Peter C. Krauter

Effect of temperature on infection, development and reproduction of the parasitic nematode Thripinema nicklewoodi in Frankliniella occidentalis

The parasitic nematodeThripinema nicklewoodi Siddiqi (Tylenchida:Allantonematidae) is currently underinvestigation for use in inoculative releasestrategies against western flower thrips (WFT),Frankliniella occidentalis Pergande(Thysanoptera: Thripidae) infesting greenhousefloricultural crops. The aim was to determinewhether temperatures within greenhouses wouldpermit the establishment of T.nicklewoodi. The abilities of T.nicklewoodi to infect, develop and reproducein WFT were assessed under a range of constantand fluctuating temperatures in the laboratory.At constant temperatures, T. nicklewoodiinfected WFT over the range of 1–30 °C,although the temperature-related infectionprofile followed an asymmetric distributionaround an optimum ∼20 °C (∼80%infection). The lower and upper thresholds forT. nicklewoodi in vivo development andreproduction were higher than for infection, at10 °C and 35 °C, respectively.Climate data recorded over 1999–2000 in acommercial greenhouse (Texas) revealed atemperature range of ∼15 °C to∼31 °C from early March through mid June,when WFT were most abundant. While low(nighttime) greenhouse temperatures areconducive for T. nicklewoodi, upperdaytime temperatures are close to the upperthreshold for infection and may reducereproductive output. However, fluctuatingtemperature bioassays in the laboratorydemonstrated that T. nicklewoodimaintained separately at the upper thresholdtemperatures for infection (30 °C) anddevelopment (35 °C) readily infected anddeveloped in WFT when they were allowedintermittent (10 h daily) exposure to apermissive temperature in the range10–20 °C. Drawing on the results, thediurnal temperature-fluctuations of variousgreenhouses growing ornamentals would permitthe establishment of T. nicklewoodi.

Protecting Unrooted Cuttings From Bemisia tabaci (Hemiptera Aleyrodidae) During Propagation

Abstract In North America, the sweetpotato whitefly, Bemisia tabaci Genn., is an important pest of greenhouse poinsettia. Growers have limited options to control this pest during propagation of cuttings, which are rooted under mist for several weeks. Early establishment of this pest increases the difficulty of managing the whitefly and retaining high aesthetic standard during the remaining crop production phase. We evaluated two neonicotinoids with translaminar activity, thiamethoxam (Flagship 25WG), and acetamiprid (TriStar 70 WSP), for control of B. tabaci pre-infested on unrooted cuttings propagated under mist. In an experimental greenhouse, both materials significantly reduced whitefly populations, providing an average reduction of 87.8% and 61.5% total recovered whitefly stages respectively, compared with controls. In another test, dipping cuttings in thiamethoxam (immersion treatment) did not improve control significantly, when compared with foliar sprays applied at label rate. In a commercial greenhouse operation, immersion treatments of thiamethoxam on pre-infested poinsettia cuttings maintained whiteflies at ≤ 0.02/plant, compared with up to 0.33/plant in untreated cuttings. Our data suggest that treating unrooted cuttings before or at the start of propagation can be part of an overall strategy for growers to manage whiteflies in poinsettia production.

Transmission of phage by glassy-winged sharpshooters, a vector of Xylella fastidiosa

ABSTRACT Xylella fastidiosa subsp. fastidiosa (Xff) is the causal agent of Pierces Disease (PD) of grapevines and is vectored by the glassy-winged sharpshooter (GWSS, Homalodisca vitripennis). Previously we have reported the development of a bacteriophage (phage) based biocontrol system for PD, but no information on insect transmission of phages has been reported. Here we communicate that laboratory reared GWSSs fed on cowpea plants (Vigna unguiculata subsp. unguiculata) harboring the virulent phage Paz were able to uptake of phage efficiently when the phage was present in high concentration, but were inefficient in transfer to plants.