Click for a hub of Extension resources related to the current COVID-19 situation.
COVID-19 Resources

Cotton aphid/Melon aphid

Article author: David Kerns
Most recently reviewed by: Pat Porter (2018)

Common Name(s): Cotton Aphid, Melon Aphid

Pest Location

Row Crop, Vegetable and Fruit

Description

Cotton or melon aphids, Aphis gossypii, are highly variable in size and color, varying from light yellow to dark green or almost black. Although size can vary based on environmental conditions, adult aphids tend to be about 1/16th inch in length, are soft bodied and pear shaped. Aphids have piercing-sucking mouthparts and have two protrusions on their rear tips called cornicles. Aphid adults can be winged (alate) or wingless (apterous). The formation of winged types is usually in response to overcrowding or poor host quality. The immatures or nymphs of the aphid are similar in appearance to the adult but smaller.

Origin and Distribution

Cotton aphid is nearly cosmopolitan, having a world-wide distribution. However, host specificity does vary depending on geographic origin.

Habitat & Hosts

Cotton aphids are extremely polyphagous and can feed on a large range of host plants covering 25 plant families. Among many others, notable hosts include asparagus, beans, begonia, catalpa, citrus, clover, cucurbits, cotton, eggplant, ground ivy, gardenia, hops, hibiscus, hydrangea, okra, peppers, potato, spinach, strawberries, tomatoes and violet. Crops typically most affected by cotton aphids include citrus, cotton and hibiscus.

Cotton aphids will initially be found feeding on the underside of new leaves, the plant terminal and flower buds, but as the population grows will infest the under side of older leaves.

Cotton aphids feed using sucking-piercing mouthparts which they use to pierce leaves and ingest copious amounts of plant sap from the phloem. Feeding robs the plant of energy that would otherwise be utilized for growth or fruit production. Heavy and prolonged infestations can cause leaves to curl downward, older leaves to turn yellow and shed, plant fruit may also shed or suffer reduction in size.

Cotton aphids excrete wastes in the form of a syrup-like substance called honeydew. Honeydew will accumulate on the leaves (and other plant structures) giving them a shiny, sticky appearance. A black sooty mold will often grow on the honeydew covering the leaf which may partially inhibit photosynthesis. More importantly, the honeydew may accumulate on the lint of open cotton bolls rendering the lint undesirable for milling.

Cotton aphid is also an important vectors of over 50 plant viruses including cucumber mosaic virus, watermelon mosaic virus 2, and zucchini yellow mosaic virus. These viruses are non-persistent viruses and may be transmitted from aphid to plant in a little as 15 seconds.

Cotton aphids are often attended by ants, which collect an feed upon their honeydew.

Life Cycle

With exception of northern latitudes, cotton aphids in the United States are all females, reproduce asexually (parthenogenically), giving birth to live young without mating. Aphids have a tremendous reproductive capacity and nymphs are born with developing embryos already present; essentially aphids are born pregnant. One female may produce as many as 80 offspring that mature within 8 to 10 days. Thus, it is possible for cotton aphids to have as many as 50 generations per year. These generations also occur as frequently as every 5 to 7 days under optimum conditions. In northern latitudes cotton aphid is capable of producing sexual forms and laying eggs on catalpa and rose of sharon for overwintering purposes.

Wingless adults overwinter in protected areas on catalpa, hibiscus, and a number of weed hosts. In the greenhouse, they can be active year-round. In spring winged females fly to suitable host plants and can disperse great distances via wind and weather fronts.

Management

If you live in the State of Texas, contact your local county agent or entomologist for management information. If you live outside of Texas, contact your local extension for management options.

Predators such as lady beetles, lacewings and syrphid flies, along with parasitoids and aphid-killing fungi are often the most effective means of managing an cotton aphids. These beneficial organisms can effectively prevent aphids from reaching the damaging levels. Aphid tending ants will often protect aphids from predators. Soil and seed applied insecticides offer protection during early plant growth, but foliarly applied insecticides are often necessary on more mature plants. Standard and organically certified insecticides are available, but cotton aphid is notorious for developing resistance to commonly used insecticides so adequate control is not certain.

