Posts tagged grubs

In search of grubs, and how to treat crabgrass and arborvitae

Linn County Master Gardener, Claire Smith, wrote the following about three of the most frequently asked questions to the Linn County Master Gardener Horticulture Hotline. The HortLine is available to answer questions from 9 am.. to noon and 1-4 p.m. Monday through Thursday  and  9 a.m. to noon on Fridays at (319)447-0647.

 

    One of the commonly asked questions in the spring concerns when to apply pre-emergent crabgrass killer.  Master Gardener Susan Long has this response:  Typically, the blooming of the forsythia or the redbud is a good indicator of when to apply pre-emergent crabgrass herbicide.  Pre-emergents must be applied before the crabgrass germinates. Ground temperatures must be a minimum of 50 degrees. If the material is applied too early, crabgrass seeds that germinate late in the season will not be controlled.  If applied too late, some crabgrass will have already germinated.  In central Iowa, this is usually mid-April to May 1.  However, if the weather warms up early or stays cool longer, then adjustments must be made based on the conditions.  Having a thick, healthy lawn that is fertilized, watered and mowed certainly discourages the growth of crabgrass. 

    Susan also answered a question about arborvitae having brown leaves due to winter burn and whether it will recover and/or should be pruned:  Avoid pruning browned, burned areas from evergreen trees and shrubs in the early spring since these branches may still have viable buds that will produce new foliage when growth resumes.  The brown will eventually fall off.  If the buds did not survive, then prune dead branches back to living tissue.  The affected trees and shrubs should look much better by late June or July.  There is no need to fertilize affected evergreens.  However, if the weather this spring is dry, periodically water evergreens to encourage new growth and speed their recovery.

    Another caller wondered what causes a lawn to be torn up at night.  Lawns that have grubs attract raccoons, skunks, and crows which turn over large patches of turf in search of the grubs.  The best time to treat is early in the summer when insecticides have the best changes of working.  The entire lawn may not need to be treated, rather treat grub “hot spots” determined by observation or sampling.  Presently trichlorfor (Dylox or Bayer 24-Hour Grub Control) and Sevin are the fastest-acting, most effective homeowner insecticides for curative grub control.  These must be watered in completely after application.  In many cases it may be preferable to repair the damage through seeding or sodding without treating.  If the old, loose sod is still green it may reattach with adequate watering.

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Centipedes, millipedes and more Japanese beetles

 

 

Master Gardener Intern, Sue Levasseur, answers two questions frequently asked of the Hortline:

 

            Q.  How can I get rid of those metallic-green bugs that are eating my plants?

The Japanese beetle has become a significant pest in Iowa during the past decade.  The head and thorax are shiny metallic-green, and the wing covers are coppery red. A row of five tufts of white hairs grow on each side of the abdomen.

            Japanese beetles are a double threat insect in the home garden.  In the larvae stage they are white C-shaped grubs that are approximately 1¼” long when fully mature.  They inhabit the soil from August until June where they feed on turf grass roots and organic matter.  Adult beetles emerge in June and eat the foliage and flowers of over 300 plants.  Foliage is consumed by eating the tissue between the veins, a type of feeding called skeletonizing.

            Control of adult beetles is difficult because they emerge every day for a period of several weeks.  Handpicking or screening of high-value plants may be of benefit in isolated situations with limited numbers of beetles.  Spot spraying infested foliage of high value plants with carbaryl (Sevin), permethrin (Eight) or cyfluthrin (Tempo) may reduce damage for several days but multiple applications are required to maintain control.  Spraying the adult stage is not an effective strategy for prevention of white grubs.  Use of floral lure and sex attractant traps is not recommended; research suggests that they are not effective in controlling moderate to heavy infestations and they may attract more beetles into a yard than would occur otherwise.  However, the traps may reduce damage and beetle populations where landscapes are isolated from other Japanese beetle breeding areas or when mass trapping (everyone in the neighborhood) is used.  

            Q.  What is the difference between centipedes and millipedes and how can I get rid of them in my house?

            House centipedes are approximately 1½” long with 15 pairs of long, threadlike legs extending from their body segments (one pair per segment). In contrast, millipedes are about 1¼” long and have 30 pairs of short legs extending from their body segments (two pair of legs per segment). 

            House centipedes are found both indoors and outdoors, but prefer living in damp portions of basements, bathrooms, and unexcavated areas under the house.  They feed on small insects, insect larvae and spiders.  Thus they are beneficial and considered harmless to people but most homeowners consider them a nuisance.

            To deter centipedes from your home dry up and clean the areas that serve as habitat and food source for centipedes as much as you can.  Residual insecticides can be applied to usual hiding places such as crawl spaces, dark corners in basements, baseboard cracks, openings in concrete slabs, under shelves and around stored boxes.

            Millipedes are usually found outdoors where they feed on decaying vegetable matter.  They are one of nature’s harmless “recyclers”.  Millipedes are accidental invaders in the house.  Capture and discard the offending invader.

Gardening Questions?  Call the Linn County Master Gardener Horticulture Line @ 319-447-0647.

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