How to thwart house­plant pests

The Progress-Index - At Home - - NEWS - By Lee Re­ich

Now that win­ter is here, scale in­sects have started show­ing up on my pot­ted cit­rus tree and some or­chids. How many other plant pests lurk, ready for a pop­u­la­tion ex­plo­sion when con­di­tions be­come ripe, typ­i­cally in late win­ter?

Dows­ing plants — es­pe­cially in­door houseplants — with pes­ti­cides is both­er­some and hazardous. Re­peat ap­pli­ca­tions usu­ally are needed to catch each wave of the emerg­ing pest pop­u­la­tion at its most sus­cep­ti­ble stage. And it's dif­fi­cult to spray a plant thor­oughly while keep­ing the mist off cur­tains, win­dows and fur­ni­ture. A num­ber of sprays can stain or even dis­solve cer­tain fin­ishes or plas­tics.

A sys­temic pes­ti­cide such as Bonide Sys­temic In­sec­ti­cide Gran­ules, which spreads within the plant, also has short­com­ings. It cre­ates a toxic plant, which can poi­son any pet or child who nib­bles a leaf. And, such ma­te­ri­als can't, of course, be used on an in­door cit­rus whose fruit you plan to eat.

In­doors, where rain and wind can't carry away residues, you have to be wary even of pes­ti­cides la­belled "nat­u­ral." Nat­u­ral does not mean non­toxic. Rotenone, for ex­am­ple, is an all-nat­u­ral pes­ti­cide ex­tracted from a trop­i­cal plant, yet it is much more toxic than, say, malathion, a syn­thetic pes­ti­cide that also might be used on houseplants. I'm not sug­gest­ing us­ing syn­thetic pes­ti­cides over nat­u­ral ones on houseplants, but be aware of the haz­ards as­so­ci­ated with any pes­ti­cide.

I try to avoid us­ing pes­ti­cides al­to­gether. They are just one ap­proach to con­trol­ling pests, and should be the last one. Other ap­proaches may de­mand greater in­ti­macy with your pests, learn­ing their habits and life cy­cles, but that's part of what makes gar­den­ing in­ter­est­ing. Books such as "The Gar­dener's Guide to Common-Sense Pest Con­trol" by Wil­liam and Helga Olkowski, and "The Or­ganic Gar­dener's Hand­book of Nat­u­ral Pest and Dis­ease Con­trol," edited by Fern Mar­shall Bradley, Bar­bara W. El­lis and Deb­o­rah Martin, de­tail ways to con­trol many house­plant pests.

For now, I'm deal­ing with scale in­sects by flick­ing any that I see off leaves with my thumb­nail. I know I won't elim­i­nate them with this brute-force method, but I can at least keep the pop­u­la­tion in check. In a cou­ple of months, they might get ahead of me, but by then per­haps the lady­bugs that call my home their home will help out, as they have in years past.

I've used sim­i­lar meth­ods against aphids, crush­ing them where they con­gre­gate on leaves near the tips of stems, and against mealy­bugs, do­ing them in with a cot­ton swab dipped in al­co­hol. Keep­ing an aphid­in­fested plant in the shower will wash the pests away and cre­ate con­di­tions in­im­i­cal to another common pest, red spi­der mites, which are hard to see but make their pres­ence known by im­part­ing a bronze cast to leaves.

Trap­ping is a more el­e­gant ap­proach to pest con­trol. Thwart aphids on sin­gle- or few-stemmed plants by block­ing travel of the ants that herd and pro­tect them: Wrap a sticky band around the stem or stems. Mask­ing tape coated with sticky Tan­gle-Trap works and lasts for weeks. If clouds of white­flies puff up when­ever you brush against your gera­ni­ums, place yel­low cards coated with oil or Tan­gle-Trap near the plants.

Good grow­ing con­di­tions also can help de­ter pests. Less fre­quent wa­ter­ing, for in­stance, is usu­ally all that's needed to deal with fun­gus gnats or sow­bugs.

Yes, the oc­ca­sional pest-rid­den house­plant will need the last re­sort, a pes­ti­cide spray (or a walk to the com­post pile, al­ways an op­tion). Even then, there are some ef­fec­tive and rel­a­tively non­toxic sprays, such as in­sec­ti­ci­dal soap, hor­ti­cul­tural oil and Bt. By the time a spray is needed, the weather likely will have warmed enough that it can be done out­doors. Hold pests at bay long enough and you can move houseplants out­doors for their sum­mer va­ca­tion, where pest prob­lems fre­quently clear up by them­selves.

In this un­dated photo, Cot­tony cush­ion scale in­sects are en­joy­ing their feast on this plant’s leaves in New Paltz, New York.

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