Gall-Making Insects And Mites - Agrilifeextension.tamu.edu
E-3979/13Gall-Making Insects and MitesMichael Merchant*A gall is an abnormal swelling of plant tissue. It canbe caused by mechanical injury or by several speciesof insects, mites, nematodes, fungi and bacteria. Infact, there are more than 2,000 species of gall-makinginsects in the United States. The association betweenthe gall-making organism and the host plant is usually quite specific. Different organisms produce gallsof characteristic size, shape and color. These visualcharacteristics are useful in species identification. Thispublication has basic information on the biology andecology of common gall-making insects and mites andsuggestions for managing galls.es associated with feeding, by insect or mite excretions, or simply by the presence of the insect or mitein or on the plant tissue. Once stimulated, the plantproduces gall tissue to surround the egg or immatureinsect or mite. As it grows, the gall and the insect/miteuse nutrients from the host plant. Gall makers maylive within individual chambers or within communal chambers inside galls, depending on the species.Mature galls stop growing and cease to use host plantnutrients. The developing insects or mites remain protected inside mature galls, grazing on the ready foodsource.Gall DevelopmentDamage and Host PlantsGalls usually occur on leaves and stems, but alsomay occur on flowers, fruits, twigs, branches, trunksand roots. Some galls are easy to recognize and thecommon terms used to describe them reflect their appearance—blister galls, bud galls, bullet galls, flowergalls, fruit galls, leaf galls, leaf spots, oak apples, pouchgalls, roly-poly galls, root galls, rosette galls, stem gallsand twig galls.Gall-making insects are generally not consideredpests, and some galls are even considered attractiveand are used in flower arrangements and other crafts.Most gall-making insects do not damage the hostplant; however, certain species may cause aestheticdamage—such as leaf discoloration, early defoliation,or twig and stem drop—to valuable plants in the nursery or landscape. Heavy infestations of the pecan stemphylloxera can reduce pecan yield.Galls develop in three phases—initiation, growthand maturation. Gall initiation is a reaction of theplant to a specific stimulus by the gall-maker. Thestimulus may occur during colonization, egg-layingor feeding. Galls can be induced by secretions fromdeveloping eggs or larvae, by saliva or other substanc-* Extension entomologist, The Texas A&M University SystemGalls occur on a wide variety of plants, but the mostcommon ones occur in oaks, hackberries, roses andtheir relatives, willows and asters. The susceptibility ofplant species varies. Some plants support only one ortwo species, while others, such as oaks and hackberries, are hosts to several species (Table 1). Individualplants of the same species, especially those propagatedfrom seed, may also show differences in susceptibility.
Table 1. Common gall-making insects and mites in Texas.Host plant(s)Type of gall(s)Classification/pestAppleGall on roots and twigsWooly apple aphidCypressSwellings on growing tipsBranchlet (midge) gall, Taxodiomyia sp.ElmBladder or finger-type leaf gallsMite, Eriophyes ulmiFicusLeaf folding and rollingCuban laurel thripsGrapeGalls on rootsGrape phylloxeraHackberryBlister, nipple, petiole, bud gall and othersTop-shaped galls on undersides of leavesPachypsylla spp.Cecicdomyid flyHickory, pecanPetiole and leaf stipule gallsPhylloxera spp.OaksLeaf vein pocket gallWoody twig gallsLeaf galls with orangish “hair”Sticky, spongy galls on twigs with seed-like structuresinsideFly gallGouty oak and horned oak gall waspsHedgehog gall waspWool sower gall waspLive oakWoody twig and stem gallsLeaf gallsMealy oak gall waspWooly leaf gall waspRed oakSpherical, spongy-filled gallsOak apple waspPoplar,cottonwoodPocket galls on leaves, leaf bases and petiolesAphidWillowCone-like gall on terminalWillow cone gall flyYaupon hollyPocket galls on leavesYaupon psyllid gallGall Waspsgalls on several species of oaks. In some species, theadults and galls are similar in the first and third generations, while very different in the second and fourthgenerations. The galls produced by the sexual generation occur in the spring or early summer and the gallsproduced by the asexual generation occur in the summer and fall of the same year.There are more than 1,000 species of gall-makingwasps worldwide (Hymenoptera: Cynipidae). Theirbiology is quite complex, with alternating sexual andasexual generations. Many species of gall wasps develop inside galls induced by other gall wasp species. Gallwasps produce species-specific and generation-specificThe mealy oak gall wasp, Disholcaspis cinerosa, isan example. It causes one of the most common gallsMealy oak galls on post oak produced by the asexualgeneration of the mealy oak gall wasp.A gall-making cynipid wasp. Photo by Anamaria DalMolin.2
