A PRACTICAL RESEARCH DIGEST FOR TURF MANAGERS TURFGRMS Volume 8, Issue 5 • May 1999 TRENDS ENTOMOLOGY IN THIS ISSUE Annual Bluegrass Annual Bluegrass Weevil Weevil: A Metropolitan A Metropolitan Nightmare Nightmare 1 Life Cycle By Dr. Patricia J. Vittum, University of Massachusetts Look for Damage he annual bluegrass weevil, Listronotus maculicollis, is also often called the Hyperodes Monitoring, weevil because it was formerly assigned to the genus Hyperodes. The insect is a major Setting Thresholds pest of golf courses in the northeastern United States, particularly in the metropoli- T Cultural, Biological and tan New York area, including Long Island; the counties just north of New York City; south- Chemical Control western Connecticut; and northern New Jersey. However, it has also been reported caus- ing damage on golf courses throughout New England, upstate New York, central and Back to Basics, How eastern Pennsylvania and around Toronto, Ontario, Canada. Tlirfgrasses Grow . .7 As its name suggests, the annual bluegrass weevil feeds primarily on annual bluegrass Leaf Initiation and Growth [Poa annua) and is particularly damaging on turf with low mowing heights. Damage is usu- ally most severe on collars and approaches, tees, greens and fairways. The weevil can cause Flowers and Stems damage to fine turf wherever annual bluegrass grows in its perennial form. Since the mul- tiple generations overlap, damage can occur any time from late May through early Sep- Rhizomes and Stolons tember. In the metropolitan New York area, the damage is usually most noticeable in early Growth Responses June and again in late July and early August. To Adverse Climates Refining Turf Where Weevils Exist Management Practices The annual bluegrass weevil has been reported in more than 30 states, but so far is only a problem on fine turfgrass in the Northeast and Middle Atlantic states. It was first report- Field Tips: Speeding Transition of Typical pattern of Overseeded Perennial annual bluegrass Ryegrass ....... .13 weevil damage along the edge of a collar. Visit us at www. landscapegroup. com TURFGRASS TRENDS Executive Editor Sue Gibson 440-891-2729; 440-891-2675 (fax) ed as a turfgrass pest in Connecticut in 1931 becomes reddish brown, just before the sgibson@advanstar. com and on Long Island in the late 1950s. Ini- adult weevil emerges. Managing Editor Bruce E Shank, BioCOM tially, turf managers blamed "spring die out" 805-274-0321 of annual bluegrass on the agronomics of Technical Editor the plant, specifically its inherent intoler- Life Cycle Nancy Stairs ance of summer temperatures. However, in As with any insect, it is important to 440-891-2623 many cases the obvious and rapid decline of understand the life cycle and to know when Senior Science Editor the insect is vulnerable to control treat- Dr. Kari Danneberger annual bluegrass can be traced to weevil activity. ments. In the metropolitan New York area, Consulting Editor Chris Sann the annual bluegrass weevil normally com- pletes two or three generations per year. Croup Editor Vern Henry Weevil Description The insect overwinters in the adult stage, Production Manager The annual bluegrass weevil, like most usually in nearby woods (especially in the Karen Lenzen weevils, is a beetle with a distinct snout litter underneath white pines) or in tufts of 218-723-9129; 218-723-9576 (fax) high grass between the rough and woods. As klenzen@advanstar. com (Figure l).The adult is about 1/8 inch long, slightly smaller than most turf billbugs, and temperatures warm, adults begin to migrate Circulation Manager Frank Christopherson the thorax only occupies about 25% of the toward the short cuts of annual bluegrass. 218-723-9271 total body length. The snout is shorter and The earliest movement typically begins in Group Publisher stouter than that of a billbug and the anten- late March, but many weevils do not begin John D. Payne nae are attached near the apex (far end) of migrating until early or mid-April. 440-891-2786; 440-891-2675 (fax) jpayne@advanstar, com the snout. Mature adults are dark brown or Once the females reach the low-mown black with gray or yellow-brown hairs and annual bluegrass (fairways or shorter), they Corporate & Editorial Office 7500 Old Oak Blvd. scales on much of the thorax and hind begin to lay eggs inside the leaf sheath. This Cleveland, OH 44130-3369 wings. Teneral adults (recently emerged usually occurs in late April or early May. Mew Subscriptions from pupae) are reddish brown. Eggs are reasonably well protected and take 1-888-527-7008 Females usually lay two or three eggs at about a week to hatch into tiny larvae. The Abstracts: 800-466-8443 a time, lined up end to end inside the leaf larvae are small enough that they can bur- Reprint: 440-891-2744 sheath. Each annual bluegrass weevil egg is row inside the grass stem and feed as borers Permission: 440-891-2742 Single copy or back issues: deposited between leaf sheaths. The egg is for about a week. Larvae molt once during Subscription/Customer Service pale yellow when laid, but turns smoky gray this stage. 