The effects of kaolin particle film on Plutella xylostella behaviour and development

Side Effects of Kaolin and Bunch-Zone Leaf Removal on Predatory Mite Populations (Acari: Phytoseiidae) Occurring in Vineyards

The effects of kaolin and bunch-zone leaf removal on populations of predatory mites Kampimodromus aberrans (Oudemans) and Typhlodromus pyri Scheuten were assessed in the context of four trials (2015-2016) carried out against Lobesia botrana (Denis and Schiffermüller) (Lepidoptera: Tortricidae) in vineyards located in north-eastern Italy. Laboratory experiments were performed to evaluate the effects of kaolin on the survival and fecundity of K. aberrans and T. pyri populations originating from the same grape-growing area. In field trials, kaolin caused a gradual decrease in population density levels of both phytoseiid species (with the maximum reduction ranging from 49 to 91%) with a complete population recovery in the next spring. In laboratory experiments, kaolin was moderately harmful to both species, reducing their fecundity significantly (around 60%). Bunch-zone leaf removal determined lower phytoseiid populations in all trials, but this effect was significant only for K. aberrans in one of them. A limited use of kaolin and the adoption of bunch-zone leaf removal did not irreversibly affect phytoseiid populations in vineyards and thus can be considered compatible with IPM strategies.

Evaluation of a Push-Pull System for the Management of Frankliniella Species (Thysanoptera: Thripidae) in Tomato

A push-pull strategy for reducing populations of the thrips Frankliniella occidentalis (Pergande), F. bispinosa (Morgan) and F. tritici (Fitch) in tomato was evaluated. Push components consisted of ultraviolet (UV)-reflective mulch and foliar applications of kaolin and the pull component consisted of the companion plant Bidens alba (L.). Replicated field experiments were conducted in 2011 and 2012. Adult and larval thrips were reduced by UV-reflective mulch during early and mid-flowering of tomato. Spray applications of kaolin were effective in reducing adult and larval thrips during early, mid- and late-flowering. The pull effects of the B. alba companion plants were additive and sometimes interactive with the push effects of UV-reflective mulch and kaolin in reducing the adult males of each thrips species and the females of F. bispinosa. The strategy was not effective in reducing the adult females of F. tritici and F. occidentalis. In addition to attracting the Frankliniella species adults, the companion plants were hosts for the thrips predator Orius insidiosus (Say). The companion plants combined with UV-reflective mulch and kaolin proved effective as a push-pull system for suppressing flower thrips, including F. occidentalis which is a serious pest of tomato worldwide.

Effects of Kaolin on Lobesia botrana (Lepidoptera: Tortricidae) and Its Compatibility With the Natural Enemy, Trichogramma cacoeciae (Hymenoptera: Trichogrammatidae)

Lobesia botrana (Denis and Schiffermüller) (Lepidoptera: Tortricidae) is an important grapevine pest in Europe recently encountered in America. Trichogramma cacoeciae Marchal (Hymenoptera: Trichogrammatidae) is amongst the most effective parasitoids for Lepidopteran species. Studies to evaluate the effect of kaolin, an inert, nontoxic mineral, on oviposition, egg hatch, and neonate mortality of these species were carried out. Efficacy on L. botrana neonate larvae, oviposition, and egg hatch was evaluated. Effects of kaolin on parasitism and emergence of T. cacoeciae from L. botrana and Ephestia kuehniella (Zeller) (Lepidoptera: Pyralidae) eggs were also evaluated. Lobesia botrana egg hatch and oviposition rates were reduced, and neonate larvae mortality was significantly greater in kaolin-treated arenas and when included in synthetic neonate larvae diet. Kaolin had no effect on T. cacoeciae parasitism in both hosts. There was only a slight but statistically insignificant effect on T. cacoeciae progeny emergence from L. botrana eggs and no effect from E. kuehniella. The results involving reductions in L. botrana oviposition and egg hatch and increase in larval mortality with kaolin suggest this compound may contribute to reduction in population densities and can be considered in rational integrated pest management strategies for L. botrana. Due to the laboratory results presented on parasitoid emergence, even though field bioassays would give a more exhaustive evaluation, it appears kaolin can be compatible with T. cacoeciae in L. botrana management.

