Wednesday, 20 February 2013

Hayahay: Happy Rice, Happy Survivors

The Plant Disease Management Team takes a look at our Rice
Survivor plots, declaring them to be fit.
Since my group, the plant disease management group, here at IRRI routinely conducts crop health assessments, including one for Achim and Leigh, I asked Dr. Nancy Castilla to organize an assessment of Team Hayahay's Rice Survivor plots. For this activity we used IRRI's survey portfolio for characterising rice pest constraints. This is a handbook that details a methodology for use in farmers' (and researchers') fields that allows us to gather information in a useful format to characterise the production situations (i.e., how farmers establish a rice crop, how much fertiliser they use, if they spray pesticides, etc.) and data related to the crop health injuries caused by insect and animal pests and diseases and then analyse the data.

During the survey there weren't many major surprises at this point during the dry season here in the Philippines. Rice whorl maggot damage was a little high at 20%, but not unacceptable and the crop will recover from this damage during the vegetative stage before the reproductive stage starts and it's common in well-watered rice fields, the fly is attracted to the water. We did find some boron toxicity as well, some leaf tips showed the typical symptoms of the burnt leaf tips. This is typically caused by our irrigation water here at the IRRI Experiment Station having high levels of boron in it. There is some incidence of tungro as well, but since we planted 222, a resistant variety, we shouldn't have much to worry about. It does look like we did a good job weeding as well with no weed above the canopy and only 4% below.

Overall the plots look good. The time to really start to be concerned about diseases is at booting and right now the rice is just at panicle initiation, so we have some time to sit back an wonder what's coming next.

Below is Dr. Castilla's report that she prepared for us.

Crop Health Assessment for Rice Survivor, Hayahay Team
Location: IRRI ES Block 824
Date of Assessment: 18 February 2013
Forty hills were randomly sampled along diagonal paths to assess the injuries caused by animal pests and diseases on the leaves or tillers. Systemic diseases, such as tungro, were assessed by counting the number of hills with typical symptoms in 20 randomly selected 1-sq.-m. areas. Weed cover was assessed in 12 randomly selected 1-sq.-m. areas. The results are summarized in the tables 1 and 2. Incidence of injuries caused by insect defoliators (i.e., leaffolder, leaf miner, thrip, and whorl maggot), leaf scald, and boron toxicity was computed as the percentage of injured leaves in a hill. Incidence of deadheart (caused by stemborers), which affect tillers was computed as the percentage of injured tillers in a hill. The incidence of tungro was computed as the percentage of hills with typical symptoms. A leaf, tiller or hill with low injury is considered injured as one that is severely injured. Weed cover was assessed as the percentage of a 1-sq.-m area that is covered by weeds above and below the rice canopy.

Table 1. Incidence of injuries.

Injury or cause of Injury
Incidence (%)
Leaf miner
Leaf scald
Whorl maggot
Other insect defoliators
Boron toxicity

Table 2. Weed assessment.

Weed cover above the rice canopy
Weed cover below the rice canopy

Most common weed species

Sphenoclea zeylanica
Ludwigia hyssopifolia
Cyperus difformis
Fimbristylis miliacea
Echinochloa spp.

The plant disease management team
warms up for their survey
activities in Hayahay's plot.
Dr. Nancy Castilla enthrals
Team Hayahay with plant
pathology stories.
Dr. Nancy Castilla gives Dr. Noel Maggor some
pointers on growing a healthy rice crop.

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