Ask the Experts

I have a small vineyard – 24 vines. This spring and into summer, I had leaf hoppers, is there a spray for them?

Leafhoppers are usually not enough of a problem in home vineyards to justify chemical control measures. Remove weeds in surrounding areas to prevent the buildup of leafhopper populations that might disperse to new grape foliage. Rely on natural enemies such as green lacewings, minute pirate bugs, lady beetles, bigeyed bugs, and spiders. Insecticidal soaps can be used if necessary.

An insecticidal soap spray will kill only insects it comes in direct contact with at the time of application. Thoroughly spray so that all insects are covered. Be aware that many insects prefer the undersides of leaves or may be under sepals or within leaf buds. As there is no residual activity, two or more sprays two or three days apart may be necessary. Try to avoid making applications when sun is on the plant. Complete kill of pests is unlikely, but soap sprays can bring populations down to tolerable levels as part of an integrated control program that includes reliance on natural enemies. Products that combine pyrethrins and soaps may increase control.

– UCCE Master Gardeners of San Mateo/San Francisco Counties

My ripe lemons have 2-3 tiny pin holes per lemon and the juice is oozing out from the holes. When the fruit is nearly ready to pick, it falls to the ground. What do I have?

These sound like they may be two separate problems. Pin holes in the fruit are likely caused by the citrus cutworm or leafroller. They are all moth larvae (caterpillars) that eat into the fruit. The citrus cutworm is a caterpillar in the spring, whereas the leafroller can be a caterpillar any time of the year, so it is more likely the leafroller. Do a close inspection of the plant. If one of these pests is present, you are likely to see chewing of the leaves as well, or rolling and webbing of the leaves. There are no effective remedies for the leafroller, but general clean up of leaves and debris beneath the tree will help deter the pests.

Some early fruit drop is typical with citrus, but if most fruit are dropping, it is likely caused by a nutrient deficiency or incorrect watering (could be too much or too little). It could also be due to excessive heat when the fruit was setting. If you also have yellowed leaves, the plant may not be absorbing iron properly (chlorosis). Feed with chelated iron.

– UCCE Master Gardeners of San Mateo/San Francisco Counties

For the last few years my Orange tree has been dropping fruit that is not ripe. There is a portion of the orange that looks rotten – about 30% of the orange. I would say out of all of the oranges that ripen; only about 10% are okay to eat. I have had this tree for 30 years or longer and it has given so many oranges that I gave 5 or 6 neighbors bags of them. Now I have a lot of oranges, but they seem to be getting infective with something. Please help.

If you can send a photo of the rotten fruit, that would be helpful in identifying the cause. It sounds like a fungus from the description. There are several fungi that afflict citrus trees. They live in the soil and can reach the plant through rain or irrigation. Make sure that the soil at the base of the tree is kept clear of debris; good mulch can also help to prevent disease. You may need to apply a Bordeaux treatment in the spring. Also, 30 years is an advanced age for a citrus tree. Like a human, it is more susceptible to disease as it gets older.

– UCCE Master Gardeners of San Mateo/San Francisco Counties

What is a good, environmentally correct spray to use on fruit trees to protect the fruit from being infested?

No spray is harm-free. There are many safer approaches which can work against pests, such as blasting the leaves with water and cleaning up debris at the base of the tree. Sprays should only be used if safer methods are not effective. Insecticidal soaps and horticultural oils are relatively safe, but they only work against soft-bodied insects. So you really need to identify what the pest is in order to determine the best approach.

– UCCE Master Gardeners of San Mateo/San Francisco Counties

What are those big black bees and what do they feed on? Before, we didn’t have them in California. Where do they come from? They are pretty scary looking. They are huge and they fly pretty slow compared to regular bees. I heard they are called carpenter bees is that correct?

California has two kinds of large bees: carpenter bees, which are generally black, and bumblebees, which generally are black and yellow. Because the coloration of some species varies, here’s an identification tip – carpenter bees abdomens are shiny, and some of the segments have hairs or fringe. They are native to California, and although they can cause some damage when the females bore into wood to lay their eggs, they are generally considered beneficial insects because they help plants.

Because of their size, and their presence around wood structures such as unpainted eaves or decks, they can be frightening, but the males cannot sting, and the females rarely attack.

– UCCE Master Gardeners of San Mateo/San Francisco Counties

I just found a red mosquito-like pest on my lawn. It is about 1.5 inches long with antenna about an inch long and very long legs and wings. I had it in a glove but when I went to put in it in a plastic bag it stung me on the right hand. It hurt too. It does not look like anything I have ever had in my garden or yard. I saved it but don’t have a camera to take a photo of it. Do you want me to drop it by somewhere for analysis?

The best bet would be for you to take the insect to your local Master Gardeners for identification. Once they have determined what this stinging beast is, they can help you determine the best approach for management.

