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Silverleaf whitefly

Article author: Erfan Vafaie
Most recently reviewed by: Pat Porter & David Kerns & Suhas Vyavhare (2018)

Common Name(s): Silverleaf Whitefly, Sweetpotato whitefly

Description

The silverleaf whitefly, Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae), is a global pest of many economically important host plants (Simmons et al. 2008) such as eggplant, tomato, sweet potato, cucumber, garden bean (Tsai & Wang 1996), cotton, and poinsettias, to name a few. Similar to other sucking insect pests, silverleaf whiteflies reduce plant vigor, growth, and can even cause mortality by piercing plant tissue and feeding on plant phloem (Bryne & Miller 1990). Whiteflies excrete waste as a sugary solution, known as honeydew. Excessive honeydew can result in inoculation of a complex of fungi, resulting in a black layer or crust forming on the surface, commonly referred to as sooty mold. In addition to causing detrimental damage by feeding, B. tabaci has been recorded to vector more than 100 plant viruses (Jones 2003), which can result in rapid widespread crop loss. Some of these viruses in Texas include Cucurbit leaf curl virus (Brown et al. 2000) and cucurbit yellow stunting disorder virus (Kao et al. 2000).

Adult whiteflies resemble very small (1 mm or 3/64-in) white moths. When disturbed, adult whiteflies will often leap off the plant and fly a short distance before landing on a nearby surface. Whitefly nymphs, especially younger nymphs, can be hard to see with the naked eye. Whitefly nymphs often blend with the leaf due to their color and relatively flat shape. The final nymph instar is often referred to as a pupa, when they become darker yellow color and are more round, making them easier to distinguish on the leaf. Once they emerge as adults, their shed ‘skin’ stays on the leaf, known as an exuvia. The exuviae stay on the leaf and resemble a small empty shell.

Adult silverleaf whiteflies can be confused for other whiteflies that may occur in Texas, with two other common ones being the badedwing whitefly (Trialeurodes abutiloneus) and greenhouse whitefly (Trialeurodes vaporariorum).

Origin and Distribution

Silverleaf whiteflies are considered a global pest, however there are certain biotypes or species that are more prevalent in different parts of the world. Texas has populations of both MEAM1 (B biotype) and MED (Q biotype) whitefly.

Life Cycle

Whiteflies are closely related to mealybugs and scale insects. Female adult whiteflies lay eggs, often in a circular pattern as result of the female using her feeding proboscis as a pivot while laying eggs. Eggs are pear-shaped and approximately 0.2 mm long (CABI MEAM1). On cotton, eggs take between 5 to 22.5 days to emerge as crawlers when held at 16.7ºC (62F) or 32.5ºC (90.5) (Butler et al. 1983), respectively. After emerging from the eggs, a mobile stage known as “crawlers” find a place nearby to settle. Once settled, whitefly nymphs are considered rather immobile until after metamorphosis. Bemisia tabaci undergo four instar stages before pupation and becoming a winged adult. The total development time from egg to adult varies from 16.6 days at 30ºC (86F) to 65.1 days at 14.9ºC (59F) in cotton (Butler et al. 1983). Adult females lay approximately 72 – 81 eggs and survive an average of 8 to 10.4 days in controlled studies (Butler et al. 1983).

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.

Silverleaf whitefly taxonomy is currently under revision, but it is generally agreed upon that there are specific groups of silverleaf whiteflies that exhibit different host plant preferences, reproductive rates, and resistance to insecticides. Originally, it was thought that silverleaf whiteflies were composed of several different ‘biotypes’, a couple well-known ones including the “B” (MEAM1) and “Q” (MED) biotypes, but now has been proposed to be made up of at least 34 morphologically indistinguishable species (Tay et al. 2012). The MEAM1 whiteflies have greater reproductive potential than the MED whiteflies, however the MED whiteflies are resistant to several different insecticides, such as pyriproxyfen and imidacloprid. Growers are encouraged to either use biological control to prevent further rise of resistance to insecticides, or rotate between insecticides that are known to be effective against both MEAM1 and MED whiteflies. See “Related Publications” below for more information.

