Biodiversity of the parasitic, predatory and pollinating hymenoptera species from rice fields on Hainan Island, China – 123 new species recorded

by
Alberto Barrion, taxonomy consultant, International Rice Research Institute, Los Baños, Philippines, Ducheng Cai, Hainan University, Haikou, China, J. Catindig, S. Villareal, International Rice Research Institute, Los Baños, Philippines and Qianhua Yuan, Hainan University, China

Biodiversity of hymenoptera species from Hainan Island

Hymenoptera is the order of insects that comprises of wasps, bees, ants and parasitoids. From the human perspectives this group of insects is probably most beneficial, as they provide important ecosystem services, biological control and pollination. There are over 130,000 recognized species, with many more remaining to be described. The name refers to the wings of the insects derived from the Ancient Greek word “hymen”, meaning membrane and “pteron”, meaning wing.

We used 6 insect sampling methods and collected 6, 531 individuals from 4 sampling sites, brought them back to laboratory, identified and counted them.  There were 816 species from 260 genera in 36 families. The most dominant families were Scelionidae (1,465 individuals), Formicidae (1,333), Trichogrammatidae (947), Eulophidae(614), Braconidae (435), Encyrtidae(365), Mymaridae(332), Elasmidae (155) and Aphelinidae (136). The highest number of species was from Scelionidae (162 species), followed by Encyrtidae (110), Eulophidae (102), Braconidae (86), Mymaridae (47), Trichogrammatidae (34), Ceraphronidae and Chalcididae (25 each) and Pteromalidae (21). Of the total number of species identified, we found 123 species or 15% were new and previously unknown to science. The proportion of uncharted arthropods in Hainan Island is impressive.  Earlier we also found new undescribed species of spiders. The large number of new species found in the expedition indicates that the arthropod biodiversity is high and many species are yet to be described.

 

Families of hymenoptera – largest number from family scelionidae

The two functional groups of Hymenoptera in rice ecosystems were parasitoids represented by 25 families and constituting 77.4% (5,055 individuals) and predators in 5 families making up 22.2% (1,448 individuals).  Only a small proportion was pollinators from 0.4% (28 individuals) from 5 families. This implies that the hymenoptera species contribute mainly to biological control services of rice ecosystems.  Since rice is a self pollinated crop, the pollination service may not be as important for production, but are important indicators of ecosystem health. In Vietnam authorities launched a campaign to motivate farmers to conserve bees and their relatives.

More than 99% of the hymenoptera were parasitoids and predators

Earlier we computed the species richness of the parasitoids and found that this index was related to the flowering flora of the neighboring habitats. Thus ecological engineering practices, like enriching the areas surrounding the rice crop with flowering plants as practiced in Vietnam and Thailand can restore resilience of rice fields to pest attacks.

The full report is available.

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Hainan Farmers’ Addiction to Insecticide Use Due to Extreme Loss Aversion?

by
M.M. Escalada, Visayas State University, Leyte, Philippines,
L Wang, Q. Yuan, D. Cai, Hainan University, Hai Kou, China and
K.L. Heong, International Rice Research Institute, Los Baños, Philippines

Farmers being interviewed by trained student enumerators.

 

In making pest management decisions, farmers always face uncertainty and often adopt the bounded rationality approach. In this approach, as opposed to unbounded rationality, farmers will tend to “satisfice” rather than “optimize.” Satisficing, a combination of sufficing and satisfying, is a word of Scottish origin to characterize decision making in conditions of limited time, knowledge, and computational capacities using simple rules or “Heuristic”, a term to refer to an informal rule-of-thumb used in decision making. Heuristics are developed through experience and guesswork about possible outcomes and may thus have inherent faults and biases. Research to understand farmers’ current heuristics and reasons for their adoption will help scientists frame alternative heuristics that improve outcomes (Escalada and Heong, 2012).

In an earlier work on the rice leaffolder, Cnaphalocrocis medinalis (Guenée), a simple rule-of-thumb or ‘heuristic’ was which was in conflict with prevailing belief that spraying was necessary, was communicated to farmers and they were encouraged to test the rule. The heuristic stated: ‘In the first 30 days after transplanting (or 40 days after sowing), leaffolder control is not necessary’.

In this leaffolder example, farmers sprayed insecticides to control the larvae (often called “chuang” or “worms”) because of they are highly visible.  Farmers tend to strongly believe that leaf damages will lead to yield loss and that the worms will multiply quickly and thus need to be killed immediately. These beliefs might stem from farmers overestimating potential losses and their loss aversion behavior.

In decision theory, loss aversion is the tendency of people to strongly prefer avoiding losses to acquiring gains. The phenomenon was first described by Amos Tversky and Daniel Kahneman (1974) when they developed Prospect Theory.

In Hainan, we surveyed 411 rice farmers in December 2010-January 2011 and found that farmers would apply insecticides regardless of whether pests were present or can potentially cause yield loss. About 58% of the sprays had no specific targets, 13% were targeted at leaf folders, 19% at planthoppers and the remaining 10 % of the sprays were targeted at stem borers and minor pests like “general worms”. Sixty-three (63%) percent of the farmers strongly thought that “all insects in rice fields are harmful” and 83% of the farmers believed that insecticides MUST be used to achieve high yields.

 

Relationship between farmers’ yields and number of insecticides applied. Means and std error bars.

When we plotted farm yields with the number of insecticide sprays used, we obtained no significance (F = 2.20; p = 0.139) and a negative regression (coefficient = – 0.081). Farm yields varied from 3 to 12 ton per ha, while number of insecticide sprays ranged from zero to 12. Two farmers sprayed more than 10 times and their yields were less than 4 tons/ha, while the 6 farmers who did not spray anything averaged 5 tons/ha. Farmers that had higher sprays seem to have higher variability.

 

Reference

Escalada, M.M. and Heong, K.L. (2012). Using decision theory and sociological tools to facilitate adoption of biodiversity-based pest management strategies. In Gurr, G.M., Wratten, S.D., Snyder, W.E., Read, D.M.Y. (Eds). Biodiversity and Insect Pests: Key Issues for Sustainable Management. John Wiley & Sons, Ltd., UK. Pp 199 – 213.

Tversky A. & Kahneman D. (1974) Judgment under uncertainty: heuristics and biases. Science. 185,1124-1131.