Spider Mite-infested Plants Research Articles

<p class="Body"><strong>Effects of alternative and natural prey on body size, locomotion and dispersal of <em>Neoseiulus bicaudus</em> (Acari: Phytoseiidae)</strong></p>

Prey are very important for the mass rearing of natural enemies and can affect the efficiency and quality of natural enemy products. Locomotion is important in dispersal of predatory mites on plants, and such activity is affected by body size and prey availability. The study evaluates the effects of prey (alternative prey: Tyrophagus putrescentiae Schrank and natural prey: Tetranychus turkestani Ugarov & Nikolskii) on the body size, locomotion and dispersal of the predatory mite Neoseiulus bicaudus Wainstein. When fed the alternative prey, the body size and locomotion of N. bicaudus were significantly lower than when fed the natural prey. However, the dispersal of N. bicaudus fed the two prey types was similar. The results suggest that long-term feeding on alternative prey could decrease the body size and locomotion of N. bicaudus. Nevertheless, the negative effects of alternative prey did not appear to affect the dispersal of N. bicaudus. The likely reason is that the type of prey does not affect the ability of the predatory mite to locate spider mites. In other words, when it fed alternative prey, N. bicaudus could still successfully disperse and locate spider mite-infested plants in the same way as when fed the natural prey.

Vines avoid coiling around neighbouring plants infested by polyphagous mites

Vines that coil around plants heavily infested with ambulate polyphagous mites can be heavily damaged by the mites. To explore whether vines avoid mite-infested plants, we observed the coiling responses of morning glory (Ipomoea nil var. Heavenly Blue) vines and bush killer (Cayratia japonica (Thunb) Gagnep) tendrils around nearby kidney bean (Phaseolus vulgaris L.) plants that were either uninfested or heavily infested with the two-spotted spider mite (Tetranychus urticae Koch). The proportions of I. nil vines that coiled around spider mite-infested and uninfested bean plants did not differ significantly; however, no C. japonica tendril coiled around spider mite-infested plants. The proportion of such tendrils was thus significantly lower than that around uninfested plants. The ability of C. japonica tendrils to avoid spider mite-infested plants would prevent serious “contact infections” by mites. We further found that tendril avoidance seemed to be attributable to the mite webs that covered infested plants; neither spider mite-induced bean volatiles nor spider mite intrusion onto tendrils seemed to explain the avoidance.

Jasmonic Acid and Herbivory Differentially Induce Carnivore-Attracting Plant Volatiles in Lima Bean Plants

Lima bean plants respond to feeding damage of two-spotted spider mites (Tetranychus urticae) with the emission of a complex blend of volatiles that are products of several different biosynthetic pathways. These volatiles attract the carnivorous mite Phytoseiulus persimilis, a specialist predator of the spider mites that exterminates entire prey populations, and thus the volatiles contribute indirectly to plant defense. The volatile blend constitutes information to the carnivores, and blend composition is an important factor in this. Jasmonic acid (JA) is involved in the signal transduction of this induced defense. Application of JA through the petiole of Lima bean plants induces a volatile blend that is similar, but not identical, to that emitted by spider mite-infested plants. The induced volatiles originate from the lipoxygenase pathway, the shikimic acid pathway, and the isoprenoid pathway. Among the induced bean plant volatiles are nitriles and oximes. Of a total of 61 components, 10 are emitted at significantly different rates. Among these are the terpene (E)-4,8-dimethyl-1,3,7-nonatriene and the phenolic methyl salicylate, two compounds that are known to attract P. persimilis. A crucial test for comparing the effect of spider mite damage and JA application on volatile induction is the response of P. persimilis. The carnivore is attracted by volatiles from JA-treated plants. Moreover, even treatment of Lima bean plants with methyl jasmonate vapor made the plants attractive to the carnivorous mites. However, the predators prefer the volatiles from spider-mite-infested Lima bean plants over those from JA-treated plants. Thus, chemical as well as behavioral analyses demonstrate that spider mite damage and JA treatment have similar, although not identical, effects on volatile induction in Lima bean plants.

Insecticide Control of Adult Western Corn Rootworm and Subsequent Effect on Twospotted Spider Mites in West Central Nebraska, 1992

Abstract Various pesticides were applied to blister stage (R6 stage) hybrid field corn on 9 Aug, near North Platte, in westcentral NE. The treatments were applied with a CO2-charged backpack sprayer through 8001 flat fan nozzles at 206,786 Pa (30 psi), in a total volume of 196.4 liter/ha (21 gal/acre). Each treatment was applied to 3 × 10 m plots, replicated 4 times in a RCBD. Three d before the pesticide application the number of WCR beetles was counted on 2 randomly-selected plants in the middle of each plot. Three d prior to application, 3 spider mite-infested plants in each plot were marked to follow population trends on the same plants. The size of twospotted spider mite colonies was rated on the underside of 3 leaves on each of these plants, one below the ear, the ear leaf and one leaf above the ear. Ratings were made on a 0-6 scale where 0 = no mites, 1 = individual mites, 2 = small colonies, 3 = large, individual colonies, 4 = large connected colonies but not completely covering the underside of the leaf, 5 = colonies completely covering the underside of the leaf, 6 = leaf dead due to spider mite damage. These plants were also evaluated for the presence of arthropod predators. Two d following application the number of rootworm beetles was evaluated by counting all beetles on two randomly selected plants in the middle of each plot. Previously marked plants were evaluated for the size of twospotted spider mite colonies and the presence of arthropod predators at 7, 14, 21 and 44 DAT. Data were statistically analyzed with analysis of variance and an LSD test was used for mean separation.