Poor Growth of Lantana Due to Grubs

Q. This season our Lantana has done poorly. For each plant we dig up there appears a bunch of grubs. What's going on?

A. Nice detective work! I would not have guessed this was the problem if you had just sent me a picture of a dying lantana. These guys are decomposers normally and people will find them in their compost piles.

Green june beetle which attacks soft fruit like figs

But these critters will also feed on small, living roots. In large numbers they can cause alot of damage or even death. In small numbers and feeding on roots the plant might appear normal with no apparent damage. The dose makes the poison!

One of the chafers or June bugs they are sometimes called

These are the immature of one of the scarab beetles such as June beetles, metallic June beetles, dung beetles and rose chafers which we have here. Another one that attacks lawn grasses is the "white grub" or sometimes just called "grubs".

One very famous and devastating scarab is the Japanese beetle which we have not yet seen in southern Nevada. 

When you find these immature larva feeding in one localized area around a living plant it is a very good sign they are feeding on it.

They are fairly easy to kill with insecticides such as the conventional insecticide Sevin used as a soil drench or organically using a treatment of bacterial spores. It is marketed under different trade names but if you look in the insect control section of your favorite nursery or garden center you should be able to find it.

Frequently the bacterial spores are referred to as "milky spore" insecticide. There are also nematode good guys that you can apply. I am not sure it is carried in Las Vegas but certainly over the internet.
http://en.wikipedia.org/wiki/Scarabaeidae