This post is a part of a series of notes taken at the International Organization of Biological Control 2017.
Plant-provided food increases indirect defense through manipulation of a mutualism
Pete Nelson, North Carolina State University
Conservation biological control in tobacco
- Spined stiltbug
Ecology theory predicts very complex tritrophic interactions
Trichomes & natural enemies (especially glandular trichomes)
- Lady beetles will get stuck on the surface of the plant in some cases
- Do plant trichomes cause more harm than good to predatory insects? (Riddick and Simmons review paper)
- Voigt & Gorb (2010) and Avila-Nunez et al (2017)
Some insects have adapted to these high-trichome dense plants, such as long legs, or insects that have a grease layer that allows them to maneuver within the trichomes and use it as protection
- Krimmel and Pearse 2013, noticed that these plants with lots of glandular trichomes had lots of dead insects on them
- Noticed that there are predatory insects that are adapted to feeding on that dead carrions
- As a result, attracting predators to the plant
- Found over 100 genera that have insects that die on the sticky plants
- Would see lots of dead insects on the surface of these plants
Tobacco: protective mutualism?
- Multiple references of spined stiltbug feeding on dead insects on the surface of leaves
- Assess this mutualism in tobacco plants (carrions on plants attract spined stiltbug predator?)
- Carrion entrapment by plant occur?
- Manipulate amount of carrion on the plants
- Plant damage: reproductive structures and leaves
Added some dead flies to the surface of tobacco transplants in the field.
- Conducted carrion survey
- Pest & predator surveys
- Plant damage
- Leaf area
Found no significant difference between insecticide and control treatments for mean number of carrions counted in 60 seconds
- Plant’s ability to attract carrion was not affected by application of systemic insecticide
Weekly addition of carrion on the tobacco plants increased the number of predators on the tobacco plants
- Big eyed bugs, green leaf spiders, and spined stiltbugs
- Adding carrion increase stiltbug population throughout the season compared to control
- Damage to reproductive structures of the plant was reduced when carrion were added to imidacloprid treated tobacco plants. Did not see decreased reproductive damage (significant) when adding carrion to control plants (i.e. not treated with any systemics)
- No significant effect of adding carrion on decreasing pest insects
Insect carrion: form of plant-provided food
- Alternate food can help sustain predators
Efficiency of different biocontrol agents to control Tetranychus urticae on greenhouse pepper crops
S. A. El Arnaouty, Cairo University
Sweet pepper is one of the most important vegetables grown in Egypt, including for exporation
- Produce about 5 – 28.8kg/m^2 and export between 50 – 90% of green peppers grown in Egypt
Twospotted spidermite an economically important agricultural pest feeding on a wide range of host plant species..
- Probably the most important pest species in the family Tetranychidae and it is known to attack about 1200 species of plants
Main method of management is chemical control
- This strategy is hindered by the development of population resistance to acaricides.
- Pesticide residues buildup on leaves
Among the potential natural enemies of T. urticae:
- Orius albidipennis, Amblyseius swirskii and Macrolophus caliginosus
Experiment was carried out in commercial greenhouse
- O. Albidipennis at 1/2 per m^2
- A swirski as 2 adults per m^2
Nine to ten releases were performed (two separate seasons).
Total of 120 plants (30 plants per treatment).
Counted moving stage of spider mites using a hand lens.
Cost-benefit was evaluated for the treatments.
A. swirskii effective at managing T. urticae.
Orius also maintained low levels of T. urticae.
M caliginosus released at 1 adult / m^2 suppressed T. urticae, but did not control as effective as A swirskii or Orius
Analysis of results showed that the time and type of biological control agent significantly affect the number of mites. All biological control agents, with A swirskii being the most effective, controlled T. urticae significantly
Release of Orius resulted in the highest cost benefits.
- Orius controlled twospotted spider mite down to about 2.9 mite/leaf
- With chemical control, spidermite was closer to 20 mites/leaf
- Also found highest production yield for sweet pepper during winter plantation with about a 31% increase in crop.
Euphodes americanus and Leucopis annulipos as potential BCAs of foxglove aphid at low temperatures
Marc Fournier, Université du Québec à Montréal
- Foxglove aphid; low economic threshold, aphid’s saliva causes leaf distortion
- Appears early in the production
- Reproduces well at low temperatures
- The only solution (without biocontrol) is insecticide treatment
- Intercept (neonicotinoid) are used by drench application
- Exploit biodiversity to optimize pest control
- Species diversity
- Genetic Diversity
- Ecosystemic diversity
Two main predators:
- Silverfly, Leucopis annulipes Zetterstedt (Diptera: Chamaemyiidae)
- Native nearctic sp.
- American hoverfly, Eupeodes americanus (Diptera: Syrphidae)
- Lower temperature threshold about 4C
Compared flight capacity at 12, 15, and 18C
Compared egg laying capacity
Hoverfly can consume at least 6 times more than silverfly and was better than silverfly in terms of height at lower temperatures. Hoverfly also laid more eggs and had surviving eggs at lower temperature compared to silverfly.
Hypothesis: a banker plant system for hoverfly can manage foxglove aphid
- 20 cages; 10 controls and 10 treatments
- 24 pepper plants with 6-8 leaves/cage
Cage was about 3 ft squared
- After 6 weeks, had about 8-fold decrease in foxglove population in cages with banker plants
- Ended up with about 29 hoverfly in the cage at the end, with approximately equal ratio of male to female.
- Release of adult whiteflies not effective; don’t find them after week three. They go to the roof of the greenhouse and try to escape.
- No eggs were found until adults from the banker plant systems emerged inside the greenhouse
- Ants tended aphids in the banker plant system. They probably preyed upon the hoverfly.
Need to find another aphid for the banker plant system. The bird cherry-oat aphid can attack other monocotyledons.
Standardization of a mass-rearing system of Apanteles gelechiidivoris Marsh (Hymenoptera: Braconidae)
Jessica Morales, Corporación Universitaria Minuto de Dios
Tomato crop is one of the most important crops in Columbia
- Produce 500,000 tonnes per year
- Tomatoes are hosts for many kinds of herbivorous pests
- Tomato leafminer (Tuta absoluta) is one of the most important pests in columbia in greenhouse tomato production
- Responsible for 100% of crop loss in greenhouse tomatoes
- Apanteles gelechiidivoris (parasitoid) responsible for more than 80% mortality of third instar larvae in the field, but don’t have a reliable constant source of the parasitoid in the supply chain
- Conducted experiments in cages, 3 replicates per treatment
- Evaluated 7 treatments: 4, 8, 12, 16, 20 or 24 females T absoluta (tomato leafminer) per plant
- Evaluated quality parameters: longevity, percentage of parasitism and sex ratio
- Increased density of leaf miner, the height of the plant (r^2=0.27) and number of leaves (r^2=0.47) decreased.
- 8 – 12 adults per plant were optimal for producing adults. Higher could result in hyperparasitism
- Females at 16 and 20 females per plant resulted in the lowest parasitism rates, perhaps due to hyperparasitism
In conclusion, found best solution to be 12 T absoluta and 8 female A gelechiidivoris per plant for mass production
Jessica just invited everyone to her Country of Columbia.