Influence of temperature, humidity, placement and formulation on residual effectiveness of insecticides for control of German cockroaches, Blattella germanica (L.)

Gary Allen Braness, Purdue University

Abstract

Emulsifiable concentrate (EC), wettable powder (WP), and microencapsulated (ME) formulations of the insecticides, chlorpyrifos and cyfluthrin, were aged at three different temperatures (23, 30, 37$\sp\circ$C) and two levels of relative humidity (40 and 70% RH) in environmental chambers. The insecticides were applied to stainless steel panels and placed opposite plywood panels to simulate crack and crevice applications commonly used in urban pest control. The amount of insecticide residue remaining on treated stainless steel surfaces and German cockroach mortality were observed at specific aging times. Chlorpyrifos ME and all formulations of cyfluthrin were long-lived (i.e., chlorpyrifos ME provided 100% mortality through 56 d; cyfluthrin provided $\geq$80% mortality through 84 d). High temperatures and high humidity decreased the half-lives of EC and WP formulations of chlorpyrifos, thereby reducing cockroach mortality. The major physical process that reduced cockroach mortality was volatilization. The influence of placement on residual effectiveness of insecticides was investigated in food-handling establishments. Crack and crevice applications were compared with exposed surface applications at various sites within food-handling establishments. The crack and crevice applications were more effective against German cockroaches than exposed surface applications, and insecticides aged at the dishwashing site were less effective than insecticides aged at other sites. A higher vapor pressure deficit at the dishwashing site caused the insecticides to volatilize more quickly than at other sites, resulting in reduced cockroach mortality. Insecticide placement, formulation, and physical properties of the insecticides (i.e., vapor pressure) had a substantial affect on residual effectiveness. Logistic models developed from the laboratory data can be used to predict the effective longevity of chlorpyrifos and cyfluthrin treatments, and show how temperature, humidity, and formulation affect that longevity. The model predicts that high temperature, aging of residues, and selection of insecticide will greatly influence cockroach mortality. The effect of ambient humidity on cockroach mortality was of less importance. Results from these laboratory and field studies can be incorporated into integrated pest management programs for German cockroaches.

Degree

Ph.D.

Advisors

Bennett, Purdue University.

Subject Area

Entomology

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