Prionus root borer, Walnut caterpillar

Transcription

1 Prionus root borer, Walnut caterpillar Dennis R. Ring Entomologist, Extension Specialist (Scientist), Professor, Board Certified Entomologist, Louisiana State University Agricultural Center LSU AgCenter Insect pest management guide

2 Prionus root borers Tilehorned prionus, Prionus imbricornis (L.) Broadnecked root borer, Prionus laticollis (Drury) Adults, long horned wood boring beetles, antennae half the length of body, brown (light to reddish) to blackish, inches long, slightly flattened, 3 toothlike projections on each side of thorax, males smaller, have larger antennae (projections). Males fly, females do not fly.

3 projections Jim Dutcher, adult male

4 Jerry A. Payne, USDA Agricultural Research Service, Bugwood.org, adult female

5 Prionus root borers Eggs, 0.2 inches long, yellow-brown, oviposited in soil (0.5 to 1.5 inches deep), some on the soil. Larvae, round headed wood boring beetles, inches, cylindrical, tapered, large, fleshy, creamy white to yellowish, 3 pairs of small legs, swelling behind head capsule, strong mandibles.

6 Jerry A. Payne, USDA Agricultural Research Service, Bugwood.org, yellow-brown

7 Biology Larvae feed for 3-5 years. In early spring pupate (ca. 3 months) in earthen cell up to 12 inches. Range, eastern U.S. to Oklahoma. Adults emerge in early evening, nocturnal, females lay about eggs, lay eggs in July, live 1-2 weeks. Feed first on root surface, then enter roots, girdling and hollowing roots, move to other roots. Tunnels may be 0.6 inches in diameter, filled with dark frass and wood chips. In summer, larvae 6-18 inches deep, up to 33 inches deep.

8 Jerry A. Payne, USDA Agricultural Research Service, Bugwood.org, larva in root

9 Jerry A. Payne, USDA Agricultural Research Service, Bugwood.org, Cylindrical, tapered, large, fleshy, creamy white to yellowish, 3 pairs of small legs, swelling behind head capsule, strong mandibles

10 Jerry A. Payne, USDA Agricultural Research Service, Bugwood.org, larva in soil, earthen cell

11 Jerry A. Payne, USDA Agricultural Research Service, Bugwood.org, pupa

12 Jerry A. Payne, USDA Agricultural Research Service, Bugwood.org, dark frass and wood chips

13 Jerry A. Payne, USDA Agricultural Research Service, Bugwood.org, larva in root

14 Injury Gradual decline, tree death. Root system is destroyed. Injured roots are channeled, tunneled, girdled, hollowed, and severed. May lose 75-90% of roots in one generation. Injured trees sparse canopy. Foliage light colored, thin, and irregular shaped. Terminal dieback. Reduced yields (3-7 times less yield). Alternate bearing more pronounced.

15 Jerry A. Payne, USDA Agricultural Research Service, Bugwood.org, injury, thin foliage

16 Jim Dutcher, light colored foliage

17 Jim Dutcher, dieback

18 Jim Dutcher, Irregular thin foliage, sparse canopy

19 Jim Dutcher, destroyed root system

20 Jim Dutcher, fallen tree

21 Jerry A. Payne, USDA Agricultural Research Service, Bugwood.org Infested

22 Management Keep trees as healthy and stress free as possible. Remove dead trees Thought that first attracted to decaying roots of weakened, stressed trees, but will eat living roots if decaying roots absent.

23 Management Very hard to manage. Many hosts: hickories, oaks, linden, blueberries, maples, chestnuts, poplars, grapes, fruit trees, dogwoods, rhododendrons, aspen, blackberry, pines. Eggs laid in soil. Larvae feed on and in roots. Pupate in the soil. Long life cycle, 5 7 years, management is long term. No short term solution. Need to prevent oviposition by killing adults for years.

24 Kill adults Dr. Jim Dutcher s work. Insecticide not kill larvae in soil. Kill adults by applying chlorpyrifos to the herbicide strip (8 oz/50 gallons of water, 4 pints/a). Adults peak emergence in June. Can use panel traps baited with prionic acid, determine when beetles are emerging. Place traps on the edge of the orchard. Lure attractive for about 6-7 weeks. Get traps from and prionic acid from

25 Timing Susceptible to insecticides when adults mate and dig in soil. Need to time insecticide application. Use traps from April until August. Lure attractive for 6 7 weeks, two lures needed for emergence period. Apply chlorpyrifos when beetles are captured in traps (inspect weekly). Dutcher used 4-10 traps per orchard. Chlorpyrifos killed beetles for 3 weeks. Females are attracted to alpha pinene (alpha scents) baited pitfall traps.

26 Mitchell Lee Crisp Peach Jim Dutcher, trap captures of adults, May through July, If treat 3 wk interval, start 2nd wk May, 3 times at Mitchell, less at others, arrows are mine.

27 Additional management May need to cut back trees if they are in decline, remove trees with crown gall. Apply chlorpyrifos when new trees are planted.

