September Tips
Monthly tips are categorized by To-Dos, What to Plant, or Pests and Diseases. Scroll through the list to see items in each category. Also, refer to our list of tips useful for any month.
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1. To-do
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Irrigation Maintenance
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Planting Trees or Shrubs
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More information: Planting for Success
- March, April, May, September, October, November -
Weed Spotlight - Bindweed
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For more information: Field Bindweed Pest Notes
- March, April, May, June, July, August, September, Any month -
Broccoli - Multiple Harvests
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More Information: Growing Broccoli
- March, April, May, June, September, October, November, December -
Shovel Pruning
- Sometimes a plant just isn’t working out in your garden and it comes time to part ways. The most drastic form of pruning is “shovel pruning” where you finally just dig the plant out. Another term for this technique is “editing the garden.” Perhaps you saw a plant you liked in another part of the country or world. If that other location had a different climate or soil type, it may not translate well to sunny, dry California with our clay soils. Perhaps you want to garden organically but the plant has too many pests or diseases and you are having trouble controlling them with organic methods. Or maybe it simply doesn’t resemble what the tag promised. It’s okay to let go. Spring and Fall are good times for new plantings, so it is also a good time to reassess the appropriateness of what’s in your yard.
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Transplanting Vegetables
- More information: Vegetable Planting Handbook (Los Angeles Master Gardeners)
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Drought Tip - Irrigate Efficiently
- Water restrictions are being put into place all over the state due to the current drought. With over half of urban water used in landscapes, it is essential to make sure your irrigation system is efficient. Watch your plants for signs of underwatering, overwatering, or uneven watering. Consider reducing irrigation times. And make sure your water bill hasn’t unexpectedly jumped. Also, adjust systems on timers monthly as the weather changes or use an automatically-adjusting smart controller. A smart controller can make the needed adjustments after initial programming with plant, location, and other relevant information. Our Santa Clara County clay soil absorbs water slowly, so only water for a few minutes at a time to avoid runoff. Then repeat until the water penetrates to the depth of the roots. Inspect drip and sprinkler systems regularly to make sure there are no leaks, emitters are not clogged and it is watering the plants and not the sidewalk, also make sure the water is going to the root zones of the plants. If you run a hose to a plant, set a kitchen or cell phone timer so you don’t forget that the water is running. Valley Water can help residents with Water Wise Outdoor Surveys and Landscape Rebate Programs.
More information: Irrigation System Audit
- March, April, May, June, July, August, September, Any month -
Drought Tip - Lawns
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More information: Drought Resources
- March, April, May, June, July, August, September, Any month -
Harvesting Oranges
- There’s a simple way to know whether your citrus fruit is ripe: taste it! Citrus varieties differ in when they first ripen and how long the fruit holds on the tree. Harvest dates depend on the variety and the climate. For example, the normal fruit season is winter for Navel orange, and summer for Valencia orange. Until you are familiar with your particular tree, sample a fruit periodically to see if it suits your taste. Allow fruit to ripen fully on the tree, as citrus does not continue to ripen once it’s picked.
More information: Harvesting and storing citrus
- January, February, July, August, September, October, November -
Oleander
- These plants are obviously not terribly picky about conditions if they live and thrive in freeway medians. Oleander is drought tolerant once established. They rarely, if ever, need to be fertilized in our local soils or sprayed or pruned. But if you want to prune them to fit into a small yard space or to make them look like a tree rather than a bush, you can do so now. As with all pruning, first cut out any dead or dying branches. Then cut any that are deformed or growing in an undesirable direction. After that, you can prune for size and shape. Cut the plant back to a little smaller than the size you ultimately want, keeping in mind that it will re-grow. Take care not to prune off more than one-third of the plant at a time. Make cuts above nodes that face out in the direction in which you want new growth to go. All parts of the plant are poisonous so do not eat it, burn it, or work on it without gloves. The good news is that this latter quality makes it deer resistant.More Information: Oleander article, Tulare/Kings County Master Gardeners
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Inspect Roots When Planting
- If you’re adding plants to your garden this spring, check the roots before putting them into the ground. Two things are particularly important. First, look for circling roots, which can eventually strangle the plant. Straighten them out as much as possible and consider pruning them if they’re too big to spread. Second, note where the roots start growing and plant at that depth, or slightly higher to allow for some settling. If planted too deeply, plant roots cannot get enough oxygen to grow and may suffocate and die. Planting too shallow can result in root damage from exposure and excessive drying.
