Decision making is a key aspect of current integrated pest management (IPM) programs and will continue to play an important role as IPM programs mature (71, 106). In an IPM context, decision making relies on protocols for deciding on the need for some management action based on an assessment of the state of a pest population (and ideally its natural enemies). These protocols, which we refer to as control decision rules, consist of at least two components and may include a third: (a) a procedure for assessing the density of the pest population, (b) an economic threshold (63)';�and (c) a phenological forecast (e.g. 49), which is often necessary to determine the appropriate time to assess popUlation densities. Assessment of pest density usually requires obtaining actual counts of the pests, and therefore, sampling is important. Because sampling is time consuming and expensive, one must know how to gather enough information about pest abundance to be able to make correct decisions without incurring excessive costs. Decision making in IPM is important for two reasons. First, decision­ making protocols can be used to reduce pesticide use. Ideally, IPM relies on benign tactics such as biological control, plant resistance, and cultural prac­ tices to maintain fluctuating pest populations below economic injury levels.

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Sampling insect populations for the purpose of IPM decision making

Economic injury level concepts and their use in sustaining environmental quality.

Quantitative sampling principles in cotton IPM.

Soybean water-loss following defoliation was investigated in two ex­ perimental systems, excised leaves and field-grown potted plants. Tran­ spiration from excised leaves increased following defoliation as a linear function of cut edge per leaf. In contrast, transpiration from soybean canopies decreased following defoliation by two lepidopteran defoliators, the green cloverworm [Plathypena scabra [F.]) and the cabbage looper (Trichoplusia ni [Hubner]), and two simulation methods, punching holes in leaflets and picking entire leaflets. Cut leaf edge, an important deter­ minant of water loss from excised leaves, only increased water loss in the first 16 hours postdefoliation. Defoliation methods also produced transi­ tory differences in transpiration rates during the first 16 hours after de­ foliation. These differences seemed related to the "hole" characteristics produced by the methods. Total water loss did not differ significantly be­ tween methods. Therefore, both punch and pick simulation methods produced acceptable fidelity in soybean water-loss to actual insect defoliation.

https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=10017&context=rtd

Soybean transpiration, vegetative morphology, and yield components following simulated and actual insect defoliation

Concepts and Directions in Arthropod Pest Management

Amethod was developed to use the sequential probability ratio test of Wald (sequential sampling) in a time-oriented sense rather than in a spatial sense. The method allows a grower or scout to decide if a population is of an endemic or outbreak type on the basis of mathematical dispersion and differential growth rates of the types. Formulas and calculations are presented for data from negative-binomial, Poisson, and binomial distributions. An example of time-sequential sampling is presented for immigrant green cloverworm adults on soybean. The use and position of time-sequential sampling in the green cloverworm pest management subsystem is indicated.

J. W. van Schaik

Papers

Time-Sequential Sampling: A New Use of the Sequential Probability Ratio Test for Pest Management Decisions