Monthly tips are categorized by: To-Dos, What to Plant, or Pests and Diseases. Scroll through the list to see items in each category.
- Citrus Fertilizing
In California, most soils contain adequate nutrients for citrus growth, except nitrogen. One-year old trees will need 1/10 of a pound of nitrogen, while mature trees need approximately 1-1/2 pounds. These amounts should be divided into three different feedings in April, June and August.
Blood meal without all the fillers is an excellent source of nitrogen, or you can purchase a balanced product that contains zinc. Spread the fertilizer evenly over the entire root area and water in.
- Clean Up Fallen Fruit
Pick up fallen fruit daily to prevent attracting critters or diseases. If your fruit is being eaten at night then rats are the likely culprit, if it's during the day it may be squirrels. Holes, rather than bites, are made by birds. In addition to harvesting regularly, ripening fruit can be protected with a netting fine enough to exclude birds and small animals- July, August
Composting is a good way to repurpose yard and kitchen waste, and it provides a free method to feed plants and improve soil structure. If you are unsure about how to begin composting, take a look at this simple how-to compost page. You can also go to the UCCE Composting Education Program website to learn more about free two-hour classes offered throughout the county.
As the weather warms up, compost piles dry out faster. Keep compost piles as damp as a wrung-out sponge to keep organisms alive and working on decomposing yard waste. Turning the pile to incorporate more oxygen also supports life in the compost pile.- January, February, March, April, May, June, July, August, September, October, November, December
- Consider Dehydrating Some Of Your Harvest
If you have more fruit than you know what to do with, dehydration can be an excellent way to preserve it. Apricots, apples, pears, figs, and tomatoes are all great candidates for drying. While making jams, jellies, cobblers, and pies is one way to use up an abundant harvest, they add fat and sugar to our diet, dried fruit can be a healthy alternative! Onions and garlic can also be dehydrated to last indefinitely.
Also see the publication on Dehydrating Basics by the UCCE Master Food Preservers of Amador/Calaveras Counties.- August
Deadheading means removing spent blossoms from your plants. Not all plants need deadheading, but if the flowers stay on the plant and become unattractive (think roses, dahlias, marigolds, coneflowers, geraniums and many more), then consider a little pruning. The technique varies by plant; some spent flowers can be snapped off by hand (dahlias), others are better done with hand pruners (roses), and some can be sheared off all together (lavender). You'll not only make the plant look better, you'll stimulate additional blooming for plants that have a long blooming season.- April, May, June, July, August, September
- Deep Watering Trees
Even if a tree gets watered every time the lawn does, it needs deep watering twice during the summer. Use a soaker or drip hose around the tree at the drip line and let it slowly drip for 2 to 3 hours. A mature ornamental tree or street tree may not need any water. Mature fruit trees should watered by filling a watering basin around the tree every three or four weeks. Young fruit trees need watering every two weeks. Don't let lawn sprinklers hit tree trunks as this may cause crown rot and damage the tree.- July, August, September
- Drip Irrigation
Consider various forms of irrigation conversion! Irrigation systems, especially drip and micro-sprinklers, have drastically improved over the last few years. For example, there are kits that convert pop-up sprinkler heads to low-flow systems. The conversion kits include a pressure regulator to control changes in pressure and a filter to improve water quality. Water usage is reduced through better water management, control of distribution and less loss from evaporation. Other advantages include :
- Water is placed more accurately and efficiently in the root zone, it is applied at a slow rate that reduces loss from runoff.
- Dry soil between plants allows you to work in the garden between irrigating.
The key to success is watering long enough to supply adequate water to the root zone. Inappropriate watering commonly damages landscape plants. As with any irrigation system, they are efficient only when soil around the plants being irrigated is regularly monitored for proper moisture levels (Reference: UC Pest Note Poor Water Management, Poor Drainage).- March, April, May, June, July, August, September
- Fertilizing Fruit Trees
As fruit starts to develop, trees and vines use nutrients to help with this energy-intensive task. This is a good time to plan a strategy for fertilizing your trees.
