We have recently posted an article on dry beans and how to increase their yields with plant nutrition and make it more profitable (if you haven’t read it yet, here is the link -link to “What you need to know about dry beans” article -. With an increased interest of farmers in growing dry beans, the importance of dedicating a whole article on its pests was noticed. Therefore, throughout this text, the major pests in each phenological state of the plant will be introduced, together with some inputs on how to prevent them.
Dry beans are also in the i-Plant Nutrition database and can be selected for the creation of fertilizer plans when using the software.
Seeds, seedlings and roots’ pests:
- Curcubit beetle (Diabrotica speciosa): its larvae feed off the seeds, roots and nodules, leading to perforated cotyledon leaves, and consequently, reducing water and nutrient absorption by the roots as well as photosynthesis.
- Teratopactus nodicollis: this beetle’s yellowish larvae with brown cephalic capsule attacks the beanstalk while its primary leaves are developing, cutting transversely the main root’s extremity. This will provoke the plant to become wilt, dry and eventually, die. In an earlier stage, it can feed on the plant’s hypocotyl killing them even before they were germinated.
- Bean Seed Fly (Delia platura): the fly’s larvae penetrate the seeds, destroying the embryo and reducing plant population on the field.
- Slugs (Sarasinula linguaeformis): the mollusks eat dry beans’ seedlings, leaving nothing but the stalk.
- Cutworms: in this group, there are larvae of a few different species, such as the Fall Armyworm (Spodoptera frugiperda), Velvetbean caterpillar (Anticarsia gemmatalis) and the Black Cutworm (Agrotis ipsilon). Comparably, they all cause the same plant damage by eating the seedlings – cutting them to the ground - and at times devouring even the seeds.
The occurrence of an underground pest population is related to the presence of host plants (usually weeds) near sowing time. The incidence of soil pests can be decreased by eliminating host plants, such as weeds or corn, at least three weeks before sowing. This will decrease the oviposition of moths in these areas thus avoiding the presence of large caterpillars (beyond 3rd instar), which cause greater damage to the crop in the initial development phases.
Pests that will scratch and suck:
- Spider mites: Species such as Two-spotted spider mite and Broad mite (Tetranychus urticae and Polyphagotarsonemus latus) will affect the bean plant by attacking its leaves. The first one, usually present on the bottom side of the leaves, will scratch the leaf’s surface and feed off the erupted sap, leading to white spots that turn into necrosis on the leaf’s upper side, whereas the Broad mite will suck the sap out of the middle part of the leaves until the leaflets edges are rolled up.
- Thrips (Thrips palmi and tabaci): This insect will feed on leaves and flowers, entailing in leaves with white spots on the upper side and silver spots on the bottom one, tissue necrosis, shoots and leaf buds’ atrophy, all leading to the abortion of buttons and pods.
- White fly (Bemisia tabaci): Besides the damage caused by sap sipping, this bug’s major harm is the introduction of the Bean Golden Mosaic Virus into the plant that results in an expressive yield loss.
- Leafhopper (Empoasca kraemeri): When feeding off the plant’s phloem – by sucking out the sap- the nymph and adult forms of the leafhopper turn the leaves yellow, with dry edges and causing a decrease in yields.
Bug attractive traps might help monitoring the pest population as well as in their control. Getting rid of this kind of dry bean pest might implicate on the use of chemical pesticides or its combination with biological enemies, such as entomopathogenic fungi and egg predators.
Stalk and stem pests:
- Been Bud Borer (Epinotia aporema): The larvae penetrate the stem through the terminal buds, forming a descending gallery, that will be used by them as shelter. They can also feed off the stem causing it to break or be more susceptible to the entrance of other pathogens.
Soybean Stalk Weevil (Sternechus subsignatus): The adult form of this bug shreds the tissue around the stem, whereas its larvae open galleries inside it. In both situations, the weevil causes the plant to break and die.
In order to control the pests in this stage, it is essential to integrate different control measures, such as crop rotation, chemical and mechanical control during soil preparation, sowing and also on the field’s surroundings. These insects need to feed off legumes once they emerge, therefore, rotating the plantation with maize, sorghum or sunflowers, for example, will force them to leave the field in search of food.
- Bed Bugs: This group includes Small Green Stink bug (Piezodorus guildinii), Southern Green Shield Bug (Nezara viridula), Neotropical Brown Stink bug (Euschistus heros) and many more. They suck the grains, which become wrinkled, hollow and darkened, reducing the germination power of seeds and the quality of the grains.
Caterpillars: Southern Armyworm (Spodoptera eridania), Legume Pod Borer (Maruca testulalis), Cotton Bollworm (Helicoverpa armigera) and many other moth and butterflies’ larvae feed off the pods and grains, destroying the ones that are still developing and spoiling the final product since the grains are damaged and covered in excrements of saprophytes that had their entrance in the beans favoured by the perforations made by the caterpillars.
The best way to control pod pests is by planning the whole season beforehand. Planning the best sowing date, when to apply pesticides according to the plant and pest stage, planning the harvest… Therefore, efficient pre-harvest planning will help you avoid unnecessary costs and yield loss in the future.
Just like the human body, healthy and well-nourished plants have greater resistance to pests and diseases, and in case of infestation, will have their productivity less affected.