According to experience, the stage when the fruit enters nutritional metabolism is also the time of the last fertilization (usually around the end of July to the beginning of August every year), applying potassium fertilizer with an amount of about 30% of the total fertilizer amount. The fruit is sweet all season long, has beautiful fruit design, and bright yellow skin. Use fertilizers with high potassium content such as Kalisulphate (K2SO4), Potassium chloride (KCl), ... to fertilize the base or use foliar fertilizers with high potassium content such as Profarm Kalisol one, Farm Potassium top, Super sweet Potassium , Epnon K36, ... for spraying; Combine watering with enough moisture to overcome the phenomenon of dry shrimp and dry citrus. Stop watering 1 - 1.5 months before harvest to make the fruit quality better and sweeter.

Currently, in Phu Tho province in general and Doan Hung district in particular, the entire commercial grapefruit area has entered the stage of stable fruit development in size, moving to the stage of accumulation and transformation in quality. quantity. This is an important stage, farmers need to focus on proper care and pest control techniques to achieve high productivity, good quality fruit, beautiful designs, and high selling prices.

According to experience, the stage when the fruit enters nutritional metabolism is also the time of the last fertilization (usually around the end of July to the beginning of August every year), applying potassium fertilizer with an amount of about 30% of the total fertilizer amount. The fruit is sweet all season long, has beautiful fruit design, and bright yellow skin. Use fertilizers with high potassium content such as Kalisulphate (K2SO4), Potassium chloride (KCl), ... to fertilize the base or use foliar fertilizers with high potassium content such as Profarm Kalisol one, Farm Potassium top, Super sweet Potassium , Epnon K36, ... for spraying; Combine watering with enough moisture to overcome the phenomenon of dry shrimp and dry citrus. Stop watering 1 - 1.5 months before harvest to make the fruit quality better and sweeter.

At this stage, farmers must not be subjective, must regularly check to detect harmful organisms, and pay attention to the objects that often appear and cause harm: fruit flies, scurvy diseases. gum disease, scar disease, ulcer disease, spiders, aphids, especially fruit flies (also known as yellow flies, fruit maggots) are very harmful insects and greatly affect productivity, design and business. income of grapefruit growers. Fruit flies (Yellow fruit flies) often cause severe damage from July onwards until harvest time. Fruit flies use ovipositors to inject deep into the fruit flesh and lay eggs there. Each injection can lay 5 - 10 eggs/hole, a female can lay 150 - 200 eggs. The fly's stings are initially as big as the tip of a needle, slightly concave (small black dots), 2-3 days later the stings gradually get bigger and dark brown, then turn yellow, with sap flowing out (pus discharge). Female flies lay eggs, after 1-2 days the eggs hatch into larvae (larvae or maggots), the maggots burrow deep into the fruit in many different winding paths. Each fruit can have many maggot-like larvae, so the level of damage caused by yellow flies is very large. From the gouge, bacteria, fungi, etc. can enter and cause fruit rot. Fruits damaged by yellow flies are often easily deformed, curled, distorted and fall off en masse.

 To manage Yellow Fly well, grapefruit growers need to synchronously apply integrated pest management (IPM) measures throughout the growth process of the tree as follows:

- Cultivation measures: Apply balanced fertilizer, prune branches to create a reasonable canopy to keep the grapefruit garden clear, manage weeds, clean the grapefruit garden, collect damaged fruit and destroy it to kill maggots.

- Manual measures: Use specialized bags to cover fruit from after the physiological fruit shedding period onwards. Manage intercropped crops well (guava, star fruit, pineapple...), harvest ripe fruit promptly to avoid attracting flies to lay eggs.

- Use attractant baits to kill adult flies: Use drugs such as Vizubon - D, Ento-Pro 150SL, Acdruoivang 900OL, ... brush on fruits with attractive scents such as pineapple, mango , guava …; Or soak cotton with medicine and place it in commercially available cages (traps) or homemade cages. Or use yellow sticky traps to hang. Trap density is about 20 - 25 traps/1 hectare, hung around the garden, not in the middle of the garden.

 How to make a homemade cage is as follows: Use a yellow plastic bottle (do not use white bottles) to cut 2 small rectangular holes facing each other about 2 x 2.5cm; Use steel wire to tie one end of the drug-soaked cotton, and the other end to pierce the bottom of the bottle to secure it and make a hanger.

- Chemical measures: It is possible to use a number of pesticides that have been registered in the list of pesticides allowed to be used in Vietnam on citrus trees containing the active ingredients Flubendiamide, Petroleum oil, etc. Drug example: Takumi 20 SC, Soka 25EC, ... use according to the instructions on the packaging.

Do Chi Thanh

Head of Doan Hung District Plant Protection and Information Station