Whitefly populations can be monitored using yellow sticky cards or searching the undersides of leaves for eggs, nymphs, pupae, exuviae, or adults. Look for other signs of infestation, such as honeydew, sooty mold, or chlorosis.

In many regions of Europe and North America, silverleaf whiteflies in protected culture (i.e. greenhouses) are managed through regular releases of biological control agents. In the USA, commercially available biological control agents that have demonstrated potential management of silverleaf whiteflies include Eretmocerus eremicus (Hoddle and van Driesche) and Amblyseius swirskii (Calvo et al. 2010).

Insecticidal management of silverleaf whiteflies are highly dependent on commodity, location, setting, and thresholds. Some active ingredients that have demonstrated efficacy against both MEAM1 and MED silverleaf whiteflies include:

  • Abamectin
  • Abamectin + Bifenthrin
  • Acetamiprid
  • Beauvaria bassiana
  • Cyantraniliprole
  • Dinotefuran
  • Isaria fumosorosea
  • Horticultural Oil*
  • Insecticidal Soap*
  • Pyridaben
  • Pyrifluquinazon
  • Spiromesifen
  • Spirotetramat
  • Thiamethoxam

(Kumar et al. 2017)
*Beware of application in extreme heat and exposure to sun. Can cause leaf burn/phytotoxicity.

For more information, consult one of our related publications below for whitefly management specific to your situation.

Related Publications

CABI Bemisia tabaci (MEAM1) fact sheet: https://www.cabi.org/isc/datasheet/8925#8440C199-FEDE-40E6-AED0-E7C195DC4E5B

CABI Bemisia tabaci (MED) fact sheet: https://www.cabi.org/isc/datasheet/112682

Byrne, David N. (1991). Whitefly biology. Annual Review of Entomology, 36: 431 – 457.

Suhas et al. (2018). Managing Cotton Insects in Texas. Texas A&M AgriLife Extension. https://agrilife.org/extensionento/resources/management-guides/managing-cotton-insects-in-texas/other-pests/

Kumar et al. (2017). Whitefly (Bemisia tabaci) management program for ornamental plants. UF/IFAS Extension. https://mrec.ifas.ufl.edu/lso/bemisia/Documents/EDIS-Whitefly-Management-Program.pdf

Citations

Brown et al. (2000). Cucurbit leaf curl virus, a new whitefly transmitted geminivirus in Arizona, Texas, and Mexico. The American Phytopathological Society, 84(7): 809.

Butler et al. (1983). Bemisia tabaci (Homoptera: Aleyrodidae): Development, oviposition, and longevity in relation to temperature. Annals of the Entomological Society of America, 76: 310 – 313.

Byrne & Miller (1990). Carbohydrate and amino acid composition of phloem sap and honeydew produced by Bemisia tabaciJournal of Insect Physiology, 36: 433 – 439.

CABI Bemisia tabaci (MEAM1) fact sheet: https://www.cabi.org/isc/datasheet/8925#8440C199-FEDE-40E6-AED0-E7C195DC4E5B

Calvo et al. (2011). Control of Bemisia tabaci and Frankliniella occidentalis in cucumber by Amblyseius swirskii. 56(2): 185 – 192.

Hoddle, M. and van Driesche, R. G. (1999). Evaluation of inundative release of Eretmocerus eremicus and Encarsia formosa Beltsville strain in commercial greenhouses for control of Bemisia argentifolii (Hemiptera: Aleyrodidae) on poinsettia stock plants. Biology and Microbial Control, 92(4): 811 – 824.

Jones D (2003). Plant viruses transmitted by whiteflies. European Journal of Plant Pathology, 109: 197 – 221.