Evaluation of a push-pull strategy for the management of Frankliniella bispinosa (Thysanoptera: Thripidae) in bell peppers

A push-pull strategy for managing the anthophilous Frankliniella bispinosa (Morgan) in pepper and increasing conservation biological control was evaluated. Push components of ultraviolet (UV)-reflective mulch and foliar applications of kaolin and the pull component of sunflower companion plants were evaluated in replicated field experiments in 2011 and 2012. Adult F. bispinosa rapidly colonized and reproduced in the peppers and sunflowers during early flowering, but populations declined later, as numbers of the predatory Orius insidiosus (Say) and Orius pumilio (Champion) increased in both hosts. Numbers of F. bispinosa were reduced by kaolin during early pepper flowering. Thrips numbers were increased on some of the later sample dates, apparently due to reduced predation that resulted from negative effects of kaolin and UV-reflective mulch on Orius populations. Numbers of thrips increased in peppers with companion plants during the first week of flowering each year, followed by declines in thrips numbers during the next 2 wk in 2011. There was little effect each year of the companion plants on the numbers of Orius in the pepper flowers. There was one date in 2011 and no dates in 2012 in which UV-reflective mulch or kaolin acted in concert with the presence of the companion plants to reduce thrips numbers in the main crop of pepper. Yield effects were not attributed to thrips damage. We conclude that sunflower companion plants did not act additively or synergistically with kaolin or UV-reflective mulch to reduce thrips and increase Orius populations in pepper.

Repellency of a kaolin particle film to potato psyllid, Bactericera cockerelli (Hemiptera: Psyllidae), on tomato under laboratory and field conditions

BACKGROUND

The potato psyllid, Bactericera cockerelli, is a vector of Candidatus Liberibacter solanacearum, causing several diseases in solanaceous crops. Laboratory and field no-choice and choice experiments were conducted to evaluate the repellency of kaolin particle film on adults of B. cockerelli on tomato plants that had been sprayed with kaolin particle film on the upper surface only, on the lower surface only and on both leaf surfaces.

RESULTS

In no-choice tests in the laboratory, the numbers of adults on leaves were not different between the kaolin particle film and the water control, regardless of which leaf surface(s) were treated, but numbers of eggs were lower on the leaves treated with kaolin particle film than on those treated with water. In choice tests on plants treated with water/plants treated with kaolin particle film at ratios of 1:1, 6:3 or 8:1, fewer adults and eggs were found on the leaves treated with kaolin particle film than on leaves treated with water. Under field conditions, in caged no-choice or choice tests, fewer adults, eggs and nymphs were found on plants treated with kaolin particle film than on plants treated with water. In an uncaged test under field conditions, plants sprayed with kaolin particle film had fewer psyllids than those sprayed with water.

CONCLUSION

Even though potato psyllid adults could land on plants treated with kaolin particle film when no choice was given, fewer eggs were laid. When given a choice, the psyllids avoided plants treated with kaolin particle film under laboratory and field conditions. Kaolin particle film treatment may be a useful alternative for management of potato psyllids under field conditions.

Effects of kaolin on Ophelimus maskelli (Hymenoptera: Eulophidae) in laboratory and nursery experiments

Although recent research has demonstrated that clays provide satisfactory control of some agricultural insect pests, the effect of clays on gall wasps that damage forest trees has not been previously reported. The aim of the current study is to evaluate the effectiveness of the clay kaolin in the laboratory and in the field in reducing the damage caused by the eulophid Ophelimus maskelli (Ashmead) on seedlings of eucalyptus (Eucalyptus L'Hér.) species. In the laboratory, kaolin + wetting agent significantly reduced the percentage of infested leaves and the number of galls per leaf. In the nursery, gall number per leaf was not correlated with leaf area with kaolin + wetting agent but was related to leaf area for all other treatments (wetting agent alone, imidacloprid, and untreated control). In the nursery, gall number per leaf was lower with kaolin + wetting agent and with imidacloprid than with the other two treatments. Overall, kaolin effectively reduced eulophid infestations, and its effect was more persistent than that of imidacloprid. Although application of kaolin might not be feasible on large forested areas, kaolin could represent a valuable control method in nurseries, where the repeated application with more toxic chemicals can result in high concentrations of residual pesticides in the soil.

Effects of kaolin particle film on Myzus persicae (Hemiptera: Aphididae) behaviour and performance

The emergence of resistance mechanisms to, and revocation of, many insecticides used in the control of the polyphagus aphid pest, Myzus persicae (Sulzer), has increased the pressure to develop novel approaches for the control of the pest in many crops. Kaolin-based particle films provide a physical barrier against insect pests and show considerable potential for controlling M. persicae. We conducted a series of laboratory experiments to investigate the mode of action of kaolin against aphids. The material appeared to have no direct effect on M. persicae; spraying adult aphids with aqueous kaolin suspension had no significant impact on their subsequent survival or reproduction on untreated plants. Similarly, when aphids were placed on kaolin-treated host-plants (Brassica oleracea), their performance (survival, growth rate and reproduction) was not significantly different from aphids on untreated plants. However, when M. persicae were given a choice between kaolin-treated and untreated (or water solvent-treated) leaf areas, both adults and nymphs exhibited a significant preference for non-kaolin-treated host-plant material. Rejection of kaolin-treated plant material occurred very rapidly (within 20 min) and this behavioural effect may be related to the efficacy of kaolin in controlling aphids under field conditions.