Home gardeners often become concerned when their fruit trees begin dropping fruit prematurely. In some cases, fruit drop is nature's way of reducing a heavy fruit load. In other cases, premature fruit drop may be caused by pests and diseases, adverse weather conditions or poor cultural practices.

Apples may have a couple of periods when fruit drop occurs. The first is often after the flower petals fall off and may last two to three weeks. The very small dropping  fruits are the ones that were not pollinated, so will not develop further. Many fruit species need to be pollinated by bees. Lack of pollination may be the result of cold or wet weather during the bloom period, or by a lack of honey bees. Also, if there is freezing weather just before the flower buds open, more fruit drop may occur.

Other adverse weather conditions may also contribute to fruit drop. For example, persimmons may drop if the weather turns suddenly hot in spring, just as the small fruits begin to develop. Trees not receiving adequate irrigation water would be more prone to dropping fruit. 

Pests and diseases may contribute to the problem of premature fruit drop. Cool wet weather during the bloom period of walnuts often  results in infections of walnut blight, a bacterial disease that damages catkins, leaves, and newly-pollinated nuts. Infected nuts may drop prematurely. Premature ripening and fruit drop often occurs in apples and pears that are infested with codling moth larvae. 

In apples and pears, a second drop occurs once the fruits are about the size of marbles, usually in May or June. This is commonly referred to as “June drop.” Fruit drop at this time of year is thought to occur as a result of competition between fruits for available resources. 

Some fruit tree species, such as plums, may experience a mid-summer fruit drop. Proper  fruit thinning can help to prevent this. How much to thin depends upon the tree species.  With peaches and nectarines, it's important to make room on the branches for each fruit to grow to 2 ½ to 3 inches in diameter. Thin by pulling off ¾ to 1-inch long fruit in April and May, leaving one fruit every 6 inches. This results in more fruit on the ground than on the tree, but it's important to produce large, flavorful fruit and to minimize limb breakage.

Thin apricots when the fruit is about ¾ inch in diameter, leaving 1 apricot every 3 inches.  Thin plums when the fruit is ¾-inch-long, leaving 1 plum every 4 to 6 inches.  Thin apples after the usual May or June drop. Leave 1 apple every 6 inches or allow only 1 apple to remain per  spur. Asian pears should be thinned to leave only 1 fruit per spur.

When mature fruit begins to drop, it's a sign that the fruit is ready for harvest.

Ed Perry is the emeritus Environmental Horticultural Advisor for University of California Cooperative Extension (UCCE) in Stanislaus County.

On Thursday, February 7, the University of California Cooperative Extension (UCCE) Stanislaus County Master Gardeners held their very first class. The topic was spring vegetable gardening. UCCE Master Gardener Royce Rhoads discussed how to tell if your seeds are still “good,” what supplies are needed to start vegetable seeds indoors, and what vegetable seeds to plant outdoors.

We were excited to have 64 people attend our first event! Feedback from participants included:

• Thanks for the opportunity to attend and learn some basics.
• Appreciated the clear and concise information.
• This program is off to a great start and will be a real asset to our community!

If you couldn't make the class, you can download our free Vegetable Gardening Guide. It has step-by-step information on preparing garden beds, proper irrigation, dealing with pests and diseases, and a guide to which vegetable crops you can grow in our area and tips for growing them.  You can also contact the UCCE Master Gardeners with your questions by calling (209) 525-6800 or sending an email to ucmgstanislaus@ucanr.edu.

Never miss a class! Stay in touch by subscribing to our newsletter blog, The Stanislaus Sprout. Look for the word "subscribe" on the top right-hand corner of the page. Add your name to receive gardening and pest management tips, as well as announcements for future classes and workshops.

Pests need food, water, and shelter to live. Unfortunately, some of us unknowingly attract and even invite pests to live in and around our homes!

Insect and animal pests can pass through small spaces. For example, mice can get through a hole the width of a pencil, and cockroaches can flatten themselves and squeeze through cracks. Here are some circumstances that attract pests, allow them access, and provide them with food, water, and shelter:

Rat on a bird feeder.

