Did you know that there are good grubs and bad grubs?
Before we get started on grubs, let’s clarify the difference between grubs and caterpillars.
Grub or caterpillar?
Grubs and caterpillars are both the larval form of certain insects. They both feed like crazy before transforming into their adult versions. They both have longish, squishy bodies. So, what’s the difference? The difference is in family lines. Caterpillars are the offspring of butterflies and moths, while grubs are baby beetles. There are other differences, as well. Caterpillars have thick, meaty legs, and several of them, while grubs have stubby, ineffective legs (if they have any at all). Also, caterpillars tend to be brightly colored, whereas grubs tend to be white or tan. Grubs are generally one inch long, can feature a dark head, and may or may not have bristles, and they tend to rest curled up in a C-shape.
Bad grubs, such as masked chafers, cutworms, Japanese beetles, armyworms, June beetles, and some weevils, can create brown patches in your lawn and wilting of fruit and vegetable crops. They do this by feeding on roots.
Not so bad grubs
While adult dried fruit beetles can cause problems, feeding on your figs, peaches, and plums, their larvae actually feed on organic material in the soil, helping in the decomposition process, making more nutrients available to your plants.
A while back, I discovered a huge grub population in a raised bed that I use for potatoes. I dug them up (below) and fed them to my chickens. Then I learned that they were green fruit beetle larvae and that they had been making better use of the aged compost I had added to the bed. Ah, well. Live and learn. The chickens were happy.
Since most grubs are root feeders, getting rid of them can help your edibles, ornamentals, and your lawn stay healthy. Hand picking is the most effective method. This means breaking up the soil and picking them up. Breaking up the soil also makes it easier for birds to get their share of those high protein snacks. As much as we would all love easy fixes, products such as diatomaceous earth and white milky spore are not your best choices against grubs. Diatomaceous earth, while it can kill grubs, will also kill off beneficial insects. White milky spore, frequently advertised as a great grub killer, is generally only effective against Japanese beetle larvae, which are not (yet) a real problem here, in California.
Beneficial nematodes can be used against grubs, but the timing must be exactly right for them to do their job. Soil temperatures must be above 60°F, making it the method of choice in summer and early fall, but completely ineffective in spring.
How do you know if you have a grub problem?
Brown patches and wilting can be caused by several factors. The easiest way to see if you have a grub problem is to conduct a drench test. To do this, fill a large watering can or bucket with 2 gallons of water and gently stir in 1/4 to 1/2 cup liquid dish detergent. Then, mark off an area, 3 feet square, with some string. Pour the soapy water evenly over this area. Within 10 minutes, you will see whatever insects are living in that particular piece of soil. If you have a problem, it will be obvious.
You can grow a surprising amount of food in your own yard. Ask me how!