More Information: Fix Those Roots Before You Plant
- February, March, April, May, September, October, November -
Wildfire Effects
- We and our gardens have all been affected to varying degrees by the wildfires. If you have fruits and vegetables in your garden, you may be wondering if they are safe to eat. The simple answer is that there will likely be some chemicals in the plants, soil, and possibly the water, yet the benefits of eating the produce are thought to outweigh any potential risks. University of California Cooperative Extension Sonoma was involved in a study after the 2017 fires and a report on Produce Safety after Urban Wildfire is available for those interested in learning more. Chemicals present in smoke vary depending on what burns: toxins from building fires differ from those of trees and grasses. When working in a garden that has been exposed to smoke and fire, consider wearing a mask and gloves. Wash produce well before eating it. To help the garden recover, amend the soil with compost or fresh soil. Keep in mind the nutritional benefits of consuming fresh produce!For the oenophiles out there, UC has published a report on the effects of fire on wine grapes. “Smoke taint” can produce undesirable flavors in the wine ranging from “wet ashtray” to “sweaty socks.”More Information: Produce Safety After a Fire
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Change to Cool-Season Planting
- More information: Vegetable calendar
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Time for Seed Saving
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More information: How to Save Seeds
- August, September, October -
Watering Trees
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The amount of water trees need in the summer depends in large part on the age of the tree. Newly planted trees with shallow roots may need weekly water. Trees that are a few years old and fairly well established may need monthly watering. Mature trees with extensive root systems may not need any supplemental water. These are just VERY general guidelines. It is essential to know the water requirements of the plants. You can determine these by researching cultural needs or knowing their native habitats, the soil type and how well it retains water, and the micro-climate in which the tree is located, e.g., shaded, windy, dry. The UC WUCOLS database has information on the water needs of over 3,500 plants used in California landscapes. Always water slowly and deeply to penetrate down to the roots. Use a soaker or drip hose around the tree at the drip line and let it slowly drip for 2 to 3 hours. Don't let lawn sprinklers hit tree trunks as this may cause crown rot and damage the tree.
- July, August, September -
Deadheading
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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.
- May, June, July, August, September -
Drought Tip - Laundry to Landscape Irrigation
- A laundry to landscape system is an easy way to save water in times of drought. It can be installed easily at a low cost to send rinse water from clothes washers directly to the landscape.
Suitable plants include fruit and ornamental trees, shrubs, and ornamental annuals. It’s not applicable where the water would come in direct contact with fruits or vegetables.
More information: Laundry-to-Landscape Graywater System
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Winter Squash Harvesting
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Winter squash is ready to pick when the stem begins to shrivel. Press the rind with your fingernail, it should resist denting. Pick before the first hard frost and cure by letting it lie in the sun for at least 3 days, turning it each day. Store in a cool, dry place. It will keep for up to 5 months.
- September -
Yellowing Leaves on Gardenias
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Chlorosis is usually caused by a lack of iron in the soil. With a mild case, the veins remain green and as it becomes more severe will turn completely yellow. Treat the soil with iron chelate according the package directions.
- September -
Grass Cycling
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Leave the clippings on the lawn when mowing. This provides nitrogen for the lawn. Mow frequently so that no more than 1/3 of the length of the grass blade is cut in any one mowing. Grass decomposes rapidly and very little thatch is formed. Small amounts of thatch can actually be beneficial to a lawn, serving as a mulch. Many parks and golf courses have been doing this for years. Other uses for grass clippings include mulching for weed control and as a great addition to your compost pile. There are some cities that no longer will allow grass clippings in their dumps.
