Not rotating vegetables causes decline in production

Q: After 17 years of growing tomatoes, I feel I have depleted most of the nutrients so I am going to dig it up, remove it and replace it with new soil. My idea is to lay down a layer of fruit pulp in a sufficient quantity and then cover with at least 12 inches of planter’s mix. I would do fish guts but I can’t find any quantity. By the 2018 spring planting season, I think I’ll have a super soil. What do you think?

A: Anytime you use raw plant products, like fresh fruit pulp, it is best decomposed or rotted first before using it in a garden. Otherwise, it causes numerous problems. The process of rotting releases nutrients tied up in fresh pulp in any raw vegetable or fruit. It’s also true of fresh versus aged or rotted animal manures.

The process of controlled rotting is composting. The ingredients needed for composting include water, air and warmth and whatever it is you are trying to rot. As long as these ingredients are not restricted and in abundance, the speed of this controlled rotting is regulated by the size of whatever it is you’re rotting and temperature.

By burying fresh juice pulp under 12 inches of soil I fear you are restricting oxygen. This is a major ingredient. This type of rotting is dangerous to plants because the compost becomes anaerobic, without enough available oxygen from the air. Anaerobic composts produce large amounts of acids, sulfur dioxide (the smell of rotten eggs) and methane gas — all of them toxic to plants.

Pulp from juicing attracts a lot of varmints, mostly insects and rodents. Your garden area might be a magnet for varmints unless they are kept away from it when it first begins to rot. Once the rotting is firmly underway, it’s not a problem anymore.

However, if you take this juice pulp, mix it with sawdust or very fine wood chips and turn it on a regular basis, you could have something valuable to plants in two or three months. Composting it with enough find wood products will make the gardener’s “black gold” or humus.

Regarding your current tomato growing area, the soil does not need to be replaced. It just needs to be again enriched with compost. A 3- to 4-inch layer of compost applied to the surface and double dug, or rototilled into the soil as deep as possible, will do the trick and you will be back in business.

Soil nutrients are removed quite quickly from a soil depending on the crop grown, the intensity of growth and how plants are managed. A small amount of compost should be added to growing areas every one to two years.

You also should be rotating your vegetables. If you don’t know what this is, Google it. Problems resulting from a lack of vegetable rotation causes a decline in production and contribute to disease problems.

Q: I think my Italian cypress has mites. Some of them are dying rapidly with pale leaves that hang out and crumble if you grab them. They are about 10 to 12 feet tall.

A: Make sure this problem is from spider mites and not watering too often. Italian cypress is a Mediterranean plant that should be watered after the soil begins drying. Otherwise frequent irrigations rot the roots and cause problems similar to what you are describing.

It would be a shame to apply pesticides when they aren’t needed. Pesticides are sometimes needed but applying pesticides, whether they are needed or not, always creates other problems. Sometimes the problems they create can be worse than the problem they solve.

Spider mites are always present on plants during the heat of the summer. They are controlled naturally and kept in check by many different predatory insects including good or predatory mites.

If you apply a pesticide to control mites, it kills the good mites as well as the bad ones. Once that happens, the bad mite population can blossom back into a big problem, and then it’s a vicious cycle between control and pesticide applications.

Most bad spider mites are web spinners; in other words, you should see webbing amongst the branches as well as a dusty appearance on the foliage if bad guys are active. This webbing is not true of all damage by mites.

Some mites are not web spinners. This dusty appearance can be from wind-blown dust but it can also be from large numbers of dead mites.

The presence of wind-blown dust on the foliage can encourage spider mite problems. The dust interferes with “hunting” by predatory insects. Hose off Italian cypress after dusty winds and once a month during the heat of the summer. Let them hunt.

Use a hand magnifying glass and look for eggs in the dust. Eggs are extremely small but round and translucent under a lens. Once mites are a problem, you will see lots of their eggs amongst the dust.

Use a white paper test. Take a plain piece of white paper and slap a living but dusty branch against it two or three times. Hold the paper still in the sunlight and look for tiny specks the size of a period (.) to crawl around. These are mites.

Browning of the leaves, webbing, a dusty appearance, round translucent eggs and little dots crawling around on a white piece of paper are clear indicators you have spider mite problems that need to be controlled.

Q: This year my grapes are again infested with leafhoppers. Before the fruit came off, I used Safer insect-killing soap approximately every seven to 10 days. I kept them at bay for the first part of the summer, however, they are now infesting the grapes heavily. Since I took the grapes off, I have been alternating soap and pyrethrin every five to seven days.

A: Leafhoppers can be a huge problem on grapes grown in the Mojave Desert. They are often confused with other insects, but if walking past your grapes and hundreds of tiny insects jump into your face, then they are probably leafhoppers.

Once reaching large populations, adult leafhoppers are extremely difficult to control without hard pesticides. Hard pesticides are not organic. If you don’t start spraying early, these insects will be a huge problem later in the season and much more difficult to control.

The key to effectively using softer pesticides, closer to organic types of control, is to look for the juveniles on the bottom of leaves early in the season. Use soft pesticides in rotation with each other and spray when the younger populations are on the rise.

Softer pesticides are not necessarily organic but are safer for humans and the environment. These pesticides, used in rotation, include insecticidal soaps such Safer, neem oil, spinosad, pyrethrin and even horticultural oils when temperatures are cooler.

Rotating these pesticides means to use a different pesticide in your arsenal each time you spray. Begin looking on the bottom of leaves when grape berries are the size of large peas.

Once leafhoppers are seen, spotcheck leaves every week. Remove leaves that surround the grape bunches very early; this is very important for insect and disease control.

Juvenile leafhoppers don’t look much like the adults. But adults will populate the undersides of the leaves with these babies quickly once they start. Inspect the bottoms of leaves weekly and spray if populations are increasing.

Use a different soft pesticide each time you spray. You may need to spray every week but this decision should be made after looking at juvenile populations. Remember, young ones are easier to kill than the adults.

Nonorganic, commercially grown grapes use hard pesticides. Hard pesticides knock problem pests back longer but are not as friendly to the environment, human consumption and other insects in the area nearby.

Softer pesticides must be repeated more often. Rotate them. Check populations and look for the juveniles. Start spraying early when the juvenile population is building.

Bob Morris is a horticulture expert and professor emeritus of the University of Nevada, Las Vegas. Visit his blog at Send questions to

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