1 Semiochemical Mediated Host Plant Preference in the Yellowmargined Leaf beetle, Microtheca ochroloma Rammohan Rao Balusu and Henry Fadamiro Department of Entomology and Plant Pathology, Auburn University

2 Introduction  Yellowmargined leaf beetle (YMLB), Microtheca ochroloma (Chrysomelidae) is a pest of cruciferous (Brassicaceae) crops Cabbage, Turnips, Mustard, Raddish, Collards, etc  Native to South America  First reported in the US in Mobile, AL in 1947  A serious pest the SE  A major problem facing organic vegetable production

Damage  Both adults and larvae feed on foliage by first making small holes; later serious defoliation Defoliation of larvae on turnipMass attack of adults on napa cabbage

Organically-managed crucifer field in south Alabama damaged by YMLB Turnip Napa cabbage

Mustard greens Napa cabbage Tet soi B. narinosa Mizuna B. rapa japonica Turnips Radish Turnips Collards Lettuce Cabbage Mixed cropping practice of different crucifer vegetables in snow’s bend organic farm in Alabama

Investigate mechanism of host plant selection and preference in yellowmargined leaf beetle (YMLB) Field observations suggest preference among crucifer plants Questions: – Do YMLB adults show preference among crucifer plants? – What cues mediate host preference? Hypothesis: – Host preference is mediated by plant semiochemicals Objective

3 ft 4 ft adult beetles 50 Turnip Cabbage Collards Napa cabbage Materials and methods Greenhouse and laboratory experiments conducted to test host preference  Q. Feeding and Ovipositional preference?

Four host plants compared: – cabbage, collards, napa cabbage and turnip Experiment (simultaneously) replicated three times (i.e. 3 cages) Data collected: – every day for the period of three weeks – number of adults and larvae per plant (up to 21 days) – damage ratings of plants Damage ratings based on a scale of 1 to 6: 1 = very light defoliation (< 10%) 2 = light defoliation (10-30%) 3 = moderate defoliation (30-50%) 4 = heavy defoliation (50-70%) 5 = very heavy defoliation (70-90%) and 6 = complete (total) defoliation (> 90%) Statistical analysis : ANOVA + Tukey HSD test Materials and methods – greenhouse study

Results: Number of YMLB adults per host plant per day

Results: Average damage rating caused by YMLB per plant per week

One week after Two weeks after Results

Laboratory bioassay with four-choice olfactometer 10 adults (2-4 days old) per replications 20 replicates per experiment per sex

Behavioral response of adult YMLB to different crucifer host plants

Summary Turnip and napa cabbage are preferred host plants over collard and cabbage Olfactory cues play a major role in host plant selection Trap crop?????? Ongoing study is focused on chemistry host plants to identify the possible attractant for YMLB

Acknowledgement Undergraduate students – Allison Tyler – David Appel – Shelia Boyt Alabama Agricultural Experiment Station for a seed grant to HYF

Thank you.. Questions?