– UCCE Master Gardeners of San Mateo/San Francisco Counties

I have fruit trees and grape vines in my back yard. Every year my pest problem has become worse. I am now using potent pesticides and still can not get rid of these creatures. Not even the white flies are dying off. A combination of pesticides and zapping bug lights just keep the population down. What do you recommend to get rid of these pests?

The first step in managing any pest is to positively identify just what is causing trouble to your fruit trees and vines. Once you know what you’re dealing with, an integrated pest management approach will be most effective – starting with reducing the habitat you’re (inadvertently) providing to the pests. If pesticides are called for, they should of course be used judiciously and at the right time, or they will just be expensive poisons.

You mention specifically that you’re having trouble with whiteflies, which can suck the sap right out of your plants. Whitefly outbreaks often occur when the natural biological control is disrupted; this pest is not well controlled with insecticides, and in fact the pesticides will kill the insect predators that would otherwise eat the whiteflies.

The best strategy for managing whiteflies is to make your garden less attractive to them. You might consider spraying the infected plants with a hose removing infested leaves, removing plants that seem to be particularly attractive to the whiteflies.

By avoiding pesticides, you can also encourage natural enemies of the whiteflies; predators of this pest include lacewings, bigeyed bugs, and minute pirate bugs.

For more information about whitefly biology and their biological controls, read the UC Management Guidelines for Whiteflies.

– UCCE Master Gardeners of San Mateo/San Francisco Counties

This is in regard to your response to a previous question about a D’Anjou pear tree. “On apples and pears, larvae penetrate into the fruit and tunnel to the core, leaving holes in the fruit that are filled with reddish-brown crumbly droppings called frass.” It is my understanding that the coddling moth larvae enter the immature fruit at some point very soon after blossom drop, (leaving no noticeable evidence of the entry) and that the tunneling and frass seen on the exterior of the mature fruit is evidence that the larvae has left the fruit and dropped to the ground in order to pupate.

Yes, codling moth larvae bore into developing fruit or nuts early in the season, and are difficult to detect until the damage has been done. This is why good sanitation is so important to managing this pest.

Beginning about 6 to 8 weeks after bloom, particularly in May and June, check fruit on trees for signs of damage every week or two. If you see any frass-filled holes, remove the infested fruit to help break the life cycle. Also, clean up and destroy any dropped fruit right away – it may also contain codling moth larvae.

– UCCE Master Gardeners of San Mateo/San Francisco Counties

I live in Benicia, CA and my neighbor’s tree, a mature cedar, started turning brown around this time last year despite routine watering. It is now completely brown and appears quite dead. I brought the condition to my neighbor’s attention last year; and she supposedly had it evaluated by an arborist. Now that it’s apparently dead, she supposedly has had it re-evaluated and scheduled for removal. My question: since both “arborists” allegedly found no evidence of insects or disease, what is the likely cause of its demise? (I have noted a lot of webbing on her trees and shrubs, but we do have quite a spider population in our area; and she believes the webs are spider’s.) I’m concerned about my trees and shrubs in proximity to my neighbor’s. Thank you for providing this avenue for questions.

– Benicia, CA


It’s a big loss to lose a mature tree like this. Without photos and more information – such as which species of cedar this is, and whether it browned from the top down or the bottom up – it’s difficult to tell what happened to the cedar, and thus whether it might affect your plantings.

Since the arborist did not detect insect damage, it’s likely that the webs are created by spiders, which are beneficial.

The problem you describe might have been caused by over fertilization. It could be caused by a fungal disease that the arborists did not detect, such as Armillaria root rot or Phythopthora root rot. The latter can spread to surrounding plants, given the proper (wet) conditions.

You might ask your neighbor whether she has a report from the arborists, which could provide more information about the demise of the cedar, and thus help you determine whether you need to do anything to protect your trees and shrubs.

– UCCE Master Gardeners of San Mateo/San Francisco Counties

Hello, I’m wondering if castor bean plants are something you deal with. I just moved here from Massachusetts a couple of months ago, and have already witnessed some major growth of huge Castor Bean plants in the canyon we live in. Is that something to be concerned about? Thank you and good luck in your battles!


In the spurge family, the castor bean (or castor oil) plant, Ricinus communis, is native to the Mediterranean region. It does quite well in California, where it is cultivated and is also naturalized. It is considered an invasive pest, because its aggressive growth pattern displaces native plants in riparian areas.

Management is often effective with manual methods – pulling the plants and their roots. Plants cut off at the crown will re-sprout, so it is important to remove as much of the root as possible. If this is not feasible, foliar sprays can be used to control this invasive pest.

For more information about the management of castor bean plants, visit the California Invasive Plant Council website

– UCCE Master Gardeners of San Mateo/San Francisco Counties