides green up, the damage will let up.  But rats will always find tasty fruit in the trees.

Read more about managing rodents and other vertebrates:

https://ipm.ucanr.edu/agriculture/citrus/managing-vertebrates/#gsc.tab=0

Actually rabbits are Lagomorphs, not rodents. Look it up.

 

vole damage

HLB Tolerance

By Manjul Dutt, Sheetal Ramekar and Gary England

The grapefruit was created by chance from a cross between a pummelo and a sweet orange. It was first discovered in Barbados in the 18th century.

All the commercially sold grapefruits today trace their roots back to the Duncan variety of grapefruit. Cultivars existing today were developed through natural and induced mutations as well as seedling selections. As a result, all grapefruits are very similar to one another, differing mostly in small variations in their DNA.

A recent study on a newly discovered bud sport of the Flame grapefruit, found in Bill Lennon's citrus grove in Lake County, Florida, has highlighted how natural variations can offer hope in the fight against HLB. This bud sport displayed several improved qualities. These include darker leaves, better canopy density and improved HLB tolerance compared to the Flame grapefruit from which it was derived.

Preliminary data seems to indicate that this bud sport is later maturing than regular Flame, and fruits reach maturity in early January under endemic HLB conditions (Figure 1).

Biochemical tests revealed higher chlorophyll content and lower starch accumulation, suggesting that the bud sport manages resources more efficiently under HLB stress.

Certified budwood of this new selection is freely available from the Florida Department of Agriculture and Consumer Services Division of Plant Industry's Citrus Budwood Program for nurseries and growers interested in producing it.

Manjul Dutt is an assistant professor, and Sheetal Ramekar is a postdoctoral research associate — both at the University of Florida Institute of Food and Agricultural Sciences (UF/IFAS) Citrus Research and Education Center in Lake Alfred. Gary England is a UF/IFAS emeritus Extension agent.

HLB Deformed Citrus

hlb defprmed citrus

IPM for Landscapers

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ground squirrel

California HLB Quarantine Area Expanded

Agricultural officials recently expanded the areas in California quarantined for citrus greening disease [also known as huanglongbing (HLB)], which is spread by Asian citrus psyllids. The quarantined area in Orange and Riverside counties was increased by a total of approximately 31 square miles. The U.S. Department of Agriculture Animal and Plant Health Inspection Service (USDA APHIS) in cooperation with the California Department of Food and Agriculture (CDFA) took this action.

The quarantine expansions were made because of citrus greening detections in plant tissue samples collected from residential properties in Orange and Riverside counties. There are approximately 3 acres of commercial citrus in Riverside County impacted by this expansion.

USDA APHIS is applying safeguarding measures on the interstate movement of regulated articles from the quarantined areas in California. These measures parallel the intrastate quarantines that CDFA established on Oct. 22. This action is necessary to prevent the spread of citrus greening to non?infested areas of the United States.

The specific changes to the quarantined areas in California can be found on the APHIS Citrus Greening and Asian Citrus Psyllid website. USDA APHIS will publish a notice of this change in the Federal Register.

Additional information may be obtained from USDA APHIS National Policy Manager Abby R. Stilwell (abby.r.stilwell@usda.gov or 919-323?6296), or from Assistant National Policy Manager Daniel Murphy (daniel.m.murphy@usda.gov or 775-221-9237).

Learn about other HLB quarantine expansions in California earlier this year.

HLB symptoms

Fire Effects on Soil

Fires are common and we usually just think of the effects it has on plants and structures, but what impact can it have on soil. I recently came across a guide book from the US Forest Service that addresses how to evaluate fire impact on soil. Following wildfires in the United States, the U.S. Department of Agriculture and U.S. Department of the Interior mobilize Burned Area Emergency Response (BAER) teams to assess immediate post-fire watershed conditions. BAER teams must determine threats from flooding, soil erosion, and instability. Developing a postfire soil burn severity map is an important first step in the rapid assessment process. It enables BAER teams to prioritize field reviews and locate burned areas that may pose a risk to critical values within or downstream of the burned area. By helping to identify indicators of soil conditions that differentiate soil burn severity classes, this field guide will help BAER teams to consistently interpret, field validate, and map soil burn severity.

The guide is here:

https://www.fs.usda.gov/rm/pubs/rmrs_gtr243.pdf

 

field guide to soil burn

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