Hedyotis corymbosa: Spotting and Controlling Diamond Flower in Rice
Hedyotis corymbosa, also called diamond flower, is a slender broadleaf weed with long, narrow leaves. It grows in irrigated and rainfed lowland rice fields in the Philippines. There, farmers call it pisak or dalumbang. This page shows you how to spot it and how it competes with your palay. Then you will learn how to control it before it sets seed.
What Is Hedyotis corymbosa?
Hedyotis corymbosa is a small annual herb in the coffee family, Rubiaceae. In English it is called diamond flower. Its thin stems branch out, and the plant either stands upright or spreads along the ground. Local names include dalumbang, kaddok na kalinga, palarapdap, pisak and pisek. Farmers also use these names for its cousin, Hedyotis biflora.
Look for it in irrigated and rainfed lowland rice fields. This weed lives for only one season. Within one crop, it sprouts, flowers, sets seed and dies. Seeds are its only way to spread. The tiny seeds drop near the mother plant and stay in the soil until the next planting. So a few plants left alone this season can turn into a thick stand next time.
| Name | Hedyotis corymbosa |
|---|---|
| English name | Diamond flower |
| Family | Rubiaceae |
| Weed group | Broadleaves (see the three groups) |
| Local names | Dalumbang, kaddok na kalinga,palarapdap, pisak, pisek |
| Life cycle | Annual |
| Spreads by | Seeds |
| Where it grows | Irrigated and rainfed lowland rice fields |
How to Identify Hedyotis corymbosa
Check the low spaces between rice hills for a slender herb with thin, branched stems. Its leaves are long and narrow, and they taper slowly to a point at the tip. The leaves look narrow, yet this is a broadleaf weed, not a grass or sedge. Instead of a leaf sheath wrapped around the stem, it has leaves set in pairs on a freely branching stem. Tiny flowers sit in small umbrella like clusters of 2 to 8.
- Long, narrow leaves that slowly taper to a fine point at the tip.
- Thin, branched stems standing upright or sprawling low between the rice hills.
- Leaves set in pairs along the stem, with no sheath wrapping the stem.
- Tiny flowers in small umbrella like clusters of 2 to 8.
- Look alike tip: Hedyotis biflora shares its local names but has oval to oblong leaves.
Why It Hurts Your Palay
This weed looks harmless, but it still competes with your palay. It draws water and nutrients from the same soil where your rice roots feed. It also takes a share of the fertilizer you pay for. When many plants sprout together, they fill the gaps between rice hills while the crop is young and weak.
Because it is an annual that spreads only by seed, each plant that flowers adds more seed to your soil. As a result, the weed returns with every new crop. Its seeds can also mix with the harvested palay. Thick patches give insects a place to hide close to your rice too.
How to Control Hedyotis corymbosa
- Walk the paddy while the rice is young and pull these slender plants early. Their thin leaves are easy to miss among rice seedlings.
- Remove plants before the tiny flower clusters set seed. Each seed you stop now is one less weed next season.
- Keep water in the paddy after planting where your field allows. Small seeded annual weeds sprout more easily on exposed soil than under water.
- Clean the bunds too. Plants growing on the pilapil can drop seed back into the field.
What to Do at Each Age of Your Rice
- 0 to 5 days: keep the soil saturated. Use a pre emergence herbicide only if the field had many weeds last season.
- 6 to 10 days: hand weed in transplanted rice. In direct seeded rice, this is the window for an early post emergence spray.
- 11 to 20 days: keep water in the field, weed by hand or with a rotary weeder, and let Azolla and the Altica beetle help. Spray only if those fail.
- 21 to 30 days: top up the water and keep weeding. Spray only if weeding fails.
- 31 to 40 days (transplanted rice): hand weed. A spray this late is only a rescue.
- After any post emergence spray, bring the water back within 1 to 3 days at 3 to 5 cm and hold it for 4 to 5 days. Keep young rice above it.
Active Ingredients That Work on Broadleaves
If water and weeding cannot hold Hedyotis corymbosa down, choose an active ingredient that works on broadleaves at the age of your rice. Each active ingredient in it is in a herbicide registered in the Philippines for rice. Shop by the ingredient on the label, never by the brand. If your field also has other kinds of weeds, the weed control helper in anee.io finds the ingredients that cover all of them.
