By Elizabeth Smith
Gardens require attention and maintenance, but even under the best of circumstances, problems can arise. Pests, disease and the wrong conditions are the main culprits when plants do not look their best. First check for the watering requirements for your particular plant. Succulents and cacti need little water while tropical plants like citrus and hibiscus will need a great deal more. Many problems can be resolved with the proper amount of watering. Also consider the location, weather and season of the plant in your garden. Does your plant need more sun? More shade? Are we having torrential rains and winds, whipping those plants around? Is this the proper season for your plant? Mother Nature sends in her clean-up crew for weak and struggling plants, so make sure it is the right time of year for your plants so they will not be susceptible. (For a comprehensive 12 month planting calendar for our particular area, go to: https://www.communitygardensoftucson.org/wp-content/uploads/12MonthPlantingGuideRevD1-1.pdf
A common problem, seen here in the desert, is heavy accumulations of salts. Chemical fertilizer and manure use can both create a buildup of salts as does watering in poor draining soil (caliche). Hot, dry weather means no salt free rain is carrying off that accumulation, so the time of year can be a factor as well.
At the first signs of problems, carefully examine the foliage, stems and roots of a sickly plant. Does it look like something is chewing on it? Garden pests that might be eating away at your plants include grubs, caterpillars, beetles, aphids, grasshoppers, birds, rodents and javelina. Different critters target different things for instance, javelina dig up plants for their roots. One neighbor of mine hangs out on top of their roof at night and sprays these huge rodents with the hose when they show up!
Beetles lay their eggs in the best soil they can find (your garden probably!) and those eggs hatch into grubs that live underground devouring roots until they emerge as adult beetles. You can sift your soil to find these guys or an easier way is to sprinkle the powder from neem seeds onto your soil every couple of months and water it in which will kill the current grubs and deter beetles from laying there.
Caterpillars will be found initially on the new growth at the top of a plant or tree because this is where the adult caterpillar (moth or butterfly) lays their eggs so that their larvae will have delicious, tender leaves to eat. But then those little eggs grow into large caterpillars like the tomato horn worm or the citrus loving dog faced caterpillar, and it is then that your foliage may become decimated. The organic remedy for this is to pluck the little, pearl like eggs off before they hatch, hand pick off the caterpillars, or introduce praying mantis to your garden.
Grasshoppers can do a lot of damage too, and some years, they are more abundant than others. Birds will be happy to take care of them for you, but they may also help themselves to your tomatoes. Birds are usually looking for water when they peck at tomatoes and fruits, so it might help to have a bird bath nearby.
Cutter bees and ants will carve out a perfect partial circle from your rose bush leaves but do little damage otherwise. Aphids are never welcome, but luckily there are a couple of easy remedies. One is to simply use the spray nozzle on your garden hose to spray them off while you’re waiting for those javelina. Another is to introduce predators like ladybugs and praying mantis or even plant “decoy” plants like sunflowers that attract the aphids but still grow just fine.
Lastly, let’s touch base on plant diseases. Diseased plants usually have discoloration and could also have sickly looking root systems. Many plants are now bred with resistant qualities, so look for these if you are finding issues in your garden. Rotating your plant varieties each year will help as well. If you decide to cut off any diseased foliage, never compost it and be sure to disinfect your pruners before using them on another plant. I keep a bottle of rubbing alcohol near my tools for this.
There are just too many diseases to go into here so for a comprehensive look at Arizona specific plant pathogens go to: https://cals.arizona.edu/extension/ornamentalhort/plantprotect/pldiseases_urban.pdf