E·680 (Revised)

1IIIIIill~lllllli~~~illll~I~13010900839 tlllrll]~'~11111111 1339 Stem Sawfly Wheat Stem Pests and Management Practices

Dean K. McBride Extension Entomologist

Dennis D. Kopp Extension Entomologist

Hessian Curtis W. Nyegaard Extension Agent Kittson County, Minnesota S 5"l/l/.3 . NCf Ag nO."~O /9C;?'l

111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111111 1IIIIIIIIIIIIIIIIIIIIIillllllllllllllllllllllllllllili1IIIIIIIIIIIIilllllllllllllllllllllllllllllllllllllili111111111I11111111 NDSU EXTENSION SERVICE APRIL 1989 North Dakota State University, Fargo, NO 58105 INTRODUCTION .JANUARY FEBRUARY MARCH APRIL MAV JUNE Three , the wheat stem sawfly, wheat stem maggot, and the Hessian fly, are important pests of wheat in North Dakota. ~ The wheat stem sawfly is native to the hollow stemmed grasses of -'Ill ----111_ J1JL .JL~ .. _ . .nL JL_ N_.. UlL. Jll_ .. _.IIL-.JV'4, lJw." .. JlLm if JtJl{~ western North America. The sawfly larvae Iransform , larvae in stubble to pupae adult emerg e readily adapted to wheat, especial­ in old stubble and deposit egg s ly spring wheat, when it replaced I most of the sawfly's native hosts in the Northern Great Plains. Today, .JULY AUGUST SEPTEMBER OCTOBER NOVEMBER DECEMBER wheat is the major host plant in North Dakota. The most obvious damage caused by the sawfly is the breaking over of stems that have been weakened by larval tun­ CD neling. 11'I ~ ..... llil _. III IIIL IlL __ .JU __ JI/... JII ._ H f-lli .. __ 1!_ The wheat stem maggot is also a J&.\V~~ ..~Li':::>liUL._.lliL. ... - JiL L native insect that can be found larvae mature larvae working larvae in stubble from eastern North America across down tnside stems and cut off stems the prairie provinces of Canada ---- and south to Mexico. Before wheat Figure 1. Diagram of Life History of the Wheat Stem Sawfly. was brought to North America, the wheat stem maggot attacked na­ tive grasses. Damage in wheat becomes evident after flowering and infected stems die and turn white. The North Dakota infestation into a larva, it feeds inside the The Hessian fly was probably reached epidemic proportions in stem until late summer. As the brought to America from Europe in 1916, but receded rapidly, and by plant starts to mature, more light used by soldiers as bedding the early 1920s the sawfly was a penetrates the stem, causing the during the Revolutionary War. By pest of slight importance. From larva to move downward and away 1898, it had spread from Long Is­ 1940 to the mid-40s the sawfly from the light until it reaches the land, New York, to most eastern again became a problem with as lower parts of the plant close to the and midwestern wheat growing much as 50 percent crop loss re­ surface of the ground. Here the lar­ areas and to areas of the Pacific ported in northwestern North Da­ va cuts a V-shaped groove around Coast. The Hessian fly causes kota. and inside the stem and plugs the stunting in seedlings plantings stub with its body wastes (Figure 2) and lodging as wheat matures. Through cultural control prac­ forming a chamber in which it hi­ tices, wheat stem sawfly damage bernates and pupates the follow­ has been held to a minimum in ing May. North Dakota from the mid-1940s to date. However, each year the sawfly takes its toll, primarily in DAMAGE western North Dakota. Sawfly damage is threefold. Wheat Stem Sawfly Fi rst, they cause 10 to 14 percent HISTORY grain yield reduction by their tun­ LIFE HISTORY (Figure 1) neling activity in the infested The sawfly was first found min­ stems. Additional loss occurs ing the stems of native grasses in A mature larva overwinters when sawfly-cut stems fall to the 1890 in California. In 1895, adults within a wheat stub below the sur­ ground and become unharvest­ were collected in the Canadian face of the soil. In the spring the able. The protein content of grain Northwest Territories, and larvae larva transforms to a pupa inside from the infested stems is also were found feeding in wheat stems the stub and the adult emerges in lower. in Manitoba. In 1906 larvae were early June (Figure 1). The female found attacking wheat in south­ will deposit a single egg per stem central North Dakota. By 1909 los­ with a preference for the growing DESCRIPTION ses of 5 to 25 percent were repor­ interstem. Plants in the stem elon­ ted in the area around Minot and in gation to boot stage are favored for When mature, the sawfly larva the Red River Valley near Fargo. egg laying. After the egg hatches measures V2 inch or longer, and is semidwarf with average yield. It has medium straw strength, medi­ um early maturity, is resistant to stem and leaf rust, has a high test weight and protein content and a good quality rating.

