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

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.

Rodenticides

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

Help the environment this Earth Day, which falls on Sunday April 22 this year, by installing insectary plants! These plants attract natural enemies such as lady beetles, lacewings, and parasitic wasps. Natural enemies provide biological pest control and can reduce the need for insecticides. Visit the new UC IPM Insectary Plants webpage to learn how to use these plants to your advantage.

Flowering insectaries also provide food for bees and other pollinators. There are both greater numbers and more kinds of native bees in fields with an insectary consisting of a row of native shrubs planted along the field edge (called a hedgerow). Native bees also stay in fields with these shrubs longer than they do in fields without them. Therefore, not only do insectaries attract natural enemies, but they can also boost crop pollination and help keep bees healthy.

Sources:

• Flower flies (Syrphidae) and other biological control agents for aphids in vegetable crops. (PDF)
• Good news for hedgerows: no effects on food safety in the field.
• Hedgerow benefits align with food production and sustainability goals.
• Habitat restoration promotes pollinator persistence and colonization in intensively managed agriculture. (PDF)
• Reducing the abundance of leafhoppers and thrips in a northern California organic vineyard through maintenance of full season floral diversity with summer cover crops.

One point I always make is that the sooner you control annual weeds, the better. This reduces crop-weed competition, along with a host of other issues caused by weeds (we'll save that for another blog). But the real key to forward-looking weed management is to kill the weed before it produces seeds. Once seeds are produced, they contribute to the seed bank, pretty much ensuring that the weed population will be a continual problem.

But suppose you miss some weeds that are starting to flower but the flowers aren't open yet? I think most growers will just pull or cut the weed and leave it in or near the field.  

I want to show you a time-lapse video I took. I cut the flowering stem off of an annual sowthistle plant and took a photo with a special camera every minute for 6 days. As you can clearly see, even though the stem was no longer receiving water or nutrients from the soil, at least the flower bud continued to mature and produce seeds. Now, having said that, I have not germinated the seeds to see if they are viable, but there is a good chance they are. Click HERE for video. It's about 1 1/2 minutes long, but most of the action happens in the first 50 seconds.

So the take home message - if the weeds have flower buds starting to open, remove them to covered piles, trash cans, or other area where they will not be a source of new weed seeds. 

 

Every year, California receives, on average, six new exotic invasive pests of concern; that's about one new pest every 60 days. These may be plants, insects or other arthropods, mollusks, plant pathogens such as fungi and bacteria, vertebrates, or any other organism not native to our state and with the capacity to negatively impact agriculture, urban environments and/or natural ecosystems. These invasive pests enter California on plant material and other biological substrates, as hitchhikers on trade goods and in ship ballast water, and sometimes even because of smuggling operations. Without the natural enemies that kept them in check in their native lands, they are free to reproduce and wreak havoc. Such pest invasions may then lead to destruction or alteration of habitat, loss of agricultural trade revenues, pronounced losses in agricultural production, and increases in pesticide applications.

The best way to combat such invasions may be through robust exclusion, inspection, early detection, and quarantine programs. Once established, they are best managed using classical and conservation biological control and the decision-making process of integrated pest management (IPM), described in detail in an earlier blog post. Urban agricultural environments are not immune to these invasions and may even be more at risk since urban environments contain many likely routes of introduction and have often been identified as point sources for invasive pests. In this article we will review the biology, ecology, and management of three recent pests that may increasingly be found in urban gardens and other urban ag environments.

Asian citrus psyllid and the huanglongbing pathogen: First found in Southern California in 2008, the Asian citrus psyllid (ACP), Diaphorina citri, feeds on citrus and related plants in the Rutaceae family, sucking sap and injecting toxins that distort new growth. Even worse, however, the psyllids can transmit an incurable citrus disease, huanglongbing (HLB) or citrus greening, from plant to plant. Currently, the psyllid's distribution is limited to urban Southern California and small parts of the citrus production areas in the San Joaquin Valley. The bacterial disease HLB is thankfully not established in California, but it has been detected (and eradicated) in urban Los Angeles County and intercepted recently at a port-of-entry in San Mateo County. If you grow citrus, make sure to check new growth during spring and fall to look for psyllid nymphs and the distinctive waxy tubules they excrete. Report any suspect finds to your County Agricultural Commissioner's office. Make sure to comply with the management tactics prescribed by these authorities; trees across the state depend on it. To learn more about ACP, HLB, management tactics, and other related topics please visit the following links: 

PESTNOTES - UC IPM Online: Asian Citrus Psyllid and Huanglongbing Disease

Center for Invasive Species Research: Asian Citrus Psyllid

UC scientists release a natural enemy of Asian citrus psyllid

 

Brown marmorated stink bug (BMSB): This large (5/8”) stink bug from eastern Asia has been an established pest in the eastern United States since 2001. Though it has been intercepted many times in California over the years, probably because of its ability to hitchhike on and in outdoor household items (such as patio furniture) and firewood, it has only recently (sometime between 2006 and 2013) become established in the state. The BMSB, Halyomorpha halys, is a key agricultural pest, reportedly attacking over 100 plant species using piercing mouthparts to suck juices and inject tissue-damaging enzymes. Damage is expected to be worst on pome fruits (apples, pears), stone fruits (peaches, nectarines), legumes, corn, tomatoes, and peppers. Stink bugs are known to aggregate in large numbers in fall, sometimes entering homes and other structures to escape harsh winter conditions. BMSB can be distinguished from several native stink bug species by two white bands on the antennae. The current distribution in California is unknown, so if you think you find BMSB you should contact your County Agricultural Commissioner's office to confirm and document its presence. To learn about BMSB identification and management, please visit the following links:

PEST NOTES - UC IPM Online: Brown Marmorated Stink Bug 

Pest Alert - UC IPM Online: Brown Marmorated Stink Bug

Center for Invasive Species Research: Brown Marmorated Stink Bug

  

Bagrada bug: This small (1/4”) relative of the BMSB, also called the painted bug, preferentially attacks many plants in the mustard family (Brassicaceae), including crops such as broccoli, Brussels sprouts, cabbage, and kale, as well as related ornamental plants such as sweet alyssum, stock, and candytuft. Native to Africa, bagrada bug was first found in urban southern California in 2008 and has been slowly moving up the coast and north within the Central Valley.  Most recently, the pests has become established within many urban gardens in the San Francisco Bay Area and in small farms in the Capay Valley. Damage is most severe on newly-planted seedlings; stunting and death are common when infestations are large. The brightly-colored (orange, black, and white) bugs are sometimes confused with the similarly-colored harlequin bug, a common American species, though these are three times larger and lack any white coloration. Similar to the BMSB, bagrada bugs may aggregate and enter structures and other protected areas during winter. As with the other invasive pests discussed, if you think you find bagrada bug in your area, then please alert your County Agricultural Commissioner's office, especially in areas where these insects have yet to be found. To learn more about bagrada bug identification and management, please visit the following links:

PEST NOTES - UC IPM Online: Bagrada Bug

Pest Alert - UC IPM Online: Bagrada Bug

Center for Invasive Species Research: Bagrada Bug