1-888-527-7008; (fax) 218-723-9437 Website address: as it matures. It is elliptical, about three When the larvae grow large enough that www. landscapegroup. com times as long as it is wide. they must leave the stem, they move down The larva (Figure 2) is cream colored the outside of the stem to the crown of the with a brown head capsule, sometimes with plant and continue feeding. Larvae pass ADVANSTAR a slight gray coloration along the back. Lar- through a total of five larval instars (three or HOLD! N G S , I N C . vae are legless but have several distinct four of which are outside the stem), spend- Chairman and "ridges" along the body and can move quite ing about five to seven days in each stage. Chief Executive Officer Robert L. Krakoff well through the thatch and upper part of After the larvae have completed feed- Vice Chairman the soil. They are somewhat elliptical, ing, they pass through a "prepupal" stage, James M. Alic although the midsection is often slightly which resembles the larvae but is slightly VP-Finance, CFO & Secretary wider than the fore or hind end. Larvae are longer. The prepupae carve out a little cell David J. Montgomery small (1/16-inch long when first emerging in the soil, just at the soil/thatch interface. Executive Vice President, to 1/5-inch long just before pupating) and (Often the tip of the larvae will "spin" in the Business Development spend most of their development inside Skip Färber soil when disturbed.) Each prepupa then grass stems in their earlier developmental transforms to a pupa, a quiescent stage dur- stages or near the crowns of plants as they ing where the insect does not move or feed. w mature. Many changes occur internally during this ADVANSTAC O M M UN |C A T 1R O N S The pupa has many adult characteris- stage, including the development of a repro- Executive Vice Presidents tics, including the developing eyes, man- ductive system and muscles to power the William J. Cooke dibles, antennae, legs and wings. Creamy wings and legs of the adult. The pupa stage Alexander S. DeBarr white when it first develops, it later lasts about five to seven days, after which Vice President & General Counsel Eric 1. Lisman Treasurer and Controller Adele D. Hartwick Figure 1. The annual bluegrass weevil adult is a dark broum or black beetle about 1/8 inch long unth a short, distinct snout. Figure 2. Larva are cream colored, legless and small (1/16 to 1/5 inch long). They have a broum head capsule unth cheunng mouthparts. Adapted from Cameron and Johnson, 1971. young ("callow") adults emerge. These September or early October, but we never adults are reddish brown for a few days and find these stages when we sample the same the exoskeleton is not as hard as it will be areas the following spring. once the insect matures fully. The callow adults tend to be more vulnerable to envi- ronmental extremes than the more mature Look for Damage "hardened" adults. Annual bluegrass weevil larvae, which The completion of the first generation is have chewing mouthparts, can cause severe marked by the emergence of adults the end damage to turf. Young larvae feed as borers of June or early in July. A second generation inside stems, sometimes depositing tan saw- then develops, with egg laying possible only dust-like material inside the stems. Howev- a week after the adults emerge. Each subse- er, the primary damage is caused by the quent developmental stage occurs more large larvae which feed at the crown of the quickly than in the spring generation plant. Studies conducted in the 1970s because summer temperatures are higher demonstrated that an individual larva can and physiological activity is accelerated. So sever 10 to 12 plants outright during its the large larvae of the second generation feeding (Cameron and Johnson 1971). often are active by the end of July or early Damaged areas first appear as small yel- August. They then pupate and 2nd genera- low-brown spots. Small spots eventually tion adults appear by mid August. coalesce into larger areas and take on a In unusually warm years, the develop- "water-soaked" appearance. Damage often ment of each generation can be accelerated coincides with, and can be confused with, enough that second generation adults anthracnose. appear in early August, which allows a third Damage from the larvae that are active generation to develop, resulting in larvae in the spring is usually concentrated along activity throughout August and into Sep- the edges of fairways or on edges of greens, tember.