Xtremehorticulture

Xtremehorticulture of the Desert

Skeletonizers on Grapes a Late Spring Problem

Leave a Comment / fruit, grape, grape insecticides, grape leaf eaten, grape leaf skeletonized, grape leaf skeletonizer, grape leaf skeletonizer pictures, Grape leaves damaged, grape leaves eaten, grape pests /

Q. I have some pest problems on my grapes that I think is grape leaf skeletonizer, but it made holes in the leaves. Is this the same skeletonizer or do I have a new problem? A. The grape leaf skeletonizer is an adult three quarter to one inch or so moth which lays eggs in clusters and is a problem with grapes every year. The short-lived adult moth, along with the small eggs, don’t do any damage. It’s the larva which burn like matchheads if they fall on your skin. It’s these larvae that “skeletonize” grape leaves that causes all the damage. These young black and yellow larvae glide across grape leaves and turn these leaves into “skeletons” three to five times every year. Skeletonizing grape leaves is what gets them bigger. This can start from April or May of every year in Las Vegas depending on their populations. If you don’t get some control of them early with sprays of spinosad or Bt, their populations may continue to get larger and larger. There is another insect problem with grapes. That is the grape flea beetle which “chews” holes in the leaves. Most of the time it can be confused with “skeletonizers”. This is because they occur at the same time, but don’t create the same type of damage. Flea beetles chew holes in leaves. They don’t skeletonize leaves. And, unlike ‘skeletonizers”, they cause grape leaf damage, at the most, twice year. Oftentimes, just once in the spring. With “skeletonizers” the preferred spray is spinosad. You can use Bt (Bacillus thuringiensis) sprays and most of the time they will work. I like spinosad sprays because they will get leafhoppers as well which Bt does not. For grape flea beetles any insecticide works. But spraying them with an insecticide isn’t always the answer. Usually, unless the infestation is heavy, just waiting three weeks is enough. The population of grape flea beetles will pass without spraying. I oftentimes will just wait for three weeks but not for the skeletonizers. You must spray and spray early. Don’t forget to spray the undersides of leaves early.

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‘Interlaken’ Grape is a Close Alternative to Thompson Seedless

Leave a Comment / blackberry, desert, grape, selection /

Q. Can ‘Interlaken’ grapes take eastern, southern or western exposure?  What about blackberries? ‘Thompson Seedless’ dessert grape. Sorry, no pictures of ‘Interlaken’ but similar. Blackberries popping up through the mulch, after removal, where ever there is irrigation. Could be ‘Womak’ or possibly ‘Rosborough’ two varieties I would recommend for our climate. A. Both grapes and blackberries should be grown in full sun, away from hot walls, along with soil improvement, irrigation, and mulch. Put them at least 10 feet from hot west and south-facing walls so the heat from the wall during the summer doesn’t hurt them. Blackberries are more of a colder climate type compared to most grapes. Neither grapes or blackberries will do well in hot locations without the air mixing so it’s not so hot. ‘Interlaken’ grape is a seedless desert grape, similar to ‘Thompson Seedless’. In fact, ‘Interlaken’ grape has ‘Thompson Seedless’ genetics in it! For that reason, it should do well in Las Vegas. All blackberries like the cooler climates of the Pacific Northwest and do quite well there ripening in about one week or less. Research done in Yuma, Arizona, by the University of Arizona points out that a few blackberries have grown well in hot desert climates.   Based on that research I grew several varieties of blackberries. Both blackberry varieties ‘Womack’ and ‘Rosborough’ did the best in our dry intense heat. ‘Brazos’ was also recommended for desert climates but it developed leaf scorch during our hot summers. But ‘Womack’ and ‘Rosborough’ varieties didn’t. All suitable blackberries for our desert climate ripened in one day in May.

