in the previous year. Tachinid flies – parasitize gypsy moth populations. While they may become quite abundant during a gypsy moth outbreak, they apparently have little effect on the population dynamics. Braconid wasps – also parasitize gypsy moths but play a minor role in their dynamics. The effectiveness of releasing or enhancing gypsy moth predators or parasites to control the moth is "difficult to determine", as rates of parasitism vary with the density of gypsy moth larvae, the range of alternate hosts for the parasite used, and the weather. Both in America and in Europe, research continues into biological control of the species, and for example the Baculoviridae viruses show potential for control. Management Several methods of managing the gypsy moth are used; these include the monitoring of populations, maintaining the health and vigor of trees, concentrating and killing caterpillars, removing egg masses and treating with insecticides to kill larvae and protecting tree foliage. To concentrate the caterpillars, a strip of dark cloth about 12 inches wide – for example, burlap or old blue jeans, is tied around the tree at eye height. A string is tied around the cloth at its midpoint to create a fold of cloth around the tree. At mid-morning or later, the bands of cloth are checked for caterpillars, which are killed. The egg masses – -inch long ovals that look like tan felt or velour – will be present from late July until May when they hatch. The egg masses are scraped off the tree and burnt or dumped in the trash. If they remain on the ground, the eggs will still be viable. Tactics suggested for homeowners may be too costly and labor-intensive for managers to use in forest stands. The gypsy moth currently occupies less than a third of its potential range in North America and considerable resources are directed at minimizing its expansion into these areas. Every year, over 100,000 pheromone traps are placed in uninfested areas in order to detect new infestations that occasionally arise when people inadvertently transport life stages into uninfested areas (for example, egg masses on recreational vehicles). When captures are positive for several consecutive years, this indicates that a population is establishing and these are eradicated, usually via the application of the bacterial pesticide Bacillus thuringiensis ('Bt'). In 2008 California agriculture officials quarantined a rural section of Ventura County near Ojai to prevent the spread of