| Rice age (days after planting) | Transplanted rice (lipat tanim) | Direct seeded rice (sabog tanim) |
|---|---|---|
| 0 to 5 days | Pretilachlor, Oxadiazon, Butachlor plus 2,4 D IBE, Pyrazosulfuron ethyl plus pretilachlor, Imazosulfuron, Penoxsulam plus butachlor, Tefuryltrione plus triafamone, Thiobencarb plus 2,4 D IBE | Pretilachlor, Oxadiazon, Pretilachlor plus butachlor, Butachlor plus 2,4 D IBE, Pendimethalin, Pyrazosulfuron ethyl plus pretilachlor, Butachlor with safener |
| 6 to 10 days | Butachlor plus propanil, Cyhalofop butyl plus bispyribac sodium, Bispyribac sodium, Penoxsulam plus cyhalofop butyl, Pendimethalin, Cyhalofop butyl plus propanil, Imazosulfuron, Propyrisulfuron, Clomazone plus propanil, Thiobencarb plus propanil, Flucetosulfuron, Cyhalofop butyl plus florpyrauxifen benzyl | Butachlor plus propanil, Cyhalofop butyl plus bispyribac sodium, Bispyribac sodium, Pyribenzoxim plus cyhalofop butyl, Penoxsulam plus cyhalofop butyl, Cyhalofop butyl plus propanil, Pyrazosulfuron ethyl plus pretilachlor, Pendimethalin, Propyrisulfuron, Clomazone plus propanil, Thiobencarb plus propanil, Pretilachlor plus pyribenzoxim, Penoxsulam, Flucetosulfuron, Cyhalofop butyl plus florpyrauxifen benzyl |
| 11 to 20 days | Cyhalofop butyl plus bispyribac sodium, Bispyribac sodium, Pyribenzoxim plus cyhalofop butyl, Penoxsulam plus cyhalofop butyl, Metamifop plus bispyribac sodium, Bentazone, Cyhalofop butyl plus ethoxysulfuron, Propyrisulfuron, Fenoxaprop P ethyl plus ethoxysulfuron, Flucetosulfuron, Carfentrazone ethyl, Florpyrauxifen benzyl, Cyhalofop butyl plus florpyrauxifen benzyl | Cyhalofop butyl plus bispyribac sodium, Bispyribac sodium, Pyribenzoxim plus cyhalofop butyl, Penoxsulam plus cyhalofop butyl, Metamifop plus bispyribac sodium, Bentazone, Pyribenzoxim, Cyhalofop butyl plus ethoxysulfuron, Propyrisulfuron, Fenoxaprop P ethyl plus ethoxysulfuron, Flucetosulfuron, Carfentrazone ethyl, Florpyrauxifen benzyl, Cyhalofop butyl plus florpyrauxifen benzyl |
| 21 to 30 days | 2,4 D amine, 2,4 D IBE, MCPA, Metamifop plus bispyribac sodium, Bentazone, Metsulfuron methyl plus chlorimuron ethyl, Fenoxaprop P ethyl plus ethoxysulfuron, Carfentrazone ethyl | 2,4 D amine, 2,4 D IBE, Cyhalofop butyl plus bispyribac sodium, Pyribenzoxim plus cyhalofop butyl, MCPA, Metamifop plus bispyribac sodium, Bentazone, Metsulfuron methyl plus chlorimuron ethyl, Pyribenzoxim, Carfentrazone ethyl |
| 31 to 40 days | Metsulfuron methyl plus chlorimuron ethyl | Not listed for direct seeded rice |
Spray Safely
Use only herbicides registered with the Fertilizer and Pesticide Authority, and follow the label on the pack: the rate, the timing, the water and the protective clothing. Switch herbicide groups between seasons so the weeds do not learn to survive them. Our guide to herbicides for rice explains the groups.
Keep Hedyotis corymbosa Out Next Season
- Plant clean, certified seed. Weed seeds mixed into the punla are the easiest way in.
- Keep the seedbed, the canals and the bunds free of weeds, so seed does not wash or blow into the paddy.
- Prepare the land well: flood, plow, let the weed seeds sprout, then kill them when you harrow. Level the field so water covers it evenly.
- Pull escapes before they flower and set seed, and carry them out of the paddy instead of leaving them on the bund.
- Keep the field clean after harvest and through the fallow, so fewer seeds build up in the soil for next season.
These steps work for every broadleaf weed in the paddy, not only this one. The weed management guide puts them in order for a whole season.
Not Sure It Is Hedyotis corymbosa?
Take a clear photo of the leaf, the stem and the flower or seed head, then ask Anee, the smart farm technician in anee.io, in Tagalog or English. Anee tells you which weed it most likely is, its group, and what to do at the age of your rice. You can also put the weeding days on your cropping calendar, so the team knows when to go in.
anee.io keeps your weeding, spraying and water on one calendar, and Anee answers when a plant looks wrong.
- Weeding days on the season calendar
- Photos and notes for every lot
- Anee, the smart farm technician, in Tagalog or English
Questions Farmers Ask About Hedyotis corymbosa
What is Hedyotis corymbosa called in the Philippines?
How do I control diamond flower in my rice field?
Why do I see more of it every season?
Get Hedyotis corymbosa out of your field
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