In the first year, a very light application of nitrogen (N) is desirable for most soils. Do not make first year applications before six to eight inches of new growth occurs. Split applications are safest, one or two months apart, so one application might be made this month.
After the first year: research indicates that summer fertilizer applications (August to mid-September) are more efficient than late winter (traditional) applications.
Fully mature fruit trees may not need fertilizing. Read more at UC Home Orchard Fertilization page.- February, August
- Fertilizing Ornamentals During Drought
One way to manage plants during drought is to reduce the amount of fertilizer used. While plants need nutrients to survive and be healthy, excess fertilizer promotes additional growth, which then demands more water.- May, June, July, August
- Fresh Fruits and Vegetables Without a Garden!
If you like the freshest possible produce but don't have the space or time to grow your own, find a certified Farmers Market or a farm selling directly to consumers. The County of Santa Clara website has a Farmers Market page with links to certified Farmers Markets and the Country Crossroads map shows where you can buy more than 100 commodities directly the farm source.- June, July, August, September
- Garden Sanitation
Remove spent blossoms, fruit, and other plant parts as your plants finish producing. Dead and decaying plant parts can attract pests and give them safe places to breed. If pests are given a nice place to spend the winter, their populations are likely to be much higher next year.- July, August, September
- Gather Herbs for Drying
Itching to do something in the garden but not sure what? Cut back some of your oregano or mint and dry it. In our climate you will likely have herbs year-round, but drying some can help you when times are busy, or perhaps your relatives in the mid-west would love some home-grown, dried herbs, for a holiday gift this year. Simply hang it upside down in a cool, dry place. Why not try putting some on a cookie sheet on your dashboard to make use of the hot temperatures in your car without turning on an oven or a dehydrator?- August
- Hand Pollinating Squash
Squash plants have male and female flowers on the same plant. The male flowers grow on stalks and the females are attached to the end of the fruit. If the squash grows a few inches and then starts to die, it is not getting pollinated. You can do it yourself by taking the center (anther) of the male flower and rubbing it on the center (stigma) of the female, or transferring the pollen with a toothbrush or q-tip. It is important to use only freshly opened flowers. They open early in the morning and are receptive for only 1 day. Or if you are fortunate a bee will do it for you.
Male blossom on the left, female on the right.- July, August
- How to Tell if Fruits and Vegetables Are Ready to Pick
The UC Davis Postharvest Technology website was designed for commercial growers, but the information on how to tell When Fruits and Vegetables are Mature is handy for home gardeners as well. There's also information about how to Store Fruits and Vegetables for Better Taste.- July, August, September
- Irrigation and Graywater
As temperatures rise, irrigation becomes more important. Container plants will begin to dry out and need to be checked every few days. Inspect irrigation systems for leaks, clogged drip emitters, misaligned sprinkler heads, and other problems which could waste water. Make sure the water is going to the root zones of the plants.
Things to consider:
Use a smart irrigation controller. These help adjust watering based on local conditions. Learn more about smart controllers.
Collect water from the shower as it heats up and use it to water any plants.
Use graywater from garage sinks and washing machines to water ornamentals and lawns. UC has a publication titled Use of Graywater in Urban Landscapes in California.- April, May, June, July, August
- Keep Up With Your Vegetable Harvest
The middle of summer is a particularly busy time of year for vegetable gardeners. It can be a challenge to keep up with harvesting—beans can become swollen and tough and zucchinis can become baseball bats! It's particularly important to keep up with plants such as beans because the production of mature seeds (inside the pod) signals the plant to stop producing. Tomatoes can split and rot on the vine in exceptionally hot weather.- July, August
- Lawn Care
If you have a lawn, be sure to water it as early in the morning as possible to avoid evaporation. This also helps reduce fungal diseases by giving grass time to dry out during the day. Poor watering practices are the main reason for dead and dying areas in lawns and a common source of urban runoff.