- June, July, August, September -
Garden Sanitation
- Keeping the garden clean can help keep it healthy. 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. Insect pests damage plants directly by eating material or sucking out juices and nutrients, and they also spread diseases between plants as they move around. Weeds compete with desirable plants for water and nutrients and even sunlight, so remove them promptly. Older leaves of some plants, like squash vines, may naturally turn yellow and die. Removing them early allows the plants’ energy to go into the actively growing parts. Pick up fallen fruit that can attract rodents and can also return disease pathogens to the soil and plant. It’s particularly important to remove dried-up fruit “mummies” so that the fungal spores don’t spread. Prune dying tree branches before they can fall and do damage. Some flowering plants will produce more flowers if you remove spent blooms, a process called deadheading. You can leave healthy fallen leaves in place to form a mulch and decompose naturally, or you can rake them up and add them to the compost pile with other disease-free plant material. Do not compost diseased material.
More information: What Does Plant Disease Sanitation Really Mean?
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Worm Composting
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Worm composting, also called vermiculture or vermicomposting, is a convenient way to decompose kitchen waste and provide nutrient-rich soil amendments for your vegetable garden.
The Santa Clara County Home Composting Education Program offers:
- February, June, September -
Drought Tip - Trees Come First during Drought
- More information: Tips to Keep Trees Alive
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Drip Irrigation
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- 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).
- April, May, June, July, August, September, Any month -
Lawn Care
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Make sure you are mowing to a height appropriate for your type of grass. Mow frequently enough so that only one-third of the leaf is removed at any one time.
Fertilizing is important, even if you are grasscycling, which only provides about 20% of a lawn's fertilizer needs. Grass is all leaf so the primary nutrient needed is nitrogen. Keep on top of weed removal.
Thatch is the layer of living and dead grass material (blades, rhizomes, stolons) that can build up on the surface of the lawn. A thin layer protects the soil surface and shallow roots from drying out from the sun, but a thick layer prevents water from getting through. You can remove dead grass material on the soil surface with a special thatch rake to allows water to reach the roots more easily.
More Information: The UC Guide to Healthy Lawns
- May, June, July, August, September, October -
How to Tell if Fruits and Vegetables Are Ready to Pick
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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 -
Preserving Fruits and Vegetables
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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 -
Fresh Fruits and Vegetables Without a Garden!
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If you like the freshest possible produce but don't have the space or time to grow your own, find a certified Farmers Market selling directly to consumers. The County of Santa Clara website has a Farmers Market page with links to certified Farmers Markets.
- June, July, August, September -
Consider Dehydrating Some Of Your Harvest
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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, September -
Summer Vegetables
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More information: Vegetable gardening
- May, June, July, August, September -
Keep Watering Until the Cool Weather Arrives
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September is still a warm month in Santa Clara County. Continue watering established trees and shrubs until temperatures cool down. As a rule of thumb, trees should have a couple of deep waterings during the summer, if you haven't done that, now is a good time. Use a soaker hose or drip hose around the drip line of the tree and slowly water for two to three hours. Mature fruit trees need a bit more, fill the surrounding basin every 3-4 weeks, young fruit trees need water every couple of weeks.
- September -
Late Tomatoes
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More information: Growing tomatoes in the home garden
- September -
Free the Trees
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As your young trees grow bigger and stronger, remove supporting stakes or loosen the straps as early as possible. Some movement of the tree is important to make it healthier in the long run. If the tree is able to stand on its own, it will develop a thicker trunk with a taper at the bottom.
- September, Any month
2. What to plant
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Planting Bulbs
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Be sure to plant them with the pointy side up because new growth will come from that point. A rule of thumb is to plant them twice as deep as the diameter of the bulb, but follow instructions for the specific flowers. Water them in at planting time.