Glenman The Montana Agricultural Ex­ periment Station released Glen­ man in 1984. It is a semidwarf of above average yield. It has strong Figure 3. The wheat stem sawfly: rna· straw strength, medium maturity, ture larva. Enlarged. is resistant to stem rust, is moder­ ately susceptible to leaf rust, has an average test weight, and a low protein rating with a very poor qual­ ity rating.

Leader Figure 2. Sawfly larva in stem (note frass plug - arrow). Leader was released by Canada in 1982. Leader is a standard height variety with average yield. It has medium straw strength, medium maturity, is resistant to stem rust, is moderately susceptible to leaf pale white or yellowish in color, rust, has a high test weight and with a well·defined head (Figure 3). protein content with a good quality rating. The adult sawfly is a slender wasp about V2 inch long with a Lew black abdomen with yellow ringed Lew was released jOintly by the markings (Figure 4). When observ· agricultural experiment stations of ed in the field, sawflies may be rec· Montana and North Dakota in con­ ognized by the unusual habit of Figure 4. Adult wheat stem sawfly, Cephus cinctus. Much enlarged. junction with the Agricultural Re­ resting head downward on the search Service in 1976. Lew is a stems of grain plants. standard height variety with aver­ age to above average yield. It has The present understanding of medium straw strength, medium the dynamics of wheat stem sawfly maturity, is resistant to stem rust, populations does not allow predic­ stripe rust and loose smut, is mod­ tion of the population next season erately susceptible to leaf rust, has based on stubble infestations. Re­ a high test weight, an average pro­ search is continuing in this area fly damage. Solidness of the lower tein rating, and an average quality and improved predictability related three internodes of the stem ac­ rating. to field populations are a realistic counts for sawfly resistance in future goal. At present, the deci­ wheat. Susceptible varieties have sion to manage wheat production hollow internodes; however, cer­ Tioga for sawfly cutting is based on the tain weather conditions may influ­ Tioga was released jointly by the history of previous loss due to this ence stem solidness. The sawfly North Dakota Agricultural Experi­ pest. If a wheat grower has observ­ resistant hard red spring varieties ment Station and the Agricultural ed an increasing loss from saw­ include: Cutless, Glenman, Leader, Research Service in 1974. Tioga is flies, management options include Lew, Tioga, and Fortuna. The infor­ a standard height variety with be­ resistant varieties, rotations with mation used to describe the six low average yield. It has medium non-susceptible crops, delayed varieties is based on the quality strong straw strength, medium ma­ planting of susceptible varieties, classifications system established turity, is susceptible to both stem and shallow fall tillage. by the North Dakota State Universi­ and leaf rust, is resistant to black ty Department of Cereal Science. , has average test weight, and has a high protein rating with a SAWFLY RESISTANT Cutless good quality rating. VARIETIES Cutless was released by the Use of resistant varieties of North Dakota Agricultural Experi­ wheat reduces the severity of saw- ment Station in 1986. Cutless is a 3 Fortuna DELAYED PLANTING NATURAL CONTROL Fortuna, a standard height varie­ The practice of planting spring At least four different wasps ty with below average yield, was re­ wheat after May 20 will reduce saw­ have been found to parasitize the leased jointly by the agricultural fly damage if a susceptible variety sawfly. However, they do not nor­ experiment stations of North Da­ is to be planted, but a reduced mally kill enough sawflies to pre­ kota and Montana and the Crops yield can be expected because of vent damage to wheat fields. The and Entomology Divisions, Agri­ the late planting date with all only time paraSitism seems to have cultural Research Service, USDA, varieties. If bad weather delays a significant effect on the sawfly in 1966. Fortuna has weak straw planting until after May 20, a high population is when weather condi­ strength, medium early maturity, is yield sawfly susceptible variety tions delay the ripening of the crop susceptible to black chaff, is resis­ should be selected since the crop for two consecutive years. tant to stem rust, is moderately will escape sawfly damage. susceptible to leaf rust, has aver­ age test weight, and has low pro­ CHEMICAL tein content with an average quali­ TILLAGE ty rating. At the present time, no effective Tillage offers a management op­ chemical treatment is available. Lancer tion for fields that have had moder­ ate to high damage due to wheat Lancer was released by Agricul­ stem sawfly. Research has demon­ ture Canada in 1985. Lancer is a strated that shallow fall tillage will conventional height, awnless varie­ provide up to 90 percent sawfly ty with a heading date similar to control. If only spring tillage is us­ Wheat Stem Maggot Len and Lew. In North Dakota ed, about 25 percent of the larvae tests, Lancer is lodging suscepti­ may be killed, depending on the LIFE HISTORY (Figure 5) ble, has a leaf spotting disease rat­ type of tillage used. Shallow tillage ing similar to Lew and is moderate­ Wheat stem maggots overwinter should dislodge stubble so the lar­ in the larval stage, inside the lower ly susceptible to leaf rust and re­ vae in the stubble will be exposed. sistant to stem rust. It has a satis­ parts of grass stems. In the spring, factory test weight but a lower the larvae pupate and adults em­ yield potential, less than Cutless erge in June. The adults are yel­ and other solid stem . Can­ lowish-white flies, about 1/5 inch adian data indicate that Lancer yields similar to Leader but has a more solid stem and is more resis­ tant to and common root rot than Leader.