on live oak. The generation-specific galls are differentin size and general appearance. Galls of the asexualgeneration are spherical, 1/8 to 1 inch in diameter,and appear on branches and twigs of live oak in latesummer and early fall. When first formed, the gallsare pink to pinkish brown outside and yellow-greeninside. The inside tissue is moist and soft in newlyformed galls but becomes brown and dry during latefall as the gall matures. Adult wasps emerge by chewing holes in the bases of the galls during Decemberand January. All adults are female (asexual generation); they do not mate before laying eggs in swollenleaf buds.Elm finger galls.Eggs laid by adults of the asexual generation hatchin early spring as leaf buds begin to open. The larvaedevelop quickly in the leaf tissue and stimulate thedevelopment of small, beige leaf galls that resemblekernels of wheat. Adults of both sexes emerge fromthese galls after a few weeks and then mate. Mated females lay eggs in twigs and branches. The eggs remaindormant for 3 to 5 months; then the larvae hatch andstimulate the formation of the spherical galls of theasexual generation.causes a gall on the undersides of hackberry leaves.Other galls caused by midges include the gouty veingall on maple, the maple leaf spot gall, the ash midribgall, and the pine needle gall.Gall PsyllidsPsyllids, or jumping plant lice (Hemiptera: Psyllidae), also cause some of the most common galls. Theseinsects resemble small cicadas and feed by suckingplant fluids. Some psyllid galls cause the leaf marginsto roll, enclosing and protecting the nymphs (immatures).Gall Midges or Gall GnatsGall midges (Diptera: Cecidomyidae) are the secondlargest group of gall-making insects, with more than800 species in North America. The larvae are 1/16 inchlong with small and poorly developed heads. Severeinfestations of Asphondylia prosopidis on mesquitetrees may reduce seed pod development. There are several kinds of midge galls on cypress, with the branchlet midge gall, Taxodiomyia cupressiananassa, on baldcypress being one of the largest and most prominent.A new species of oak gall midge, Arnoldiola atra, wasdetected in 1999 on live oaks in Houston. This midgeseems to cause a general unhealthy appearance in treesbut it is localized to small areas. Phytophaga painteriHackberry trees host several species of gall psyllids.They form 1/8- to 1/4-inch galls on the leaves and petioles. The insects overwinter as adults in bark crevicesand other sheltered locations (including home sidingand window frames). After mating in the spring, thefemales lay eggs on the undersides of leaves. Nymphsemerge from eggs in about 2 weeks and begin feeding,which stimulates gall formation. The nymphs developthrough several stages before emerging as adults in thefall, completing one generation per year.Hackberry nipple galls induced by the jumping plantlouse or psyllid (Pachpsylla spp.).Galls produced by the gall midge fly on cypress.3
Galls caused by the oak apple wasp on red oak.Pocket galls on yaupon.Leaf pocket gall on cottonwood.Yaupon psyllid and pocket gall.PhylloxeransFor more information on pecan leaf phyloxera andother pecan insects, please see Texas A&M AgriLifeExtension Service publications E-145 and E-215 available at the Texas A&M AgriLife ns (Hemiptera: Phylloxeridae), whichare very similar to aphids, usually cause blister-likegalls on leaves. There are at least five phylloxera thatoccur on pecans, but the pecan leaf phylloxera, Caryaillinoinensis, is the most serious and it is the only onethat has more than one generation per year. Adultsare small, soft-bodied and pale yellow. Though pecanphylloxerans are small and difficult to see, the gallsthey produce are prominent. Galls are 1/8- to 1/4 inchin diameter and develop between leaf veins. New gallscan be formed throughout the season as long as newfoliage is present. Severe infestations can be economically damaging.Managing Gall-FormingInsects and MitesPrevention and cultural control. The only sure wayto prevent galls is to choose plants that are not hoststo gall-making insects and mites. Should a susceptibleplant already be in place, good horticultural practiceswill help keep it healthy. Gall-forming insects mustattack host plants at a precise stage of tissue development in order to induce gall formation. Occasionally,certain trees will bear more galls than adjacent treesof the same species. For example, studies showed thatoak trees whose buds opened earlier than those ofnearby trees had many more galls because the waspcausing the galls needed open buds in which to layeggs.Phylloxera overwinter as eggs in bark crevices. Thesmall nymphs emerge in spring during budbreak andfeed on tender new growth. Their feeding stimulatesgall development. Two generations are completedwithin the galls. Galls open in mid-May and the adult,winged phylloxera emerge to begin a new generation.4