More Information: Bulb Planting Schedule , Tips for Growing Bulbs
- September, October, November -
Cover Crops
- You may want to rest in the winter, but the soil life needs to remain active and protected and preferably weed-free. If you’re not planting vegetables or ornamentals in an area for a few months, try plants designed to feed the soil and the organisms that live in it. Cover crops are ideal for putting nutrients back into your soil and keeping weed growth to a minimum. Fava beans are the most popular cover crop in this area and can be seen in abundance in community gardens. Other common crops are clover, vetch, and bell beans. Different cover crops provide a variety of benefits. Beans and other members of the legume family fix nitrogen from the air and make it available in the soil and to plants. The roots also break up heavy clay soil and improve its structure. While fava beans are edible, they provide the most nitrogen to the soil if they are cut up and dug in while they are still in the flowering stage.
More Information: Choosing and Using Cover Crops
- September, October -
Asian Vegetables
- You can easily grow some vegetables used in different types of Asian cuisine and found in Asian markets. They are not necessarily native to Asia but have found their way into various cuisines. One way to decide which food to grow yourself is to choose varieties that aren't readily available or are more expensive in your local markets. It’s also fun to impress your family, friends, and neighbors with something they may not have seen growing before. Possibilities include sesame seeds, bitter melon, opo, sigua (loofah) in summer and bok choy, napa cabbage, daikon radishes, gai choy in spring or winter.
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Don't Plant an Invasive Plant
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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 timberlands."
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).
With just a little research you can avoid using plants that are unfriendly to the Bay Area. -
Attracting Bees
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Bees are pollination workhorses, increasing garden production. Many plants will not produce fruit unless flowers are pollinated. Colorful annuals, such as Cosmos, edible African Blue Basil, and Salvias attract bees. You can also allow herbs and other plants to flower to create bee-friendly landscapes.
The University of California at Davis has a garden dedicated to bees. The Honey Bee Haven website has more resources, including a list of plants they grow.
- March, April, May, June, September, October -
Cool-Season Vegetables
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If starting from seed, August is the time to start seedlings for fall vegetables. Broccoli, cauliflower, beets, and fennel will take about 6 weeks to grow to transplant size. Greens such as lettuce, spinach, arugula, chard, and kale will be ready in 4 weeks. So for planting in mid-to-late September, aim to start them in early to mid-August. You can direct seed them on the ground if you have the space. The soil should still be warm enough for seeds to germinate but shade them from the hottest afternoon sun, and keep the seeds moist.
If buying transplants from a nursery, you can wait until September. In Santa Clara County, many of the cool-season crops that are planted in September or October can be planted again in February and March. You can get in another crop before it's time to put summer vegetables in the ground.
A big advantage of cool-season vegetables is that they need less supplemental water due to lower temperatures, fewer daylight hours, and rain. There are also fewer pest problems in the winter. Cool-season vegetables grow well in temperatures ranging from 55°F to 75°F, at locations with 6–8 hours daily of sun.
Check out our videos page for videos on cool season vegetables, including a 3-session course for more inspiration.- August, September, October -
Planting Ornamentals
- Spring is when thoughts turn to planting, yet fall is an excellent time to plant perennials. You can plant many trees, shrubs, and other long-lasting plants in the fall. This applies particularly well to California native plants. Putting them in now will give them a chance to start developing strong root systems with the winter rains before they are stressed by summer heat. Make sure to water new plantings regularly until they have established good root systems and can survive with less supplemental water.
When choosing plants, consider our general Mediterranean climate as well as the microclimate of your yard. Local California natives in particular need little to no amending of the soil because they have evolved in our clay soils. Sun times, water needs, wind exposure, and soil type can all impact the success of a plant. Make sure you know how large the plant will become, even if it looks fine now in a one-gallon or five-gallon container.More Information: Mediterranean Plant List
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Winter Vegetables
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Camellias
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More information: Camellia Pests
- January, February, March, April, May, September, October, November, December -
Native Wildflowers
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More information: Native Wildflowers
- September, October, November -
Peas
- An old American tradition says that planting peas on St. Patrick’s Day will bring good luck at harvest time. But the best planting date actually depends on the climate where you live. Planting on St. Patrick’s Day in the northeast may lead to a second planting weeks later when frost gets the first batch. Yet in warmer climates like ours, we can plant weeks earlier and may even be eating peas from the garden on St. Patrick’s Day. (We can also plant them here in the fall.) You may want to soak the seeds overnight to help get them ready to germinate. They can be planted directly in the ground, about half an inch deep. Keep the seeds evenly moist until they start to sprout. Provide a trellis or some kind of support for the vertical vines if you are growing pole peas; bush peas can stand on their own.