CROP ROTATION Sawfly damage has been most severe in fields which are continu­ ously cropped to hard red spring wheat and where stubble is left un­ disturbed. Sawflies emerging from the previous year's stubble can in­ fest wheat in the same or adjacent fields. Therefore, the use of non­ host crops should be considered in these areas.

Sawflies do not damage oats, flax, mustard, sunflower, safflow­ er, and legumes. Other crops that are susceptible but only allow a small number of larvae to survive are , wheat, and winter . Winter wheat will usually mature before the saw­ fly has time to complete its devel­ opment and is too far along to be Figure 5. Life cycle of the wheat stem maggot. (Modified from Allen and Painter attractive for egg laying. 1937). 4 long, with three conspicuous black stripes on the thorax and abdomen and bright green eyes (Figure 6). After mating, females deposit their eggs on the leaves or stems of grasses. The young maggot crawls down beneath a leaf sheath and tunnels into the stem. The stem is partially severed causing the head to turn white. The head and ter­ minal straw of maggot-infested wheat will pullout easily due to the internal chewing damage by the larvae. The larva pupates within a cigar-shaped, pale green puparium. The adults emerge about midsum­ Figure 6_ The wheat stem maggot, Meromyza americana adult; 11 times natural size. mer and lay their eggs on wild gras­ ses or volunteer grain. The re­ sulting larvae overwinter in the stems of the wild grasses and vol­ unteer grain. DAMAGE exceed 2 percent, but occasionally may be somewhat higher. The wheat stem maggot damage becomes evident after flowering The presence of white heads when begin to develop. Nor­ alone is not always an accurate as­ mally the first indication of its sessment of damage. The maggots presence is the dying and whiten­ can also infest young tillers prior ing of the wheat heads and upper to the boot stage causing the af­ internodes (Figure 7) while the fected tiller to abort. These aborted lower stem and leaves remain tillers can account for an unseen green. A single maggot will be loss in yield. found inside the straw just above the last node (Figure 8). The plant The principal cultivated crop stem pulls out very easily and if lar­ hosts of the wheat stem maggot vae are not found, the stem is usu­ are wheat ( and durum), rye ally cut off. Infestation levels rarely and barley, with wheat being pre­ ferred. It also attacks bluegrass, timothy, quackgrass, slender and western wheat grass, wild barley, bromegrass, green and yellow fox­ tail and bluestem grass.