Check lawns for weeds such as spurge, burr clover, and whatever happens to invade your neighborhood. When mowing in the summer, set the blade height as high as you are comfortable with—taller grass shades the soil, reducing evaporation and protecting valuable earthworms in the soil. Use the UC Guide to Healthy Lawns to learn more about mowing, irrigating, fertilizing, detaching and aerating. Better yet, take advantage of the County's Lawn Replacement Program!- May, June, July, August, September
- Mulch - a Gardener's Best Friend
Mulching around your plants has many benefits. It holds in moisture by reducing evaporation from the soil, keeps weed seeds from being able to germinate, and moderates the temperature of the soil so that it doesn't vary as much with direct sun and changes in air temperature. Mulching can cool the soil for plants like blueberries and it will help hold some heat in for summer vegetables as the air gets cooler.
Mulch will guard against soil erosion when the rains start. Organic mulch such as wood chips or bark will slowly break down and improve your soil over time.
It is recommended to keep mulch six inches away from trunks and twelve inches away from buildings. If you are confused about the difference between compost and mulch, then UCCE's Soil Management - Compost versus Mulch Comparison will help.
Many local tree trimming companies are happy to deliver free wood trimmings that can excellent mulch - just be sure that the trimmings are disease- and palm- and eucalyptus- free. This can be hard to guarantee. Straw (not hay) from the local feed store can also be inexpensive, effective mulch.- May, June, July, August, September
- Preserving Fruits and Vegetables
Interested in how to preserve fruits and vegetables? UC Food Safety has lots of information including "Safe Handling of Fruits and Vegetables", "Safe Methods of Canning Vegetables", "Chart on Storing Fresh Fruits and Vegetables", and more. Visit their web page UC Home Preservation and Storage Publications for more details.- August, September
- Prune Apricot and Cherry Trees
Apricot and cherry trees should be pruned at least 6 weeks before the first rain falls. If it rains before the pruning cuts heal, the tree are more susceptible to infection by Eutypa spores that cause dieback. See UC Pest Note on Eutypa Dieback. The UC Home Orchard website has more advice on Pruning Apricots.- August, September
- Pruning Hydrangeas
For better-looking hydrangeas, prune out the spent blossoms. Hydrangeas are fast growing and need pruning to control size and shape. Cut out the older stems that have flowered, leaving the ones that have not flowered. For the biggest flower clusters, reduce the number of stems. For lots of medium size flowers, keep more stems.- August
- Pruning Roses to Minimize Disease
A chemical-free way to keep roses healthy and minimize disease associated with foggy summer mornings is to prune to improve air circulation. Think of your rose bushes as large vases, with open centers. Good air circulation allows the morning dew to dry, and helps prevent rust and powdery mildew. UCCE's Center for Landscape and Urban Horticulture has more info about the Fundamentals of Pruning Roses. The UC Pest Note on Roses has more about general cultural practices and weed control.- May, June, July, August
- Soil Solarization
Soil solarization can be used to control diseases, nematodes and weeds by baking everything under plastic sheeting.The best time for solarization of soil is from June to August. Leave the soil covered for 4 –6 weeks. Refer to the UC Pest Note on Soil Solarization for Gardens & Landscapes.- June, July, August
- Tomato Bottom Scarring
Sometimes scarring can be seen on the bottom (blossom end) of tomatoes. This can be caused by weather conditions such as cool and cloudy weather at bloom time, making the blossom stick longer to the small fruit. The fruit is perfectly good to eat with the damaged part cut out. Some large heirloom tomatoes are more susceptible to this condition.