More Information: Peas
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Herbs
- Many herbs can be grown both indoors and out, in pots or in the ground. Rosemary grows large and needs to be in the ground or a big pot. If you use basil to make pesto, you may want a row of it in the garden. Yet most herbs tend to be used in small quantities for seasoning and so they can be grown in small containers. They can be on the kitchen counter or a windowsill for ease of use in cooking. They can be on a patio if you are in an apartment or condo. And they are well suited to container gardening outdoors. Woody herbs can be grown from cuttings, lemongrass can be started from stalks from the store, and most others can be started from seed. After harvesting, many can be dried as well as used fresh.More Information: Growing Herbs
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Seed Viability
- Seed packets have a “packed for” date on the back. Yet seeds can still be viable for years beyond that date if stored correctly. Ideal storage conditions are cool and dry. The older the seeds are, the lower the germination rate will be. So plant more of the older seeds than the number of plants you ultimately want. You can do a germination test by putting seeds on a damp paper towel and enclosing them in plastic to keep them uniformly moist. Do this right before planting time so you can transplant the ones that successfully germinate. Or you can take your chances and just plant them directly and see what comes up. If you are saving your own seeds, make sure to choose seeds from the healthiest plants.
Whenever it's hard to find flower seedlings, if you have some old flower seed packets, you can scatter the seeds randomly in a section of your yard and enjoy whatever flowers.
More Information: Vegetable Seed Viability -
Growing Purple Carrots
- If you only buy carrots at the supermarket, you may think that they are all orange. It is believed that carrots were originally purple, with orange becoming popular through Dutch breeding. Several colors are now available at Farmers’ Markets and by growing your own. Springtime is a good time to start carrots from seed. Transplanting is not advised because you can easily damage the roots which are the relevant plant part. Loose soil is important so that the carrots will grow straight. Scatter the seeds over the soil with as thin a covering as possible, keep moist until germination, and harvest when the tops expand to a good size. The Master Gardeners have done germination and growing experiments with different varieties and soil blends. Covering seeds with a thin layer of vermiculite yielded the fastest and highest rate of germination. Carrots are slow to germinate and could take as long as 3 weeks. Thin to 2 or 3 inches apart. For growing, a soil blend of 1/3 compost and 2/3 soil produced higher-weight carrots than blends with half of the soil replaced with either sand or perlite.
Some common problems are twisted roots from planting too close together, forked or deformed roots from clods and rocks in the soil, a hairy root from too much nitrogen and splitting from too much water.
More Information: Growing Carrots
- February, March, April, September
3. Pests and Diseases
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Pepper Weevil
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More information: Pepper Weevil
- July, August, September -
Root Knot Nematodes
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More information: Nematodes Pest Note
- September, October, Any month -
Citrus Leafminer
- What causes young, healthy citrus leaves to become gnarled and disfigured and what can be done about it? This damage is due to the citrus leafminer moth that lays eggs on new citrus leaves. Its larvae burrow into the leaf and leave tunnels as they feed, visible as meandering serpentine mines. Our advice: don’t worry about it. Leafminers can slow the growth of young trees but even heavily damaged trees are unlikely to die. Leafminers only attack young leaves — the tough leaves of mature plants resist infestation and fruit is not affected. Damaged leaves still produce food for the tree, so don’t cut them off. If you do, it will stimulate the tree to produce more new leaves — which will attract more leafminers!
More information: Citrus Leafminer
- January, February, March, April, May, September, October, November, December -
Today’s Grubs Are Tomorrow’s Beetles
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More Information: What are White Grubs?
