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UC Agriculture & Natural Resources News

Saving a Butterfly: A World Where Kindness Matters

Newly eclosed anise swallowtail, Papilio zelicaon. (Photo by Kathy Keatley Garvey)

It was a long awaited process, but it's a girl! And she's beautiful! It all began with finding two anise swallowtail chrysalids clinging last July to the fennel stems in our pollinator garden in Vacaville, Calif. To protect them from predators and the elements, we tucked them inside a zippered...

Waterprimrose shows disturbance-related dispersal along the Russian River

Uruguay waterprimrose

It may be widely understood that most aquatic and wetland weeds are spread by water currents, but the patchwork of colonizing exotic plants can be puzzling. Why do weeds establish in some places but not others? Generally, the number of propagules (seeds or plant fragments) moving in a watershed is...

Posted on Monday, July 16, 2018 at 8:50 AM
Tags: aquatic (38), Aquatic Plants (23), aquatic weeds (44)

Weed ID: Traditional Tools to Smartphone Apps

Weeds of CA

Why is weed identification important? Simply stated, because not all management strategies are equally effective against all weed species. The weed community present in a given field, orchard, or vineyard may be comprised of species that are differentially sensitive to different herbicide modes of...

Posted on Sunday, July 15, 2018 at 5:04 PM
Focus Area Tags: Agriculture Pest Management

Rat Management in School and Community Gardens.

It is important for food-safety reasons to manage rats in school and community gardens. Rats and other wildlife can carry a number of diseases that can be deposited in the form of urine and feces on fruit, vegetables, and in the soil. Rats can also directly damage fruit and vegetables by consuming the produce entirely or by gnawing on parts of it and making it unfit for human consumption. Norway rats create burrows that can compromise beds and root systems. While rats can also chew on drip irrigation and damage the tubes, it is more common for some other wildlife species to chew on these.

Managing rodents in and around school and community gardens can be difficult. One of the easiest ways to keep many rodents at bay is to remove their food source. Given that the main purpose of a garden is to grow food, it would be counter-intuitive to remove the food. However, there are many management options available to people working in gardens that are trying to protect their food from rat damage. 

Habitat modification and sanitation

Making sure that the landscape surrounding your garden is well maintained may help with the management of rats.  Lots of cover in the form of landscaped shrubs, trees, untrimmed palm trees etc. can provide a lot of harborage for rats to live in. These should be trimmed up and off the ground and should not be densely planted if they are in the area. Compost can provide ample harborage for rats.  It is recommended to not compost food in the immediate vicinity of your garden and any other green waste should be attended to regularly to make sure that rats do not establish colonies in compost piles. Feeding of wildlife is illegal in the State of California. Therefore, the provision of food for any wildlife is illegal.  The provision of food is not only illegal but it can also induce secondary pest problems like rodent outbreaks. The feeding of feral cats should also be strongly discouraged, particularly in areas where their feces could contaminate soils and other food.


Trapping can be a very useful tool for the management of rats in gardens. If you have a rat problem in your garden it is important to be realistic about the number of snap traps that will be required to manage the issue. One or two snap traps will not curb a population.  It is important to saturate an area with snap traps. Consider trapping at multiple levels also (inside beds, outside beds, on the ground, on fence lines etc.). Please be mindful of other community garden volunteers. It is important to let them know where snap traps are to reduce the risk of injury on encountering a snap trap.  If you are working in a school, snap traps can be set in the evening and checked in the morning before the children get to the garden. Snap traps should not be set in gardens during the day when children are present unless they are secured in trapping stations that can be provided under contract from a pest management professional. Snap traps can also capture nontarget wildlife such as birds and reptiles. Please be mindful of these when setting traps. Nontarget mortality can be reduced by trapping only at night or by using trapping stations that can exclude nontarget wildlife. It is not advised to live-trap any wildlife in a garden.  Once you trap a rat, under law, you must either release it right where you captured it, or euthanize it humanely.


The use of rodenticides to manage rats in and around gardens is actually not considered legal.  The majority of rodenticides available for purchase for unlicensed applicators are for structural use only.  It is permitted to have rodenticide in gardens as long as you are using it to control rodents that are invading a man-made structure such as a shed, storage barn, or building.  All rodenticides that are registered to manage rats must be applied in bait stations no more than 50ft away from the man-made structure, although some labels permit going further away (up to 100ft).


Placement of snap traps: (a) single trap with trigger next to wall; (b) the double set increases your success; (c) double set placed parallel to the wall with triggers to the outside.

Adapted from The Rat: Its Biology and Control, Howard, W. E., and R. E. Marsh. 1981. Oakland: Univ. Calif. Div. Agric. Sci. Leaflet 2896

Posted on Friday, July 13, 2018 at 6:08 PM
Tags: Community Garden (5), IPM (37), Rat Management (1), Rats (3), School Garden (6)

Christian Nansen Lab: Groundbreaking Research on Plant-to-Plant Communication

An illustration of plant-plant communication by the Christian Nansen lab, in the Plant Methods journal

Professor Rick Karban of the UC Davis Department of Entomology and Nematology, author of the landmark book, Plant Sensing and Communication (University of Chicago Press), says that plants can eavesdrop, sense danger in the environment, and can distinguish friend from foe. They can also do...

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