Kao et al. (2000). First report of Cucurbit yellow stunting disorder virus (genus Crinivirus) in North America. The American Phytopathological Society, 84(1): 101.

Kumar et al. (2017). Whitefly (Bemisia tabaci) management program for ornamental plants. UF/IFAS Extension. https://mrec.ifas.ufl.edu/lso/bemisia/Documents/EDIS-Whitefly-Management-Program.pdf

Simmons et al. (2008). Forty-nine new host plant species for Bemisia tabaci (Hemiptera: Aleyrodidae). Entomological Science, 11: 385 – 390.

Tay et al. (2012). Will the real Bemisia tabaci please stand up? PLoS ONE, 7(11): 7 – 11.

Tsai & Wang (1996). Development and reproduction of Bemisia argentifolii (Homoptera: Aleyrodidae) on five host plants. Environmental Entomology, 25(4): 810 – 816.

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Soybean Podworm

Article author: David Kerns, Pat Porter
Most recently reviewed by: (1970)

Common Name(s): Corn earworm, Cotton Bollworm, Sorghum headworm, Soybean Podworm, Tomato Fruitworm

Description

The soybean podworm is also known as the corn earworm, cotton bollworm, sorghum headworm and tomato fruitworm and can be found on many garden and farm crops and non-crop vegetation. In most soybean production, soybean podworm is referred to as corn earworm. 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.

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. Soybean podworm 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.

A very similar pest that may be found infesting soybean is the tobacco budworm. Eggs and larvae of soybean podworm and tobacco budworm indistinguishable without fine magnification. Tobacco budworm larvae have a tooth-like projection, called a retinaculum, on the inside surface of the mandibles and fine short hairs on the first, second and eighth abdominal projection (tubercle) which bear a single, prominent spine. If the projection and hairs are absent, this indicates a podworm. Damage and management of these two pests are the same in soybean. Soybean podworm may be distinguished from other soybean infesting caterpillars primarily based on the number of pairs of abdominal prolegs.

 

Origin and Distribution

The soybean podworm 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

Soybean podworm 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, sunflower, squash, watermelon, potato, sweet potato, asparagus, artichoke, cowpea, snap pea, green bean, cabbage, cantaloupe, collard, cucumber eggplant, pepper, watermelon and others. The first generation of soybean podworm primarily develops on wild hosts, principally clovers. The second generation develops primarily on corn. Among soybean podworm hosts, corn is the most suitable of all hosts. The third and fourth generations generally occur in other agronomic host crops such as soybean, cotton, and grain sorghum with the fifth generation occurring primarily on volunteer crop plants after harvest and on other non-crop wild hosts.

Host preference of soybean podworm is positively correlated to plant maturity and it strongly prefers plants in the flowering stage. Thus, egg lay in soybean most often occurs during flowering or the R1-R2 stages. Later infestations may occur but are much less common. High infestations of soybean podworm often follow pyrethroid applications during bloom, due to destruction of natural enemies.

Although a less common pest of soybean in Texas, in other parts of the southern U.S. soybean podworm is often the most economically important insect pest of soybean. Soybean podworm causes damage to soybean through defoliation and from consuming pods. Early instars typically feed on blooms and and leaves. Feeding on blooms is not considered economical and defoliation by podworms alone is usually not severe enough to warrant control. Most damage is associated with 3rd-6th instar larvae which will feed upon leaves, but more importantly soybean pods. One larva can consume 15-20 flat pods or 6-10 older pods.

 

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. 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. Soybean podworm 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 northern parts of the state. However, the growing season starts later in the north, and soybean podworm is usually quite abundant by the time vegetables and other crops reach susceptible stages.

Soybean podworm larvae are cannibalistic but in soybean they are usually not confined to groups in small areas so this behavior is inconsequential.

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.

