Hessian fly ( Mayetiola destructor )

1. Hessian fly (Mayetiola destructor)

2. 30 25 20 15 10 5 0 same adjacent 0.25 mile >0.25 mile Why does wheat acreage matter so much? A AB AB B Percent infested stems Oversummering Pupae P=0.26

3. Tillage and Rotation 2009 Alabama Hessian Fly Survey 100 1 2 Hessian Fly Infestation 6 4 4 80 5 none 60 1 Low 1-20% Percent of Fields* 6 6 Moderate 21-45% 14 40 5 High >45% 5 20 5 2 2 1 0 rotated - no till rotated - disked wheat after wheat after wheat - no till wheat - disked Tillage and Rotation Practices Percent infested tillers 28.6b P=0.07 18.3a

4. Bird-cherry oat aphid, Rhopalosiphum padi • will feed below ground • arrive early-mid fall, most abundant aphid in winter R. Padi on wheat, courtesy Susan Halbert

5. yellow sugarcane aphid corn leaf aphid, R. maidis bird-cherry oat aphid, R. padi English grain aphid S. (Macrosphum) avenae greenbug, S. graminum rice root aphid

6. Barley Yellow Dwarf • Disease on small grains world wide, effect on yield more pronounced on barley, oat and wheat (Lister & Ranieri 1995) • Symptoms include reddening/yellowing of the leaves, stunting of leaves and roots (D’Arcy 1995) • Affect photosynthesis, assimilate translocation and may reduce yield up to 80% (Jansen & D’Arcy 1995, Pike 1990)

7. Sampling for aphids can be tricky - sometimes it seems they are here today and gone tomorrow small, hard to see anyway hiding below ground? killed by natural enemies? choose warmer days, look at the entire plant, including the base of the plant below the soil line

8. Thresholds for Aphids in Barley Yellow Dwarf Publication Scout at the time nitrogen is applied in spring – can tank mix an insecticide if aphids are present Later in season – will be too late for controlling aphids that will spread BYDV Keep an eye on heads – too many English grain aphids can cause yield loss

10. North Alabama June 2008 December planting Aphid rate of Cruiser Wheat-soybean-wheat Conservation tillage

11. Headland, AL Small Grain Variety Test April 2009 Progeny 117 (susceptible) 57% infested stems 0 bu/A Oglethorpe (H13 resistant) 3% infested stems 30 bu/A

12. Infested plants were stunted and had 6 or more Hessian flies per tiller Hessian fly larvae (white) and puparia (brown)

13. Oversummering flaxseeds led to heavily infested volunteer wheat

14. Hessian fly life stages Adult  puparia* Larvae  Eggs on upper leaf Photos courtesy of R. Ratcliffe, slide courtesy David Buntin * Oversummering stage

15. Buntin UGA

16. Results Introduction Objectives Methodology Barley Yellow Dwarf • Disease on small grains world wide, effect on yield more pronounced on barley, oat and wheat (Lister & Ranieri 1995) • Symptoms include reddening/yellowing of the leaves, stunting of leaves and roots (D’Arcy 1995) • Affect photosynthesis, assimilate translocation and may reduce yield up to 80% (Jansen & D’Arcy 1995, Pike 1990)

17. Results Introduction Objectives Methodology BYD: Virus and Vectors • BYDV/CYDV are phloem limited and exclusively transmitted by aphids in non-propagative persistent manner (Gray & Gildow 2003) • Names of the strains was originally derived from the names of aphid species thought to transmit it the best PAV Sitobionavenae, Rhopalosiphumpadi RPV Rhopalosiphumpadi MAV Sitobionavenae SGV Schizaphisgraminum RMV Rhopalosiphummaidis  Variation in transmission efficiency of geographic clones of the same aphid species is well documented (Halbert et al. 1992, Gray et al. 1998)

18. Introduction Objectives Methodology Events in BYD Epidemiology www.aces.edu www.ext.nodak.edu www.ars.usda.gov www.iah.bbsrc.ac.uk Wheat Season Oct Nov Dec Jan Feb Mar Apr May Jun

19. English grain aphid Greenbug Aphids as virus vectors Hessian fly Cereal leaf beetle Fall armyworm Armyworm Chinch bug

21. Chinch bug Armyworm Fall armyworm See text

22. aphids insert their stylets into the phloem to feed Direct injury Indirect injury virus transmission barley yellow dwarf Healthy Infested (honeydew and sooty mold)

23. Winged form alatae or alates Wingless forms apterae develop within the field can be from the same field, surrounding fields, or from long distances (rose grass aphids, Univ. of CA photos)

24. winged bird-cherry oat aphids Buntin photo? Buntin photo? aphids can colonize the small grain as soon as it emerges

25. most aphids on small grain are parthenogentic females - asexual reproduction give "birth" to aphid nymphs by the time they are 7-18 days old, have 50-60 young during 20-30 days aphids are cold-blooded so development rate is faster during the fall and the spring than in the winter biological control agents such as ladybugs and parasitic wasps can control populations

26. Sampling for aphids can be tricky - sometimes it seems they are here today and gone tomorrow small, hard to see anyway hiding below ground? killed by natural enemies? choose warmer days, look at the entire plant, including the base of the plant below the soil line

27. Six most common grain aphids in the Southeast rice root aphid

28. Why is is necessary to know which aphids are which? • Greenbugs and English grain aphids often cause direct feeding damage • Oat bird-cherry aphids may be the most important as far as barley yellow dwarf virus goes, particularly within-field • The other aphids could be bringing bydv into the fields in the fall from other crops or from wild hosts

29. "knees" color pattern hairs "feet"

30. yellow sugarcane aphid corn leaf aphid, R. maidis bird-cherry oat aphid, R. padi English grain aphid S. (Macrosphum) avenae greenbug, S. graminum rice root aphid

31. Hessian fly Mayetiola destructor Hessian fly lays eggs on the uppermost expanded leaf blade Eggs hatch and tiny maggots wriggle down into the leaf sheath as far as they can go

32. Hessian fly Mayetiola destructor puparia older larva

33. Hessian fly oversummers in the pupal stage in crop stubble and debris In late summer to early fall, the adult flies emerge, mate, and lay eggs in volunteer or early planted small grains Hessian fly can infest small grains as early as the first leaf stage

34. There are 4-6 generations each year. A generation takes about 35 days at 75 º F, longer at cooler temperatures. Development occurs between 40-80 º F

35. Toxins in saliva cause stunting, plant death, yield and quality losses A thin stand of stunted plants (right) is a classic symptom of Hessian fly infestation

36. Hessian fly damage looks different, depending on when the wheat was infested early infestation results in stunting so leaf blades only partially emerge from the ground

37. Infested (left) Healthy (right)

38. Hessian fly damage looks different, depending on when the wheat was infested sometimes a wide leaf blade is a symptom. Often the wide blade has a blue-green hue.

39. Infested tillers often die, particularly when subjected to cold stress in winter

40. More dead tillers, thin stand

41. When stems are infested after jointing, the internode will be shorter than normal, so the grain heads may be at half the height of a normal wheat plant Infested tillers may break over and lodge

42. Hessian fly can be managed through the use of resistant varieties Other strategies include later planting to avoid infestation, burying wheat stubble, burning wheat debris, controlling volunteer wheat, crop rotation, at-planting insecticides

43. When a population of Hessian flies overcomes the host plant resistance, it is called a biotype. Numerous plant resistance genes have been identified for Hessian flies. As they are deployed, new biotypes emerge. It is important to know what biotypes are present in order to choose the right Hessian fly "resistant" variety