Also known as catfacing.- June, July, August
- Water the Roots, Not the Plants
It's tempting to get the hose out and spray your dry, thirsty plants, but you don't want to waste water. Keep their feet nice and cool, but resist the urge to squirt the leaves unless they need a cleaning (for dust or white fly for instance). While it's a common belief that daytime water on the leaves will burn them, it's not very likely based on a study by scientists - the water will evaporate and not do your plants much good during the day, and could encourage fungal pathogens if wet overnight.- June, July, August
- Watering Hydrophobic Soil
Just as a dry sponge repels water, overly dry soil can do the same thing. This dried out soil is called hydrophobic. Hydrophobic soil can waste a lot of water as water drains away from the plant's root zone.
In pots: learn more about how to re-wet very dry soil on our Watering Hydrophobic Soil page. In the yard: setting sprinklers to run for 5 minutes, waiting for the water to soak in, and then running for a longer time can prevent water loss due to hydrophobic soil.- May, June, July, August
2. What to plant
- Don't Plant an Invasive Plant
According to PlantRight, so-called invasive plants "escape into open landscapes and cause a variety of ecological problems. They displace native plants and wildlife, increase wildfire and flood danger, clog valuable waterways, degrade recreational opportunities, and destroy productive range and timber lands."
PlantRight has identified the following as invasive in Northern California: Green fountain grass (Pennisetum setaceum), Periwinkle (Vinca major), Pampas grass (Cortaderia selloana), Highway iceplant (Carpobrotus edulis), Mexican feathergrass (Stipa / Nassella tenuissima), Yellow Flag Iris (Iris pseudacrorus), Water Hyacinth (Eichhornia crassipes). For details and recommended alternatives, please consult their website.- April, May, June, July, August, September
- Vegetable Planting Chart
Wondering what vegetables can be planted now? To get the best success—whether planting from seed or transplants—refer to our Santa Clara County Vegetable Planting Chart. It's based on our own garden experiences.- February, March, May, June, July, August, November
3. Pests and Diseases
- Ailing Ornamental Trees
If you have an ailing tree, here are some questions you can ask yourself to begin diagnosing the problem: is the entire canopy of the tree affected? If the answer is yes, you can reasonably guess that something is wrong below the soil. A lack of nutrients (refer to the UC Pest Note on Mineral Deficiencies) will likely cause the leaves to either die (necrosis) or lose color (chlorosis). Too much or too little water will also cause foliage problems (See UC Pest Note on Poor Water Management, Poor Drainage).
If only parts of the tree are affected, it is likely your problem is above ground. Is there a pattern to the distress? You can rule out or suspect sunscald by determining which side of the tree faces the harshest sun (UC Pest Note on Sunburn).
What kind of tree is it? Is there new growth? If there is, that’s a great sign that a single event rather than an ongoing problem distressed your tree. The UC IPM website will direct you to species-specific pests and disorders to begin diagnosing your tree's ailments.- August
- Ant Control
On outdoor and sometimes indoor plants, ants protect and care for honeydew-producing insects such as aphids, soft scales, whiteflies, and mealybugs, increasing damage from these pests.
Ants are among the most prevalent pests in households. UC IPM offers steps to follow in an Ant Emergency.
Ant management requires diligent efforts and the combined use of mechanical, cultural, sanitation, and often chemical control methods. It is unrealistic and impractical to attempt to totally eliminate ants from an outdoor area. Focus your management efforts on excluding ants from buildings or valuable plants and eliminating their food and water sources. Reducing outdoor sources of ants near buildings will reduce the likelihood of ants coming indoors.
Ants on Trees and Shrubs
When numerous ants are found on plants, they are probably attracted to the sweet honeydew deposited on the plants by honeydew-producing insects such as aphids or soft scales. Ants may also be attracted up into trees or shrubs by floral nectar or ripening or rotten sweet fruit. These ants can be kept out by banding tree trunks with sticky substances such as Tanglefoot. Trim branches to keep them from touching structures or plants so that ants are forced to try to climb up the trunk to reach the foliage.
