June Desert Garden Problems

The male cicadas’ mating calls are a cacophony of sound that permeates the desert air and often heralds to the gardener that summer has arrived. The Apache cicada is common to low-desert regions and the adult has a black body with a pale band behind its head. The nymphs spend almost their entire life underground feeding on the roots of many desert trees, shrubs and other ornamentals. As the nymph becomes an adult, it will then surface from the soil and will undergo one last shedding of its exoskeleton. The adult cicada will feed on the plant sap of many urban trees or shrubs. After mating, females will make small “hatch” marks on the slender tips of trees or shrubs lay their eggs. This physical damage can cause the tips to “die” back, but is not detrimental to the plant and is often thought of as “natural pruning”. There is no need to control cicadas as they are part of the desert ecology. Allow natural predators to control the population as many birds and lizards find the cicada nymph and adult to be a tasty treat.

If we had a dry spring, rabbits may be nibbling on plants that they may not have eaten before. Most mature plants can handle rabbit sampling, but newly planted plants should be protected until they have attained a larger size. Protect plants with a wire cage or spray Liquid Fence TM to help deter these animals.

Fine webbing between leaves or stippling on leaves may indicate the presence of spider mites. These plant mites cause damage by sucking contents from the leaves and are difficult to detect due to their small size. Plants that are water stressed may become susceptible to infestation. Dusty conditions can also lead to spider mite outbreaks. Make sure your plants are well-watered and wash off accumulated dust on plants to manage spider mite problems. You can also remove by using a fast spray of water or by spraying insecticidal soap to control populations. There are many biological controls that feed on spider mites including lacewings, predatory mites, lady bugs and big-eyed bugs. Using insecticides is not recommended as insecticides do not help manage the population, but can actually cause the population to intensify. Insecticides used will often kill their natural enemies and can even accelerate mite reproduction.

Agave snout weevils become active during the warm months and infestation may not be apparent until it is too late.

If you notice a rank odor and black ooze dripping down the saguaro stem(s), the plant may have developed an infection as a result of an injury or frost damage. The infection is caused by the Erwinia bacteria, a common bacterium found in the environment.

Cochineal scale, the cottony, white substance on your Prickly-pears (Opuntia spp.) and Chollas (Cylindropunita spp.) may be active now. Remove by using a fast stream of water or spray insecticidal soap.

The large, black-brown beetle bumbling onto your porch during the sweltering summer nights is the Palo Verde Beetle. It has just emerged from its subterranean home looking for a mate. For the past two to four years it has lived underground as a grub or larva feeding on the roots of many native and non-native plants, not just Palo Verde trees as the common name suggests. When the grubs become adults they will surface and can be seen in late June, July, August and September particularly after rainfall. Once the female adults mate, they lay their eggs and die soon after making their life span about one month. Using insecticides is not recommended as the beetle is already gone by the time you notice any damage. To prevent root borers keep your plants healthy as possible as they seldom cause problems to healthy plants.  There are many natural predators of the adult beetle including roadrunners, coyotes, owls and even bobcats. Grubs are eaten by skunks.