The grub is a broad name for the larval stages of different beetle species in Scarabaeidae and order Coleoptera. Most beetle grubs feed on the secondary and tertiary roots of the turfgrasses and are chiefly considered the turfgrasses pests. The heavy infestation of the beetle grubs slows down the growth of turfgrasses besides creating bad patches and breaking the linkage between roots and upper foliage like a carpet piece. Generally, the infestation remains poor in healthy and summer turfgrasses. Whereas the winter turf cultivars are more prone to infestation. The grubs of concern belong to European Chafer, Japanese, Junebug, rose chafer, Oriental, and Asiatic Garden beetles, and together they are called scarab beetles. Mature beetles are least damaging for turfgrasses and garden landscapes, But grubs do the maximum damage because they can't relocate and repeatedly feed in the location. The beetle grubs often exhibit the full potential of their Phyllophagus features and damage landscapes and lawn throughout North America.
The European chafer originated from continental Europe and remains invasive throughout North America on cultivated and wild grasses. It is also the number one enemy of turfgrasses in cool latitudes. The Japanese beetle pedigrees from Japan and reported in southern New Jersey in 1916 in the United States. The Japanese beetle is also an invasive pest of serious concern in the Eastern US. Otherwise, they have significantly expanded to Minnesota, Iowa, Missouri, Ontario, Georgia, Arkansas, and Alabama in turfgrasses and pastures. Most June bug species are native to North America, whereas some hail from Asia and Europe, and some common species include Ten-lined beetle, Common June bug, and Green fruit beetle. Besides these species, the grubs of rose chafer, Oriental, and Asiatic Garden beetles infest turfgrasses and some garden plants throughout the US.
European Chafer grubs are ¾ inches long, six-legged, and often grayish-white with a brown head. They also have parallel thorny dins on the raster, and their anal slit is 'y' shaped.
Japanese Beetle grubs also have a light brown head, and the last segment of the raster contains a 'V' mark.
The grubs of June beetles are often larger than European Chafer, and their heads are also dark brown. The remaining body color is creamy white. A most distinctive feature of all beetle grubs remains to curl the entire body into a 'C' shape on disturbance.
European chafers lay their eggs mid-summer, whereas the Japanese beetles in late summer. The eggs are deposited in the soil, and finding them on the soil surface is often hard, and they range from 60 to 75 per female. The eggs hatch in 10 to 21 days in different grub species, including the June bugs. The grubs start feeding on turf roots within 15-days after hatching. Hatching is more successful where soil moisture is plentiful. Otherwise, they start dying in arid soil. The grubs continue feeding until late fall, and then they burrow themselves deep in the soil to overwinter. The beetle grubs keep hibernating until spring and resume feeding when surface temperatures arise. European chafers Japanese beetle grubs start feeding on the roots of turfgrasses. Whereas, the June grubs join them later in mid-summer. Some beetle grubs can hardly raise one generation per year, while others take 3-years to complete one generation.
On heavy infestation, the chewed turfgrasses roots stop the uptake of essential nutrients and water from the soil, and the foliage turns brown. Once the linkage between foliage and roots is abolished, wind can blow up the spongy grass from its original position. Several bad patches appear due to the vigorous feeding of beetle grubs. Beetle grubs feed on both newly emerged and established turfgrasses roots. Even if the irrigation requirement of turfgrasses is met, the bad patches continue to increase giving the turfgrasses an ugly appearance. Grubs-affected turfgrasses are rolled back like a carpet, and sometimes the predatory birds also look busy digging the turfgrasses. Such damage is more prevalent from late summer through early, and beetle grubs' pervasiveness is more critical in the areas with moderate temperature and rainfall.
The beetle grubs start moving towards the soil surface when the turfgrasses temperature rises in spring, and their feeding activity peaks in summer that continues until early fall. The beetle grubs live, lay eggs, and overwinter in turfgrasses in the soil, where they feed on the roots of turfgrasses.
Besides following all preventions and cultural control practices if beetle grubs still damage your turfgrasses, here are the most proven ways to suppress their population using the biological, organic, and chemical methodologies;
Botanigard Maxx consists of 0.06% Beauveria bassiana and 0.75% Pyrethrins. Both ingredients come from natural sources that apply at and around edible plants, including the turfgrasses where grubs live in the soil. Beauveria bassiana is best applied when the turfgrass's surface temperatures remain between 40 to 85°F, often during late spring or early summer throughout the beetle grubs' affected areas. Moreover, it mixes with several insecticides and nutritional additives that turfgrasses need. Apply using an ultra-low volume sprayer and if the turfgrasses are growing on a fully-level soil, drench it early morning or late afternoon for best results.
Mix 0.50 to 0.64 ounces of product per gallon of water and apply on 200 to 250 square feet of turf.
This grub control contains milky spores of Bacillus popilliae, and each gram of product consists of 3 million bacteria. Its full-farm is Paenibacillus popilliae, and these are soil-living, rod-like, gram-positive bacterium that induces milky spore disease in the grubs living in the soil under the turfgrasses. Paenibacillus popilliae is a fastidious microorganism that grows only if, special nutrients are in the culture. Otherwise, it ceases its growth. It is not effective on other grub species other than Japanese beetles, and their entire stages remain susceptible to the bacterium for which ingestion is mandatory. The bacterium spores re-germinate in the grubs' body and turn the body fluid into opaque while that kills them. This fluid disperses and affects other beetle grubs, offering prolonged control.
Milky Spore is granular form and spreads on the turfgrasses with ease. A 20-pound bag is enough for applying in 7000 square feet of grub’s affected turfgrass.
Basillus Thuringiensis is another soil-dwelling bacterium applied to turfgrasses from spring through fall. It contains 6 million active spores per milligram of the product. The active bacterium concentration is about 98.35%, and it produces CRY proteins while passing through the midgut of the grubs, rupturing them and causing their death. The grubs must ingest the materials containing Bt. Bt applies to the turfgrasses mixed with irrigation water that reaches throughout the turf-growing areas. Otherwise, flooding the turfgrasses before the Bt application gives control.
Bt’s Kurstaki strain kills only Japanese beetle grubs are just the assumptions. Research proves it’s equally effective against all types of beetle grubs that harm your turfgrasses. Mix one tablespoon per gallon of water, spray on the turf, and apply at least half-inch irrigation.
Although the gardeners use this product for controlling different pests on the foliage of the plants, it also kills the soil-dwelling grubs and worms without any discrimination. However, a bit more dose per square foot is required when using turfgrasses to control all types of beetle grubs. It contains 0.5% Spinosad that induces speedy muscle contraction not only in beetle grubs but, the entire soil-living pests that feed on the roots of the turfgrasses and garden plants. The gardeners can spray the desired quantity of concentrate on the turfgrass and water them immediately after application.
Mix 2-ounces of the product per gallon of water, and spray on the turfgrass followed by irrigation of up to ½ an inch.
Season Long Grub Killer contains 0.08% chlorantraniliprole, an insecticide from the Ryanoid class, and works on ingestion and contacts poison. Its mode of action resembles Spinosad and disrupts calcium balance in the grubs' body instead of inducing rapid muscle contraction, But results are similar; paralysis to death. Chlorantraniliprole translocates in turfgrasses roots when applied as a surface insecticide.
A 14-pounds bag is enough for spreading in 5000 square feet of turfgrass.
Due to the variable regulations around (de)registration of pesticides, your national list of registered pesticides or relevant authorities should be consulted to determine which products are legally allowed for use in your country when considering chemical control. Pesticides should always be used lawfully, consistent with the product's label.
Check out our other guides on common garden bugs.
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