Spanish Dagger (Yucca) and Curve-Leaf Yucca are Not Cacti

Q. I have a five-foot yucca tree that I cannot get to be disease free after two years of trying.  I have tried the following chemicals; Bayer Advanced complete Insect Killer, Bonide Thuricide and Bonide Tree and Shrub Insect Control Systemic. Any suggestions on how to save it.

Judging from the picture and your problems it might be Spanish Dagger, a native of the SE part of the US. Spanish Dagger, Yucca gloriosa, does not handle the heat and should not be planted in south or westerly landscapes. Not sent to me by the author.

A. Judging from the picture you sent to me your yucca tree is Yucca gloriosa, a.k.a. Spanish dagger. Spanish dagger is a yucca native to the SE that gets brown spots on its leaves that resemble disease but it is either planted in the wrong location or planted incorrectly or both. This plant is both mesic (high in its water use) and not a desert yucca native.

Looks like Yucca recurvifolia (aka Y. pendula) another yucca native to the southeastern and southern US that may scorch if planted in a hot location. Readers picture.

Spanish dagger is an Eastern coastal native from South Carolina to Florida. If planted in our desert Southwest, this yucca will look diseased if it’s planted on the West or South sides of a home, surrounded by rock, or watered like a cactus.

Because it’s a native of the southeastern United States, Spanish dagger should be planted so that it gets shade in the afternoon; on the East or north side of a home landscape in afternoon shade. Also, plant it with compost amending the soil and surrounded by other mesic plants to help moisten the soil.

Increase Grape Berry Size by Thinning Fruit Early

Q. When do you harvest green grapes and how do you increase their individual size?

'Italia' seeded grape ready for harvest in North Las Vegas.

A. Increasing the size of the berries (individual fruit) is a two-step process starting when the berries are very small. The correct time to begin this operation in our climate could begin as early as the end of March or the first part of April. At this time the berries have already begun to increase their size. The correct time to begin is when the berries are about the size of a young, early pea.

Remove small clusters of grape berries when this size

            First, leave only the large bunches and remove any small bunches. You want the average distance between bunches of about eight or 12 inches depending on how much was set. You want the remaining bunches to be big and long.

Remove the bottom 1/3 of the grape cluster by pinching.

            After removing the smaller bunches and getting the correct average distance apart, next reduce the size of each bunch by one third. Pinch the bottom one third of each bunch of grapes and remove it. It will decompose on the soil or mulch surface. The result is a fewer berries and fewer bunches. This results in larger fruit.

1. Keep an eye on your grapes in mid Spring.

2. When grape "berries" are young and pea-sized thin out the clusters.

3. Next pinch each remaining cluster so it is reduced by 1/3.

            This is the “organic” method. There is an “inorganic” method involving spraying the bunches with hormonal sprays when they are increasing in size but the “organic” method should be adequate for most homeowners.

            When to harvest is more difficult with green grapes than red grapes. Green grapes have a slight color change when they are ready to harvest. This change in color of the berries is from green to yellowish green or “bronzy” in color.

To determine the harvesting date, taste a few of the berries. If the berries are to your liking, then harvest them. Birds begin their damage (pecking or stealing berries) when the sugar content rises in fruit. Seldom do they damage fruit when the sugar content is low unless they are a stupid or young and inexperienced. Whenever you start to see significant bird damage, begin harvesting ripe fruit. After the grapes are harvested there is little to no change in “sweetness”.

Grape Berries Drying Up and Shriveling in Early Summer

Q. The berries on my ‘Red Flame’ grape are shriveling and turning gray but the vine looks healthy. Do you know what the problem is?

This is probably one of the bunch rot diseases, either powdery mildew or botrytis. Nothing can be done now.

A. From the pictures you sent it’s one of the “bunch” diseases. The bunch diseases attack only grape bunches. At the beginning of summer is when we notice disease problems on the berries of grapes such as the so-called “bunch rots”. But that’s not the time to treat. Grape fruit (the berries) develop nicely up until that time and everything appears normal. But you can’t see the disease yet.

This particular disease is either botrytis or powdery mildew of grape bunches. The cause was a fungal disease, and the grape vine needed a chemical spray for protecting the grapes in about late March or early April. There’s nothing you can do now. Fungicide sprays must be applied shortly before or right after the berries start developing.

            Fungicides act differently than insecticides. Disease control using fungicides and bactericides must be applied months before the disease is seen. For homeowners, copper fungicides should be applied to these bunches (you must spray the entire vine) to protect the bunches from this disease. The exact disease name is not necessary but the fungicide is.

You can apply a fungicide to your ‘Red Flame’ grapes now, but it won’t do you any good. The disease will continue and more grapes will turn “gray”.. The infection is already “inside” the berries but can’t be seen. The graying of the berries is a visual “sign” the disease is present. Using chemicals to control diseases is usually a “protective” spray. Controlling insects by applying insecticides are different. Very seldom are insecticides applied as a “protectant”; a.k.a., applied before we see the problem. Insecticides are applied usually as a “curative”; after we see they are present.

How to know when to apply fungicides? Commercial growers use the weather and understand that if they don’t apply the right disease control there are risks that they could lose their fruit. If the weather is right, fungicides and bactericides may be applied to susceptible plants. Any time windy or wet weather precedes fruit development or flowering, disease control (fungicides, bactericides, viricides) are applied to highly susceptible plants.