IPM Packages for Crops

diseases | identification, descriptions, and images

DISEASES

MINOR PESTS

Fruit Rot [ Phytophthora palmivora (Peronosporales: Peronosporaceae)] This is one of the most serious fungal diseases of longan. Young shoots, pani- cles, and fruits are most affected. It can survive in the soil and can spread through irrigation water, ants, and human activity. It causes necrosis of young shoots, flower drop, irregular lesions on fruits, and premature fruit drop. This disease is particularly harmful during cool weather after 2-3 days of rain. Proper sanitation, aeration, and reducing humidity by pruning decreases disease incidence. Ceratocystis Blight [ Ceratocystis fimbriata (Microascales: Ceratocystidaceae)] This fungal disease initially infects branch- es and later on causes wilting and eventu- ally affects the whole tree. Abiotic factors such as water stress, extreme high or low temperatures, and micro-nutrient deficien - cy increases the damage caused by this fungus. Mechanical damage caused by scolytid beetles, contaminated tools used for pruning, and ringing transmit this dis- ease to healthy plants. Some varieties are more susceptible. Pruning and removal of infected plant parts help in managing this disease. Anthracnose [ Colletotrichum gloeosporioides (Incer- taesedis: Glomerellaceae)] It is a foliar fungal disease and attacks both leaves and fruits. Symptoms on older leaves that appear as small spots in the margins coalesce to form large patches with brown borders. On young leaves and fruits dark brown lesions appear on the surface. Wet conditions increase its infec- tion rates. Proper sanitation, aeration, and reducing humidity by pruning decreases disease incidence.

Sooty mold [ Meliola sp. (Meliolales: Meliolaceae)] Sooty mold fungus affects both fruit and leaves of longan that are attacked by sap-sucking mealybugs, Planococcus lilacinus, Pseudococcus sp., and Nipaecoc- cus sp. scale insects, longan wax scale, Ceroplastes ceriferus, and soft scale, Dre- panococcus chiton. These insects secrete honeydew that nourishes sooty mold. Al- though it does not cause direct damage, it reduces photosynthetic surface on leaves and infected fruits are downgraded. By controlling these insects, this fungus can be managed. Downy Blossom Blight [ Peronophythora litchi (Pythiales: Pythia- ceae)] This fungal disease is common on litchi. On longan, it was first reported in 2000 in Taiwan. This disease causes droopy leaves and leaf blight. Watersoaked lesions appear on young leaves, which turn into brown, round, or irregular lesions. Dis- eased leaves wither and collapse eventual- ly. Humid conditions and continuous rain are favorable for this disease. Sheathoid nematode ( Hemicriconemoides litchi ) (Tylenchida: Criconematidae) The sheathoid nematodes are root-ectopar- asitic. Recently, Hemicriconemoides litchi is found to be associated with the root sys- tem of longan in Taiwan. This nematode causes root malformation and nutrient deficiencies on agricultural fruit trees. However, above-ground evidence of dam- age may not become immediately obvious. NEMATODES

Leaf miner ( Acrocercops cramerella ) (Lepidoptera: Gracillariidae) Mealybug ( Pseudococcus sp.) (Hemiptera: Pseudo- coccidae) Spherical mealybug ( Nipaecoccus sp.) (Hemiptera: Pseudococ- cidae) Grasshopper ( Oxya sp.) (Orthoptera: Acrididae) Indian wax scale ( Ceroplastes ceriferus ) (Hemiptera: Coc- cidae)

Ceratocytis fimbriata