Chinch Bugs or White Grubs?

By: John Degroot

August 21 2010

Chinch Bugs or White Grubs? - Garden Clippings for August 21, 2010

                Gardeners struggling to keep their lawn green and healthy have plenty company.  This summer’s heat and drought has placed turf under stress while the weeds, fungus and bugs are having a heyday.

                  The two most prevalent insects causing damage to lawns in southwestern Ontario are Hairy Chinch Bugs and White Grubs.  Both are found in heavier than normal numbers this year.

                At first glance, symptoms of White Grubs and Chinch Bugs are similar.  Both cause irregularly shaped yellow to brown patches in the lawn.  But if we examine the issue carefully, it is quite easy to detect the difference between the two.

                White Grubs do most of their damage in early spring and in fall.  The adults, Japanese Beetles, resemble June bugs but are smaller, more slender and have shiny copper coloured wings.  The adults don’t damage grass, but feed voraciously on many plants, trees, perennials.  They often skeletonize a leaf, eating the meat, but leaving the veins.  They do most of their eating in July and August.

                  Beginning in mid August, adult Japanese Beetles lay eggs which hatch in a few weeks.  The eggs become tiny White Grubs with quite an appetite.  They eat grass roots causing irregularly shaped dead patches.  Damage is minimal when the grubs are tiny, but as they mature later in the fall, damage can be quite extensive.

                 When weather becomes cool, White Grubs go deep into the soil.  In spring the grubs emerge and begin feeding again.  When the grubs are fully grown they transforms into adults and the process repeats itself.

                To control White Grubs and the subsequent Japanese Beetles, apply nemetodes which are tiny naturally found organisms that feed on the grubs.  Ideally, nemetodes should be applied beginning late summer to early fall, when the grubs are small.   Add at least 3 inches of water  to the lawn before and after application so the nemetodes have the ability to travel.

                Hairy Chinch Bugs do most of their damage in midsummer during periods of hot, dry weather.  With their piercing mouths they suck juices from the crown and stems of grass, causing small sections of grass to appear sunken, yellow and finally brown.  As damage progresses the small spots can run together to become large dead patches. Chinch Bugs dislike water.

                The life cycle of Chinch Bugs is quite different than that of White Grubs.  The adults spend their winter in shrubbery, under trees and in flower beds.  In spring the adult becomes active and deposits eggs into the lawn.  The eggs quickly become tiny nymphs by early June and become adults by mid July.  Damage begins to become evident by the end of July.

                  Small infestations of Chinch Bugs won’t cause noticeable damage, but after several weeks of hot, dry weather damage can be quite severe.

                The easiest way to detect the presence of Chinch Bugs is to make a cylinder out of a large tin can.  Coffee containers or 48 oz tomato juice containers will do the trick just fine.  Sink the can partway into the soil and fill with water.  Within minutes tiny bugs will emerge and float to the top.  Those of us who are over 50 may need glasses, because the Chinch Bugs are only 4 mm long.

                  The best time to do a Chinch Bug test is late July or August when the bugs are most abundant.  The best place to do the test is at the edge of a suspected affected area.

                Chinch bugs are now difficult to control.  Since Ontario’s Cosmetic Pesticide Act came into place, Diazinon, Chlorpyrifos and Sevin are no longer available and Ontario Ministry of Agriculture and Food publications are mum on control measures.

                  I have had several gardeners tell me that Insecticidal Soap is effective against Chinch Bugs.  Insecticidal Soap is readily available, safe to use, and approved for insect control in Ontario gardens.

                 The best defense against insects in the lawn is a healthy lawn.  Start with good soil. Fertilize faithfully to keep the grass growing.  Water during dry spells.  Mow regularly and punctually, and don’t cut the grass too short.

                  As lawn care becomes more challenging, rejuvenating the lawn makes more sense.  If your lawn is weak, dying or dead, apply a layer of top dressing topsoil and sow a good quality grass seed.  The best time to apply grass seed is late summer and fall.