Garden Guy: Falling fruit, an oozing tree and a whopper of an orange

Hi, Nick! I planted another Tahitian lime a couple of years ago since my first one did not do well. As soon as the fruits developed, they fell. This is happening to the new lime tree that I have. I suspect it has a virus. Is there anything I can do to solve the problem? Thank you. — ERG

The good news is you probably do not have a virus.

The common virus that attacks citrus here, as well as around the world, is known as tristeza, meaning sadness in Portuguese. Moderately affected are some sweet oranges, including the Washington navel. The Tahitian lime, however, according to a CTAHR publication, along with the Hawaiian or Kona orange, Valencia and lemons, is unaffected or asymptomatic (does not show symptoms).

The dropping of young fruit is quite common in a rainy environment. We discussed this on a number of occasions and I will refer you to my website for a detailed explanation about dropped fruit. See www.gardenguyhawaii.com and look under the “citrus” heading.

I am having a problem with a soursop tree. It’s only about 2 years old and about three months ago, the leaves started to turn brown and fall off, and branches are getting brown. I found black spots on the trunk of the tree. It looks like tar coming out of the bark and running down the tree. I’m sending you some pictures so you can get a better idea what I’m talking about. Any information would be helpful. Thank you. — Bert

Leaves turning brown and falling off causing branches to dieback is a symptom of a number of maladies, including crown and root rot. The pictures you sent of the dark substance exuding from the trunk is quite similar to a disorder known as gummosis and is common in citrus.

In this case, the bark of the soursop tree is most likely infected with a similar fungus, perhaps a phytophthora species. In response to this fungal attack, the defense mechanism of the tree produces a gummy substance in an attempt to wall off the invader.

If cuts are made into the bark around the oozing site, you will discover the normally light tissue has turned dark brown; this is the site of infection. Now, it is a battle between the tree’s defenses and the advance of the fungus.

I’m not sure the tree is going to win. There is nothing you can do at this point, the infection is internal.

If the tree dies, do not plant another of the same type at this site. Switch to another family and plant a new soursop on the other site of the garden.

Hi, Nick. I read your articles all the time and have learned a lot. Can you tell me how large a tangerine can get to be? I picked one the other day that weighed 1 pound and is almost 5 inches in length. This is the first tangerine I have ever seen this big. Is this unusual? Thank you. — Lynn

Yes, I would say it is unusual.

Are you sure it is a tangerine (mandarin)? There are, however, some mandarins characterized as “large.” They include minneolas and the king mandarin.

Minneolas are sometimes seen in supermarkets. They originated in 1931 from a cross between a Duncan grapefruit and a Dancy tangerine. The fruit is large, round with a pronounced and distinctive neck, also known as sheepnose. A large minneola could attain the size you describe.

The king mandarin was first brought to California in 1880 from Saigon, Vietnam. Its fruit is large like many oranges. The thick to very thick rind is yellowish-orange in color and is rough and uneven in texture.

Another factor to consider is first year fruit is often larger than normal. In addition, when trees produce few fruit as in alternate bearing, they will tend to be larger. When the tree produces an abundance of fruit, those will tend to be smaller — there’s only so much energy to go around.

Hilo resident Nick Sakovich is a professor emeritus of the University of California. He has worked in the field of agriculture for 30 years. Email your questions to Sakovich at askthegarden guy@earthlink.net. You also can visit his website at www.gardenguyhawaii.com.