Most states have well defined action threshold to aid in management decision making. Sampling for soybean podworm usually involves sweep net or drop cloth. In much of the southern U.S., pyrethroid resistance is common in soybean podworm populations so caution should be used if using a pyrethroid for podworm control. Commonly used insecticides for soybean podworm and tobacco budworm include products containing chlorantraniliprole, spinetoram or spinosad. Additionally, the nucleaopolyhedrovirus, i.e. Heligen, has proven to be an effective alternative to chemical insecticides.

Related Publications

Citations

Adams, B.P., D.R. Cook, A.L. Catchot, J. Gore, F. Musser, S.D. Stewart, D. L. Kerns, G. M. Lorenz, J.T. Irby and B. Golden. 2016. Evaluation of corn earworm, Helicoverpa zea, (Lepidoptera: Noctuidae), economic injury levels in Mid-South reporductive stage soybean. J. Econ. Entomol. 109: 1161–1166.

Flanders, K. and R. Smith. 2008. Identifying caterpillars in field, forage, and horticultural crops. Alabama Cooperative Extension, ANR-1121. http://www.aces.edu/pubs/docs/A/ANR-1121/ANR-1121.pdf.

Hartstack, A. W., J. P. Hollingsworth, R. L. Ridgway, and J. R. Coppedge. 1973. A population dynamics study of the bollworm and the tobacco budworm with light traps. Environ. Entomol. 2: 244–252.

Mueller, A. J., and B. W. Engroff. 1980. Effects of infestation levels of Heliothis zea on soybean. J. Econ. Entomol. 73: 271–275.

Smith, R. H., and M. H. Bass. 1972. Soybean response to various levels of podworm damage. J. Econ. Entomol. 65: 193–195.

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Minute pirate bug

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

Common Name(s): minute pirate bug, Pirate bug

Description

Adults are tiny (1/8 inch) black bugs with white markings at the base of the front wings (hemelytra), resulting in a band-like appearance across the body when wings are at rest. Wingless immature stages (nymphs) are orange. Insects in this family (Anthocoridae) are occasionally mistaken for chinch bugs (family Blissidae), particularly in the early nymphal stages.  

Origin and Distribution

Orius species are most common in the eastern United States, although they occur across the southwestern United States to Utah and southern California, then south into Mexico and Central and South America (Herring 1966). They also occur in Cuba, Puerto Rico, and many other islands of the West Indies (Herring 1966). There are at least eight species found in the United States. 

Habitat & Hosts

Nymphs and adults prey upon a wide variety of arthropods including aphids, chinch bugs, springtails, plant bugs, thrips, eggs and small larvae of corn earworms, whiteflies and spider mites. Sucking mouthparts are inserted into prey and body fluids are removed. When corn earworm eggs are plentiful, Orius sp. eat about one egg per day. They are important natural enemies of pests of many agronomic and horticultural crops including corn, cotton, sorghum, soybeans. They may also feed on tender plants. Anthocorids can be found on many kinds of plants, particularly agricultural crops, where they can be abundant. Some Orius species are sold commercially for augmentative biological control releases.

Orius species are capable of using their sucking mouthparts to bite humans. The insidious flower bug, O. insidiosus (Say), is often the more abundant species in east Texas.

Life Cycle

Adults overwinter in protected habitats such as in leaf litter. Female Orius sp. insert eggs into plant tissue. Nymphs develop through several stages (instars) before becoming winged adults. Development from egg to adult takes approximately 20 days, and there are several generations per year. 

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.

Orius species are considered to be beneficial; nymphs and adults prey on a number of small arthropod life stages. 

Related Publications

Orius species on Bugguide.

Citations

Marshall, S. A. (2006). True Bugs and Other Hemipteroids . In S. Marshall (Ed.), Insects Their Natural History and Diversity . United States : Firefly Books Ltd.

Herring JL. 1966. The genus Orius of the Western Hemisphere (Hemiptera: Anthocoridae). Annals of the Entomological Society of America. 59: 1093-1109.

University of California: http://ipm.ucanr.edu/PMG/NE/minute_pirate_bug.html

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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.

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