Related Publications

Citations

Blackman, R.L. and V. F. Eastop. 2000. Aphids on the worlds crops: an identification and information guide 2nd edition. Chichester, UK: John Wiley & Sons Ltd.

Kerns, D.L., J.A. Yates and B.A Baugh. 2015. Economic threshold for cotton aphid (Hemiptera: Aphididae) on Cotton in the Southwestern United States. J. Econ. Entomol.108: 1795-1803.

Suhas, V., D. Kerns, C. Allen, R. Bowling, M. Brewer and M. Parajulee. 2017. Managing cotton insects in Texas. ENTO-075, 38 pp. http://www.agrilifebookstore.org/Managing-Cotton-Insects-in-Texas-p/ento-075.htm.

Bugwood Images

Corn earworm

Article author: Pat Porter
Most recently reviewed by: Ed Bynum (2018)

Common Name(s): Corn earworm, Cotton Bollworm, Tomato Fruitworm

Pest Location

Row Crop

Description

Corn earworm moth. Photo: Ed Bynum, AgriLife Extension

Corn earworm moth

The corn earworm is also the pest known as the cotton bollworm and tomato fruitworm and can be found on many garden and farm crops and non-crop vegetation. Adults have buff-colored wings and rather stout bodies. The wingspan is approximately 1½ inches. They are good fliers and can easily move from field to field and often arrive in large numbers on storm fronts. The moths only feed on nectar and are not pests.

 Corn earworm egg. Photo: Pat Porter, AgriLife Extension

Corn earworm egg

However, each female can lay 500 or more eggs. The eggs are laid singly and, when new, are pearly white. The color changes to a yellow/dull white tint over time before hatching. Small caterpillars look much like the small caterpillars of other species, and it is difficult to identify them without a microscope. Corn earworm caterpillars have many microspines on the back and sides of the body, and these are not found on most other common caterpillar pests. Larvae have a tan head and alternating dark and light stripes running lengthwise down the body, and they have numerous tubercles (dark spots) with long spines. Other pest species have stripes as well, but they do not have the abundance of microspines and tubercles, and a 10x hand lens will allow differentiation. There is no “typical” larval color, and it is common to find larvae that are either light green, dark green to grey green, or pink. Full grown larvae are approximately 1.5 inches long.

Origin and Distribution

The corn earworm is a New World insect (Western Hemisphere) and is present throughout this region. It overwinters only in areas with mild winters, but flies to other areas during the course of the spring, summer and fall.

Habitat & Hosts

Corn earworm has a very wide host range, and in Texas is usually the caterpillar found in ears of corn. Other cultivated hosts include tomato, sorghum, cotton, soybean, sunflower, squash, watermelon, potato, sweet potato, asparagus, artichoke, cowpea, snap pea, green bean, cabbage, cantaloupe, collard, cucumber eggplant, pepper, watermelon and others.

Life Cycle

Adults are quite mobile and can lay eggs on any host that is at a susceptible stage. Eggs are often laid near or on fruiting structures, but they can be laid on leaves and stems as well. Moths prefer to lay eggs directly on the green silks of field corn and sweet corn, and the larvae then consume the silk and move toward the ear tip.

Eggs hatch in 3-5 days and there will be five to six larval instars, each separated by a molt to a larger caterpillar. The larval stage lasts from 13 to 31 days depending on temperature. Insects develop faster under higher temperatures. After the last larval stage, the larvae move to the soil and construct a burrow where they will remain while in the pupal stage, which lasts from 10 – 25 days depending on temperature. Adults then emerge and will live for an average of 10 days, some more and some less. Corn earworm overwinters in south Texas, and often flies north carried on storm fronts. There are several generations per year and the insect can be expected to be present for most of the growing season in the south, but only increases gradually in number in more northern parts of the state. However, the growing season starts later in the north, and corn earworm is usually quite abundant by the time vegetables and other crops are susceptible.

Corn earworm larvae are cannibalistic and, even though there may be several small larvae in an ear of corn, these will eventually be reduced to one, or less commonly two, per ear. As fruit feeders, even one larva can cause significant damage in vegetable crops, but in agricultural crops like field corn, corn earworm is rarely an economic worry

Management

If you live in the State of Texas, contact your local county agent or entomologist for management information. If you live outside of Texas, contact your local extension for management options.