- April, May, June, July, August, September, October -
Giant Whiteflies
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Giant whiteflies were only discovered in California in 1992, but the infestation is now widespread in the San Francisco Bay Area. Plants most affected are ornamentals, such as begonia, hibiscus, bird of paradise, mulberry, and others. Adults produce spirals of wax primarily on the underside of leaves and lay their eggs in waxy bands which grow heavier as the population increases. Wax filaments grow to lengths of up to 2 inches, but in shielded areas, they can reach ten inches long! Even though affected plants weaken, they rarely die. Manage giant whiteflies by removing infected leaves, washing the undersides of leaves with strong streams of water, and encouraging beneficial insects to control populations.
More Information: Giant Whiteflies in Your Garden
- June, July, August, September -
Identifying Beneficial Insects
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More information: Beneficial Insects
- March, April, May, June, July, August, September -
Tomato blossom end rot
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A brown depression on the bottom of tomatoes is usually blossom end rot (BER). 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. For more detailed information about BER please view Managing Blossom-End Rot in Tomatoes and Peppers.
- July, August, September -
Bug Patrol
- It’s never helpful to have critters competing with you for your food. Damage can be done by squirrels, raccoons, rats, birds, and caterpillars, yet it is the tiniest creatures that can be the hardest to detect. That’s why it’s helpful to do a regular inspection, as often as once or twice a day if possible. Knowing what it is will help you figure out what to do to maximize the productivity of your garden. Some pests are out during the day and others do their damage at night, so you may want to take a flashlight out at non-peak gardening hours. Holding a piece of white paper under a plant and shaking the plant can make insects fall off for identification. The most common place to find pests is on the undersides of leaves so make sure to closely inspect those parts. A magnifying glass of some sort is a useful tool. You can also take a picture with your cell phone and then zoom in for a closer view. It’s important to be able to recognize the eggs, the larval and nymph stages, and the adult form, and to be able to differentiate between beneficial insects and harmful pests. Don’t indiscriminately squish everything that moves! Once you have done your detective work, you can go to the University of California IPM website for identification and management tips, or contact the Master Gardener Help Desk for guidance.More Information: Beneficial Predators – These are the ones you want!
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Spiders in Your Garden
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More information: Arachnophobia Video
- August, September, October, November -
White Butterflies and Green Caterpillars
- Have you seen these small yellowish-white butterflies fluttering around? Cabbage white butterflies feed on many flowers, but for laying their eggs. They favor the cabbage family, such as broccoli, cauliflower, and mustard. The velvety green caterpillars, also called imported cabbageworms, feed on the leaves after hatching. While mature plants tolerate a few holes munched in their leaves, young seedlings don't have foliage to spare. Cultural controls include handpicking the caterpillars, brushing the eggs off the undersides of leaves, and using row covers to protect the seedlings. UC lists additional options in the link below.
More information: Managing Imported Cabbageworms
- March, April, May, June, July, August, September, October, November -
Boxwood Blight
- Boxwood is an evergreen shrub typically grown as a short border hedge. It is often pruned in a straight, formal style. It has been falling out of favor as native, drought-resistant plantings are increasing in popularity. Another reason for reconsidering its use is the fairly recent arrival of a fungal disease called Boxwood Blight. It was first detected in the U.S. in Connecticut in 2011 and reported in Santa Clara County in 2017. It is spread by contact through pruning tools, gardeners’ clothing, and irrigation. This blight can show symptoms in as little as a week. Look for brown leaf spots with dark edges, white spores on the undersides of leaves, black lesions on stems, and severe dieback. Humidity and overhead watering contribute to the disease being able to take hold. Pruning infected branches, with sterilization of tools between each cut, may help. Fungicides cannot control the disease once it starts. More likely the plant will have to be removed, bagged, and thrown in the garbage.Boxwood Blight, Purdue Botany and Plant Pathology
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Mosaic Virus
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Mosaic virus on squash and cucumber plants is a disease spread by aphids and cucumber beetles. The leaves become rough and mottled, the plant becomes stunted and the fruit can be whitish. Pull the plant and put it in the trash. Do not compost. For more information see UC Pest Note on Squash Mosaic Virus.
