Common Beneficial Arthropods Found in Field Crops There are hundreds of species of insects and spi- mon in fields that have not been sprayed for ders that attack arthropod pests found in cotton, pests. When scouting, be aware that assassin bugs corn, soybeans, and other field crops. This publi- can deliver a painful bite. cation presents a few common and representative examples. With few exceptions, these beneficial Description and Biology arthropods are native and common in the south- The most common species of assassin bugs ern United States. The cumulative value of insect found in row crops (e.g., Zelus species) are one- predators and parasitoids should not be underes- half to three-fourths of an inch long and have an timated, and this publication does not address elongate head that is often cocked slightly important diseases that also attack insect and upward. A long beak originates from the front of mite pests. Without biological control, many pest the head and curves under the body. Most range populations would routinely reach epidemic lev- in color from light brownish-green to dark els in field crops. Insecticide applications typical- brown. Periodically, the adult female lays cylin- ly reduce populations of beneficial insects, often drical brown eggs in clusters. Nymphs are wing- resulting in secondary pest outbreaks. For this less and smaller than adults but otherwise simi- reason, you should use insecticides only when lar in appearance. Assassin bugs can easily be pest populations cannot be controlled with natu- confused with damsel bugs, but damsel bugs are ral and biological control agents. usually smaller. PREDATORY INSECTS AND SPIDERS Prey Assassin Bugs Assassin bugs are generalist predators that feed on caterpillar eggs and larvae, plant bugs, and other pests and beneficial insects. Bigger species can tackle the largest insect pests found in cotton and other crops. Big-eyed Bugs (Geocoris spp.) These insects are a primarily preda- tory group of Hemiptera (“true bugs”) belonging to the family Reduviidae. Some representative members of this family include thread-legged bugs, ambush bugs, and wheel bugs. Although they are seldom present in large numbers, several species can be important predators of caterpillar This is one of the more abundant and easily pests found in many crops. Wheel bugs can grow detected predators. It is an important predator in to a length of 1½ inch. Assassin bugs are highly cotton, corn, and soybeans. These insects are susceptible to insecticides, so they are more com- commonly found in pre-blooming cotton or in young corn or soybean fields after flying in as Insidious Flower Bug (Orius insidiosus) adults from surrounding vegetation. In the absence of insecticide sprays, they will remain in the field for the remainder of the season. In cot- ton, populations of 20–40 per 100 sweeps can sometimes be found, especially in fields that have not had many early insecticide treatments. Higher populations of tobacco budworms and bollworms can be tolerated if many big-eyed bugs are present. Despite their distinctive appear- ance, they are sometimes mistaken for plant bugs. There are several species of big-eyed bugs, so they are sometimes referred to by their genus name, Geocoris. Geocoris punctipes is the most com- mon species encountered and is the one This insect is often a very important predator in described here. field crops. However, because of its small size, it is commonly overlooked. Orius occurs in all Description major row crops, and it is present throughout the Both the nymphs and adults are well described season. It is an important predator of thrips and by their common name. The head is as wide as often appears in fields shortly after emergence. the body, and the eyes are notably large. Adults Quite often, it is the smaller, less noticeable pred- are about three-sixteenths of an inch long and ators that provide the greatest benefit, and this is are dull gray with transparent, shiny wings. The definitely the case with Orius. This is one preda- nymphs resemble the adults in general body tor that all scouts need to learn to recognize and shape, but they are a distinctive metallic silver- appreciate. They often build to relatively high gray. The eggs are white to pink and shaped like numbers on early-season populations of thrips hotdogs, but they are only one-twenty-fifth of an and mites. When this occurs, they can be of real inch long. These eggs are often found in cotton benefit in “buffering” populations of many cater- terminals and are often mistaken for plant bug pillar pests during mid- and late-seasons. eggs. However, plant bug eggs are almost always inserted into plant tissue and are rarely Description