Pest Attractors and Supporters

• Pet food and water bowls (indoors and outside)
• Bird feeders
• Leaking water spigots
• Open food packages in your kitchen
• Hedges and shrubs near doors or windows

Entry Points

• Holes in windows and screen doors
• Cracks in the foundation of your house
• Holes in the roof or attic
• Crevices around pipes indoors (bathrooms, laundry area, kitchens) and outside

Oriental cockroach colony. (Credit: Jack Kelly Clark, UC IPM)

Use IPM to Manage Pests
Use integrated pest management or IPM to help you pest proof your home.  First, walk in and around your home to inspect for the above pest attractors, supporters, and entry points. Once you find a pest, for help with identification contact the UCCE Master Gardeners of Stanislaus County at (209) 525-6800.

If you can't personally inspect your home or don't have time, you can call a pest control company and ask them to do it for you. This is helpful for hard to access places like basements and attics.

For Quick Tips on common pests and their management and prevention from the UC IPM website, click below. 

• Ants 
• Carpet Beetles 
• Cockroaches 
• House Mouse 
• Pantry Pests 
• Rats 

Other Helpful Links
What is IPM?
UC IPM Website
Pest Notes Library 

Use a caulking gun to seal up cracks. (Credit: Jack Kelly Clark, UC IPM)

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Many gardeners are interested in knowing how winter temperatures affect garden pests. The hope is that following a cold winter–such as this year–fewer pests will survive to plague the garden. Unfortunately, both insect pests and plant diseases have ways of surviving our harshest winters. However, there are some things that you can do to lessen potential pest problems, mostly by eliminating the places where pests and disease may overwinter.

Although a few pests can migrate great distances, many come from sources within your garden or nearby areas, surviving on weeds, in crop debris, as pupae in soil, or as seeds, spores or eggs. You can also unknowingly bring some pests into your garden on infested transplants or contaminated soil or equipment. 

Codling moth larvae inside a fruit. [Credit: Jack Kelly Clark, UC IPM]

Good common-sense sanitation practices will help to eliminate overwintering garden pests. In your fruit trees, be sure to remove and destroy old fruit “mummies” hanging in trees and pick up and destroy any fallen nuts. Old fruits and nuts often contain pests such as codling moths. It's also very important to get rid of pruned branches, especially those from your fruit trees, that might be infested with disease or borers. Bark beetles may emerge from infested branches in late winter or early spring, so be sure to dispose of prunings as soon as possible. Don't forget to treat your fruit trees, especially peach and nectarine trees, with fungicide sprays to prevent spring diseases such as peach leaf curl; oil sprays applied now will also help to control overwintering insect and mite pests on deciduous trees.

Also, remove any weeds around your garden well before planting any new crops. Not only do weeds produce seeds that may find their way into your garden, but they are also likely to harbor numerous migrating pests. For instance, cutworms, earwigs, stink bugs, thrips and certain viruses carried by aphids and leafhoppers are all pests associated with weedy areas. If you wait until your garden is planted before destroying these weeds, the pests will move into your crops. Waiting for the weeds to dry out naturally will also encourage pest migrations. Besides, it's easier to control weeds when they're seedlings, rather than waiting until they've matured and set seeds.

Fruit mummies may harbor pests. [Credit: Jack Kelly Clark, UC IPM)

Good sanitation also means making sure the planting stock you're using is free of pests. Check transplants or other greenhouse stock for aphids, diseases, nematodes and other pests. Use certified seed or stock if available. Make sure any organic soil amendments you use are free of weed seeds and pathogens, and don't move soil infested with nematodes, Bermudagrass stems, or nutsedge tubers to other parts of your garden. If you're not sure whether the soil is infested with pests, it's best to not take the chance. Also, clean equipment before moving it from infested areas.

Always be sure plant debris, particularly residue from previous vegetable crops, is completely decayed or removed before planting a new crop. A good way to destroy most crop and weed residues around your garden is by composting.  Composting destroys most of the pests that may be harbored in the residues.

You can download a free copy of Composting is Good for Your Garden and the Environment to learn more.

Ed Perry is the emeritus Environmental Horticultural Advisor for University of California Cooperative Extension (UCCE) in Stanislaus County.