9/25/2013. Soil pests 2: White Grubs. Sclerotized head Chewing mouthparts 3 pr segmented legs No prolegs C shaped soft body

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1 Soil pests 2: White Grubs Coleoptera Scarabaeidae (scarabs) Leaf feeders, decomposers, dung beetles Larvae are white grubs White Grubs Sclerotized head Chewing mouthparts 3 pr segmented legs No prolegs C shaped soft body 1

2 Scarab beetle life stages Rainfall / Irrigation Soil moisture Trigger adult emergence & flight Selection of egg laying sites Affect egg hatch and grub survival Notice swollen eggs compared to unswollen at top left 2

3 1) Length of larval stage A. Annual 1 year B. 2 to 3 year Annual and multi year grubs Annual grubs 3

4 Multi year grubs Identifying white grubs What the grubs do 1. Root pruners feeder roots and back 2. Damage to below ground tubers 3. Churners uprooting seedlings 4

5 1) Root pruners A. Crops B. Turf Root pruning Annual and multi year grubs 5

6 White Grubs Damage appears more than 2 weeks after plant emergence delayed wilting or stunting Wilt, missing plants, dead plants worse with dry soils White Grubs Can be spotty Dig, assess stand Overwinter as larvae in soil A. Crops May / June beetles Phyllophaga spp (2 3 yr) 6

7 Adults dark brown to black Raster spines and bristles Raster 2 long parallel rows of hooked spines A. Crops May / June beetles Phyllophaga spp (2 3 yr) Even stunted plants are relatively large Damage began after seedling stage 7

8 Possible pattern to damage Related to low spot higher soil moisture / weed growth Lack of finer roots May beetle feeding on oak 8

9 Management No rescue treatment after damage found Insecticide at planting for preventive control Identify type 2 3 year problem next year B. Turf Annual grubs High numbers of grubs some years Intense root feeding drought period High input systems Aesthetically important White spots on side of adult V shaped raster of grub Japanese beetle V pattern 9

10 Masked Chafer Light tan night flying beetles Random spine and bristle pattern on raster Irrigation effect on grubs Oasis during dry summers Increased egg hatch and larval survival White grub damage turf Rolls up like carpet No root system August / Sept 10

11 Treated Insecticides Preventive or Rescue Not Treated Optimal timing for preventive control: mid-june to mid-july Grub treatments can be applied as granules or sprays 11

12 Remember: Water to activate insecticide Rescue Treatments: No insecticide consistently gives more than partial control (about 75%) once grubs are full size Dylox (trichlorfon) or Sevin (carbaryl) are fastest current products for rescue treatments Preventive insecticides are too slow for rescue treatments Why Grub Treatments Sometimes Fail o Improper timing (too early, too late) o Too much thatch o Insufficient watering o Incorrect rates, poor calibration o Big grubs are hard to control 12

13 Thatch can bind insecticides before they reach the target zone One White Grub Delight on whole wheat no onions! Natural enemies can be a problem Racoons 100 grubs per night Skunks Aug / Sept 13

14 Pencil diameter holes in turf from starlings and grackles feeding on white grubs August / Sept Adult beetle activity can help predict site and type of grub problems Japanese Beetle May / June beetles Masked Chafer Green June Beetle 2) Tuber feeders 14

15 White grub damage to potatoes Shallow gouge usually wider and deeper than wireworm Avoid root crops following sod 2 to 3 years of other crops with high plant populations beans Preventive use of entomophagous nematodes 3) Churners uproot seedlings 15

16 Green June beetle Feed on organic matter visit surface regularly surface back crawlers 2 irregular Parallel rows of large and small spines below anal opening Green June beetle 16

17 Pulaski Co - September Your shovel is your friend Green June beetle larvae 17

18 High organic matter soil Intensive grazing hay residue Manure buildup Sports turf Holes in turf No root damage 18

19 Grubs accumulating in dugouts and on base paths Result of insecticide application Natural enemies Spring Tiphia wasp Japanese beetle Resembles winged carpenter ant 19

20 Natural enemies Blue winged wasp Japanese beetle & green June beetle Larva similar to Tiphia 20