PUNCH LIST: How to han­dle Ja­panese bee­tles

The Denver Post - - LIFE&CULTURE - By Betty Cahill Betty Cahill speaks and writes about gar­den­ing in Colorado.

En­joy reg­u­lar strolls through the gar­den? Might as well re­move spent blooms, pull weeds and plan. “A gar­den is never so good as it will be next year” said Thomas Cooper, a 19th-cen­tury philoso­pher.

In the land­scape

•Take pho­tos of your gar­den this month to help plan for fu­ture ad­di­tions, changes or re­minders of sum­mer blooms and time spent out­doors.

•Of­ten in­door house­plants take a back seat to care dur­ing the sum­mer. They al­ways ap­pre­ci­ate an over­head shower to clean the fo­liage and re­duce any spi­der mites. While on va­ca­tion, in­crease hu­mid­ity by mov­ing plants close to each other and plac­ing a gravel tray cov­ered with wa­ter un­der plants.

Tomato trou­bleshoot­ing

•Weather and proper cul­tural care make a huge dif­fer­ence with crop suc­cesses and chal­lenges, es­pe­cially toma­toes.

•Hot days (in the 90s) have pre­sented chal­lenges, in­clud­ing blos­som drop and less fruit on the plants.

•Some ar­eas have been hit reg­u­larly with heavy July mon­soonal rains may be deal­ing with wa­ter­logged soils.

•Cat faced, growth cracked or mis­shapen fruit is com­mon af­ter fast growth dur­ing dry weather fol­lowed by too much ir­ri­ga­tion or nat­u­ral rain­fall. Early ripen­ing fruit is most af­fected and, if not too dam­aged, should be OK to eat when ripe. Later sum­mer and fall ma­tur­ing fruits are usu­ally just fine.

•En­vi­ron­men­tal fac­tors in­clud­ing heat, drought, wind or un­even wa­ter­ing can cause tomato leaves to curl or twist. No treat­ment needed; just main­tain good cul­tural care. Other leaf-curl cul­prits in­clude her­bi­cide drift or pos­si­bly a virus. Vi­ral-in­fected plants need to be re­moved to pre­vent spread­ing to other plants.

•Fun­gus is­sues like early blight are gen­er­ally more com­mon on toma­toes than bac­te­rial dis­eases. In some years, like this one, both can be present. They have sim­i­lar look­ing leaf symp­toms: lower-leaf yel­low­ing and brown to black spots.

•Take pho­tos of plants or bring some leaves and fruit to your lo­cal Colorado State Univer­sity Ex­ten­sion of­fice or knowl­edge­able gar­den cen­ter for di­ag­no­sis of tomato is­sues or dis­eases.

•Good cul­tural care in­cludes mulching to pre­vent soil splash back on the plants and avoid work­ing in the gar­den when plants are wet.

Bat­tling Ja­panese bee­tles

•Given free reign, adult Ja­panese bee­tles will skele­tonize or eat en­tire leaves, buds or flow­ers of roses, Vir­ginia creeper, dahlias, grape, green beans, lin­den and ap­ple trees and scores of other land­scape and agri­cul­tural plants.

•They have moved in to new ar­eas of metro Den­ver this sum­mer.

•Ja­panese bee­tles have a 1-year life cycle. Tim­ing is im­por­tant for re­duc­ing adult and lar­vae num­bers, which means less plant dam­age and hope­fully fewer bee­tles next year.

•Their off­spring — eggs/lar­vae/pu­pae — are be­ing laid now and will live be­low and feed on grass turf through next sum­mer, when they emerge as adults.

•Even though adult bee­tles can fly up to 5 miles from other yards, parks and busi­nesses, con­sider treat­ing your lawn while fe­males are lay­ing eggs (next year’s gen­er­a­tion).

•Large num­bers of lar­vae may harm or kill grass turf.

•Many in­sec­ti­ci­dal con­trol prod­ucts are avail­able and are very ef­fec­tive on grubs. Bi­o­log­i­cal al­ter­na­tives us­ing par­a­sitic ne­ma­todes or milky spore bac­terium are ad­di­tional op­tions to con­sider.

•As grubs get larger in the fall, con­trol prod­ucts are not as ef­fec­tive as treat­ing lawns early in the sea­son. So do not wait — ap­ply con­trols now.

•Cul­tur­ally the lawn can be made less de­sir­able to fe­males dur­ing the sum­mer egg-lay­ing pe­riod. Keep the lawn drier and taller.

•Re­search on Ja­panese bee­tles con­firms that re­mov­ing adult bee­tles re­duces fur­ther dam­age to plants and in­creases the at­trac­tive­ness of the plants. As volatile com­pounds are re­leased from chewed plants, the more bee­tles are at­tracted to those plants.

•Re­duce adult beetle num­bers by tap­ping them into a jar of soapy wa­ter early or late in the day, when they are slow-mov­ing.

•It is OK to squish bee­tles. The re­search says that upon emer­gence from the soil, fe­male vir­gin bee­tles are quickly mated. Af­ter mat­ing they no longer have the much-sought-af­ter scent that draws more bee­tles to the area.

•Traps are not rec­om­mended to re­duce num­bers; they at­tract more bee­tles to sur­round­ing plants. If your neigh­bor is us­ing a trap, you may have fewer bee­tles com­ing to your yard.

•There are sev­eral in­sec­ti­ci­dal spray con­trol op­tions for adult bee­tles. Use care; read all la­bels and never ap­ply when bees, ben­e­fi­cial in­sects and pol­li­na­tors are ac­tive in the area.

•Read more in­for­ma­tion in­clud­ing sug­gested con­trol prod­ucts on this help­ful fact sheet from Colorado State Univer­sity: http://ex­ten­sion.colostate.edu/topic-ar­eas/in­sects/japane­se­bee­tle-5-601/

Betty Cahill, Spe­cial to The Den­ver Post

Adult Ja­panese bee­tles will de­vour en­tire leaves in the gar­den. Here they're shown on hi­bis­cus.

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