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Grape Bunch Diseases are Now Here

Leave a Comment / botrytis, bunch disease, downy, grape, mildew, powdery /

Q. I am a big fan of your (Las Vegas Review Journal newspaper) column, but I haven’t seen any answers about what’s happening to my grapes. Please advise. This the stuff isn’t on all my grapes. I have four plants and maybe 10-15% have this white stuff on certain bunches. This is what are called collectively, “bunch diseases”. But are usually either Botrytis or powdery mildew. A. I thought this might happen mostly because of our wet spring. Bayer tells us, when treating for grape bunch diseases, that about half of the improvement is due to better air circulation and the other half using a copper-based fungicide. They are right! Collectively, both botrytis and powdery mildew are called “bunch diseases”. Warning. Grapes must be present on the label because of testing and recommendations concerning the rate of application. Sometimes, months after we see the disease during wet weather, the bunch disease shows up as dried berries. Too late to do much about it now.             This looks like one of the grape diseases, probably grape botrytis or downy mildew. Try removing bunches and leaves so that you have one bunch every foot. If it is tight with leaves, remove some of the leaves as well. Don’t remove too many leaves so that you get direct sunlight on the grapes or limbs. You want to improve the air circulation around the bunches and the berries but without putting the bunches (and limbs) in direct strong sunlight for any length of time. In severe cases, the grape bunch may just dry up!             You can apply a spray mixture of a copper-based fungicide according to the label. Copper sulfate, Liqui-Cop, and Bordeaux sprays come to mind, but any copper-based fungicide should work. You may have to repeat the application. Read the label. Remember fungicides help stop plant diseases but do not “cure” the plant of a particular disease. You are spraying to prevent the spread of grape botrytis and powdery mildew. There is some evidence that Neem oil has given some protection, but copper-based fungicides are better. One of the copper-based fungicides. Any fungicide that contains copper in it is considered a “copper-based” fungicide. https://www.gardeningknowhow.com/garden-how-to/info/what-is-copper-fungicide.htm             You may be too late with this application, but it is worth a try. Do it very soon and follow label directions for controlling these “bunch diseases” on grapes.

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Colder than Normal Spring Weather and Tomatoes

Leave a Comment / Cherry, cold spring weather, grape, pear, plastic, tomatoes /

Q. We read your early spring article in the RJ on tomatoes and planted 6 plants in mid-March.  We planted a mix of ‘Sweet 100s’, ‘Champion’ and another plum tomato.  We have been watering, using Miracle Gro for tomatoes and watching them closely.  The plants appear stunted.  We have them in cages, and they have only grown a short distance up the cage. Any suggestions? The smaller tomatoes, pear, cherry and grapes are always a sure thing in Las Vegas. The larger tomato is ‘Black from Tula’, an heirloom type. When the spring season is long and cooler, tomatoes do better. A. Planting dates for tomatoes in our climate can range from mid-February to mid-March. Watch the weather and use your weather app on your phone. It’s been cold lately. Wait for temperatures to warm up a bit. Tomatoes are a “warm season” crop, and they prefer soil and air temperatures a bit warmer than our spring provides at times. Our spring temperatures have been erratic. Low soil temperatures can slow tomato growth even if the air temperatures are high.  Its short stature gives this away as a determinate type of tomato.             About a week before you are to plant tomatoes, cover the soil with clear plastic and seal the edges. This is so the warm temperatures under the plastic don’t “leak out”. Warm the soil temperature to at least 65 F in the top few inches. I would slit the plastic and plant at that temperature. A soil thermometer stuck in the soil an inch or two deep helps you to check it. Tomatoes can be started a bit earlier if the soil is covered with plastic and there is good weather.             Raised beds in full sun warm up much faster in the spring than those raised beds in the shadow of a wall or home. Have two raised beds: one for early production in the spring and another for later production.

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Increase Grape Berry Size by Thinning Fruit Early

Leave a Comment / berry size, grape, naturally /

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”.

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Grape Berries Drying Up and Shriveling in Early Summer

Leave a Comment / berry, disease, grape, shriveling /

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.

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