Because most galls and gall-forming insects are nota threat to plant health, attempting to control them isnot usually warranted. Learning to recognize different galls and the insects or mites that cause them mayprovide peace of mind and can be a good way to enjoynature at our doorstep! If galls are considered unsightly, they can be removed by hand or infested plantparts can be pruned and discarded. However, this maynot prevent future infestations. Removing the hostplant and replacing it with a non-susceptible species ora more resistant specimen is the only sure method ofcontrol.old galls house beneficial organisms that feed on insectpests. The honeydew-like substances associated withsome galls may attract ants, wasps and bees.Chemical control. Although there are some insecticides and miticides registered for use against gallmaking insects (including insecticidal soaps, horticultural oils and several formulations of acephate andcarbaryl), their use is generally unwarranted. It is veryimportant to know the basic biology of the specificgall-making insect or mite involved before applying apesticide. Unless pesticides are applied when adults arelaying eggs or during the crawler stage (pecan phylloxera), they may not control the pest. Once galls begin toform, the insects and mites are protected inside themand can not be killed with either a surface-appliedpesticide or a systemic pesticide. Furthermore, pesticides may kill the beneficial insects that help controlgall-making insects.Biological control. Several species of wasps parasitize gall-forming insects and reduce the number ofgalls formed. These wasps are natural enemies of gallmaking insects and function as their biological controlagents. To protect these beneficial wasps, avoid usingbroad-spectrum insecticides during the time they aresearching for hosts (from late spring through earlysummer).AcknowledgementsCarlos E. Bográn, Bastiaan M. Drees, and JeremyL. Hudgeons wrote the original manuscript for thispublication. E. Riley helped identify galls of cypress,and Scott Ludwig, Jim Reinert, and John Jackmanreviewed the publication.Adult gall-forming insects leave galls through exitholes. The vacated space is almost immediately occupied by small spiders and other beneficial insectssuch as lacewing larvae, ants or parasitic wasps. Thus,The information given herein is for educational purposes only. Reference to commercial products or trade names is made withthe understanding that no discrimination is intended and no endorsement by the Texas A&M AgriLife Extension Service is implied.Texas A&M AgriLife Extension ServiceAgriLifeExtension.tamu.eduMore Extension publications can be found at AgriLifeBookstore.orgEducational programs of the Texas A&M AgriLife Extension Service are open to all people without regardto race, color, sex, religion, national origin, age, disability, genetic information, or veteran status.The Texas A&M University System, U.S. Department of Agriculture, and the County Commissioners Courts of Texas Cooperating.Revision5
The mealy oak gall wasp, Disholcaspis cinerosa, is an example. It causes one of the most common galls A gall-making cynipid wasp. Photo by Anamaria DalMolin. Mealy oak galls on post oak produced by the asexual generation of the mealy oak gall wasp. Table 1. Common gall-making insects and mites in Texas.
Flat mite identification tool on the Web. Flat mites, such as false spider mites, red palm mites, citrus mites, and peacock mites, are devastating pests on citrus, tea, bananas, coconuts, date palms, olive, eucalyptus, and ornamental palms. In addition to directly causing
The mealy-oak gall is one of the most common galls on live oak in Texas (figure 1). The gall is induced by a small wasp, Disholcaspis cinerosa (figure 2). Gall-infested live oak trees occur throughout Texas in natural and planted situations. The gall wasp also is reported from the same host in certain parts of Mexico and from western Louisiana. The
b. Insects play an important part in the food chain by providing food for other animals. c. Some insects destroy other insects that are considered harmful. d. Insects pollinate crops. e. Insects damage or destroy crops, food and fiber products, and wood. f. Insects provide food (honey from the h
3/30/2015 2 Pollinators Bees Wasps Flies Others Decomposers Break down dead animals and plants Recycle nutrients Natural Enemies Beneficial insects or other organisms that destroy harmful insects Predators eat other insects Parasitoids develop in other insects Pathogens cause diseases in insects P
Oak Apple Gall Wasp. Gall formation follows: Insect adults laying eggs to form larvae Chemical reaction: Insect excretions mix with plant chemicals Abnormal cell growth Immatures are protected by and can feed on galls. Mealy Oak Gall Wasp. Hackberry . Nipple Gall. Eggs. Aphids Black sooty mold (honeydew) forms on
Insects and Mites, Insect Orders. Lepidoptera (moths and butterflies) Differ from other orders by their large, scale-covered wings Have coiled, tube-like mouthparts that can extend to suck up liquids Larvae are caterpillars and have chewing mouthparts Have 2 to five pairs of ‘prolegs’ which are appendages on the abdomen
To be called aquatic insects, insects must spend part of their lives in water. They may live beneath the water surface or skim along the top. Some examples of aquatic insects are mosquitoes, dragonflies and caddisflies. Aquatic insects come in many shapes and sizes, and they all have some interesting ways of dealing with living in and on water.
Tank 6 API-653 In-Service, Internal Inspection Report less severe corrosion than the west perimeter. The average thickness of the sketch plates away from the west perimeter was 0.281”. Other than the perimeter corrosion noted, the remainder of the tank bottom showed no signs of significant metal loss and the thickness readings appeared consistent with the readings from the 2004 robotic .