- September -
Rat Management
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Rats show up when your citrus, tomato, or fruit first starts to ripen. Rats are agile climbers and usually live and nest in shrubs, trees, and dense ground cover like ivy. One management strategy is to prevent access to the tree by cutting branches away from fences or other trees, leaving a gap of at least 2–3 feet, 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.
Per the UC pest note (linked below), trapping is the safest and easiest method for controlling rats. Read the pest note for other management strategies as well.
More information: Rat Management
- January, February, March, April, July, August, September, Any month -
Leafcutter Bees - a Beneficial Insect
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Do your rose bush leaves have smooth round holes in them? The likely culprit is the female leafcutter bee. The bee cuts smooth round or oval leaf fragments and uses them to line each underground brood cell that she fills with nectar and pollen. When the cell is ready, a single egg is sealed inside. The larva pupates (matures) in the chamber and emerges in the spring.
Rose leaves seem to be their favorite. The hole in the leaf is much larger than an ordinary caterpillar would make and is very smooth as if a miniature cookie cutter was used. The bee can chew off a leaf fragment in less then a minute with its sharp jaws.
Like all bees, leafcutter bees are important pollinators and should not be killed.
- September -
Powdery Mildew
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Powdery mildew likes warm days and cool nights. Unlike most other fungi, it does not need moisture to thrive. Early symptoms include yellow chlorotic spots on the leaves. The presence of the fungus becomes obvious as it starts to produce spores that look like white powder on leaves. Eventually, the leaves will turn brown and dry.
The best defense is to plant varieties that are resistant to powdery mildew. Also helpful is planting in full sun with good air circulation through the plants. Washing off the leaves, preferably in the morning, can buy some time. Powdery mildew generally affects the older leaves first, and you can remove these when they are too covered to be able to photosynthesize. Fungicides can help but you want to be careful about using them around something you are going to eat. At some point, the plant may decline so much that it needs to be removed.
More Information: Powdery Mildew on Vegetables -
Birds
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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 -
Sooty Mold
- If your citrus leaves have a black coating, you may have a sooty mold problem. This black mold can also be seen on citrus fruit, avocado leaves, magnolia leaves, hibiscus, other host plants, and even on sidewalks beneath trees.
The sooty mold fungi grow on “honeydew”, a sticky substance excreted by plant-sucking insects such as aphids, scale, mealybug, and whitefly. They suck the sap out of plants and excrete excess sugars. It exists purely on the surface of a plant and is not a systemic issue. 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, thus reduce photosynthesis.
Ants protect the sucking insects from their predators so they can 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.
Pruning branches to allow better air circulation also helps. You can hose off the mold itself with a strong jet of water. And you can eat the fruit once you wash off the sooty mold.For more information, see Sooty Mold Management Guide. -
Brown Marmorated Stink Bug
- Native to Eastern Asia, this pest was introduced to the United States in the 1990s and has been established in Santa Clara County. Some features to distinguish these bugs from other stink bugs are white stripes on the antennae, a blunt head shape, and smooth shoulder margins.
They feed and reproduce on a variety of plants and are particularly damaging to fruit. You can cut cosmetic damage off fruit and still eat the rest of the fruit. To keep out stink bugs, cover vegetable plants with row covers. You can pick the bugs off plants and squish them or knock them off into soapy water. They are attracted to light and can get into homes where if vacuumed up, they can stink up your vacuum bag.
More Information: Brown Marmorated Stick Bug Pest Note -
Bitter Pit (Brown Spots) on Apples
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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 which leads to small brown, sunken lesions that become dark and corky. Highly susceptible cultivars include Red Delicious, Granny Smith, Golden Delicious, Jonathan and Gravenstein. The UC Bitter Pit Pest Note recommends cultural practices for control.
For even more information, the UC Postharvest Technology Center website has grower information, including using calcium sprays starting in June.
- August, September -
Whiteflies
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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.