White gubs are white with a dark head. They have three pairs of legs on the thorax and usually assume a C-shape when at rest.
Adults are various types of scarab beetles - known variously as May/June beetles, "June bugs', chafers and by other names. They have a generally oval form. May/June beetles tend to be dark brown, chafers are lighter brown.
Eggs are laid in the soil. Females tunnel and inch or more and lay eggs in small groups. The larvae feed on roots and actively move through the soil. The length of time required to complete development varies by species. The chafers have a life cycle that is completed in a single year and adults are present in late June and July. Two or three years are required to complete the life cycle of May/June beetles and adults are usually present in late spring.
Larvae chew roots. Significant pruning can produce serious drought stress. With high populations of grubs, particularly of larger species such as May/June beetles, grasses can be killed.
Problems are uncommon in sod farms. The likelihood of serious white grub infestations is highest during droughty periods when egg laying may be concentrated in irrigated areas.
Insect parasitic nematodes of the genus Heterorhabditis can provide control of white grubs.
Sod will usually recover from white grub, given the care common in sod production.
Adults are attracted to lights and observations of numbers attracted to light traps can provide an indication of whether high populations of egg laying adults are present.
Control of white grubs can be is difficult for several reasons. Larvae become increasingly resistant to insecticides as the insect ages, so applications are best made to coincide with egg laying/egg hatch periods. Adequate watering is essential to allow movement of insecticides or insect parasitic nematodes into the root zone.
There are several turfgrass insecticides that are not effective for white grub control - notably pyrethroids (Talstar, Scimitar, DeltaGard) and Dursban. These insecticides have a high affinity for organic matter and are bound tightly to the grass blades and thatch. They also are not highly water soluble. They will not control white grub larvae present in the root zone of turfgrass.
On the other hand, insect parasitic nematodes can be an effective biological control for billbug larvae. These are microscopic roundworms that penetrate insects and kill them rapidly from injection of bacteria. Only species of the genus Heterorhabditis species are effective for white grubs; Steinernema species are not effective. Several suppliers are available in the United States and pricing is variable.
When applying insect parasitic nematodes some special handling and application considerations are important. They are perishable and should be used shortly after receipt. Insect parasitic nematodes are also sensitive to drying and light. Ideally applications should be made very early or late in the day and post treatment irrigation is essential. For more information on insect parasitic nematodes see http://www.ext.colostate.edu/PUBS/INSECT/05573.html
Heterorhaditis bacteriophora, Heterorhabditis megadis and others
Insect parasitic nematodes are typically applied at rate of 100 million to 1 billion per acre. They are living organisms sensitive to UV light and drying. Irrigation immediately after application is essential. Some pretreatment irrigation may also be useful. Applications should not be made during the middle of the day to avoid excessive heat and light. Billbug larvae are typically killed within 3-7 days after application.
Product List for White Grubs in Sod Farms:
Insecticide |
Labeled Use Rate |
Reentry, Remarks |
|
Merit 2
|
1.25-1.6 pt/A |
12 hour reentry. Neonicotinoid insecticide (imidacloprid). Moderate to low water solubility, but will move to crown, upper root zone with irrigation. Slow-acting and may take a couple of weeks to kill larvae. |
|
Merit 75WP, WSP |
6.4-8.6 oz/A |
12 hour reentry. Neonicotinoid insecticide (imidacloprid). Moderate to low water solubility, but will move to crown, upper root zone with irrigation. Slow-acting and may take a couple of weeks to kill larvae. |
|
Mach 2 1.5G |
133 lbs/A |
12 hour reentry, 7 days must elapse before harvest. Insect growth regulator (halofenozide) that interferes with molting. Moderate to low water solubility, but will move to crown, upper root zone with irrigation. Fairly slow-acting and may take a week or more to kill larvae. |
|
Mach 2 SC |
4 qts/A |
12 hour reentry, 7 days must elapse before harvest. Insect growth regulator (halofenozide) that interferes with molting. Moderate to low water solubility, but will move to crown, upper root zone with irrigation. Fairly slow-acting and may take a week or more to kill larvae. |
|
Chipco Sevin 80WSP |
10 lbs/A |
12 hour reentry. Carbamate insecticide (carbaryl) that is moderately water soluble. Breaks down rapidly in high pH soils. |
The information herein is supplied with the understanding that no discrimination is intended and that listing of commercial products, necessary to this guide, implies no endorsement by the authors or the Extension Services of Nebraska, Colorado, Wyoming or Montana. Criticism of products or equipment not listed is neither implied nor intended. Due to constantly changing labels, laws and regulations, the Extension Services can assume no liability for the suggested use of chemicals contained herein. Pesticides must be applied legally complying with all label directions and precautions on the pesticide container and any supplemental labeling and rules of state and federal pesticide regulatory agencies. State rules and regulations and special pesticide use allowances may vary from state to state: contact your State Department of Agriculture for the rules, regulations and allowances applicable in your state and locality. |
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Categories: Sod, Turf, Insects, White Grubs
Date: 04/12/2004