In the same way that red lights warn drivers and pedestrians, the color red in nature is a warning signal to predators. Whether it’s an instinctive or learned behavior, animals associate red with causing pain or tasting awful. Little red bugs all over your backyard can be disconcerting, but don’t reach for the bug fogger too quickly. Some of those creatures might be helping your garden. Proper identification is essential for making effective treatment decisions.
Red Velvet Mites
Those little red bugs in your backyard might not be bugs at all. Related to spiders, red velvet mites (Thrombidiidae spp) are less than 1/4-inch long with bright red, plush-appearing bodies. There is no need to get rid of these creatures. They are harmless to you and your pets, and they feed on pest insects, such as beetles, grasshoppers and plant hoppers, that may be damaging your plants.
The red clover mite (Bryobia praetiosa) is approximately 1/32-inch long and distinguished from other red mites by its long front legs. Clover mites are common plant-feeding backyard and indoor pests, particularly after rain in spring. To eliminate these pests outdoors, mix two tablespoons of liquid dish soap and one gallon of water into a garden sprayer. Spray over the infested area and repeat the application as necessary. Prevent clover mites from becoming a problem indoors by removing "mite bridges" from your yard to your building. These include plants, landscaping stones and plant debris. Loosen the soil in a strip up to 24 inches wide around your house. Clover mites avoid crossing cultivated soil.
If you or your pets experience itchy, swollen welts after spending time in the backyard, the little red creatures responsible might be harvest mites (Trombicula alfreddugesi), also called "chiggers." At 1/64- to 1/20-inch-long, these eight-legged creatures are difficult to see. As adults, they are harmless. However, their six-legged larvae inject digestive enzymes into human and animal skin, and then feed on the affected cells. Chiggers can remain attached to the skin for several days. Scrub them off with hot, soapy water. To prevent bites, wear protective clothing and insect repellent containing DEET. To reduce or eliminate chiggers in the yard, clear away brush piles, prune bushes and mow lawns as close to the ground as possible. These methods help to reduce ground level humidity, a condition favored by harvest mites.
Box Elder Bugs
Boxelder bugs (Boisea trivittata) are less than 1/2-inch long, dark grey, elongated insects with three red lines on the area behind their head. Immature nymphs of boxelder bugs are often bright red. Both feed on shade or fruit trees and often congregate on tree trunks. Remove boxelder bugs with a forceful spray of water from the garden hose. Alternately, use a wet-dry shop vacuum to suck up the congregating bugs, but be sure to add a bit of water and a few drops of liquid dish soap to the vacuum tank to kill the bugs and prevent their foul odor from adhering to the equipment.
Red bugs, or stainers, are aptly named true bugs in the family Pyrrhocoridae. The cotton stainer (Dysdercus suturellus) is the only stainer known to be native to the United States, and gets it name from its habit of leaving yellowish stains on cotton bolls as it feeds on them. An introduced species, Mediterranean red bug (Scantius aegyptius), however, has recently arrived in California, where it is considered an invasive species. First documented in 2009, the adult insects are slightly more than 1/4-inch long with black markings on their red forewings. Nymphs are a solid, bright red color. Stainers are similarly-colored, and may also be found feeding on backyard fruit trees. Invasive red bugs congregate in large masses and feed on a variety of plants and seeds on the ground. Some evidence suggests that ants may be natural predators of red bugs. For small infestations of red bugs, pick off or knock the pests into a bucket of soapy water. You can also use small piles of seeds or fruit as bait to attract the insects to one area then kill them with soapy or hot water. Tanglefoot will keep stainers from climbing trees to attack fruit.