Comparing Rice Stink Bug Sampling Methods: University vs Consultant M. O. Way, R. A. Pearson and C. M. Curtice

Size: px
Start display at page:

Download "Comparing Rice Stink Bug Sampling Methods: University vs Consultant M. O. Way, R. A. Pearson and C. M. Curtice"

Transcription

1 Comparing : University vs M. O. Way, R. A. Pearson and C. M. Curtice Abstract The rice stink bug (RSB) is a key pest of rice in Texas as well as other southern riceproducing states. Current economic thresholds for this grain-attacking pest are based on sweep net sampling developed and published by Texas A&M AgriLife Research. This methodology should be revised because Texas Crop s do not employ and for good reason---this methodology. Because of the widespread adoption of high yielding varieties (including hybrids) and improved agronomic and pest management practices, commercial rice fields have closed, thick canopies during maturation which physically impedes sweep net sampling as recommended by Texas A&M AgriLife Research (A&M). Crop sampling methodology (CC) is physically less strenuous but requires more time than that of A&M. In this presentation, we describe and quantitatively compare the 2 methodologies. Introduction The RSB is native to the southeastern US and is a key pest of rice in southern riceproducing states (Espino and Way, 28). The main damage caused by RSB is peck, a bullseyeshaped discoloration of brown and milled rice (Espino et al. 28a and b). Peck is caused by the probing of rice grains by RSB in combination with selected microorganisms which can enter the grain via the probing wounds (Way, 218). Farmers are docked monetarily (discounted) for the amount of peck found in their rice (Harper et al. 1993). RSB-published thresholds in Texas are currently based on A&M sweep net sampling which is performed with a 38 cm (15 inch) diameter net attached to a 91 cm (3 ft) long handle (Way and Espino, 214). The operator takes 1, 18 degree sweep with each step moving forward through the field/canopy until 1 sweeps are performed. The top of the net coincides with the top of the rice canopy during sweeping. Then the number of nymph and adult RSBs are recorded for all 1 sweeps. Because of the dense canopy of maturing, high-yielding rice in Texas, the operator employing the A&M method has difficulty taking 1 consecutive sweeps without stumbling or falling which obviously disturbs the insects ahead of the sweep net. The CC method uses the same size net as far as diameter and handle length, but the operator takes a single sweep, then prevents collected insects from escaping by closing off the open end of the net by hand or by dipping the net in the floodwater. The operator then takes 3-4 leisurely steps forward without sweeping, followed by another sweep. This is repeated until 1 sweeps are performed. Finally, nymphs and adults collected in 1 sweeps are recorded. Materials and Methods During the summer of 217, we compared CC and A&M sampling methods in various commercial main crop rice fields in the Texas Rice Belt. Fields varied in maturation from milk to dough. Some were planted to hybrids and some were planted to inbreds. All were long-grain varieties commonly grown in Texas. All sampling was performed after dew evaporated from the rice canopies. In addition, all fields had not been treated for RSB and visually were projected to yield well. in other words, these fields were typical, well-managed, high-yielding fields. In this poster presentation, we did not separate data as to variety or stage of maturation. Two operators were deployed away from the field margins [at least 18 m (6ft)]. One operator performed CC and the other A&M methodology. The operators were opposite one another but separated by at least 9 m (3 ft). We assumed this distance was adequate to avoid interference between methodologies. 46

2 Sampling was performed at the same time by each operator. Several operators were utilized throughout the experiment. CC sampling took more time than A&M sampling and stretched over more distance due to the extra steps between sweeps. Thus, when the CC operator finished a 1- sweep sample, the A&M operator moved up opposite and another pair of samples was taken. Sweep net contents were separated by nymphs and adults. In all, we performed 53 pairs of samples. Data (nymphs, adults and nymphs + adults) were analyzed by simple linear correlation between CC and A&M counts. Results and Discussion The R-squared values for nymphs, adults and nymph + adults were low ,.2478 and.2278, respectively---(figs. 1-3). Basically, all we can conclude is CC methodology collects more RSBs than A&M methodology. Thus, we cannot draw useable conclusions from these data. We plan to improve the experiment in 218. We will take more paired samples and we will separate data by conventional and hybrid variety and stage of maturation. Perhaps intra-field distribution of RSBs is spatially highly variable. 3 A/1 sweeps y =.2586x R² = Figure 1. Number of rice stink bug adults per 1 sweeps 47

3 4.5 N/1 sweeps y =.1348x R² = Figure 2. Number of rice stink bug nymphs per 1 sweeps 48

4 3 N + A/1 sweeps y =.2492x R² = Figure 3. Number of rice stink bug adults and nymphs per 1 sweeps References Espino, L. and M. O. Way. 28. Attractiveness of stages of rice panicle development to Oebalus pugnax (Hemiptera: Pentatomidae). J. Econ. Entomol. 11(4): Espino, L., M. O. Way, and L. T. Wilson. 28a. Determination of Oebalus pugnax (Hemiptera: Pentatomidae) Spatial Pattern in Rice and Development of Visual Sampling Methods and Population Sampling Plans. Journal of Economic Entomology 11 (1): Espino, L., M. O. Way, and L. T. Wilson. 28b. Sequential Sampling Plans for Sweep Net and Visual Sampling of Oebalus pugnax in Rice. Southwestern Entomologist 33 (1): Harper, J. K., M. O. Way, B. M. Drees, M. E. Rister, and J. W. Mjelde Damage function analysis for the rice stink bug (Hemiptera: Pentatomidae). Journal of Economic Entomology. 86 (4): Way, M. O Arthropod pests. In: Compendium of Rice Diseases and Pests (2nd edition). The American Phytopathological Society (APS) Press. St. Paul Minnesota. pp

5 Way, M. O. and L. Espino Insect management. In: 214 Texas Rice Production Guidelines. Eds. M. O. Way, G. N. McCauley, X. G. Zhou and L. T. Wilson. Bulletin Pp