I Have White Grubs in Dead Cacti

Grubs: The Basics

• Grubs look similar to caterpillars and are the offspring of an adult insect. They do not have legs, however, and are limited to a fairly small region for food and a growth habitat. Many beetles and crawling insects lay eggs that hatch into grubs. These larva are second stage insects whose only job is to eat and grow. Grubs are generally below ground denizens or in the case of the cactus, live inside of the plant. They are usually light to white in color, the lack of pigment likely due to their lightless homes. Grubs feed on dead and decaying matter.

Potential Culprits

• The list of pests in cactus cultivation is rather long, but if we narrow it down to a beetle, we are left with May or June beetles. Agave snout weevil is also a possibility, and its offspring are characterized as white grubs. It is a particular pest among succulents but cactus are a close cousin and have been known to be infested with the insect. Another potential is the root mealy bug, also purported to have white grub offspring. It can be spotted early by the white fuzz it leaves around the plant base on the soil.

Postmortem

• The likely cause of death is from internal ingestion. If the cactus was not too big, a single, large white grub could have eaten all the good bits inside, leaving it hollow and decidedly dead. If there are more of the pests, it would be a certainty unless the cactus was extremely over watered and rotted. This would be smelly, however, and certainly noticed. Grubs do nothing but eat as they evolve into adults. Any other stress on the cactus in the form of pests, disease or unsatisfactory growing conditions would weaken it enough to succumb to one little grub.

Prevention

• Cactus should always be examined carefully after purchase. The plants are often grown in reputable nurseries but there is a popular cacti trade on the Internet. Some of these cactus were propagated from cuttings of potentially infested specimens and the insects would be transferred to the new plant. Additionally, many adult insects lay their eggs in soil, so the soil should be immediately changed and the roots of the cactus inspected to prevent introduction of more pests into your home garden.