Long-term residual efficacy of commerical formulations of 16 pesticides toTyphlodromus pyri Scheuten (Acari: Phytoseiidae) inhabiting commerical vineyards
The long-term residual efficacy of 16 pesticides to the predatory phytoseiid mite,Typhlodromus pyri Scheuten, inhabiting commercial sprayed vineyards in South Moravia, Czchoslovakia, was evaluated in laboratory bioassays. Omethoate, chlorpyrifos-methyl and esfenvalerate were assessed as harmful and should not be sprayed. Mancozeb-efosite-Al mixture, diazinon, dicofol, bromopropylate, azinphos-ethyl and phosmet were assessed as moderately harmful. Fenitrothion, phosalone and mancozeb were assessed as slightly harmful and some of them had delayed detrimental effect on the predatory mites. These pesticides can be used only cautiously in IPM programs. Sulphur, penconazole, trimorfamid and endosulfan were assessed as harmless and can be recommended for vineyards withT. pyri.
Threshold conditions for integrated pest management models with pesticides that have residual effects
Impulsive differential equations (hybrid dynamical systems) can provide a natural description of pulse-like actions such as when a pesticide kills a pest instantly. However, pesticides may have long-term residual effects, with some remaining active against pests for several weeks, months or years. Therefore, a more realistic method for modelling chemical control in such cases is to use continuous or piecewise-continuous periodic functions which affect growth rates. How to evaluate the effects of the duration of the pesticide residual effectiveness on successful pest control is key to the implementation of integrated pest management (IPM) in practice. To address these questions in detail, we have modelled IPM including residual effects of pesticides in terms of fixed pulse-type actions. The stability threshold conditions for pest eradication are given. Moreover, effects of the killing efficiency rate and the decay rate of the pesticide on the pest and on its natural enemies, the duration of residual effectiveness, the number of pesticide applications and the number of natural enemy releases on the threshold conditions are investigated with regard to the extent of depression or resurgence resulting from pulses of pesticide applications and predator releases. Latin Hypercube Sampling/Partial Rank Correlation uncertainty and sensitivity analysis techniques are employed to investigate the key control parameters which are most significantly related to threshold values. The findings combined with Volterra’s principle confirm that when the pesticide has a strong effect on the natural enemies, repeated use of the same pesticide can result in target pest resurgence. The results also indicate that there exists an optimal number of pesticide applications which can suppress the pest most effectively, and this may help in the design of an optimal control strategy.
The Pesticide Tolerance of Typhlodromus fallacis (Garman) and Phytoseiulus persimilis A. H. with Some Observations on the Predator Efficiency of P. persimilis
Two species of predaceous typhlodromid mites Typhlodromus fallacie (Garman) and Phytoseiulus persimilis A.-H. are important natural biological agents in the suppression of spider mite populations. A study was made to determine the possibility of developing an integrated biological-chemical control program by selecting pesticides least toxic to the typhlodromids and yet effective as control for diseases and insects on the host crops. Of 31 pesticides tested, the predaceous mites tolerated residues of 12 chemicals that included the insecticides aldrin, dieldrin and endrin; the acaricides Aramitc® (2-( p-tert -butylphenoxy) isopropyl 2-chloroethyl sulfite), chlorobenzilate, Kelthane® (1,1-bis( p -chlorophenyl)-2,2,2-trichloroethanol), tetradifon, and ovex; and the fungicides captan, maneb, Folpet® ( N -(trichloromethylthio) phthalimide), and zineb. The results of present studies encourage further investigations to evaluate the control of spider mite populations using predator mite releases alone or in combination with a selective spray program.