Ask A Master Gardener: July/August 2016


July 11, 2016

Ask a Master GardenerIssue 19: July/August 2016

Have a question about your garden?
Submit it through the form below or on our Facebook page, or call the Pima County Master Gardener Plant Clinic at 520.626.5161

When should I fertilize
my citrus trees?

Last year, the University of Arizona Cooperative Extension modified the recommended schedule for fertilizing citrus based on new research. Historically, we’ve been instructed to feed citrus three times each year using Valentine’s Day as the first application date followed by Memorial Day and Labor Day. These dates were based upon Southern California’s growing season and are not suitable for our warmer and drier climate. The new recommendations are to add fertilizer on the following schedule:

  • For oranges, tangerines and grapefruit: Apply a third of the recommended range of fertilizer in January-February, a third in March-April, and a third in May-June.
  • For lemons and limes: Apply a third of the recommended range of fertilizer in January-February, a third in March-April and a third in August-September.

Fertilizing plants is really about increasing the fertility of the soil. The macronutrients—nitrogen, phosphorous, and potassium—are the basic necessities for plant nutrition. Each of the macronutrients is important for healthy citrus, but nitrogen and phosphorous are considered the most important. Because of this, the new recommendations from the University of Arizona focus on those two. In addition to macronutrients, there are the minerals called micronutrients that help to support plant nutrition. Iron, zinc, manganese, magnesium, sulfur, and calcium are the most important micronutrients for growing citrus. Studies indicate that potassium, calcium, magnesium, and sulfur are rarely deficient in citrus grown by homeowners.

Figeater beetle (Cotinis mutabilis).

Figeater beetle (Cotinis mutabilis).

How can I protect my figs
from the beetles and birds?

One of the benefits of growing fig trees is that they are relatively pest free. The only insect pest of concern is the bright green fig beetle (Cotinis mutabilis), which devours the ripening fruit. They’re seen all over the Southwest during the monsoon months of July to September. In addition to figs, fig beetles love to eat apricots, pears, peaches, apples, melons, grapes, tomatoes, and cactus fruit. They also like to huddle around mesquite and desert broom tree wounds that are oozing sap. The beetles are fairly large (up to 1 inch or more) and noisy as they buzz around. They’re poor pilots that fly slowly, and often bump into you accidentally. But they’re one of the showiest insects in our area.

Birds can also be pests of ripening fruit. As they peck on the fruit, they expose it to the beetles. One common sense line of defense against both of these pests is to harvest fruit early and keep fallen fruit cleaned

up. In this way, you maximize the harvest, and minimize the pest attraction.

Other ways of discouraging and controlling the fig beetle take advantage of its scarab beetle family role in recycling organic matter. During their larval stage they are voracious eaters. So you can shut off their food and shelter by covering, screening, or removing manure, compost, and heavy leaf litter. You may also turn your compost frequently to heat it up. Any exposed grubs will be welcomed by the birds.

By following these suggestions you can reduce your fig pest problems to a manageable level and enjoy a bountiful harvest of a delicious fruit. ✜

  • If selected, your question may be featured in an upcoming issue of Edible Baja Arizona magazine or on our blog.

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