L-1131

House and WHITE GRUBS IN Landscape Pests TEXAS TURFGRASS M.E. Merchant and R.L. Crocker*

White grubs are the larval stage of masked chafer, lurida. Another interesting kind of white commonly known as May Warm season grasses like grub is the green June , or June (or Junebugs). bermudagrass, zoysiagrass, St. Cotinus nitida. These rather large Almost 100 species live in Texas, Augustinegrass, and grubs feed primarily on decaying most of which do not cause signif- buffalograss are organic matter and normally do icant economic damage to crops or attacked not injure turf; however, turf can horticultural plantings. A few readily by be damaged by their burrowing species, however, commonly dam- both types of activity. Larvae are especially com- age turfgrass and other cultivated white grubs, mon underneath fruit trees, in plants. with most compost piles, and in soils with lawn damage occur- high organic content, such as may White grubs, sometimes referred ring during summer be found in heavily mulched gar- to as grubworms, injure turf by and fall months. dens and flower beds. Daytime feeding on roots and other under- resting sites of green June beetle ground plant parts. Damaged larvae can often be found near areas within lawns lose vigor and Figure 2. Adult white grubs, often such sites and are marked by turn brown (Figure 1). Severely called May or June beetles, are com- small mounds of soil on the lawn damaged turf can be lifted by monly attracted to lights at night. surface. The larvae have a curious hand or rolled up from the ground The optimal time to treat grub- habit of crawling on their backs like a carpet. infested lawns is 5-6 weeks after the peak adult flights. across the soil surface to move from one site to another. Adults of the green June beetle are velvet- green on the top, metallic green Cool season grasses such as the below, and are approximately 1 fescues, bluegrass, and ryegrass inch in length. Adults fly during are also susceptible to the June the day and feed on over-ripe beetle and southern masked fruit. chafer, though they tend to be attacked more frequently by a May beetle, Phyllophaga congrua. Life Cycle Damage from May beetles often Figure 1. Golf course fairway dam- appears in the spring and early Most turfgrass-feeding white aged by white grubs. summer, before injury from other grubs in Texas, such as the June white grubs becomes evident. beetle and southern masked The most important turfgrass- Other white grub species occasion- chafer, require one year to com- infesting white grubs in Texas are ally recorded as pests in Texas plete their life cycle (a two-year the June beetle, Phyllophaga crinita turfgrass include Cyclocephala cycle is suspected in a portion of (Figure 2) and the southern pasadenae and Phyllophaga sub- the grub populations in north mucida. Texas). The May beetle, *Extension Urban Entomologist and Phyllophaga congrua, requires two Research Entomologist, respectively, The years to develop. For simplicity, Texas A&M University System. the following discussion will be

Texas Agricultural Extension Service ¥ Zerle L. Carpenter, Director ¥ The Texas A&M University System ¥ College Station, Texas limited to species with one-year passes through three larval life- spring and lasts approximately life cycles. stages, or instars. These instars are three weeks. Pupae can be found similar in appearance, except for in small earthen cells 3 to 6 inches Once a year, in late spring or sum- their size. First- and second-instars below the soil surface. White grub mer, adult beetles emerge from the each require about three weeks to treatments applied during the soil to mate. Mated females then develop to the next life-stage. The pupal life stage are both ineffec- return to the soil to lay eggs. third-instar actively feeds until tive and unnecessary. Within about two weeks the eggs co