May 2002

Grower 101: Scouting for Mites, Part I By Kevin Donovan

To effectively implement a mite management program, you must first identify the mite species, understand its life cycle and determine whether populations are at an economically damaging threshold. This is accomplished through a scouting plan that is performed routinely and in a systematic manner.

Scouting, also known as monitoring, is the cornerstone of anIntegrated Pest Management (IPM) program. When mites are found on only a fewplants or in a small area, localized control tactics should be used. Not onlyare spot treatments more economical, they also prevent overuse, reduceresistance build up and preserve beneficial organisms. Look for tips onidentifying mites in the June issue of GPN.

General Scouting Information

Scouts must have a thorough understanding of, andappreciation for, the systematic approach to pest management. Working within aframework of ecological and economic factors, a scout must gather theinformation necessary to make pest management decisions. This endeavor requiresan understanding of the agricultural ecosystem, including knowledge of plantand pest biology, pest life cycles, host plants, beneficial insects, mites andorganisms, damage caused by the presence of pests and other environmental riskfactors. IPM relies on a scout’s data to determine whether a pest’spopulation has attained an economically damaging threshold.

Employees can be trained to scout, or you can do your ownscouting. The advantages of in-house monitoring include a familiarity with thegreenhouse, knowledge of crop production practices and the ability to promptlyinspect incoming plant material.

Growers may also hire private pest-management consultants.Some of the advantages of private consultants include their ability to scoutquickly and efficiently and their specialized up-to-date knowledge ofpest-management materials and practices. It is recommended that a grower hire aconsultant or professional scout if employees’ schedules do not allowconsistent scouting and monitoring practices.

Scouting guidelines

It is important to scout routinely, at least once everyweek, through a crop’s entire production cycle. Scouting twice each weekis an even better production practice. Scout on a specific day and time andkeep the same schedule throughout the season. The common pests found ingreenhouse crops do not distribute themselves evenly through a crop; therefore,the entire greenhouse must be scouted in a consistent pattern, and since mitestend to be densely aggregated, random plant inspection is needed to locate the variousinfestations. For each area of 4,000 square feet, samples should be taken from at least 5-10 random sites.

Scouting should start from a major doorway, as this is oftenwhere mite problems begin. Special attention should be paid to plants aroundany openings in the greenhouse, especially those on the outside rows ofbenches. Also, closely inspect other potential problem areas, such as themiddle of the bench, which may have received less spray coverage, or the endsof benches where there may be less air circulation. Be sure to inspect allcrops.

At least 10 minutes should be spent inspecting 20 or moreplants for every 1,000 square feet of population area.

A Standard “M” or zig-zag-shaped scoutingpattern down aisles and between benches will provide good sampling coverage(See Figure 1).

Select plants randomly, but choose plants from every benchand from the ends and the middle of each bench.

Inspect each plant at the soil surface, and work your way upthe plant.

Most mites will be on the underside of the leaves. Start byturning over the older, lower leaves. Then examine younger leaves further upthe stalk. Special attention should be paid to buds and blooms.

When you find a plant with a mite (or mites), flag it. Thisway you can relocate the pot and watch pest development. The flagged plant isyour indicator plant. Several days after you treat, turn the leaf over and seeif you have eliminated the mite problem.

Next month’s article will provide information aboutidentifying the mites found during scouting.