When using Tanglefoot on young or sensitive trees, protect them from possible injury by wrapping the trunk with a collar of heavy paper, duct tape, or fabric tree wrap and coating this with the sticky material. Check the coating every one or two weeks and stir it with a stick to prevent the material from getting clogged with debris and dead ants, which will allow ants to cross. Ant stakes with bait can also be used around trees.
For more information about what ant baits and insecticides to use, please consult the UC Pest Note on Ants.- June, July, August
Birds can cause extensive damage to tree fruit crops. Unlike squirrels, birds are more likely to peck at one piece of fruit until it’s gone. If they are doing too much damage, netting over a tree can keep them away from the fruit. If you use visual repellents (such as Mylar streamers or noisemakers) to frighten them, be sure to vary the method so that the birds don’t become immune to the effects. Read the UC Pest Note on Birds on Tree Fruits and Vines for more information.- July, August, September
- Bitter Pit on Apples
Bitter pit is a physiological disorder that affects many varieties of apples. The condition develops after fruit has been picked. It is caused by low levels of calcium in fruit tissues, and fruit will develop small brown, sunken lesions that become dark and corky. Fruit that develops on vigorous, leafy, upright growing branches is more likely to be affected than fruit on spurs or horizontal wood. Highly susceptible cultivars include Red Delicious, Granny Smith, Golden Delicious, Jonathan and Gravenstein. The condition generally is caused by vigorous leaf growth, poor fruit set, and hot, dry growing conditions, which cause calcium to the diverted to the leaves. Spraying with a calcium nitrate solution (one-half teaspoon per gallon of water) just after bloom and again six weeks later may help.
The UC Postharvest Technology Center website has more information.- August
- Brown Marmorated Stink Bug
Native to Eastern Asia, this pest was introduced to the United States in the 1990's and has been found in Santa Clara County. Described as “one of the worst invasive pests we’ve ever had in California” by UC Cooperative Extension advisor Chuck Ingels, this insect affects many different crops and is a serious residential problem. There's more information in the UC Pest Note on Brown Marmorated Stink Bug. View a map showing the distribution of the BMSB in California.*file246257*- August
- Brown Spots on Apples
You may have noticed small areas just under the skin that are brown and corky. The spots may even appear after harvest. This is called bitter pit and is caused by a calcium deficiency early in the spring. Bitter pit can be treated by spraying the leaves with calcium nitrate at the rate of one tablespoon per gallon of water in the spring just after bloom and again one or two months later. Mark your calendar as a reminder.- August, September
- Codling Moth
"Worms" in your apples are actually the larval form of the codling moth. Codling moth larvae can cause a great deal of damage to apples, pears, plums and walnuts by penetrating the fruit and boring into the core.
Trees should be monitored every week for signs of infestation. Infested fruit should be removed and discarded, to break the coddling moth life cycle. Sanitation is an important non-chemical step in controlling this pest. Make sure to pick up fallen fruit promptly, and pick apples with holes that are still on the tree. This will keep future populations down.
Pheromone traps can be hung in isolated trees. But if you have just one apple tree don't bother. You will just attract codling moths to your tree.
