PEST MANAGEMENT predators in a turfgrass system are generalists , fostering conditions that provide alternative food sources will help to ensure that they are present in sufficient populations to provide control during the time of year when pest insects are present . Research has shown that some beneficial predators ’ alternative food sources are more available when turf is maintained at a higher mowing height . Mowing height should accommodate the intended use of the field and functionality of the playing surface , but mowing a little higher while accomplishing these goals is beneficial .
GRUBS A primary group of insects found on cool-season grasses includes species of white grubs . This insect group belongs to the Scarab family of beetles and are turfgrass root feeders as juveniles ( grubs ). Common anatomical characteristics of grubs include a creamy white C-shaped body , six legs and a brown-black head capsule . Grub species include Japanese beetles , masked and European chafers , Oriental beetles , May-June beetles and Asiatic garden beetles . These species can be identified by their raster pattern , which is the arrangement of bristles and hairs located on the underside of their abdomen .
Throughout most of the northeast , transition zone and Midwest , the most common grubs are Japanese beetles and masked chafers . These are “ annual grubs ” that only go through one life cycle within a 12-month period . Beginning as an egg laid by females in mid- July to early August , grubs hatch and progress through three juvenile instars from August-September / October , growing progressively larger . With cooler autumn temperatures , grubs will travel deeper into the soil to overwinter as third instar larva . With warmer spring temperatures , grubs will slowly move further up in the soil profile and resume feeding on turfgrass roots before going into pupation in late May-June . They then emerge as adults , which feed on ornamental plants and mate by mid-July , starting the cycle over .
DAMAGE AND SYMPTOMS Lighter damage may occur in the spring in areas with high grub populations , but turf damage is most evident in August through early October since cool-season grasses have fewer roots at the end of summer and additional stress from root-feeding grubs can compromise plant health . Damage can be worse in droughty summers . Symptoms of grub feeding include gradual thinning of the turf stand , wilting , yellowing / browning of turf , and irregular dead patches . Additionally , birds , skunks and raccoons may be observed digging up grub-infested areas , causing further damage . Dead patches will roll back easily ( like lifting a carpet ) since the grass roots have been eaten .
To monitor grub populations , cut a few square-foot sections of sod and peel back to examine the top 2 ” of soil and count the C-shaped grubs observed . Repeat this procedure in three to four samples around the field . If there is an average of 10-12 grubs / square foot or greater , a chemical control may be necessary ( especially if the field has had grub damage in past seasons ). Fields at or below this threshold can typically survive well with extra care in watering and making sure fertilizer applications and fertility levels are adequate .
If the field has had grub infestations from previous seasons , and monitoring in April / early May indicates populations above threshold levels , apply an insecticide labeled for season-long grub control in May . These products are applied to prevent grub infestation later in the summer , and include imidacloprid or the neonicotinoid alternative chlorantraniliprole . Additionally , an OMRI-certified product containing Bacillus thuringensis var . galleriae can be used as an “ early curative ” control . This product works best when applied at the first instar stage of the grubs ( late July to mid-August ).
PREVENTION AND CULTURAL PRACTICES Cultural practices are a key to maintaining turfgrass health , enabling a field to lower pest pressures . Proper fertility and increasing mowing heights while still maintaining playability of the field will help grow a healthier plant and a robust root system that will withstand grub infestations better . Additionally , keeping the field on the “ drier side ” in the late summer and early autumn can be helpful by desiccating white grub eggs that are laid in July .
CHINCH BUGS Chinch bugs feed by inserting their piercing-sucking mouthparts into leaf sheaths and crown tissue and suck out plant fluids , causing localized yellow or brown patches . Non-endophyte turfgrasses such as Kentucky bluegrass tend to be more susceptible to chinch bug feeding , and heat- and drought-stressed turf is the first to show damage . A majority of chinch bug damage occurs in mid- to late summer . For biological control , the big-eyed bug is the primary predator of hairy chinch bugs . Products with systemic activity ( i . e ., neonicotinoids or chlorantraniliprole ) are recommended if spring adult populations are significant . Contact products can be used curatively . sportsfieldmanagementonline . com September 2023 | SportsField Management
29