Management

RESISTANT VARIETIES At present, no wheat varieties have resistance but research indi­ cates that late maturing varieties suffer less damage than early ma­ turing varieties.

CROP ROTATION Rotation with non-susceptible crops such as corn, sunflowers, Figure 8_ Larva of wheat stem maggot flax, soybeans, safflower or le­ Figure 7_ White head symptom of and typical damage that occurs above gumes will reduce the numbers of wheat stem maggot on right, compared the top node of the stem, causing white this pest. to a normal wheat head on left. heads. 5 TILLAGE a mosquito (Figure 9), and are very fragile. They cannot fly very far but Plowing under volunteer grain may be carried considerable dis­ will reduce populations of this in­ tances by wind. sect. The abdomens of females are orange-red and lay reddish eggs in NATURAL CONTROL the grooves on the upper sides of Several parasites attack the the wheat leaves (Figure 10). The wheat stem maggot but control is females can deposit up to 300 eggs not consistent enough to provide and can only live three to four days. reliable annual control.

DAMAGE CHEMICAL The type of injury caused by the No effective chemical treatment Hessian fly is not conspicuous and Figure 10. Eggs of the Hessian fly. is available. is easily overlooked. Hard red Much enlarged. spring wheat infested in the spring and early summer will take on a dark bluish-green color and be­ come distinctly thickened and stunted. The central growing shoot is often absent. Small white or greenish-white, shiny, legless and July). Heavily infested fields can head-less maggots about 3/16 inch have as high as 75 percent of the Hessian Fly long (Figure 11) or brown puparia broken. LIFE HISTORY (Figure 12) (capsule-like cases often called flaxseed) that contain white mag­ The injury is caused by the lar­ The Hessian fly overwinters as a gots and are about 1/8 inch long vae, which withdraw sap from the full-grown maggot in the prepupal will be found beneath the sheaths lower parts of the stem for a period . ("flaxseed") stage in stubble, vol­ of the lower leaves of the plant of seven to 14 days. However, the unteer spring wheat, and early sometimes as high as the second larvae cause little apparent physi­ seeded winter wheat. Maggots pu­ or third joints. The most conspicu­ cal plant tissue damage. The injury pate in early spring and adult flies ous injury is the breaking over of is caused by a toxic salivary secre­ emerge from April to May. The flies infested stems when the heads tion into the plant which interferes are sootY-black, much smaller than begin to fill (Figure 12, June and with metabolism and growth. Infes­ ted tillers are less than half the size of noninfested healthy tillers. Stunted tillers, especially in young­ er plants, wither and die. If they survive, the growth and yield will be reduced. Second brood infesta­ tions usually cause poorly filled heads with fewer kernels and lower test weight.

Figure 11. Larva (left) and flaxseed of Figure 9. Hessian fly - female, destructor. Enlarged. the Hessian fly. Enlarged. 6 MAY JUNE JULY AUGUST SEPTEMBER ica. Heavy parasitism of Hessian fly by parasitic wasps has occurred in the Pacific Northwest states but cannot be counted on to consis­ tently control the fly populations. 10I , .-J.--:---~\\o ~, IlIA' \\ \ "\ \ '\ \ CHEMICAL " I \ . I " I ' Insecticides currently registered --' ..... " as planting time treatments for Hessian fly control include phorate 20% granules for both hard red OCTOBER NOVEMBER DECEMBER i JANUARY I FEBRUARY MARCH spring wheat and winter wheat and disulfoton 15% granules for winter wheat only.