Fruit can be bagged for protection, but this is a very labor intensive method. Heavy infestations may require the use of pesticides on the moths, before fruit is affected. For more information, refer to the UC Pest Note on Codling Moths.- March, April, May, June, August, September, October, November
Although there's no such thing as a deer-proof plant, some can be called deer-resistant. Plants with strong smells, woolly or hairy leaves, or prickly or thorny parts are less appetizing to deer. Other strategies include deer repellents, enclosing plants in wire cages, netting, or tall fences. Read more in the UC Pest Note on Deer and use our search for Deer Resistant Plants.- August
- Giant Whiteflies
If you see white beardlike filaments handing from the leaves of your hibiscus, bird of paradise, or other plants, you may have giant whitefly. Another sign is the distinctive wax spirals on the undersides of the leaves. They can usually be controlled by washing them off or removing affected leaves. For more information see UC Pest Note on Giant Whitefly.- August
- Integrated Pest Management and Beneficial Insects
Our gardens contain far more beneficial insects than pests. Any time pesticides are used, both good and bad insects die. This upsets garden ecosystems. Use of pesticides can also pollute waterways and may put our children and pets at risk, along with other environmental consequences. We can dramatically reduce pest problems by practicing Integrated Pest Management, which includes planting native species, following good cultural practices, and encouraging beneficial insects, such as lady beetles, lacewings and soldier beetles- March, April, May, June, July, August, September, October
- Mosquitoes May Be Breeding In Your Yard
According to Santa Clara County Vector Control, many people are unaware they may be raising mosquitoes in their backyard, they offer tips on identifying possible Mosquito Breeding Grounds. UC has created a video titled Don't Let Mosquitoes Breed in Your Yard.- May, June, July, August, September, October
Have you found snail empty shells stashed in out of the way places, hollowed out Navel oranges, Meyer lemons with no skins, tomatoes with bite marks, fruit with holes gnawed in them or grape skins or cherry tomato skins scattered around? This could indicate the presence of rats. The UC IPM Pest Note on Rats provides a wealth of scientific information.
Rats show up when your citrus, tomato or fruit first start to ripen. Rats are agile climbers and usually live and nest in shrubs, trees, and dense ground cover like ivy. Good sanitation is required. Garbage and garden debris should be eliminated. Use tight fitting lids on garbage cans. Thin out dense vegetation to make the habitat less desirable. Mow ivy once a year to the ground. Climbing ivies on fences or buildings should be removed.
Trapping is the safest and easiest method for controlling rats. The simple snap trap is effective. The most important thing about trapping rats is to have lots of patience and keep trying. Wet some oatmeal enough for it to hold together, add dog or cat kibble or bits of lightly cooked bacon mixed in. Tie a walnut to the trigger and add a dab of peanut butter.
Other baits to try are peanut butter and fresh fruit, but try to have something tied to the trigger. Set traps where rats are likely to travel or where you see droppings along fence lines or buildings. Bait the trap but do not set it for several days. Try different baits in multiple traps until you find one the rats like. Put two traps facing each other. After the rats are accustomed to being fed, then set the traps. If the rat springs the trap but doesn't get caught, move the traps to a different place and change to different baits. Rats prefer secluded spots and will be less wary there. Be sure to secure the trap with a wire or nails. Above all be patient and use multiple traps.- March, April, July, August, September
- Sooty Mold
Aphids, scale, mealybug and whitefly all excrete sticky honeydew that is colonized by sooty mold fungi. By itself, the fungi cannot kill the plant but it can coat the leaves to the extent that sunlight is prevented from reaching the leaf surface. A strong stream of water will wash the mold off leaves. The mold can be washed off fruit with mild soap and water. See UC Pest Note on Sooty Mold for more information.
Ants protect the sucking insects from their predators in order to eat the honeydew. Keep ants out of trees and away from honeydew-producing insects by applying a sticky compound such as Tanglefoot on a tape wrapped around the trunk.
Trim tree limbs touching buildings, fences or other access points as well. Baits such as ant stakes placed under trees and shrubs may help reduce ant foraging in some cases.
