The impact of cotton plant resistance on spider mites and their natural enemies

Abstract

A spider mite-resistant and a spider mite-susceptible variety of cotton were planted in the field in a replicated design. An acaricide (dicofol) and an insecticide (acephate) were used to manipulate numbers of spider mites and their natural enemies. In general, numbers of spider mites remained low until just before midseason when 650°D air temperature had accumulated. At 650°D, mite numbers began to increase more sharply and reached significantly (P<O.OOI) greater levels on susceptible plants than on resistant plants. Although natural enemies, such as Geocoris pallens SdU, Orius tristicolor (White), and Frankliniella occidentalis (Pergande), were slightly more apparent on susceptible plants than on resistant plants, these differences were not statistically significant, and cotton varietal resistance was compatible with biological control.Acephate significantly (P<0.05) reduced predator densities for up to 2 weeks following each application, and after 550°D mite populations had begun to explode on plants sprayed with acephate. Predators had a greater impact on mites on susceptible plants than on resistant plants, which was attributed to greater densities of spider mite prey on susceptible plants. After 900°D, spider mites were out of control on susceptible plants treated with acephate, and the acaricide dicofol had no observable effect on mite numbers. Rapidly increasing mite populations appear to exhibit Continued inside back cover.An important feature of evolutionary success of colonizing species, such· as spider mites, is the capacity for rapid population increase. Host-plant resistance can be effective in reducing the reproductive fitness (i.e., potential for increase) of spider mites on cotton (Schuster, Maxwell, and Jenkins 1972;Schuster et al. 1973;Trichilo and Leigh 1985). Plant resistance that induces chronic toxicity would slow herbivore population growth rates, increase exposure of phytophagous pests (i.e., spider mites) to natural enemies, and thereby augment the efficacy of both HPR and biological control (van Emden 1966;van Emden and Wearing 1965).

An ecosystem analysis of spider mite outbreaks: physiological stimulation or natural enemy suppression

“…Our estimates of survival are also based on several studies showing that standard application rates of pyrethroids have minor lethal effects on spider mites (Roush and Hoy, 1978;Rock, 1979;Penman and Chapman, 1988). Low early season densities of Geocoris eggs and mobile stages of Orius, support earlier observations (Gonzalez and Wilson, 1982;Trichilo and Leigh, 1986;Wilson et al, 1991b) that in terms of density, E occidentalis is the dominant biological control agent of spider mites on cotton at this time. However, Wilson et al (1991 b) showed that even at low densities, Geocoris and Orius may be significant in delaying mid-to late-season buildup of spider mite populations.…”

“…While predatory mites seem to be the primary predators of spider mites on fruit trees (Hoyt et aL, 1978;Zwick and Fields, 1978;AliNiazee and Cranham, 1980;Hull et al, 1985), the major natural enemies of spider mites on cotton in Calitbrnia, belong to a complex of generalist predators, that reach high densities in undisturbed fields (Eveleens et al, 1973;Ehler and van den Bosch, 1974;Ehler and Miller, 1978;Trichilo and Leigh, 1986). The simulations suggest that increased fecundity and shorter developmental duration make a smaller contribution to spider mite population growth on cotton, than does the loss of natural enemies, and therefore could not solely be responsible for outbreaks that were observed to occur in the field.…”

“…A prolonged period of declining effect mimics the dilution of pyrethroid activity due to plant growth and the degradation of the pesticide with time (Matsumura, 1985), and thc time delay in the re-establishment of natural enemies following insecticide sprays. Field data show that densities of natural enemies decrease soon after an insecticide application, but build up to or exceed pre-treatment densities within three to five weeks following the application (Trichilo and Leigh, 1986).…”

“…The possibility of reduced interspecific competition was not addressed, because at the time of our recorded pyrethroid applications on cotton, the only other major arthropod herbivore present was F. occidentalis. Even in combination, densities of spider mites and flower thrips were not high enough to cause tbod (or space) to be a limiting factor, especially as the cotton plants are growing very rapidly at this time of the season (see Trichilo and Leigh, 1986;Wilson et aI., 1991b). Because the effect of pyrethroids on sex-ratio is poorly documented, the role of this potential mechanism was likewise not addressed in this study.…”

Geïntegreerde bestrijding van plagen in de sierteelt onder glas : een systeembenadering met preventieve biologische bestrijding als basis

“…Dit is al snel het geval bij de californische trips, Frankliniella occidentalis. Deze trips is eigenlijk een omnivoor en eet niet alleen van de plant, maar ook van dierlijke prooien (zoals spint, wittevlieg en roofmijteieren) (Trichilo & Leigh 1986;Faraji et al 2002b;van Maanen et al 2012 occidentalis (van Houten et al 1995;Messelink et al 2006). In roos, en veel andere sierteeltgewassen gaat het echter veel moeizamer dan in gewassen als komkommer en paprika (Pijnakker & Ramakers 2008 Aanvullend is bepaald wat het effect van stuifmeeltoediening op het gewas is op de bestrijding van trips met A.…”