Predatory Neoseiulus barkeri restricts out- breaks of bulb scale mite in Hippeastrum (amaryllis) G.J. Messelink, R. van Holstein-Saj & J.A.M. Kromwijk e-mail: [email protected], [email protected]

The bulb scale mite Steneotarsonemus laticeps is a serious pest in the Greenhouse experiment culture of Hippeastrum (amaryllis). These tiny can cause dramatic The ability of N. barkeri and Amblyseius andersoni to control the bulb scale growth inhibition and flower deformation. Since effective biological control mite in amaryllis was assessed in a greenhouse. The pest was introduced by agents are lacking, control relies heavily on chemicals. interplanting infested bulbs. The visible damage in the mite treatments was much lower, reaching a maximum of 10% in the plots with N. barkeri and Greenhouse survey of predatory mites about 30% with A. andersoni (Figure 2).

A survey of naturally occurring predatory mites with a potential to control 80 e it S. laticeps was conducted on 15 commercial greenhouses with amaryllis. 70 untreated control e m

al N. barkeri 15 species of predatory mites were found. The most abundant species was sc 60 A. andersoni e lb 3 release of A. andersoni

bu 50

Neoseiulus barkeri, which was found on almost half of the nurseries sampled of

m s 40 e and was observed frequently in colonies of S. laticeps. to 2 release of predatory mites mp

sy 30 Figure 2. th e

wi 20 1 release of predatory mites

Laboratory predation experiments bs Mean percentages of visible ul 10

Laboratory predation tests were set up with Neoseiulus barkeri as well as % b damage by bulb scale mites on 0 commercially available predatory mites to evaluate their ability to feed on S. 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 amaryllis bulbs. laticeps. Predators were tested after a starvation period of 48 hours. Results Time (week number in 2006) indicate to be a promising candidate for biological control of the N. barkeri The number of damaged bulbs (foto 2) was bulb scale mite in amaryllis (Table 1). much higher at the final assessment when Table 1. Mean fraction of predation attempt and successful predation with the bulb all bulbs were sliced and examined carefully. scale mite as prey during five minutes observations in the laboratory. The number of damaged bulbs and leaves was significantly lower in the predator Predatory mite Predation attempt* Successful predation treatments, with N. barkeri significantly Neoseiulus barkeri 0.917 a 0.854 a better than A. andersoni (Table 2). Neither N. barkeri nor A. andersoni appear to be Amblyseius andersoni 0.833 a 0.708 ab able to completely eliminate a bulb scale 0.833 a 0.688 b mite infection in amaryllis. Hypoaspis miles 0.083 b 0.083 c N. barkeri colonized the amaryllis crop Hypoaspis aculeifer 0.021 b 0.000 c throughout the observation period, though in * Means within a column are significantly different (p < 0.05) if not followed by the same low numbers. A. andersoni could not be detected anymore from week 22, in letter. spite of an additional introduction.

Table 2: Mean percentage of leaves and bulbs injured by the bulb scale mite at the final assessment in week number 23.

Mean percentage of injury*

Treatment Leaves bulbs

Control 57 a 98 a Foto 1: Female of Neoseiulus barkeri feeding on N. barkeri 4 c 45 c Steneotarsonemus laticeps. A. andersoni 19 b 70 b

Predation efficacy was correlated with body size of the various species. * Means within a column are significantly different (p < 0.05) if not followed by the same The small body size and short hairs of N. barkeri are believed to enable this letter. species to follow S. laticeps in hidden places deep inside the bulbs (Figure 1). The results of this study show the potential of N. barkeri to establish in an 1.0 amaryllis crop and restrict hot spots with bulb scale mites. Ways should be 0.9 N. barkeri 0.8 found to improve the establishment of this predator for further improvement s

on A. andersoni ti 0.7 N. cucumeris

da of the quality of bulb scale mite control. re 0.6

e p observed iv 0.5 simulation c t

ffe Messelink, G.J. & van Holstein-Saj R. 2006: Potential for biological control of the bulb scale mite e 0.4 on ti 0.3

a c y = -0.0044x + 2.4067 Figure 1: (: ) by predatory mites in amaryllis. Proc. Neth. Entomol. Soc. Meet. 17: 113-118. fr 2 0.2 R = 0.9938

0.1 H. miles Correlation between predatory mite size Messelink, G.J. & van Holstein-Saj R. 2007: Biological control of the bulb scale mite Steneotrasonemus H. aculeifer 0.0 and predation efficacy with the bulb scale laticeps (Acari: Tarsonemidae) with Neoseiulus barkeri (Acari: ) in amaryllis. IOBC/wprs 300 350 400 450 500 550 600 mean body length female predatory mite (µm) mite as prey. Bulletin 30 (5): 81-85.

Wageningen UR Greenhouse Horticulture P.O. Box 20, 2665 ZG Bleiswijk, The Netherlands Tel: +31 317 485 606 - Fax: +31 10 522 51 93 E-mail: [email protected] Internet: www.greenhousehorticulture.wur.nl