For ant information, see the UC IPM Pest Note on Ants.- August, September, October, November
- Squirrel Control
Squirrels can be particularly annoying because they tend to take one bite out of each piece of fruit, rather than eating the whole thing and leaving the other fruit intact. They are difficult to control, but you can try some of the methods recommended in UC Pest Note on Tree Squirrels and UC Pest Note on Ground Squirrels.- June, July, August
- Sunscald on Fruits and Vegetables
Fruits and vegetables can get sunburned in the summer heat. This is more commonly called sunscald and it frequently affects peppers, tomatoes, and persimmons. The leaves shield the produce from the sun, so it helps to make sure the plants have sufficient fertilizer and water for a healthy plant. You can cut out the damaged parts and eat the rest of the fruit.- July, August
- Tomato blossom end rot
A brown depression on the bottom of tomatoes is usually blossom end rot. This disorder is related to a calcium deficiency aggravated by irregular watering. Since most soils have adequate calcium, watering is usually the problem. Without regular watering, the calcium in the soil cannot reach the plant. Mulching can help. Water tomatoes regularly. Avoid flooding them so the roots sit in water.- July, August, September
- Tomato Russet Mite
Tomato russet mites deplete juice from the cells of leaves, stems and fruit. They usually start at the base of the plant and move upward. If not controlled, these pests can kill plants. At first sign of damage, treat with sulfur dust or a spray solution of wettable sulfur and spreader-sticker. More information ia found in UC Pest Note on Tomato Russet Mite.- June, July, August
- Verticillium Wilt
Verticillium wilt is a soil-borne fungal disease that damages plant veins. The damage is characterized by affecting one side of the plant. The leaves may wilt and turn brown, dying upward from the base of the branch to the tip. Dead leaves often fall, but may not. Mildly affected plants may survive if fertilized and encouraged into vigorous growth. The fungus can live for years in the soil.
Planting tomatoes, peppers, eggplants, and potatoes (all members of the Solanaceae or nightshade family) in the same place no more than once every three years helps reduce the fungal population to non-harmful levels. Soil solarization may eliminate Verticillium wilt from infected soils. Crop rotation with cereals or broccolis can reduce the pathogen. Avoid high nitrogen fertilizers. Plant Verticillium wilt-resistant varieties of tomatoes, potatoes or strawberries. Refer to the UC Pest Note information on Tomato, Potato, and Strawberry for species-specific suggestions.- May, June, July, August
Whiteflies are tiny, sap-sucking insects that may become abundant in vegetable and ornamental plantings, especially during warm weather. They excrete sticky honeydew and cause yellowing or death of leaves. Outbreaks often occur when the natural biological control is disrupted. Management is difficult once populations are high.- June, July, August, September
Whiteflies use their piercing, needlelike mouthparts to suck sap from phloem, the food-conducting tissues in plant stems and leaves. Large populations can cause leaves to turn yellow, appear dry, or fall off plants. Like aphids, whiteflies excrete a sugary liquid called honeydew, so leaves may be sticky or covered with black sooty mold that grows on honeydew (See UC Pest Note on Sooty Mold). The honeydew attracts ants, which interfere with the activities of natural enemies that may control whiteflies and other pests.
Management of heavy whitefly infestations is difficult. The best strategy is to prevent problems from developing in your garden or landscape. In many situations, natural enemies will provide adequate control of whiteflies; outbreaks often occur when natural enemies are disrupted by insecticide applications, dusty conditions, or interference by ants. Avoid or remove plants that repeatedly host high populations of whiteflies.
In gardens, whitefly populations in the early stages of population development can be held down by a vigilant program of removing infested leaves or hosing down with water sprays. Reflective mulches can repel whiteflies from vegetable gardens, and yellow sticky traps can be used to monitor or, at high levels, reduce whitefly numbers. If you choose to use insecticides, insecticidal soaps or oils such as neem oil may reduce but not eliminate populations. Systemic insecticides may be more effective but can have negative impacts on beneficial insects and pollinators.
For more information see UC Pest Note on Whiteflies.
- Yellowjackets and Wasps
These insects can be solitary or live in group nests above and below ground. Yellowjackets can be aggressive when defending their nests so avoid the area where possible. Paper wasps on the other hand will avoid contact. When eating outdoors, keep foods well covered. One strategy is to put out bait such as a piece of meat or an opened soda can some distance from the table before setting out the human food. Trapping the queens in the spring and workers during the summer can reduce local populations. See the UC Pest Note on Yellowjackets and Other Social Wasps for more information.- August