Indicator species – early warning for pest attack

Any IPM plan should incorporate a monitoring scheme that allows the size of a pest population to be guaged, over time. By understanding the state of a population it’s then possible to make more informed decisions about whether to act and how to act.

Not all plant species in the display acted as hosts to pest insects, in fact 26 species never had any pests on them at all. The significance of this is that the species which had the most pests on them can then act as indicators for the state of pest populations in the glasshouse as a whole.

The figure below provides data on how many different plant species were host to pests and at which dates.

number of plants with pest type present

The range of plants on which pests insects were found

Pseudococcus viburni – Glasshouse Mealybug

Mealybugs were on a total of 33 plant species and thrived in the glasshouse during the sample period. Species on which mealybug were found at the highest densities were: Okra  Abelmoschus esculentes, Perennial peanut Arachis glabrata, Coffee Coffea arabica, Tea Camellia sinensis, White lead tree Leuceana leucocephala and Avocado Persea americana.

The flowering heads of Papyrus Cyperus papyrus acted as ideal nesting material for the egg sacs that the glasshouse mealybug produce. Papyrus grow from the pond in the display and the water acts as a physical barrier, preventing pregnant females from reaching the plant. However; one papyrus head in particular dangled in to the white lead tree, providing access for the mealybug.

Trialeurodes vaporariorum – Glasshouse whitefly

I found whitefly on 20 different plant species during sampling. Lantana camara, Chaenostoma cordata and Cuphea ‘Tiny mice’ had the highest densities of all whitefly stages on them and acted as breeding grounds for T. vaporariorum. Interestingly parasitized larval stages were found on these species. I have calculated the percentage of parasitized whitefly to healthy ones and shall post them on the profiles of these plants.

Aphis fabae Black bean aphid

The two aphid species Aphis fabae and Aulacorthum solani occupied similar plant hosts, however the black bean aphid Aphis fabae was much more abundant and densely populated.

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