28 Bill Ree, panel trap, Prionus

29 Jim Dutcher Light trap How many female beetles trapped?

30 Jim Dutcher

31 Jim Dutcher, pitfall trap

32 Root regeneration Injured tap roots and lateral roots form callus, new roots regenerated. Woodroof and Woodroof, pecan trees double the number of lateral roots coming from the tap root to compensate for root pruning.

33 Jim Dutcher, root regeneration

34 Walnut Caterpilar Walnut caterpillar found in the U.S. east of the Great Plains. Hosts are trees of the walnut family (pecan, hickory, walnut). Pupa overwinters in the soil. Pupae are shiny reddish brown or dark brown and 0.8 to 1 inch long. Adults emerge from overwintering pupae in May.

35 Datana pupae, Gerald J. Lenhard, Louisiana State University, Bugwood.org

36 Moth, eggs Front wings of the moth are reddish tan. Four narrow dark lines run from the front edge of the wing to the back edge of each wing. Hind wings are lighter brown without lines. Wingspan is 1.5 to 2 inches. Eggs are laid in masses on the undersides of leaves. Masses are made up of several hundred eggs laid in one layer. Larvae emerge from eggs in 7-10 days.

37 Lacy L. Hyche, Auburn University, Bugwood.org, adult, brown FW, 4 lines, lighter HW, brown head

38 Mark Dreiling, Bugwood. org moth

39 Bill Ree, eggs before emergence

40 Lacy L. Hyche, Auburn University, Bugwood.org, eggs after larval emergence

41 Recently emerged larvae are light colored. Become red to purplish, has 4 white lines on each side,. 5 th instar is blueberry to black colored, 1.8 to 2.2 inches long, and covered in long white hairs. Larvae feed in colonies. First instar larvae skeletonize the underside of a leaf, later instars eat leaves. The colony strips foliage from one branch and moves to another.

42 Bill Ree, first instar larvae, light colored

43 Lacy L. Hyche, Auburn University, Bugwood.org, behavior following alarm, red, 4 stripes

44 James Solomon, USDA Forest Service, Bugwood.org, colony feeding

45 Bill Ree, 5 th instar, blueberry color, white hairs, alarm behavior

46 Lacy L. Hyche, Auburn University, Bugwood.org, skeletonized leaf

47 Bill Ree, stripped foliage

48 Life stages Walnut caterpillar moths emerge in the spring Deposit eggs in masses of 600 or more on the undersides of leaves. Egg masses are round, about the size of a half-dollar and are not covered with hairs or scales. Larvae emerge in about 10 days; feed for about 25 days. Young larvae are reddish-brown with yellow lines running the length of the body. Full-grown larvae ca. 2 inches long, blueberry to black with grayish lines, covered with long, soft, white to gray hairs.

49 Molt, pupate Larvae congregate in large masses on the trunk and scaffold limbs to shed their skins before crawling back to complete their feeding on leaves. 80 % of the foliage is eated by the last instar larvae (prevent this injury), defoliation can occur very quickly. Mature larvae crawl to the soil to pupate. A generation is completed in about 6 to 8 weeks and there are two to three generations each year. Outbreak biology.

50 Defoliation Larvae stop feeding and raise their heads and tails when disturbed. Larvae move down to the trunk or a big limb to molt. Then they go back up the tree to feed and leave a mass of hairy cast skins. Larvae develop over days, crawl to the soil and pupate. There are 2 (<245 FFD) to 3 ( 245 FFD) generations per year. Defoliation may be partial and injury is minimal. Healthy trees recover from one defoliation (nut production will be decreased). Two or more defoliations result in dieback and possibly tree death.

51 Ward Upham, Kansas State University, Bugwood.org, molting

52 James Solomon, USDA Forest Service, Bugwood.org Molting on trunk

53 Lacy L. Hyche, Auburn University, Bugwood.org Cast skins

54 Bill Ree, predator

55 Sample Does not make tents or webs, infestations may go unnoticed until leaf injury is obvious. Look for egg masses or leaf feeding to detect infestations early. Look for larvae on trunk, limbs, or foliage. Egg masses can be detected at night by shining a flashlight on the undersides of leaves and looking for white spots about the size of a half dollar.

56 Inspect Inspect every 3 weeks for walnut caterpillar from pollination through October. Once walnut caterpillars are observed, make the following inspections every 6 weeks. 10 colonies per acre is considered economic. May spot treat.

57 Management Prevent 5 th instar from causing 80% percent of the injury during the last 3 to 4 days of feeding. Smaller larvae are easier to kill with insecticides than larger larvae, and control of small larvae prevents serious injury and economic loss. Insecticide treatment may be necessary if large infestations threaten to defoliate trees.

58 Bill Ree, egg masses

59 Bill Ree, frass

60 Management Larvae strip the foliage, leaving only the leaf rachis (the extension of the petiole that bears the leaflets). Do not produce webs, easy to miss. Inspect trees on all sides from top to bottom. Treat before 4th Instar Older larvae are harder to kill, want to treat shortly after larvae have emerged from eggs.

61 Walnut Caterpillar Insecticides Intrepid 2F methoxyfenozide; incomplete, early molt Intrepid edge 2F methoxyfenozide, spinetoram; nerve Confirm 2F tebufenozide; unsuccessful molt

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