seen by scouts. Like the tarnished plant bug and big-eyed bugs, Orius is a true bug and belongs to the order Prey Hemiptera. The adults are sometimes mistaken Both the nymphs and adults feed on aphids, for chinch bugs, but although they resemble whiteflies, mites, and the eggs and larvae of chinch bugs superficially, the adults are much caterpillars, such as tobacco budworms, boll- smaller (about one-sixteenth of an inch long). The worms, and soybean loopers. They are also pred- adult Orius is black with a white band across its ators of plant bugs, especially the younger back and a white area over the end of its nymphs. In one laboratory study, big-eyed bug abdomen. The nymphs are elongate and yellow- nymphs consumed an average of 151 tobacco ish or yellow-orange. They are often mistaken for budworm eggs or 76 first instar larvae during the thrips, one of their primary prey items. 21–31 days required to complete all five nymphal instars. Late instar nymphs consumed approxi- Prey mately 10 eggs per day. Like many predatory Insidious flower bugs feed primarily on thrips insects in this order, big-eyed bugs also feed on and spider mites, and when these pests are nectar and directly on plants, causing little or no numerous, Orius can build to notably high num- damage. In-furrow systemic insecticides may bers. One reference reports that nymphs are capa- affect their populations. ble of eating an average of 33 mites per day. Eggs of caterpillars, such as bollworms and tobacco budworms, also are favored prey, along with angle downward at the back third of the newly hatched larvae. This predator is common abdomen. Nymphs resemble adults, except for in corn, where it is often found searching for boll- the lack of wings. worm eggs on the silks, and it has been reported to consume as much as 54 percent of the eggs. It Prey is also an important predator of eggs and small Both the nymphs and adults are predatory and caterpillars in soybeans. In cotton, Orius are often feed on a variety of prey. Almost any insect that found in the blooms, where their primary prey is is smaller or slower is subject to attack, including flower thrips. They will also readily attack the other predators. In addition to aphids and white- small larvae of various pest species that they flies, they commonly feed on eggs and larvae of encounter. This makes them an important preda- caterpillar pests such as tobacco budworms and tor of bollworm and fall armyworm larvae. bollworms. They will also attack plant bug nymphs. They occasionally bite scouts as well. Damsel Bugs (Nabis spp.) Spined Soldier Bug (Podisus maculaventris) Like the insidious flower bug and the big-eyed bug, damsel bugs belong to the order Hemiptera and are considered true bugs. They are predators with piercing–sucking mouthparts. Damsel bugs are usually much less numerous than insidious The spined soldier bug is a predatory stink bug flower bugs and big-eyed bugs, but it is not that is sometimes found in cotton, soybeans, and uncommon to find numbers in the range of 2–6 other crops. These predators can easily be con- per 100 sweeps in pre-blooming cotton. They also fused with plant-feeding stink bugs, such as the are important predators in corn and soybeans. brown stink bug. So it is important that scouts Damsel bugs are sometimes mistaken for plant learn to recognize this as a beneficial insect rather bugs, so it’s important that scouts know the dif- than a pest. ference. Damsel bugs belong to the family Nabidae and are also referred to as Nabids. Description Adult spined soldier bugs are medium-sized Description (three-sixteenths to one-half of an inch long) and There are several species of damsel bugs that can brown. They are shield-shaped with a prominent be found in cotton. Most adults are gray to light spine extending outward from each “shoulder.” brown and are about three-eighths to one-half of Unlike plant-feeding species, the tips of the wings an inch long. Adult damsel bugs resemble plant extend past the tip of the abdomen, and there is bugs somewhat in general body shape, but their often a dark line at the wing tips when they over- bodies and legs are longer and more slender. lap. These predators have a strong, stout beak Also, the wings are flat over the entire length of compared to plant-feeding stink bugs, which the abdomen; this distinguishes them from tar- have more slender beaks. The beak is kept folded nished plant bug adults, which have wings that under the body unless feeding. The eggs of spined soldier bugs are laid in a loose mass of age in trees, although it can be found in row 17–70 eggs. Each egg has a characteristic crown of crops as well. This predator has become well- “spines” that rings its top.