o I Application of the granular in­ I I secticides can be made through a I I properly calibrated grass seeder at­ tachment or approved granular ap­ ,It,,,·,1.. , /t /,l " . """:~ ""'C:<"""""i plicator attachment for grain drills. ), .. ~ >,' , I "'~"/ ,,' , I These granular insecticides should WEAKENED PLANT FLAXSEED ABOUT t.'AGGOT BECO"'ES FLAXSEED READY FLAXSEED WINT ERING FLAXSEED WINTERING I FLAXSEED FOR WINTERING FAILING TO TILLE"! TO BECOME FL Y not be directly mixed with the Figure 12. Seasonal development of the Hessian fly. in the drill box. Plastic tubes should be extended from the grass seeder or granular applicator into the drill spcuts so that the gran­ ules drop directly into the seed fur­ rows.

Phorate 20% G should be ap­ Research in South Dakota indi­ CROP ROTATION plied at 1.2 oz of formulated prod­ cates that the yield impact is di­ uct per 1,000 feet of row for any rectly related to the time of infest­ Rotate wheat (or other suscepti­ row spacing (minimum 8 inch spac­ ation and the number of larvae per ble grain crops) with nonsuscepti­ ing) at planting time or disulfoton plant from the first brood and the ble crops such as oats, corn, sun­ 15 G at 1.7 oz of formulated prod­ number of larvae per stem with the flowers, flax, soybeans, safflower uct may be applied per 1,000 feet of second brood. Fall injury to winter and legumes. row at 7 or 8 inch row spacing for wheat from Hessian fly resembles Hessian fly control. early season damage to spring wheat. DELAYED PLANTING Do not feed or graze foliage treated with phorate for 45 days Planting date of hard red spring after application. Foliage treated The adult Hessian fly prefers to wheat has no effect on the Hessian with disulfoton should not be fed lay its eggs on spring, winter, and fly. durum wheat, with a preference be­ or grazed within 30 days of treat­ ing shown for spring wheat. Light ment. infestations have been observed on barley, rye, and several grasses TILLAGE Read, study, and follow all other including bromegrass. Moldboard plowing in the fall label restrictions and precautions after the first killing frost, or early regarding the use and handling of in the spring before fly emergence, these insecticides. RESISTANT VARIETIES helps to suppress adult popula­ tions. Guard, released by South Dakota in 1983, is the only Hessian fly resis­ tant hard red spring wheat avail­ NATURAL CONTROL able. It is a semi dwarf with above ACKNOWLEDGMENTS At least three species of average yield, strong straw The authors want to gratefu Ily strength, medium early maturity, is parasitic wasps are known to at­ acknowlede the suggestions, input and resistant to stem and leaf rust. has tack the Hessian fly in South Da­ help provided by Dr. Michael J. Weiss a high test weight, low protein'con­ kota, yet only relatively low levels in the development of this circular. tent, and has a poor quality rating. of parasitism have been observed. Thanks is also expressed to Dr. Carl A total of 35 parasitic species have Fanning and Dr. William S. Ball for their been recorded from North Amer- helpful review suggestions.

7 Summary of Management Practices for Wheat Stem Sawfly, Wheat Stem Maggot and Hessian Fly. Insect Management Practice Wheat Stem Wheat Stem Hessian Sawfly Maggot Fly Resistant Varieties Cutlass, Glenman None Guard Leader, Tioga Lew, Fortuna, Lancer Rotation with Non­ Yes Yes Yes Susceptible Crop Delayed Planting Yes - with Yes No susceptible variety Tillage Fall-shallow Fall or Fall-after Spring-shallow Spring frost Spring-early Natural Control Parasitic Parasistic Parasistic Wasps Wasps Wasps Chemical None None phorate 20G (hard red spring and winter wheat) Disulfoton 15 G (winter wheat only)

. Helping You Put Knowledge To Work NDSU Extension Service, North Dakota State University of Agriculture and Applied SCience, and U.S. Department of Agriculture cooperating. Robert J. Christman, Interim Director, Fargo, North Dakota. Distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914. We offer our programs and facilities to ali persons regardless of race, color, national origin, religion, sex, disability, age, Vietnam era veterans status, or sexual orientation; and are an equal opportunity employer. 1111 i11111111111 1500-12·94