Home garden control options include:

  • Spinosad (Rate varies by brand name)
  • Permethrin
  • Synthetic pyrethroids
  • Bacillus thuringiensis (Bt. subspecies Kurstaki)

See Understanding Common House and Garden Insecticides ( https://citybugs.tamu.edu/factsheets/ipm/ent-4002/ ) for more information on insecticides.

Related Publications

Bugwood Images

Click Beetle / Wireworm


Most recently reviewed by: Janet Hurley & Pat Porter (2018)

Common Name(s): Click beetle, Wireworm

Description

Click beetles are elongated, parallel-sided and usually bear backward projections on the side corners of the shield behind the head (pronotum). They are somewhat flattened and range in size and color by species. Smaller species are about 1/4 inches long. Most species are brown to black in color, although some have reddish and yellowish colors and patterns. The eyed click beetle, Alaus oculatus (Linnaeus), reaches 1-½ inches in length and is beautifully marked with prominent oval eye spots on the pronotum and mottled gray wing covers. When placed on their backs, these beetles characteristically “click”, snapping their thoracic segments (prothorax and mesothorax) to cause their bodies to flip in the air to right themselves. Larvae, called “wireworms,” are usually hard-bodied, brownish, ½ to 2-½ inch long and cylindrical, with three pairs of tiny true legs behind the head and a flattened, and an ornamented shield-like segment on the tail end of the body.

The false click beetles (Eucnemidae) are similar to click beetles, and some species can even “click.” They are less common and usually occur in wood just beginning to decay. The Texas beetle, Brachypsectrida fulva LeConte (Coleoptera: Brachypsectridae) somewhat resembles a 3/16-inch long click beetle without the clicking mechanism. There is only one species in this family.

Habitat & Hosts

Larval stages (wireworms) damage seeds and seedlings of a wide variety of crops including alfalfa, beans, beets, clovers, corn, cotton, grasses, small grains (wheat, oats, etc.) many vegetable and bedding plants.  They also tunnel into potato and sweet potato tubers. Larvae of some species, such as the eyed click beetle, occur in dead trees and rotting stumps and logs.  Adults of Deilater have two light-producing spots on the thorax and one of the abdomen, somewhat similar to that of lightning bugs (Lampyridea).

In some years, adults are extremely numerous and enter homes and other structures in significant numbers. Adults do not damage plants.

Life Cycle

Biology varies by species. In general, adults and larvae overwinter in the ground, becoming active in the spring. Adult females dig burrows and lay eggs around the base of host plants. Eggs hatch within a few weeks and larvae develop through several molts over a period of time from several months to over 4 years. They pupate in the cells within the soil in late summer or fall, and emerge as adults a few weeks thereafter. Generations can greatly overlap.

Management

If you live in the State of Texas, contact your local county agent or entomologist for management information. If you live outside of Texas, contact your local extension for management options.

Minimize wireworm infestations through clean cultivation and clean fallowing. Infestations are most severe in no-tillage or reduced-tillage situations, particularly following alfalfa, cover crops, or grain. Planting shallow and under warm conditions often allows cotton seeds to germinate quickly so plants can outgrow wireworm injury potential rapidly.

Larvae of some species damage seeds and underground parts of crop plants. Management in agricultural settings varies by crop, and growers should consult publications specific to the crop being grown. It is often the case that significant stand damage requires a replant of the crop.

Wireworm damage can be difficult to diagnose, in part because the larvae are highly mobile in the soil and may no longer be present. Look for chewed tissue on seeds and young plant parts below ground.

Wireworm damage to cotton seedlings. Photo credit: Patrick Porter.

Wireworm damage to cotton seedlings. Photo credit: Patrick Porter.

 

Time-lapse video showing wireworm larvae seeking shelter in soil. Video credit: Patrick Porter.

Related Publications

Insects in the City “Click beetles gone wild

Wireworms at cottonbugs.tamu.edu

Bugwood Images